Admittedly I could be wrong, but it would appear that a significant amount of credit should be shown to the inquiry board, test engineers and BOAC for their determination to get to the bottom of the problem. By all accounts this wasn't covered up or hidden from public scrutiny - the process seemed to have been relatively transparent, (not a window gag) although the damage was already done to the reputation of the aircraft.
@@rrknl5187 I beg to differ! The whole investigation process for all aviation accidents and near misses is to find root causes and ensure they are eliminated! There is obviously pressure from corporate to make it quick and cover any guilt, but the investigations are always good!
@@totherarf The degree of corruption and influence to protect industry or protect pilots varies as you move through space and time. Watch the last Mini Air Crash Investigations video and tell me that wasn't a cover-up, to say nothing of what happened with the Max. I won't disagree that the attitude of "find the problems" over "punish the troublemakers" or "prove the aircraft works okay" gets far better results. But, between the national investigators (NTSB and relvant counterparts), investigators from manufacturers, and investigators from airlines, there are a lot of competing interests in any investigation, and we don't always succeed in keeping those interests out of the way of doing good work.
@@totherarf I'd suggest that you are both correct. The aviation industry probably holds itself to different standards than other industries in this regard. @RR KNL didn't specify the aviation industry, and in many other industries there are (to varying degrees) cover ups - construction, manufacturing, oil, gas, coal and mining have all faced transparency problems over the years when things go wrong - we've seen plenty of examples on this channel. @Mentour Pilot is a fantastic aviation channel which looks at, amongst other things, aviation incidents, accidents and disasters - not in a distasteful, insensitive or crass way - the content creator hopes to illustrate that the aviation industry is constantly learning and improving through post crash investigations - something that other industries could learn from.
There is one thing that was missed - well, three things, if you count in the fact that the rivet holes on the Comet 1 were punched rather than drilled, which gave rise to the stress fractures in first place: The Comet 1 design was deliberately made as light as it could be. The Comet 1 was relatively underpowered, having four de Havilland Ghost 50 Mk1 engines which only offered about 5050 lbf per engine. From the Comet 2 onwards, Rolls-Royce Avon engines were fitted instead, which were significantly more powerful - the Avon Mk.524s on the Comet 4 offered 9,500 lbf per engine. As a result, from the Comet 2 onward, the aircraft were built significantly stronger. The lighter structure on the Comet 1 was part of the reason why it failed so spectacularly: it simply was not designed for the sort of stresses that it would see in real life, even though engineers at the time could not have been aware of this. Another thing is, that prior to the Comet disasters, the prevalent design philosophy used in British aircraft engineering was that of the Safe Life - a predetermined limit set at which the structural safety of the aircraft was thought to expire, and after which the aircraft should be withdrawn from service. Going from prior tests using individual components, IIRC De Havilland calculated the Safe Life of the Comet 1 around 16000 pressurisation cycles. Following the second series of tests which used an entire fuselage, however, the Safe Life of the Comet was proven to be dramatically shorter than previously calculated - failure expected to occur at any point between 1000 and 9000 cycles (or as it proved in both crashes, 900 cycles for G-ALYY/SAA Flight 201; and 1290 cycles for G-ALYP/BOAC Flight 781). Following this, the design philosophy in aviation gradually moved from Safe Life (i.e. a precalculated failure point before which the aircraft would be retired) to Fail Safe design (i.e. designing the aircraft structure in such a way that any failure would not result in catastrophic/fatal damage). On a side note, the earlier crashes mentioned also revealed different issues. BOAC's G-ALYZ (October 26th 1952) and Canadian Pacific's CF-CUN (March 3rd 1953) both crashed at take-off after their crews over-rotated the aircraft. Subsequent investigation showed that when the nose was raised beyond a certain point, the airflow over the wings was interrupted leading to a loss of lift, rendering a take-off near-impossible; as a result the wings' leading edge was redesigned. BOAC's G-ALYV (Flight 783, May 2nd 1953) broke up in a thunderstorm; subsequent investigation revealed the aircraft was over-stressed by turbulence occurring inside the thunderstorm. Failure in this aircraft was found to have started with its elevators rather than the fuselage itself; the accident was thus not caused by fuselage depressurisation, but rather the tail surfaces tearing off in-flight under negative stresses, which caused the aircraft to lose control and quickly disintegrate (within seconds, losing its elevators, then its wings; witnesses saw the wingless fuselage appear out of the cloud base and crash in flames). A similar accident occurred 13 years later with a BOAC Boeing 707 over Mount Fuji (BOAC Flight 911, March 5th 1966). In this case, the cause of the accident was clear-air turbulence, but the sequence of the structural break-up of the aircraft mirrored that of Flight 783 (failure of tail - failure of wings - crash).
So if they were made properly, could square windows still be used in airplanes? Or are they inherently weaker than round windows?
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@@BlackRavenFeather565 Concentrating stress on four corners of the window would require a lot of reinforcements making the aircraft heavier and more complicated than it has to be. It's even better to have bigger rounded window than smaller square one. That's why almost all aircraft windows are rounded. Not perfectly round though, just enough to spread the stress evenly over the edge.
@@BlackRavenFeather565 Any material that has a square edge cut into it will have a "stress riser" or concentration in that corner. It's something we learned in structural engineering class. So a filet or rounded corner will spread or redirect the stress rather than concentrating it. Shafts, slots in metal, and those holes for windows have the rounded edges to keep that from occurring. See this video for a visual around a square notch th-cam.com/video/vDZ5yISiADM/w-d-xo.html and this one shows the stresses around a round hole th-cam.com/video/5mvATvu5WIM/w-d-xo.html. The stress moves around the curved surface, while it concentrates on the angled one. The repetition of pressurisation cycles will cause cracks the migrate throught the material until it fails. I could probably restate this better, but at least you can SEE what is being talked about with the two videos mentioned.
*Following this, the design philosophy in aviation gradually moved from Safe Life [...] to Fail Safe design* This is really interesting. The design philosophy changed from "let it crash and burn after X cycles" (ironically called "Safe Life", it's obviously a cost saving measure it should be called Save Costs) to "let it not crash and burn". I think that's a positive change.
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@@holz_name No, that's not how it was intended to work. Safe Life was simply the designed lifespan of an airplane which should be safe to operate and after which it should be decommissioned. Like a car that is guaranteed to work for 150k km and then should be scrapped as it may become dangerous. The second approach is to make something that will be fail safe - should be safe even in case of failure. It's like a car without lifespan limit that may break after 50k km but will not kill you. It has much longer lifespan but requires regular maintenance to keep it safe.
I’d recommend a visit to The DeHavilland Museum in Radlett, Hertfordshire. They have the fuselage of a Comet there plus numerous other aircraft built by this historic company, including the Mosquito. It only takes a few hours to visit but very well worth the visit as its run my a dedicated team of volunteers
The Mosquito original prototype at that! I was lucky enough to get to be invited by the curator to sit in it when I was a child. Don't think they would allow it today!
That sounds really cool! We've only been to England once (our first trip) and didn't travel about as much as we would have liked (we were getting our feet wet basically) -- this is definitely going on the list!
@@andrewrixon2347 oh I know, it’s not going to be anytime soon! We have a lot of comic-cons coming back this year. Hopefully 2023 if things don’t go squiffy. We were planning before 2019 to be able to make a trip for the Queen’s Jubilee time but best laid plans and all that…
The biggest problem was that the stress tested fuselage was cold worked and was tougher than normal. Thus De Havilland got misleading strength data. If all if the fuselages had been stress tested in the same way, these accidents might never have happened.
Square holes concentrated stress at the corners of the holes, allowing premature stress cracking of the fuselage, when the crack grew long enough to reach another window (window is any penetration of the fuselage, whether an actual window, or an antannae) causing a failure making the pressurized fuselage pop like a balloon. The British had almost no experience with pressurization at that point. Pretty much Boeing, and curtiss were the only companies that had built pressurized aircraft at that time.
Later versions of the comet would have these issues rectified, but it already had a bad reputation and by that time Boeing and Douglas had far superior aircraft in production. The Military however loved them for antisubmarine and airborne early warning use. The U.S. had a similar experience with the lockheed Electra propjet airliner that had a resonence problem, but once fixed had a long career with the U.S. Navy as the P-3 Orion.
You missed the source of the cracks. The rivet holes around the windows weren't made properly. That resulted in the creation of micro fractures around the holes. As the planes went through pressurisation cycles and increased stress was applied against the corners of the windows, the micro fractures became cracks that spread very quickly until the fuselage could no longer hold itself together.
I've heard the same thing. Also, I heard the widows were designed with "squareness" taken into account so their shape was not really the problem. I wonder if it compounded the problem..?
The rivet holes were punched instead of being drilled. Also the fact that they used the same pressure cabin for overpressure testing, then afterwards to test the number of regular pressure cycles that it took to fail came into play, as the overpressure test cold-worked the metal, changing its crystalline structure in a way that made it much more resistant to metal fatigue.
@TheJudgementalCat Try reporting that comment - it'll disappear, then reappear, despite breaking more than one of TH-cam"s own guidelines - spam and explicit material. Like many, many others I've had loads of comments disappear for no apparent reason - no curse words/swearing, no bullying, no sketchy terminology or "trigger" words, (certainly not knowingly) yet the comments keep vanishing. TH-cam don't give out warnings or even offer any opportunity to edit - the comments just disappear, which can be extremely annoying if they are detailed or lengthy, yet explicit spam is allowed - YT is broken
Before this flight Comet was taken on a selling tour of the US. Eddie Rickenbacker, President of Eastern Airlines with his whole board were aboard. Rickenbacker noticed vibration around the windows. Upon landing he rejected a purchase and forbade Eastern senior board from flying on any one aircraft. Per his autibiography
@itsjohndell While I'm not doubting that Rickenbacker made that claim, (and by extension I'm not disputing your retelling of the claim) I have trouble actually believing it. It's a bit of a stretch to think that he noticed it on one flight when the aircraft would have gone through extensive testing with, apparently, no-one else picking up on the problem. The aircraft went through many hundreds of pressurisation/depressurisation cycles before the stress fractures became apparent, and there was no mention of excessive vibration anyway - admittedly a pretty vague term. Also, when did he publicly say this? Was it after the findings of the inquiry were made public? I suppose we'll never know the truth of the matter, but I have my doubts.
I did want to fly on a Comet. In fact, I had several miniatures as a child and was dead in love with them. It was those engines embedded into the wings that always took my heart. They logged many miles in my childhood hands without a failure. If only the reality could have been more true. Who would have guessed that square windows could cause so much havoc? Great video, and an interesting but sad reminder of something that one could call, "Plainly Difficult."
None of the catastrophic in-flight structural failures were related to the passenger windows.. The aircraft's fuselage ruptured along the roof at the point of the fuselage hoop with the highest hoop stress. de Havilland made the hoops too weak, the skin too thin, lacked proper doubler plates and safe riveting techniques. 100s of fatal flaws were discovered in the wings, engine inlets, control systems even the toilets had to be redesigned to make the Comet safe to carry passengers.
I love the sleek Art Deco design of the DeHavilland Comet with the gleaming engine nacelles on its wing. Actually, squared windows don't fit with that aesthetic. If they'd kept to the rounded theme of the overall design, the problem could have been avoided. Oddly, it's often the other way around, with artsy design leading to functional flaws.
The engines were also one of the Comet's fatal flaws, the inlets were changed to make the plane safer but no other aircraft in uses this horribly bad design
@sandervanderkammen9230 There was nothing wrong with the Comet's engine position or intake position . There are some advantages for that design & some disadvantages for the podded pylon mount engine design.
@@petemaly8950 Since the point of failure had been found to be exactly the corners of the passenger windows and the automatic-direction-finding window t's evident the radiusing was not enough. "just add enough material to make it work" is not a great solution when there are weight constraints, and the material you are working with has not a fatigue limit.
@@petemaly8950 Since both the real-scale tests performed at Farnborough and the analysis of the wrecks shown the points of failures being exactly the corners of the passengers' windows and the automatic-direction-finding window, its' quite evident they didn't test enough before the first flight.
"And this children, is why airplane windows are round"... There are a handful of other metal fatigue and explosive decompression incidents/accidents which may be worthwhile looking into if not already featured on this channel.
Nope, the windows are rounded so the earth looks round in flight,. Remember the earth is a pizza on the back of a sea turtle. I won't even get into chem trails , 5G, HAARP and the evil bowl of Jello located in a volcano that controls the world.
I might be wrong, but the problems that square windows or metal fatigue effects more on pressurised airplane cabin.. I think I have seen small aircraft that fly in low attitude (with unpressurised cabin) that have square windows (not that 90 degree square, but with rounded edges)
I really hope one day he tackles McDonnell Douglas and DC-10 cargo door issues, and the infamous investigation and blatant colluding with the then head of the FAA.
I've heard the story of the Comet before, but not the fact that they did pressure-cycle testing -- including of the window areas -- while it was being designed. It sounds like they must have come close to catching the fatal problem, but still missed it.
Imagine being like.... that one guy who was probably like "We should have done that test..." or however they figured out the problems. (I still need to watch the video but I swear there's always that one guy no one listens to.)
They ran tests, but probably not nearly enough, and the tests were not properly organized (some of the stress testing was on parts that had already been tested for overpressure (this changes the structure of the hull and invalidates the later tests). DeHaviland didn't allocate enough time and most importantly enough hulls for comprehensive testing. Boeing and Douglass were VERY slow to get into jet airliners, by the time Boeing brought the 707 into service it had a lot of data from the B-47 bomber (and the negatives from Comet) to work with. The other big problem Comet had was that especially the Comet 1 was VERY short ranged (it could not fly the Atlantic) and rather small. The 2,3 and 4 were bigger, but not of the size that was really needed for many routes. Comet was an attempt to do an end-run on existing airliners and make British Aviation a player. It didn't really work, but the Princess flying boat and Brabazon were even bigger failures (the Comet at least entered service, and served as an anti sub platform "Nimrod" for decades to come).
@@PlainlyDifficult Their is an easy demonstration that shows what happens. First punch sheet of A4 paper using a punch that is used to store papers in a ring folder, then carefully cut one of the holes into a square. Then put the paper into a folder and carefully rip it out, observing which hole rips first. The difference is considerable and similar to nicking the edge of cellophane in order to rip it. Research has now shown that it was a similar thing that caused the Titanic to break in half. The ends of bitumen filled expansion joints at intervals along the hull became the origin of a stress fracture. This was already known by Harland and Wolfe and the slots ended with a circular bulb, similar to a thermometer. Why these were cut on her sister ship, but not the Titanic remains a mystery.
Don't forget one thing that is sadly prevalent in disasters like this, the possibility that the engineers had either designed in extra strength or the &^%$##%^&*((**&^%$ management overruled their engineers. And you know the engineers were screaming bloody murder about replacing drilling the rivet holes with punching them. Well until silenced by the "genius" at the top.
As flawed as this plane is, the British sure knew how to make something look good. A later variant was operated by the RAF as the Nimrod until the 90s.
Always have a radius! Round edges are of outmost importance. I worked with fibreglass for years and anytime there is a cutout or angled edge it MUST have a radius to absorb any stress…otherwise CRACK! You’d think they would have taken a lead from the marine industry…ship windows are round!🙄
Hindsight is always 20/20, it's easy to call the failure now that we know. Still, I'm a little surprised that not one of the engineers - experienced with pressure vessel designs - had an instinctive reaction to make the corners round.
@@johnladuke6475 The windows had radiused corners. They proved the design was good during the extensive & protracted testing activities It's possible to use sharp 90° corners for the passenger cabin windows on a pressurised airliner, it's just a matter of making sure there's enough material for adequate strength around the window, if sharp corners & big square windows etc are used it results in a lot of unwanted & unnecessary extra weight which is the last thing we want for an airliner design.
A flawed beauty, no question about it. One can only speculate as to how things would've turned out had de Havilland caught that fatal flaw at the testing stage. Another fine vid, sir.
Which flaw? The Comet 1 was permanently grounded and its airworthiness certificate was revoked after investigation uncovered over 100 design, safety, construction and materials flaws.
It wasn't just the accidents though. Those in-wing engines look stunning, very Flash Gordon but nacelles are just way more practical making maintenance turnarounds faster and cheaper. That's a legitimate selling point. Fair dos has to go to Boeing for choosing that design.
In the Comet it was a obliged choice, sinche the engines of the Comet I, Ghost 50 Mk 1, were a little underpowered for the aircraft, so De Havilland used the same "trick" of the Mosquito, that had the radiators in the wings to reduce drag.
Oddly enough, this design could still be in use today. But it does not get *_ALL_* of the profits, so to corporations it is completely pointless. Being profitable is not nearly enough, whatever it is *_MUST_* get *_ALL_* the profits.
@@unvergebeneid airbus came about not through british but french and german consolidation, and RR would have their own problems on commerical jets such as the lockheed tristar
@@danielduncan6806 not strictly true, pylon mounted engines eventually won out for their ease of upgrade and ease of maintenance. the brits kept on the integrated engine though with their V-Bombers
The De Havilland Comet, despite it's flaws, was still an incredible aircraft. Unfortunately when making huge technological leaps mistakes will inevitably occur - being the first always carries risks.
It wasn’t a huge technological leap, as nearly every Comet misconception would have you believe. It was the first commercial jet airliner, but the TECHNOLOGY wasn’t groundbreaking. Boeing already had the swept-wing, PODDED engine B-47 stratojet flying TWO years before the first Comet flew; it also had a far more advanced swept tail design than the Comet’s straight prop-era tail design. The genius was in applying known technologies to a different market, not so much the plane itself. Also (largely unknown or ignored) is the fact that Boeing had already implemented a huge array of construction and fuselage features into the -80 design which would have made the structural failure of the comet impossible. Guess what? They did all of that BEFORE the Comet crashes. Spot welding instead of punch riveting, tear-strips in the fuselage, and above all else, the aluminum skin was MUCH thicker than the Comets - again, all included in initial design specifications before the Comet crashes. It is possible that while being a groundbreaking aircraft for commercial jet travel, de Havilland ALSO royally (no pun intended) screwed up!
@@EstorilEm Nazi Germany had the first jet-powered aircraft (the Me 262), and the first operational jet squadrons. B-47 was post-WWII, but the Convair B-36B/D's (post WWII w/jet engines and conventional engines on one aircraft was operational in 1946-47). B-47 was not fully operational until 1953.
@@EstorilEm The "tear strips" or rip-stop strips were lacking in the Comet I, no doubt to save weight. Virtually all American jet liners had/have them. Keep cracks from propagating. There are also other areas where ground tests, including wind tunnel testing doesn't show up potential catastrophic failures. The Lockheed Electra I, for example, a four-engine turboprop, was tested extensively in wind tunnel testing. Unfortunately, it did not reveal the dynamic augment of the outboard engine/nacelle, which, under certain conditions inflight hit the natural frequency of the wing. The result was the Tell City, Indiana, crash, killing everyone onboard. Until the cause was found, airlines were instructed to reduce the cruise speed, which did keep the phenomena from happening. That was very fortunate for me and my Dad, as we took the same flight number, on the same type of aircraft, the next day! When the cause was found, Lockheed beefed up the wing structure and made other changes. The "new" plane was called the Electra II. While it didn't remain in commercial service much longer, the Navy and Air Force adopted it with all sorts of anti-submarine gear, and called it the P-3 Orion, which remained in service until being replaced recently by the P-8.
The Comet Disaster was certainly not the result of cutting edge technology... rather the lack of modern technology. The Comet Disaster could have been easily prevented if de Havilland had simply followed existing, well-known Industry standards for the design and construction of all-metal aircraft with riveted aluminum alloys and cabin pressurization.
Great video... But... Your failed to mention a couple of things. 1) the first two runway crash were from what some call a cockpit flaw which created a blind spot outside the windshield. From it the pilots thought they were taking off but weren't. Many Comets had to have their dash panel refurbished to eliminate the blind spot. 2) it was found that during the manufacture of the comet's to allow the square windows and and access point like the door and radio antenna, the holes for rivets and welding were punched into skin and not drilled. This created tiny micro fractures into the metal skin and accelerated the stress crack failure of the Comet's skin and frame. After this all manufactured aircraft would have their metal frames and skin panels drilled and not punched through.
The Comet was later converted into an anti-submarine and maritime patrol aircraft for the Royal Air Force. Renamed the Nimrod. It was used by the RAF until June 2011.
@@skylined5534 Yep it’s a Comet airframe with a anti shipping radar in the nose, a bomb / torpedo bay fitted underneath and an anti submarine magnetic object detector on the end of the tail. And it used similar Rolls Royce Spey engines as the RAF Phantoms and Buccaneers.
Sandtbum The Nimrod started life based on a Comet 3 and production Nimrods were vased on the Comet 4, all design work being by the design team at Hatfield, in other words by DH.
I believe also that Boeings designs provided for "rip stops" in the fuselage. These would prevent a skin tear from propagating to the point of total failure. However the Comet did not have rip stops so when a tear started, there was nothing preventing it from running the length of that section of skin.
I especially liked this Comet episode. I’ve seen other Comet documentaries too. Thanks for covering the square passenger windows and also the antenna windows on top of the plane. Plainly cracking report.
Great overview! I'm glad you covered how the Comet, or more precisely its individual components, was extensively tested before it went into service. Most of the documentaries I've seen overlook this and give the impression it wasn't. The fundamental problem was it was not tested as a whole airplane in real-world conditions (no cold working of metal, no effects of wing/fuselage flex, etc.) and so the tests were misleading. One trivial thing: in the early 1950s, G-ALYP was "George Able Love Yoke Peter" rather than "Golf Alpha Lima Yankee Papa" ;)
The fact that it takes more to make a square window than a round one structurally sound when you bring pressurization into consideration is why NASA's Mercury capsule had a round window, was lighter to put a round one in than a square one.
I gotta admit the comet was a beautiful plane! Just the shape of it, and the way the engines are built into the wings with those round ports! Today's jet liners focus more on functionality, and less on style.
The Comet's shape, in particular the engine placement was a fatal flaw that caused at 3 crashes. No other airliner ever copied this deadly design error.
@@Stevie-J Aircraft engineers never place the engine inlets of a jet aircraft in the leading edge of the wing, this was a serious fatal flaw that was modified but still plagued later Comet aircraft.
As usual a great video, which does a great job of presenting a problem, and its causes. There's a lot more to the Comet's history though - which might tale a couple of hours to properly present. While the structural issues put the nail into the Comet I (and IA), it must be pointed out that the two losses due to runway overruns mentioned are also significant, and exposed a critical problem with the early Comets - The Comet I, like all early jets, was severely underpowered, and takeoff performance was marginal. The airfoil used on the Comet's wings did not have good low speed characteristics - When taking off in an early Comet, the airplane had to be, at a precise speed, rotated exactly 10 degrees nose up to take off successfully. at 9 degrees, the wings would not develop enough lift to get the airplane off the ground on any runway that they could use, and if rotated to 11 degrees, the increased induced drag would prevent the airplane from accelerating to a speed where it could fly. On the Comet teaching lessons in metal fatigue - in some respects that is overstated, I think - Boeing, which, at the time of the Comet losses over the Med, was beginning testing of the Model 367-80, (First flight July 15, 1954) had more experience with large pressurized aircraft (Model 307 prewar, the B-29 and B-50 bombers, the B-47 jet medium bomber, the B-52, and the 367/377 Stratucruiser airliners and C/KC-97 military cargo carriers and refueling tankers) than the rest of the world combined. Fatigue concerns by potential buyers, among them by Eastern Airlines in the U.S. led to lost or cancelled orders before the inflight breakups.
*The **_Comet Disaster_** is the worst engineering failure in commercial aviation history... the real tragedy of this disaster is that it could have been easily prevented if de Haviland had simply followed well-known and understood industry standards for the design and construction of pressurized cabins made from riveted aluminum alloys.* *de Havilland had very limited knowledge of building all- metal aircraft and were still building jet aircraft primarily from wood and fabric..*
I have seen and read many recountings of the Comet crashes. You still managed to add facts I had not encountered and as per usual I found your narration riveting. Thank you for all the work you put into educating us as you entertain us, I sincerely appreciate it.
I flew casevac Comet 2 from RAF Changi Singapore in June 1958. Was supposed to be stretchered in forward compartment but was asked if I would take a seat to allow a priority evac to use my stretcher. I was quite happy to as the stretchers were piled pretty close together! Sitting rearward facing was not a problem as I had previously flown on Hastings. Nice smooth trip and a great aircraft. Hastings to Singapore was five days...... Comet just a day.
Dear Plainly Difficult. Thank you for taking such a task to study these historical events and replay them for us to understand in their entirety. This is truthfully a bunch of large video projects that you make, and I want to appreciate you for it. Thank you for your hard work and great entertainment.
It's always easy to call it in hindsight, but every time I hear this story I'm still a little surprised at the designers. The average layman might see nothing wrong with a square window hole. Still, you might expect an engineer who works on pressure-bearing designs to think twice about anything that's square when it could be round. Of course, if they had been round from the first, it might have taken much longer and many more lives lost to learn about microfractures.
@@allangibson2408 On the recovered aircraft it was the antenna mounting (squared holes as well). In the tested one it were the windows. Another problem were the rivets' holes. Punched instead of drilled, they were already microfractured.
The catastrophic in-flight structural failures were were not related to the passenger windows at all. The fuselage ruptured exactly where Pascals Law tells us it should, at the reinforcing hoop with the highest surface area at its weakest point.
The fuselage hoops were too weak, the skins were way too thin, there were not enough doubler plates and the design and construction of the rivet joints were substandard. 100s of modifications and reinforcements were required to make the Comet 4 airworthy. Earlier Comets were modified with round windows but were still unsafe to carry passengers and the Comet 1's airworthiness certification was permanently revoked in September 1958.
Glad you covered this one. I’ve always found the Comet a particularly fascinating plane, so remarkably advanced. And also very attractive look at. Whilst engineeringly less good I do like the engines embedded in the wings. Also think the enquiry into this was fascinating and really paved the way for modern disaster investigation. The idea of creating a water tank test now is bizarre to us now but i love the idea of it. Simple but very clever. A huge shame for the U.K. aerospace market though because as you say Boeing and Douglas both admitted they’d have had similar issues if their products flew first! Thank you as always for the cracking content 🙂
The engines inlets are clear evidence of bad design at de Havilland. Wishful British thinking... the effects of metal fatigue in pressurized cabins was already well-known and understood by German and American manufacturers... de Havilland was doomed to failure because it was still building aircraft primarily from WOOD and was years behind in aircraft design and construction technology.
Junkers, Boeing, Douglas and Lockheed were already manufacturing pressurized cabins from riveted aluminum well before the Comet Disaster without any accidents... It was de Havillands negligence not cutting-edge technology that killed 426 people.
The 707 was the basis for all commercial jet design so it was the futuristic aircraft. Burying the engines in the fuselage was a dangerous design and also more difficult to service. The Comet was also smaller than a DC-6 with 1/3 the range. Boeing had been building pressurized cabin commercial aircraft since the 307 in 1938, which the Comets nose resembles greatly.
Absolutely. de Havilland were very, very inexperienced in building pressurised aircraft. Apart from one experimental Vampire, I don't think they had built ANY pressurised aircraft prior to the Comet. Boeing, on the other hand, had been building pressurised aircraft since 1938 - starting with the 307 Stratoliner. Before the Comet ever flew, Boeing had also built the pressurised B-29 Superfortress and the 307 Stratocruiser.
I flew in a Comet flying to Mallorca for a holiday with my mum and she asked if the purser could see if could ask the flight crew if it would be possible to let me into the flight deck. Not only did the Captain point out all the instruments and what they did (which probably increased my lifelong passion in aviation - at the time my dad was a CFI and I spent all my summer holidays flying in lots of different types of aircraft, Vernair in Liverpool had a fleet of KingAirs and they took me all around the UK and there was a pilot who had his own plane and took a shine to me so at least once or twice a week he would take me to the Isle of Man in his Mooney). Anyway, I digress. The Captain in the Comet gave me a brass badge in the shape of wings, and I was as happy as a clam!
@@WilhelmKarsten Kharzeestan Krappenz DiktorBummer Jurkzxoffenz etc and co - they should note good with much awestruckness & many extreme wondermentals. *UPDATE MORE BREAKING NEWS ETC* *_It's interesting that some of the aircraft on the list should really have been noticeably safer than the Comet due to being a similar type but of much later design & manufacture but they definately were not safer._* How things were back then - *_Accident losses - % of aircraft built._* DeHavilland Comet 4 UK 14% DeHavilland Comet all mks 17% Vickers VC10 UK 5% *_The DH Comet had better safety than or similar safety to many other commercial passenger aircraft of a similar era_* Douglas DC-1 99% Douglas DC-2 47% Douglas DC-3 30% Douglas DC-4 26% Boeing s300 72% Boeing 307 70% Boeing 247 48% Boeing 707 20% Lockheed Electra Turboprop 29% Fairchild FH-227 30% McDonnell Douglas DC-8 14% Sud Aviation Caravelle 15% Canadair CL-44 Turboprop 46% Convair CV-580 Turboprop 22% A comparison of more recent aircraft. Accident losses comparison examples. 1970s - 1980s % of total Aircraft built Similar aircraft type, date / decade, useage, size. Biz Jets BAe-125-800 1.7 % Beechcraft Beechjet 400 2.2 % Cessna 550 Citation II 7.1 % Learjet 35 / 36 12 % Beechcraft 1900 6% Dassault Falcon 10 11.5% Aérospatiale SN.601 22.5% Medium size jets / Turboprops. BAe-146 5.1% Fokker 100 6% McDonnell Douglas DC-9-30 9.5% Fairchild FH-227 30% McDonnell Douglas DC-8 14% Canadair CL-44 Turboprop 46% Convair CV-580 Turboprop 22% Beechcraft, Fokker, McDonnell Douglass, Learjet, Fairchild, Aerospatiale, Canadair, Convair companies defunct. All Comets, including some Comet 1s, had full civilian use certification at some point after 1954, civilian use certification only being withdrawn after commercial flying stopped. Examples were flying until 1997 - one example did a signals research global circumnavigation flight series in 1993 via Australia virtually without a rest travelling 28000 miles, only had an ice warning indicator issue during the flights. *The DH Comet - World Firsts.* 1st gas turbine jet powered airliner. 1st high altitude 8psi pressurised full fuselage length passenger cabin airliner, not a trivial feature as structure strength required for pressurisation considerably exceeded strength required for normal flying stress. Nobody else had done anything similar before the Comet. The b-47 used 2 relatively small, heavily built pressurised modules (the aircraft where 6 had their wings fold up in 2 months while flying & some had their wings fall off while parked). The 1937 Boeing piston engined airliner pressurised passenger cabin was pressurised to 2 psi only - in fact that could easily be done as the normal unpressurized fuselage cabin structure strength for flying stresses only was all that was needed to be adequate so no significant weight increase issues needed addressing. 1st all hydraulically powered flying surface controls & actuators airliner with under carriage wheel disk brakes + ABS. 1st jet airliner to cross the Atlantic. 1st jet aircraft to do a world circumnavigation flights series. *Of course De Havilland had prior experience building many all metal construction airframe aircraft including thousands of jet powered fighter aircraft that were primarily of metal construction with pressurised cockpits & jet engines built by De-Havilland & we know the world's first all metal construction airframe airliner was built in England in the 1920s by Handley Page.* *_De Havilland did indeed always work to better than industry standards at the time, no evidence of negligence ever being produced in relation to the DH Comet._* The course of De Havilland & the general UK aerospace industry sector was not affected even slightly by the DH Comet. *_Other interesting World firsts_* _World's first turboprop aircraft._ *Vickers Viscount Turboprop Airliner 1947.* *A 1945 Gloster Meteor Aircraft with Turboprop Gas Turbine Engine.* They might like to answer these questions. *Which airline has just ordered* *60 RR England Trent XWB Engines* *& What aircraft are the engines for?* _Bonus question for 10 points._ Which country has the *World's Highest Combined Per Capita* *Nuclear + Defence + Aerospace Sector Activity?* 👍 Cheers 🙂
@@sandervanderkammen9230 Krappenz DiktorBummer KARZEESTAN Jurkzxoffenzstadt & co - they should all note with much awestruckness and great wonderment. ***** *How come they can't answer simple questions - why is that?* ***** *_DID SOMEBODY ACTUALLY SAY SOMEWHERE THAT THERE'S AIRLINER ASSEMBLY LINES OR SIMILAR IN THE UK OR IRELAND OR THAT Airbus or BOW-WING is actually British? (B-47 wings on many occasions folded up in flight or dropped off while parked)._* Of course Brazil makes very good airliners & Brazil is 100th down list along with Indonesia for wealth per capita. *Norway Holland Denmark Ireland Belgium - Top 20 wealth per capita - Don't make airliners - its as simple as that.* BAe Systems & RR combined now do more Airbus work than Germany on an absolute basis & significantly more work than that on a per capita basis. Per capita for the home nation BAe Systems is the world's largest defence contractor. _BAe systems announced the recent £4 Billion takeover of Colorado based US based Ball Aerospace._ *BAE systems now does a significantly higher value of work for Airbus than it did when it was a major Airbus shareholder before 2005.* *_RR now owns US Engine maker Allison for example which does classified Aerospace work for the US Govt._* The UK has more important stuff to do these days. _Routine simple passenger aircraft airframe assembly is becoming more of a 3rd world / trailer park area thing._ *_The DH Comet - world's first high altitude capable pressurised passenger cabin jet airliner in regular service, world's first jet airliner aircraft to cross the Atlantic, worlds first jet airliner aircraft to complete a global circumnavigation flight series._* *They might try to sensibly answer this question - why do they believe that BAE Systems & RR (aero engines etc) & other companies, for example should be doing anything other than what they currently do & where do they get the idea from that the DH Comet had any affect at all on the progression UK aerospace sector.* *Anybody currently flying on a widebody airliner stands a good chance of being on an aircraft powered by RR gas turbine aero engines built in England.* 📯📯📯📯 *The New RR Trent Ultrafan* *Built In England* *_World's Largest (see T&Cs)_* *_Gas Turbine Aero Engine_* 📯📯📯📯 👍Manufactured by the people on a small island with less than 1% of the world's population.👍 *_A typical but small glimpse of what goes on in the very internationally orientated British aerospace sector._* - Boeing Apache Attack Helicopter. AH-64: *75 UK suppliers,* 7% UK content, global fleet of 1280+ aircraft. *F35B more than 130 UK Suppliers, more than 30% UK content.* *_F35A & F35C more than 130 UK Suppliers, more than 15% UK content._* They might like to answer these questions. *Which airline has just ordered* *60 RR England Trent XWB Engines* *& What aircraft are the engines for?* _Bonus question for 10 extra points._ Which country has the *World's Highest Combined Per Capita* *Nuclear / Defence / Aerospace Sector Activity?* 👍 & 🙂 & of course 😎 indeed. Cheers. _Toodle_ -PIP- *Old* *_Chap._*
The tragedy of the Comet Disaster is it could have been easily prevented if de Havilland had followed well-known and understood engineering standards for riveted aluminum airframes. Prior to the Comet Disaster de Havilland was still building aircraft primarily from WOOD and was years behind in aircraft design and construction technology.
@@sandervanderkammen9230 - Which "well-known and understood engineering standards" were these? De Havilland were working on the bleeding edge of scientific knowledge regarding materials - no civil aircraft of that size had ever routinely cruised at those altitudes before. Furthermore, the DH Mosquito fighter/bomber was designed and made of wood not because DH lacked experience working with aluminium, but because the entirety of the aluminium available to the British Empire had already been requisitioned for other purposes. The whole point was that any joiner, cabinet maker or piano builder in the country could turn their hand to making parts for the Mosquito - which among other things severely pissed Hermann Goering off. Boeing probably had the most experience building aircraft with pressurised cabins with the pre-war Stratoliner, B-29 and Stratocruiser - and when De Havilland released their data regarding metal fatigue in the wake of the investigation, Boeing's engineers freely admitted that if it hadn't happened to the Comet, it would have happened to the jetliner they were working on.
@@turricanedtc3764 Metal fatigue was not discovered by de Havilland, it was already known to aircraft manufacturers... all but de Havilland. The Comet Disaster investigations revealed 100s of fatal flaws, design flaws, material flaws, shoddy workmanship and appalling quality control.
@@turricanedtc3764 Absolutely false, de Havilland made several unsuccessful attempts at building aircraft from aluminum alloys. de Havilland was still building aircraft primarily from WOOD when the company went tits-up in 1958. The industry leaders like Boeing, Douglas, Junkers and Lockheed were building all-metal, pressurized monoplane airliners before the war while de Havilland was still building wood and fabric biplanes like the Dragon Rapide!!!
From memory, the cracks were initially started from the drilling and riveting process around the windows, work-hardening the metal resulting in it becoming brittle in those areas, further exacerbated by the pressurisation cycles and thermal stresses over time, which tragically resulted in the incidents of the planes basically popping like balloons... :(
This design was one of the simplest, yet had a timeless grace and elegance about it. I love, especially the sleek eyebrow cowling around the Rolls Royce engines. Great post.
Indeed it's fairly clear that - 5:20 The idea that only the crew & passenger areas were pressurised is absurd obviously. Every part of the fuselage was pressurised from the nose to the rear fuselage bulkhead including the entire cargo area. Cheers.
Kind of unrelated, Boeing’s top test pilot of the time Tex Johnson famously rolled a 707 2 times in a row to impress potential buyers without prior ‘permission’. He was called into the office the next day and asked what exactly he thought he was doing? He said: ‘I was selling airplanes’. Apparently it worked as we found out by the end of the video.
Douglas may have learned something from Comets missteps but I don't think Boeing needed those lessons. Boeing was easily the most experienced manufacturer of large pressurized aircraft, indeed lack of hands on experience of pressurising large airframe by British aircraft industry showed in Comet's design. Both Lockheed's Constellation airliner and Boeing's model 377 Stratocruiser had rounded windows (they were squarish but without sharp corners). Lockheed & Boeing had built pressurised aircrafts in WW2 and worked out kinks, De Havilland just didn't have that kind of experience. Indeed pressurized aircraft needing rounded windows was not a unknown thing within industry at the time of Comet's construction, I often wonder why De Havilland team missed it.
The explosive decompression would have knocked the people out very quickly, if not instantly. Many on board were thrown headfirst into the ceiling of the fuselage by the decompression. On top of that, the shock to the lungs from the decompression would have quickly rendered them unconscious.
Thanks for the topic, super interesting. I looked up flying back then and the cost was 5x more expensive then. I read that having an engine fall off on any plane was so common, it didn't count as an accident if the plane landed safely. Not me!
I've noticed when people complain about comfort and service in coach they try to compare it to the 50's and 60's; what they don't realize is that back then flying at all was the equivalent of first class, and if you adjust for inflation the airfrare was more expensive than an equivalent first class ticket today.
It’s important to note that they didn’t immediately throw an aircraft in the water tank and start testing as you imply. There was significant pushback from both the operators and de Havilland at the time, due to the initial testing you mentioned. It was thought to be absolutely impossible, and everyone involved were incredibly stubborn, prideful, and naive, contributing to a number of needless deaths. The Comet story is well-known, but I find it ridiculous that it’s always accompanied by the belief that it wasn’t REALLY de Havilland’s fault, due to the groundbreaking design of the aircraft. The only thing more important than not killing a bunch of people in plane crashes, is that of typical British pride and retaining their proper and polished image on the world stage. I find the governments balancing act absolutely fascinating in this situation. They wanted to be known as the nation that pioneered commercial jet travel, but were possibly going to be remembered as the nation who crashed more jets in a given period of time than anyone in history. The British state-owned airline ie BOAC (and largest operator of the Comet, not counting the later Dan-Air) was pretty much a proxy for the government’s thoughts on this as well, which is clearly shown in their initial handling of the Comet crashes which was borderline coverup status. In any event, by their own admission (ie they DID initially test the frames and components to check for metal fatigue and structural issues) they WERE aware of potential dangers that wear and cycles cause on aircraft. Yet, they STILL screwed up the design. History doesn’t often give events like this a free-pass (Titanic’s design certainly didn’t - though the disaster was also due to British engineering arrogance…. weird) however unfortunately, it seems to in this case.
"The British state-owned airline ie BOAC (and largest operator of the Comet, not counting the later Dan-Air) was pretty much a proxy for the government’s thoughts on this as well, which is clearly shown in their initial handling of the Comet crashes which was borderline coverup status. " The consequent depth and level of accident investigation by the RAE and Cohen Committee - following the three fatal Comet hull failures - were completely revolutionary, setting the precedent for future air safety. It was a surprisingly open process. The cutting edge of aviation history is littered with accidents and incidents. It's how people learnt, improved and adapted from experience. "In any event, by their own admission (ie they DID initially test the frames and components to check for metal fatigue and structural issues) they WERE aware of potential dangers that wear and cycles cause on aircraft. Yet, they STILL screwed up the design." Evidence?
@@alexwinfield9540 I’m not a Boeing fan actually, luckily their shortcomings hardly reflect the most cutting edge aerospace companies in the world (most of which do indeed reside in the US) - save for EADS/Airbus which are hands-down my favorite aerospace / defense contractor.
The Comet Disaster is the worst engineering failure in commercial jet aviation history... the real tragedy of this was it could have been easily prevented if de Havilland had simply followed well-known and understood industry standards
I'd rather fly in a plane that had disasters, and the reasons for those were identified and rectified, than on a newer plane that can possibly have hidden faults.
The same reason I absolutely REFUSE to drive a vehicle newer than 10 years old... I won't even look at it. Cutting edge tech' bring cutting edge bugs... ;o)
@@skylined5534 As if traffic ain't a borderline clusterf*** as it is... YAY!!! Let the 10 - 13 year olds GNU open-source all they need to play GTA with REAL cars!!! Maybe somebody should just develop an app' for that "Augmented Reality" Game!!! AND post it for public consumption... ;o)
Mr. Difficult, Would K-219 be a story of interest to you? It has nuclear weapons accidents, a nuclear reactor with bent control rods, it can Cold war era boat with the incident being relatively recent. Great work as always. It is the main reason I would like to see your telling of K-219
It also has Seaman Sergei Preminin, the sailor with the biggest brass balls in the history of the Soviet navy. The channel jiveturkey actually has a great video detailing the whole incident as part of his sub-briefs series.
@@tiberiusweaver-zeman2520 Sub Brief with Jive Turkey was the first 219 documentary I had ever seen in subsequent reason for asking. His episode on finding that there were survivors on the thresher and it was just declassified 10 months ago blew my mind.
It's worth noting that, although the stress cracks were blamed on the "square" windows, the windows were not actually square. Some of the photos in your video show how rounded the window corners were. Decades later, a re-examination of the evidence indicated that the cracks were caused by the method of making the rivet holes around the window frames.
May 8, 2023 - While this video is very well made (I recommend following Plainly Difficult) I think it needs a little correction. Mentor Now! has a new video highlighting the problems of the Comet and how the "windows" being the starting point of stress fractures leading to the accidents were NOT the "square" passenger windows as assumed by the press but rather the "ADF Aerial Windows" on the roof through which the plane's antennas were mounted. Full Video: th-cam.com/video/-DjnG74DDno/w-d-xo.html Jump to the Time Index: th-cam.com/video/-DjnG74DDno/w-d-xo.html?t=1022
Later Comet Disaster investigations recovered wreckage that confirmed that the passenger windows were not the cause. But the original investigation uncovered that the Comet was structurally unsound and lacked adequate materials and safety factors. In particular the aluminum skins were fat too thin and the alloys too brittle. And the planes lacked basic rip-stop doubler joints between panels. The fuselage reinforcement hoops were too narrow and spaced too far apart to prevent cracks from jumping to other segments and the rivets were substandard and did not have proper quality controls.
@sandervanderkammen9230 Kharzeestan Krappenz DiktorBummer Jurkzxoffenz etc and co - they should note good with much awestruckness & many extreme wondermentals. *UPDATE MORE BREAKING NEWS ETC* The skin was not found to be too thin. The original alloy used became unavailable & so an improved alloy was used. *_It's interesting that some of the aircraft on the list should really have been noticeably safer than the Comet due to being a similar type but of much later design & manufacture but they definately were not safer._* How things were back then - *_Accident losses - % of aircraft built._* DeHavilland Comet 4 UK 14% DeHavilland Comet all mks 17% Vickers VC10 UK 5% *_The DH Comet had better safety than or similar safety to many other commercial passenger aircraft of a similar era_* Douglas DC-1 99% Douglas DC-2 47% Douglas DC-3 30% Douglas DC-4 26% Boeing s300 72% Boeing 307 70% Boeing 247 48% Boeing 707 20% Lockheed Electra Turboprop 29% Fairchild FH-227 30% McDonnell Douglas DC-8 14% Sud Aviation Caravelle 15% Canadair CL-44 Turboprop 46% Convair CV-580 Turboprop 22% A comparison of more recent aircraft. Accident losses comparison examples. 1970s - 1980s % of total Aircraft built Similar aircraft type, date / decade, useage, size. Biz Jets BAe-125-800 1.7 % Beechcraft Beechjet 400 2.2 % Cessna 550 Citation II 7.1 % Learjet 35 / 36 12 % Beechcraft 1900 6% Dassault Falcon 10 11.5% Aérospatiale SN.601 22.5% Medium size jets / Turboprops. BAe-146 5.1% Fokker 100 6% McDonnell Douglas DC-9-30 9.5% Fairchild FH-227 30% McDonnell Douglas DC-8 14% Canadair CL-44 Turboprop 46% Convair CV-580 Turboprop 22% Beechcraft, Fokker, McDonnell Douglass, Learjet, Fairchild, Aerospatiale, Canadair, Convair companies defunct. All Comets, including some Comet 1s, had full civilian use certification at some point after 1954, civilian use certification only being withdrawn after commercial flying stopped. Examples were flying until 1997 - one example did a signals research global circumnavigation flight series in 1993 via Australia virtually without a rest travelling 28000 miles, only had an ice warning indicator issue during the flights. *The DH Comet - World Firsts.* 1st gas turbine jet powered airliner. 1st high altitude 8psi pressurised full fuselage length passenger cabin airliner, not a trivial feature as structure strength required for pressurisation considerably exceeded strength required for normal flying stress. Nobody else had done anything similar before the Comet. The b-47 used 2 relatively small, heavily built pressurised modules (the aircraft where 6 had their wings fold up in 2 months while flying & some had their wings fall off while parked). The 1937 Boeing piston engined airliner pressurised passenger cabin was pressurised to 2 psi only - in fact that could easily be done as the normal unpressurized fuselage cabin structure strength for flying stresses only was all that was needed to be adequate so no significant weight increase issues needed addressing. 1st all hydraulically powered flying surface controls & actuators airliner with under carriage wheel disk brakes + ABS. 1st jet airliner to cross the Atlantic. 1st jet aircraft to do a world circumnavigation flights series. *Of course De Havilland had prior experience building many all metal construction airframe aircraft including thousands of jet powered fighter aircraft that were primarily of metal construction with pressurised cockpits & jet engines built by De-Havilland & we know the world's first all metal construction airframe airliner was built in England in the 1920s by Handley Page.* *_De Havilland did indeed always work to better than industry standards at the time, no evidence of negligence ever being produced in relation to the DH Comet._* The course of De Havilland & the general UK aerospace industry sector was not affected even slightly by the DH Comet. *_Other interesting World firsts_* _World's first turboprop aircraft._ *Vickers Viscount Turboprop Airliner 1947.* *A 1945 Gloster Meteor Aircraft with Turboprop Gas Turbine Engine.* They might like to answer these questions. *Which airline has just ordered* *60 RR England Trent XWB Engines* *& What aircraft are the engines for?* _Bonus question for 10 points._ Which country has the *World's Highest Combined Per Capita* *Nuclear + Defence + Aerospace Sector Activity?* 👍 Cheers 🙂 & 👍 & 🙂 & of course 😎 indeed. Cheers etc. _Toodle_ -PIP- *Old* *_Chap._*
"At the time, passenger flight were noisy and uncomfortable experiences..." Now, we're plugged into narrow seats with no leg room with screaming children vomiting directly behind us.
No, no, no, no, noooo. You're wrong. It's always pilot error, or maybe, just sometimes, a bomb. Bombs are scary and stop people getting on the (money making machine) plane, not as scary though as the plane being bad and falling apart though. So remember, PILOT ERROR. OK?
What an awesome looking design, too bad it had such a tragic flaw. I wonder if we'll ever see beautiful plains in the travel industry again. Great video lad, always love your stuff.
What sometimes get missed with the Comet is there were actually two root causes. The shape of the windows was a major contributor. But the biggest underlying problem was the new unique and revolutionary formulation of ultra thin aluminum that the aircraft was skinned with. Which turned out to be far more brittle and prone to micro fractures than was anticipated. Boeing actually had previously discovered some of the issues later brought forth with the Comet during WW2. They had a lot of early development problems with the B-29 involving pressurization cycles and the problems they caused. Particularly those involving squared off openings in the pressure compartment skin. But pretty much everything involving the B-29 and later B-36 development was beyond classified back then. And the Comet had a much thinner skin and was introducing stresses beyond anything they had seen in the two slower bombers. The 707 didn’t just learn from seeing what happened to the Comet. It was a late in the development cycle cross conversion from a military aircraft design, so much of it was being built to the military specs, just to share common tooling. So it used the same standard aluminum thickness and formulation as the USAF required.
de Havilland simply lacked the technical experience in designing and building aircraft from riveted aluminum. The skins were far too thin and weak, there were too few fuselage reinforcement hoops and they were too weak, not enough rip-stop doubler joints the design and production techniques used in riveting was well below industry standards even for unpressurized aircraft. De Havilland recieved technical data on the B-29 pressurized cabins from Boeings during WW2 but engineers at de Havilland were still building aircraft from WOOD. De Havillands post-war jets wete made primarily from WOOD not riveted aluminum which was rhe industry standard.
@@TheJononator Rolls-Royce did not have a axial flow turbojet available when the Comet was designed.. Of course the placement of the engines was also another fatal flaw that caused several crashes. Based on an aerodynamic theory that later proved to be completely wrong, no other airliner ever copied the flawed engine placement of the Comet.
@@sandervanderkammen9230 A lot of fighters and bombers of the era did use a somewhat similar engine placement. But they had very different needs. The big revolution of Boeing and McDonald Douglas hanging the engines on underwing pylons was less an aerodynamic leap as it was one of serviceability and cabin noise comfort. The airlines loved it because it made servicing the engines much easier.
@@andrewtaylor940 Not true at all, while some supersonic fighters have their inlets in the Wing Root none have them in the actual leading edge causing a disruption of airflow to the engines at high angles of attack and reducing wing lift, in the case of the British V-bombers there are some subtle but important differences with placement of the inlets ahead and below the leading edge line of the wing that reduce the problem but were still based on the flawed theory and a lack of good wind tunnel data. Boeing engineer George Schairer was a member of the Von Karman Mission that discovered the Top Secret German _Luftfahrtforschungsantalt_ supersonic wind tunnel research lab in Braunschweig. Boeing stole or copied top secret data on jet engine placement and the plans for the P.1107 which became the B-47. The Boeing 707 Jet Stratoliner is directly based on the B-47 and the German wind tunnel data on jet engine placement.
The Comet was so badly designed and built that half of them crashed and the type was grounded in 1954 and its certificate of airworthiness was permanently revoked..
Do you have a framework video that describes why you rate things in particular ways on your Disaster and Legacy scales? I've always been curious on what goes into that rating as this disaster, which killed 21, rated 8, while other disasters you've covered which killed and injured many more rate much lower on the Disaster scale. I enjoy your breakdowns regardless, especially the technical details!
He's said a few times that the Disaster Scale is "mostly arbitrary" so I doubt there is a real process. I think he started using the Legacy Scale to differentiate between how horrifying a disaster is, and how much it actually changed things for the better.
The Comet is anything but a footnote. The engineering and forensic techniques it spawned, not to mention the lessons learned from the mistakes it made, are the foundation of modern commercial air travel.
While the plane had historical significance and the accidents lead to breakthoughs in aircraft design, material knowledge and accident investigation rating them 8 on the disaster scale seems far fetched and higly subjective since they only lead to a total of several dozen lives lost and no lasting impacts beyond those mentioned above to anyone besides the manufacturer and the perception of flight safety among the british public. I feel the author is letting his nationality color his judgment here and that any of the radiation events or chemical spills he’s covered would rate far higher on this scale. Surely these crashes can not be more than a 3 on that scale.
@@skylined5534 I mean, I know high-bypass engines are much more efficient and having the nacelles detach from the wing is much safer. So on a rational level I know today's planes are better aircraft. But that doesn't change the fact that they look cumbersome.
I love it when disasters I've never heard of rank high on the PPD scales!! It means I'm about to learn something new that I should've already know about 😃
This video has some BS included. For example - 5:20 The idea that only the crew & passenger areas were pressurised is absurd obviously. In fact every part of the fuselage was pressurised from the nose to the rear fuselage bulkhead including the entire cargo area. Besides that. The engine position & inlet design were not flaws or fatal flaws, there were good reasons for that design choice at the time. Comets flew until 1997. The Comet design had military use as a requirement. Nimrod development began at De Havilland before 1953. Nimrods were not withdrawn due to structure problems or other airframe issues it was entirely a significant upgrade snag & resultant basic economics & an end of line sale happening at Boeing at the same time. We feel we can shed some light on some common misunderstandings. At the time the Comet wasn't particularly dangerous. Losses comparisons How things were in those days. DeHavilland Comet 4 UK 14% DeHavilland Comet all mks 17% Boeing 307 70% Boeing 247 48% Boeing 707 . 20% Boeing 707 20% Lockheed Electra Turboprop 29% Canadair CL-44 Turboprop 46% Convair CV-580 Turboprop 22% Convair CV-880 (ff 1959) 27% Convair CV-990 (ff 1961) 35% Of course De Havilland had prior experience building many all metal construction airframe aircraft including thousands of jet powered fighter aircraft that were primarily of metal construction with pressurised cockpits & jet engines built by De-Havilland. De Havilland carried out full stress analysis & engaged in a comprehensive & protracted testing program which is why key De Havilland people were happy to be aboard flying DH Comet aircraft. The DH Comet was the first passenger airliner with full length fuselage pressurisation at 8psi pressure differential. Handley Page built the world's first airliner. Of course ripstop provision was provided. The skin alloy used became unavailable at the time due to R & D at the manufacturers which resulted in the original alloy being discontinued. The skin thickness used for the Comet was used for similar later aircraft. Frame spacing was not found to be too large & frame width was not found to be too small. De Havilland did indeed always work to better than industry standards at the time, used up to date knowledge for the design & construction & no evidence of negligence or criminal negligence was ever produced in relation to the DH Comet. The DH Comet had no effect on the course of the aerospace industry in the UK. The UK now has the world's largest combined nuclear, aerospace & defence sector per capita activity. The investigation committee did not find hundreds of fatal flaws or evidence of design defects, structural defects, defective materials or shoddy workmanship. Ripstop provision was included. Claimed incidents did not involve cracks starting from window corners. Pretty much all changes were just in case changes or were planned development modifications & improvements that were scheduled regardless of incidents. De Havilland designers knew all there was to know about metal fatigue at the time they designed the DH Comet. Hope this helps. Cheers 👍.
“Air travel was noisy and uncomfortable “ … as compared to today? Great video. The details of the development and initial stress testing was new to me. I remembered seeing the 1951 film “No Highway in the Sky”. The aeronautical engineer played by James Stewart goes to great lengths to prove that a new aircraft was susceptible to metal fatigue. Maybe if the DeHavilland engineers had gone to the cinema more often….
Elizabeth, you have no conception of how loud it was. I secured a flight on one of the vintage 10A Electras operated by Trans Canada Airlines. In the cabin it was bad - you had to shout to be heard. In the cockpit, in-line with the props of the twin Wasp Junior radial engines, the word "deafening" was inadequate - at take-off power the pilot and co-pilot could not communicate with each other, no matter how loud they screamed. Remember, this is with modern headsets with microphones! They communicated with hand signals until they could pull back to cruising power. So, that was an easy dig, but it minimizes how wonderful modern air transport really is.
Haha,indeed.I'd rather deal with noisy props than screaming children and drunken passenger meltdowns nowadays.The British deserve particular credit for being so radically innovative.I realize they weren't as commercially successful as their American counterparts (who were indepted to De Havilland).The Brits produced some real beauties though,the Comet,VC 10,and Vanguard.And that was a great old movie.Marlene Dietrich was so intriguing.There's also a book on the topic by Neville Shute(sp) titled Airframe.He's the author of On The Beach as well.
It wasn't the cabin windows. The failures originated at the cutouts for the ADF units on top of the fuselage. These were known as ADF "windows" which is where the confusion arises. Once the failure occurred it ripped through the thin skin of the fuselage and the plane explosively depressurised and broke up. The structure just wasn't strong enough.
Excellent comments. True, wreckage recovered proved conclusively that the passenger windows were not the cause. Investigators found that the Comet used skins that were too thin and made from an alloy that was too brittle. It lacked proper rip-stop doubler joints. The fuselage reinforcement loops were too narrow and spaced too far apart and riveted joints were poorly designed and not made to a high enough standard and lacked adequate quality control.
@@sandervanderkammen9230 No evidence that the skin was too thin or too brittle etc. The particular alyminium alloy used became unavailable after being upgraded. @sandervanderkammen9230 Kharzeestan Krappenz DiktorBummer Jurkzxoffenz etc and co - they should note good with much awestruckness & many extreme wondermentals. *UPDATE MORE BREAKING NEWS ETC* *_It's interesting that some of the aircraft on the list should really have been noticeably safer than the Comet due to being a similar type but of much later design & manufacture but they definately were not safer._* How things were back then - *_Accident losses - % of aircraft built._* DeHavilland Comet 4 UK 14% DeHavilland Comet all mks 17% Vickers VC10 UK 5% *_The DH Comet had better safety than or similar safety to many other commercial passenger aircraft of a similar era_* Douglas DC-1 99% Douglas DC-2 47% Douglas DC-3 30% Douglas DC-4 26% Boeing s300 72% Boeing 307 70% Boeing 247 48% Boeing 707 20% Lockheed Electra Turboprop 29% Fairchild FH-227 30% McDonnell Douglas DC-8 14% Sud Aviation Caravelle 15% Canadair CL-44 Turboprop 46% Convair CV-580 Turboprop 22% A comparison of more recent aircraft. Accident losses comparison examples. 1970s - 1980s % of total Aircraft built Similar aircraft type, date / decade, useage, size. Biz Jets BAe-125-800 1.7 % Beechcraft Beechjet 400 2.2 % Cessna 550 Citation II 7.1 % Learjet 35 / 36 12 % Beechcraft 1900 6% Dassault Falcon 10 11.5% Aérospatiale SN.601 22.5% Medium size jets / Turboprops. BAe-146 5.1% Fokker 100 6% McDonnell Douglas DC-9-30 9.5% Fairchild FH-227 30% McDonnell Douglas DC-8 14% Canadair CL-44 Turboprop 46% Convair CV-580 Turboprop 22% Beechcraft, Fokker, McDonnell Douglass, Learjet, Fairchild, Aerospatiale, Canadair, Convair companies defunct. All Comets, including some Comet 1s, had full civilian use certification at some point after 1954, civilian use certification only being withdrawn after commercial flying stopped. Examples were flying until 1997 - one example did a signals research global circumnavigation flight series in 1993 via Australia virtually without a rest travelling 28000 miles, only had an ice warning indicator issue during the flights. *The DH Comet - World Firsts.* 1st gas turbine jet powered airliner. 1st high altitude 8psi pressurised full fuselage length passenger cabin airliner, not a trivial feature as structure strength required for pressurisation considerably exceeded strength required for normal flying stress. Nobody else had done anything similar before the Comet. The b-47 used 2 relatively small, heavily built pressurised modules (the aircraft where 6 had their wings fold up in 2 months while flying & some had their wings fall off while parked). The 1937 Boeing piston engined airliner pressurised passenger cabin was pressurised to 2 psi only - in fact that could easily be done as the normal unpressurized fuselage cabin structure strength for flying stresses only was all that was needed to be adequate so no significant weight increase issues needed addressing. 1st all hydraulically powered flying surface controls & actuators airliner with under carriage wheel disk brakes + ABS. 1st jet airliner to cross the Atlantic. 1st jet aircraft to do a world circumnavigation flights series. *Of course De Havilland had prior experience building many all metal construction airframe aircraft including thousands of jet powered fighter aircraft that were primarily of metal construction with pressurised cockpits & jet engines built by De-Havilland & we know the world's first all metal construction airframe airliner was built in England in the 1920s by Handley Page.* *_De Havilland did indeed always work to better than industry standards at the time, no evidence of negligence ever being produced in relation to the DH Comet._* The course of De Havilland & the general UK aerospace industry sector was not affected even slightly by the DH Comet. *_Other interesting World firsts_* _World's first turboprop aircraft._ *Vickers Viscount Turboprop Airliner 1947.* *A 1945 Gloster Meteor Aircraft with Turboprop Gas Turbine Engine.* They might like to answer these questions. *Which airline has just ordered* *60 RR England Trent XWB Engines* *& What aircraft are the engines for?* _Bonus question for 10 points._ Which country has the *World's Highest Combined Per Capita* *Nuclear + Defence + Aerospace Sector Activity?* 👍 Cheers 🙂 & 👍 & 🙂 & of course 😎 indeed. Cheers etc. _Toodle_ -PIP- *Old* *_Chap._*
@@sandervanderkammen9230 Kharzeestan Krappenz DiktorBummer Jurkzxoffenz etc & co - they should note with much awestruckness and great wonderment. *Wrong.* *_Larger stressed skin pressurised passenger cabin airliners needed thicker skin simply because they were often 3 x heavier with 2 x the fuselage length & 20% higher passenger cabin diameter resulting in 20% higher pressure differential hoop stress._* Cheers & 😎 & 🙂 & Of Course 👍 indeed. *_Toodle_* -PIP- *Old* -Chap.-
De Havilland apparently had a reputation in the industry for building fragile aircraft. I believe the correct word is "souls" on board not "lives" ? I expect right off the bat putting engines in an intergrated cowling loads up maintainence time, which the military has plenty of, but not so much civil aviation?
One factor that contributed to a failure to detect this problem in testing was they would do overpressure tests and THEN do pressure cycling. The overpressure work-hardened the metal which made it relatively more resistant to cycles of loading so hid how early cracks would appear.
Would you have wanted to travel on the Comet? Let me know below!
Comet? No! Nimrod? Yes!
Thank you for making these videos
Only on one with round windows 🙈
well the improved comet that has the round windows then yeah
Is the idea romantic? Sure. Would it be enjoyable more than once? Certainly not, four turbojet engines that close would be exceedingly loud.
"Welcome to Plane Difficult"? Sneaky.
Planely difficult
Plane difficultly.
It does sound that way but it isn't
Meanwhile the auto generated subtitles: welcome to playing difficult
Wi tu lo
Admittedly I could be wrong, but it would appear that a significant amount of credit should be shown to the inquiry board, test engineers and BOAC for their determination to get to the bottom of the problem.
By all accounts this wasn't covered up or hidden from public scrutiny - the process seemed to have been relatively transparent, (not a window gag) although the damage was already done to the reputation of the aircraft.
Very true
Back then, the main focus of any investigation was to find what went wrong and fix it.
These days it's mostly to protect corporate profits.
@@rrknl5187 I beg to differ!
The whole investigation process for all aviation accidents and near misses is to find root causes and ensure they are eliminated! There is obviously pressure from corporate to make it quick and cover any guilt, but the investigations are always good!
@@totherarf The degree of corruption and influence to protect industry or protect pilots varies as you move through space and time. Watch the last Mini Air Crash Investigations video and tell me that wasn't a cover-up, to say nothing of what happened with the Max. I won't disagree that the attitude of "find the problems" over "punish the troublemakers" or "prove the aircraft works okay" gets far better results. But, between the national investigators (NTSB and relvant counterparts), investigators from manufacturers, and investigators from airlines, there are a lot of competing interests in any investigation, and we don't always succeed in keeping those interests out of the way of doing good work.
@@totherarf I'd suggest that you are both correct.
The aviation industry probably holds itself to different standards than other industries in this regard.
@RR KNL didn't specify the aviation industry, and in many other industries there are (to varying degrees) cover ups - construction, manufacturing, oil, gas, coal and mining have all faced transparency problems over the years when things go wrong - we've seen plenty of examples on this channel.
@Mentour Pilot is a fantastic aviation channel which looks at, amongst other things, aviation incidents, accidents and disasters - not in a distasteful, insensitive or crass way - the content creator hopes to illustrate that the aviation industry is constantly learning and improving through post crash investigations - something that other industries could learn from.
There is one thing that was missed - well, three things, if you count in the fact that the rivet holes on the Comet 1 were punched rather than drilled, which gave rise to the stress fractures in first place:
The Comet 1 design was deliberately made as light as it could be. The Comet 1 was relatively underpowered, having four de Havilland Ghost 50 Mk1 engines which only offered about 5050 lbf per engine. From the Comet 2 onwards, Rolls-Royce Avon engines were fitted instead, which were significantly more powerful - the Avon Mk.524s on the Comet 4 offered 9,500 lbf per engine. As a result, from the Comet 2 onward, the aircraft were built significantly stronger. The lighter structure on the Comet 1 was part of the reason why it failed so spectacularly: it simply was not designed for the sort of stresses that it would see in real life, even though engineers at the time could not have been aware of this.
Another thing is, that prior to the Comet disasters, the prevalent design philosophy used in British aircraft engineering was that of the Safe Life - a predetermined limit set at which the structural safety of the aircraft was thought to expire, and after which the aircraft should be withdrawn from service. Going from prior tests using individual components, IIRC De Havilland calculated the Safe Life of the Comet 1 around 16000 pressurisation cycles. Following the second series of tests which used an entire fuselage, however, the Safe Life of the Comet was proven to be dramatically shorter than previously calculated - failure expected to occur at any point between 1000 and 9000 cycles (or as it proved in both crashes, 900 cycles for G-ALYY/SAA Flight 201; and 1290 cycles for G-ALYP/BOAC Flight 781). Following this, the design philosophy in aviation gradually moved from Safe Life (i.e. a precalculated failure point before which the aircraft would be retired) to Fail Safe design (i.e. designing the aircraft structure in such a way that any failure would not result in catastrophic/fatal damage).
On a side note, the earlier crashes mentioned also revealed different issues. BOAC's G-ALYZ (October 26th 1952) and Canadian Pacific's CF-CUN (March 3rd 1953) both crashed at take-off after their crews over-rotated the aircraft. Subsequent investigation showed that when the nose was raised beyond a certain point, the airflow over the wings was interrupted leading to a loss of lift, rendering a take-off near-impossible; as a result the wings' leading edge was redesigned.
BOAC's G-ALYV (Flight 783, May 2nd 1953) broke up in a thunderstorm; subsequent investigation revealed the aircraft was over-stressed by turbulence occurring inside the thunderstorm. Failure in this aircraft was found to have started with its elevators rather than the fuselage itself; the accident was thus not caused by fuselage depressurisation, but rather the tail surfaces tearing off in-flight under negative stresses, which caused the aircraft to lose control and quickly disintegrate (within seconds, losing its elevators, then its wings; witnesses saw the wingless fuselage appear out of the cloud base and crash in flames). A similar accident occurred 13 years later with a BOAC Boeing 707 over Mount Fuji (BOAC Flight 911, March 5th 1966). In this case, the cause of the accident was clear-air turbulence, but the sequence of the structural break-up of the aircraft mirrored that of Flight 783 (failure of tail - failure of wings - crash).
So if they were made properly, could square windows still be used in airplanes? Or are they inherently weaker than round windows?
@@BlackRavenFeather565 Concentrating stress on four corners of the window would require a lot of reinforcements making the aircraft heavier and more complicated than it has to be. It's even better to have bigger rounded window than smaller square one. That's why almost all aircraft windows are rounded. Not perfectly round though, just enough to spread the stress evenly over the edge.
@@BlackRavenFeather565 Any material that has a square edge cut into it will have a "stress riser" or concentration in that corner. It's something we learned in structural engineering class. So a filet or rounded corner will spread or redirect the stress rather than concentrating it. Shafts, slots in metal, and those holes for windows have the rounded edges to keep that from occurring. See this video for a visual around a square notch th-cam.com/video/vDZ5yISiADM/w-d-xo.html and this one shows the stresses around a round hole th-cam.com/video/5mvATvu5WIM/w-d-xo.html. The stress moves around the curved surface, while it concentrates on the angled one. The repetition of pressurisation cycles will cause cracks the migrate throught the material until it fails. I could probably restate this better, but at least you can SEE what is being talked about with the two videos mentioned.
*Following this, the design philosophy in aviation gradually moved from Safe Life [...] to Fail Safe design*
This is really interesting. The design philosophy changed from "let it crash and burn after X cycles" (ironically called "Safe Life", it's obviously a cost saving measure it should be called Save Costs) to "let it not crash and burn". I think that's a positive change.
@@holz_name No, that's not how it was intended to work. Safe Life was simply the designed lifespan of an airplane which should be safe to operate and after which it should be decommissioned. Like a car that is guaranteed to work for 150k km and then should be scrapped as it may become dangerous. The second approach is to make something that will be fail safe - should be safe even in case of failure. It's like a car without lifespan limit that may break after 50k km but will not kill you. It has much longer lifespan but requires regular maintenance to keep it safe.
I’d recommend a visit to The DeHavilland Museum in Radlett, Hertfordshire. They have the fuselage of a Comet there plus numerous other aircraft built by this historic company, including the Mosquito. It only takes a few hours to visit but very well worth the visit as its run my a dedicated team of volunteers
The Mosquito original prototype at that! I was lucky enough to get to be invited by the curator to sit in it when I was a child. Don't think they would allow it today!
That sounds really cool! We've only been to England once (our first trip) and didn't travel about as much as we would have liked (we were getting our feet wet basically) -- this is definitely going on the list!
@@palmspringsmarythomson6354 I’m sure you’ll have a nice time but I’d recommend checking their website for opening times !
@@andrewrixon2347 oh I know, it’s not going to be anytime soon! We have a lot of comic-cons coming back this year. Hopefully 2023 if things don’t go squiffy. We were planning before 2019 to be able to make a trip for the Queen’s Jubilee time but best laid plans and all that…
@@palmspringsmarythomson6354 would also recommend iwm duxford in duxford near Cambridge
The biggest problem was that the stress tested fuselage was cold worked and was tougher than normal. Thus De Havilland got misleading strength data. If all if the fuselages had been stress tested in the same way, these accidents might never have happened.
Interesting. Do you have, a sauce, sorry, a source.
@@Margarinetaylorgrease Rivert duHamel's video on YT covers it succinctly.
Square holes concentrated stress at the corners of the holes, allowing premature stress cracking of the fuselage, when the crack grew long enough to reach another window (window is any penetration of the fuselage, whether an actual window, or an antannae) causing a failure making the pressurized fuselage pop like a balloon. The British had almost no experience with pressurization at that point. Pretty much Boeing, and curtiss were the only companies that had built pressurized aircraft at that time.
Later versions of the comet would have these issues rectified, but it already had a bad reputation and by that time Boeing and Douglas had far superior aircraft in production. The Military however loved them for antisubmarine and airborne early warning use. The U.S. had a similar experience with the lockheed Electra propjet airliner that had a resonence problem, but once fixed had a long career with the U.S. Navy as the P-3 Orion.
@@kdrapertrucker The problems were never solved, the fatigue life of the aircraft was severely reduced as a result.
You missed the source of the cracks. The rivet holes around the windows weren't made properly. That resulted in the creation of micro fractures around the holes. As the planes went through pressurisation cycles and increased stress was applied against the corners of the windows, the micro fractures became cracks that spread very quickly until the fuselage could no longer hold itself together.
I've heard the same thing. Also, I heard the widows were designed with "squareness" taken into account so their shape was not really the problem. I wonder if it compounded the problem..?
@@lomaii2847 go away spammer
The rivet holes were punched instead of being drilled. Also the fact that they used the same pressure cabin for overpressure testing, then afterwards to test the number of regular pressure cycles that it took to fail came into play, as the overpressure test cold-worked the metal, changing its crystalline structure in a way that made it much more resistant to metal fatigue.
@TheJudgementalCat Try reporting that comment - it'll disappear, then reappear, despite breaking more than one of TH-cam"s own guidelines - spam and explicit material.
Like many, many others I've had loads of comments disappear for no apparent reason - no curse words/swearing, no bullying, no sketchy terminology or "trigger" words, (certainly not knowingly) yet the comments keep vanishing.
TH-cam don't give out warnings or even offer any opportunity to edit - the comments just disappear, which can be extremely annoying if they are detailed or lengthy, yet explicit spam is allowed - YT is broken
You are correct sir.
Before this flight Comet was taken on a selling tour of the US. Eddie Rickenbacker, President of Eastern Airlines with his whole board were aboard. Rickenbacker noticed vibration around the windows. Upon landing he rejected a purchase and forbade Eastern senior board from flying on any one aircraft. Per his autibiography
That’s pretty interesting.
When trusting your gut feeling saves a whole lot of lives.
He was also on the board of Boeing advisors. Maybe a bit of conflict of interest.
@itsjohndell
While I'm not doubting that Rickenbacker made that claim, (and by extension I'm not disputing your retelling of the claim) I have trouble actually believing it.
It's a bit of a stretch to think that he noticed it on one flight when the aircraft would have gone through extensive testing with, apparently, no-one else picking up on the problem.
The aircraft went through many hundreds of pressurisation/depressurisation cycles before the stress fractures became apparent, and there was no mention of excessive vibration anyway - admittedly a pretty vague term.
Also, when did he publicly say this?
Was it after the findings of the inquiry were made public?
I suppose we'll never know the truth of the matter, but I have my doubts.
@@connclark2154 So? He saved lives.
I did want to fly on a Comet. In fact, I had several miniatures as a child and was dead in love with them. It was those engines embedded into the wings that always took my heart. They logged many miles in my childhood hands without a failure. If only the reality could have been more true. Who would have guessed that square windows could cause so much havoc? Great video, and an interesting but sad reminder of something that one could call, "Plainly Difficult."
Ship builders. They knew round(ed) windows where the way to go.
@@RoadkillbunnyUK I always kinda wondered why ships don’t have square windows. So it’s a pressure thing?
None of the catastrophic in-flight structural failures were related to the passenger windows..
The aircraft's fuselage ruptured along the roof at the point of the fuselage hoop with the highest hoop stress.
de Havilland made the hoops too weak, the skin too thin, lacked proper doubler plates and safe riveting techniques.
100s of fatal flaws were discovered in the wings, engine inlets, control systems even the toilets had to be redesigned to make the Comet safe to carry passengers.
@@sandervanderkammen9230 you here as well? Why am I not surprised 😃
Well observed, by the way.
@John Higgins Those 426 people that died because of de Havillands incompetence are still dead....
I love the sleek Art Deco design of the DeHavilland Comet with the gleaming engine nacelles on its wing. Actually, squared windows don't fit with that aesthetic. If they'd kept to the rounded theme of the overall design, the problem could have been avoided. Oddly, it's often the other way around, with artsy design leading to functional flaws.
There's a reason ships' portholes are not square, and it's exactly the same reason. The designers should have taken the hint.
The engines were also one of the Comet's fatal flaws, the inlets were changed to make the plane safer but no other aircraft in uses this horribly bad design
@sandervanderkammen9230
There was nothing wrong with the Comet's engine position or intake position .
There are some advantages for that design & some disadvantages for the podded pylon mount engine design.
@@petemaly8950 Since the point of failure had been found to be exactly the corners of the passenger windows and the automatic-direction-finding window t's evident the radiusing was not enough.
"just add enough material to make it work" is not a great solution when there are weight constraints, and the material you are working with has not a fatigue limit.
@@petemaly8950 Since both the real-scale tests performed at Farnborough and the analysis of the wrecks shown the points of failures being exactly the corners of the passengers' windows and the automatic-direction-finding window, its' quite evident they didn't test enough before the first flight.
"And this children, is why airplane windows are round"... There are a handful of other metal fatigue and explosive decompression incidents/accidents which may be worthwhile looking into if not already featured on this channel.
Nope, the windows are rounded so the earth looks round in flight,. Remember the earth is a pizza on the back of a sea turtle. I won't even get into chem trails , 5G, HAARP and the evil bowl of Jello located in a volcano that controls the world.
I might be wrong, but the problems that square windows or metal fatigue effects more on pressurised airplane cabin.. I think I have seen small aircraft that fly in low attitude (with unpressurised cabin) that have square windows (not that 90 degree square, but with rounded edges)
@@bobroberts2371 you forgot the cat that pushes everything off the edge of the pizza every 100 years
I really hope one day he tackles McDonnell Douglas and DC-10 cargo door issues, and the infamous investigation and blatant colluding with the then head of the FAA.
Ezcept for the fact that the comets already had round off cornered and not pointy square windows already
I've heard the story of the Comet before, but not the fact that they did pressure-cycle testing -- including of the window areas -- while it was being designed. It sounds like they must have come close to catching the fatal problem, but still missed it.
Sadly true
Imagine being like.... that one guy who was probably like "We should have done that test..." or however they figured out the problems. (I still need to watch the video but I swear there's always that one guy no one listens to.)
They ran tests, but probably not nearly enough, and the tests were not properly organized (some of the stress testing was on parts that had already been tested for overpressure (this changes the structure of the hull and invalidates the later tests). DeHaviland didn't allocate enough time and most importantly enough hulls for comprehensive testing. Boeing and Douglass were VERY slow to get into jet airliners, by the time Boeing brought the 707 into service it had a lot of data from the B-47 bomber (and the negatives from Comet) to work with.
The other big problem Comet had was that especially the Comet 1 was VERY short ranged (it could not fly the Atlantic) and rather small. The 2,3 and 4 were bigger, but not of the size that was really needed for many routes. Comet was an attempt to do an end-run on existing airliners and make British Aviation a player. It didn't really work, but the Princess flying boat and Brabazon were even bigger failures (the Comet at least entered service, and served as an anti sub platform "Nimrod" for decades to come).
@@PlainlyDifficult Their is an easy demonstration that shows what happens.
First punch sheet of A4 paper using a punch that is used to store papers in a ring folder, then carefully cut one of the holes into a square.
Then put the paper into a folder and carefully rip it out, observing which hole rips first. The difference is considerable and similar to nicking the edge of cellophane in order to rip it.
Research has now shown that it was a similar thing that caused the Titanic to break in half. The ends of bitumen filled expansion joints at intervals along the hull became the origin of a stress fracture. This was already known by Harland and Wolfe and the slots ended with a circular bulb, similar to a thermometer.
Why these were cut on her sister ship, but not the Titanic remains a mystery.
Don't forget one thing that is sadly prevalent in disasters like this, the possibility that the engineers had either designed in extra strength or the &^%$##%^&*((**&^%$ management overruled their engineers.
And you know the engineers were screaming bloody murder about replacing drilling the rivet holes with punching them. Well until silenced by the "genius" at the top.
As flawed as this plane is, the British sure knew how to make something look good. A later variant was operated by the RAF as the Nimrod until the 90s.
I recently saw a surviving example at the Yorkshire Air museum UK, a very visually striking aircraft with nuclear capability.
Always have a radius! Round edges are of outmost importance. I worked with fibreglass for years and anytime there is a cutout or angled edge it MUST have a radius to absorb any stress…otherwise CRACK!
You’d think they would have taken a lead from the marine industry…ship windows are round!🙄
Hindsight is always 20/20, it's easy to call the failure now that we know. Still, I'm a little surprised that not one of the engineers - experienced with pressure vessel designs - had an instinctive reaction to make the corners round.
The Liberty Ships had stress fractures and failures owing to square rather than radiused deck openings.
@@johnladuke6475 The corners were round.
@@johnladuke6475
The windows had radiused corners.
They proved the design was good during the extensive & protracted testing activities
It's possible to use sharp 90° corners for the passenger cabin windows on a pressurised airliner, it's just a matter of making sure there's enough material for adequate strength around the window, if sharp corners & big square windows etc are used it results in a lot of unwanted & unnecessary extra weight which is the last thing we want for an airliner design.
A flawed beauty, no question about it. One can only speculate as to how things would've turned out had de Havilland caught that fatal flaw at the testing stage. Another fine vid, sir.
Which flaw? The Comet 1 was permanently grounded and its airworthiness certificate was revoked after investigation uncovered over 100 design, safety, construction and materials flaws.
It wasn't just the accidents though. Those in-wing engines look stunning, very Flash Gordon but nacelles are just way more practical making maintenance turnarounds faster and cheaper. That's a legitimate selling point. Fair dos has to go to Boeing for choosing that design.
In the Comet it was a obliged choice, sinche the engines of the Comet I, Ghost 50 Mk 1, were a little underpowered for the aircraft, so De Havilland used the same "trick" of the Mosquito, that had the radiators in the wings to reduce drag.
Such a stunning looking plane. It’s a shame that the U.K. lost the lead in the jet age.
The picture of G-ALYU ready to be destroyed was some how quite moving, who knows how many lives it saved…
Airbus builds fine aircraft and Rolls Royce great engines. Don't beat yourself down too much!
Oddly enough, this design could still be in use today. But it does not get *_ALL_* of the profits, so to corporations it is completely pointless. Being profitable is not nearly enough, whatever it is *_MUST_* get *_ALL_* the profits.
@@unvergebeneid airbus came about not through british but french and german consolidation, and RR would have their own problems on commerical jets such as the lockheed tristar
@@danielduncan6806 not strictly true, pylon mounted engines eventually won out for their ease of upgrade and ease of maintenance. the brits kept on the integrated engine though with their V-Bombers
The De Havilland Comet, despite it's flaws, was still an incredible aircraft.
Unfortunately when making huge technological leaps mistakes will inevitably occur - being the first always carries risks.
The early bird gets the worm, but the second mouse gets the cheese.
It wasn’t a huge technological leap, as nearly every Comet misconception would have you believe. It was the first commercial jet airliner, but the TECHNOLOGY wasn’t groundbreaking.
Boeing already had the swept-wing, PODDED engine B-47 stratojet flying TWO years before the first Comet flew; it also had a far more advanced swept tail design than the Comet’s straight prop-era tail design.
The genius was in applying known technologies to a different market, not so much the plane itself.
Also (largely unknown or ignored) is the fact that Boeing had already implemented a huge array of construction and fuselage features into the -80 design which would have made the structural failure of the comet impossible. Guess what? They did all of that BEFORE the Comet crashes. Spot welding instead of punch riveting, tear-strips in the fuselage, and above all else, the aluminum skin was MUCH thicker than the Comets - again, all included in initial design specifications before the Comet crashes.
It is possible that while being a groundbreaking aircraft for commercial jet travel, de Havilland ALSO royally (no pun intended) screwed up!
@@EstorilEm Nazi Germany had the first jet-powered aircraft (the Me 262), and the first operational jet squadrons. B-47 was post-WWII, but the Convair B-36B/D's (post WWII w/jet engines and conventional engines on one aircraft was operational in 1946-47). B-47 was not fully operational until 1953.
@@EstorilEm
The "tear strips" or rip-stop strips were lacking in the Comet I, no doubt to save weight. Virtually all American jet liners had/have them. Keep cracks from propagating. There are also other areas where ground tests, including wind tunnel testing doesn't show up potential catastrophic failures. The Lockheed Electra I, for example, a four-engine turboprop, was tested extensively in wind tunnel testing. Unfortunately, it did not reveal the dynamic augment of the outboard engine/nacelle, which, under certain conditions inflight hit the natural frequency of the wing. The result was the Tell City, Indiana, crash, killing everyone onboard. Until the cause was found, airlines were instructed to reduce the cruise speed, which did keep the phenomena from happening. That was very fortunate for me and my Dad, as we took the same flight number, on the same type of aircraft, the next day! When the cause was found, Lockheed beefed up the wing structure and made other changes. The "new" plane was called the Electra II. While it didn't remain in commercial service much longer, the Navy and Air Force adopted it with all sorts of anti-submarine gear, and called it the P-3 Orion, which remained in service until being replaced recently by the P-8.
The Comet Disaster was certainly not the result of cutting edge technology... rather the lack of modern technology.
The Comet Disaster could have been easily prevented if de Havilland had simply followed existing, well-known Industry standards for the design and construction of all-metal aircraft with riveted aluminum alloys and cabin pressurization.
Great video... But...
Your failed to mention a couple of things.
1) the first two runway crash were from what some call a cockpit flaw which created a blind spot outside the windshield. From it the pilots thought they were taking off but weren't. Many Comets had to have their dash panel refurbished to eliminate the blind spot.
2) it was found that during the manufacture of the comet's to allow the square windows and and access point like the door and radio antenna, the holes for rivets and welding were punched into skin and not drilled. This created tiny micro fractures into the metal skin and accelerated the stress crack failure of the Comet's skin and frame. After this all manufactured aircraft would have their metal frames and skin panels drilled and not punched through.
The Comet was later converted into an anti-submarine and maritime patrol aircraft for the Royal Air Force. Renamed the Nimrod. It was used by the RAF until June 2011.
I didn't realise the Nimrod was a military version of the Comet, cool!
@@skylined5534 Yep it’s a Comet airframe with a anti shipping radar in the nose, a bomb / torpedo bay fitted underneath and an anti submarine magnetic object detector on the end of the tail. And it used similar Rolls Royce Spey engines as the RAF Phantoms and Buccaneers.
The Nimrod is a completely different aircraft designed by Hawker Siddeley 2 decades later... not a Comet.
@@skylined5534 its not a Comet.
Sandtbum The Nimrod started life based on a Comet 3 and production Nimrods were vased on the Comet 4, all design work being by the design team at Hatfield, in other words by DH.
I believe also that Boeings designs provided for "rip stops" in the fuselage. These would prevent a skin tear from propagating to the point of total failure. However the Comet did not have rip stops so when a tear started, there was nothing preventing it from running the length of that section of skin.
Explosive decompression is a serious deadly problem until today by airliners.
well, any kinds of explosives is a deadly problems for any airplane😂😂
@@davidaprians explosive diarrhea for example
Indeed but even the worst of 'em brung 'er in fer a landin'. Flight 800 notwithstanding as it had other issues.
@@Miki90Mar 😂
They still are, there have been a couple southwest hull loses in recent years
I especially liked this Comet episode.
I’ve seen other Comet documentaries too.
Thanks for covering the square passenger windows and also the antenna windows on top of the plane.
Plainly cracking report.
Great overview! I'm glad you covered how the Comet, or more precisely its individual components, was extensively tested before it went into service. Most of the documentaries I've seen overlook this and give the impression it wasn't. The fundamental problem was it was not tested as a whole airplane in real-world conditions (no cold working of metal, no effects of wing/fuselage flex, etc.) and so the tests were misleading.
One trivial thing: in the early 1950s, G-ALYP was "George Able Love Yoke Peter" rather than "Golf Alpha Lima Yankee Papa" ;)
The fact that it takes more to make a square window than a round one structurally sound when you bring pressurization into consideration is why NASA's Mercury capsule had a round window, was lighter to put a round one in than a square one.
I gotta admit the comet was a beautiful plane! Just the shape of it, and the way the engines are built into the wings with those round ports! Today's jet liners focus more on functionality, and less on style.
you mean 'more on safety and less on style'?
The engines in the wing were a horrible unsafe design decision.
The Comet's shape, in particular the engine placement was a fatal flaw that caused at 3 crashes.
No other airliner ever copied this deadly design error.
@@Stevie-J Aircraft engineers never place the engine inlets of a jet aircraft in the leading edge of the wing, this was a serious fatal flaw that was modified but still plagued later Comet aircraft.
@@sandervanderkammen9230 * laughs in TU-104 *
@@nickcher7071 You don't see the huge glaring difference???
The Tu-104 doesn't have the fatal flaw that the Comet has... think about it.
More in the Planely Difficult series please! :D
The only TH-cam channel Im a member of and it's worth every penny, thank you
As usual a great video, which does a great job of presenting a problem, and its causes. There's a lot more to the Comet's history though - which might tale a couple of hours to properly present.
While the structural issues put the nail into the Comet I (and IA), it must be pointed out that the two losses due to runway overruns mentioned are also significant, and exposed a critical problem with the early Comets - The Comet I, like all early jets, was severely underpowered, and takeoff performance was marginal. The airfoil used on the Comet's wings did not have good low speed characteristics - When taking off in an early Comet, the airplane had to be, at a precise speed, rotated exactly 10 degrees nose up to take off successfully. at 9 degrees, the wings would not develop enough lift to get the airplane off the ground on any runway that they could use, and if rotated to 11 degrees, the increased induced drag would prevent the airplane from accelerating to a speed where it could fly.
On the Comet teaching lessons in metal fatigue - in some respects that is overstated, I think - Boeing, which, at the time of the Comet losses over the Med, was beginning testing of the Model 367-80, (First flight July 15, 1954) had more experience with large pressurized aircraft (Model 307 prewar, the B-29 and B-50 bombers, the B-47 jet medium bomber, the B-52, and the 367/377 Stratucruiser airliners and C/KC-97 military cargo carriers and refueling tankers) than the rest of the world combined. Fatigue concerns by potential buyers, among them by Eastern Airlines in the U.S. led to lost or cancelled orders before the inflight breakups.
Obviously very sad and tragic for those lives lost, but the Comet was a beautiful aircraft and someone had design the first jet airliner.
*The **_Comet Disaster_** is the worst engineering failure in commercial aviation history... the real tragedy of this disaster is that it could have been easily prevented if de Haviland had simply followed well-known and understood industry standards for the design and construction of pressurized cabins made from riveted aluminum alloys.*
*de Havilland had very limited knowledge of building all- metal aircraft and were still building jet aircraft primarily from wood and fabric..*
Arizona (USA) resident here… love that you used the front page of the Arizona Republic at 10:45! Absolutely love your videos; keep up the great work!
I've seen one of these during refurbishment, there were marks around rivets where there was excess stress from what I remember
Mmmm square windows why not. Cheers for another nice video, your upload schedule is incredible
Thank you!
I have seen and read many recountings of the Comet crashes. You still managed to add facts I had not encountered and as per usual I found your narration riveting.
Thank you for all the work you put into educating us as you entertain us, I sincerely appreciate it.
Thank you!
I love airline accident investigation. Keep these up please!
I flew casevac Comet 2 from RAF Changi Singapore in June 1958. Was supposed to be stretchered in forward compartment but was asked if I would take a seat to allow a priority evac to use my stretcher. I was quite happy to as the stretchers were piled pretty close together! Sitting rearward facing was not a problem as I had previously flown on Hastings. Nice smooth trip and a great aircraft. Hastings to Singapore was five days...... Comet just a day.
Dear Plainly Difficult. Thank you for taking such a task to study these historical events and replay them for us to understand in their entirety. This is truthfully a bunch of large video projects that you make, and I want to appreciate you for it. Thank you for your hard work and great entertainment.
It's always easy to call it in hindsight, but every time I hear this story I'm still a little surprised at the designers. The average layman might see nothing wrong with a square window hole. Still, you might expect an engineer who works on pressure-bearing designs to think twice about anything that's square when it could be round. Of course, if they had been round from the first, it might have taken much longer and many more lives lost to learn about microfractures.
Where it failed wasn’t a window. It was an antenna mounting on the cabin roof…
To be fair to the engineers, the windows weren't completely square, they had rounded corners, the radius was just too small.
@@allangibson2408 On the recovered aircraft it was the antenna mounting (squared holes as well). In the tested one it were the windows.
Another problem were the rivets' holes. Punched instead of drilled, they were already microfractured.
The catastrophic in-flight structural failures were were not related to the passenger windows at all.
The fuselage ruptured exactly where Pascals Law tells us it should, at the reinforcing hoop with the highest surface area at its weakest point.
The fuselage hoops were too weak, the skins were way too thin, there were not enough doubler plates and the design and construction of the rivet joints were substandard.
100s of modifications and reinforcements were required to make the Comet 4 airworthy.
Earlier Comets were modified with round windows but were still unsafe to carry passengers and the Comet 1's airworthiness certification was permanently revoked in September 1958.
Glad you covered this one. I’ve always found the Comet a particularly fascinating plane, so remarkably advanced. And also very attractive look at. Whilst engineeringly less good I do like the engines embedded in the wings.
Also think the enquiry into this was fascinating and really paved the way for modern disaster investigation. The idea of creating a water tank test now is bizarre to us now but i love the idea of it. Simple but very clever.
A huge shame for the U.K. aerospace market though because as you say Boeing and Douglas both admitted they’d have had similar issues if their products flew first!
Thank you as always for the cracking content 🙂
The engines inlets are clear evidence of bad design at de Havilland.
Wishful British thinking... the effects of metal fatigue in pressurized cabins was already well-known and understood by German and American manufacturers...
de Havilland was doomed to failure because it was still building aircraft primarily from WOOD and was years behind in aircraft design and construction technology.
Junkers, Boeing, Douglas and Lockheed were already manufacturing pressurized cabins from riveted aluminum well before the Comet Disaster without any accidents...
It was de Havillands negligence not cutting-edge technology that killed 426 people.
Sandybum, Drbummer teling lirs as always.
The 707 was the basis for all commercial jet design so it was the futuristic aircraft. Burying the engines in the fuselage was a dangerous design and also more difficult to service. The Comet was also smaller than a DC-6 with 1/3 the range. Boeing had been building pressurized cabin commercial aircraft since the 307 in 1938, which the Comets nose resembles greatly.
Absolutely. de Havilland were very, very inexperienced in building pressurised aircraft. Apart from one experimental Vampire, I don't think they had built ANY pressurised aircraft prior to the Comet. Boeing, on the other hand, had been building pressurised aircraft since 1938 - starting with the 307 Stratoliner. Before the Comet ever flew, Boeing had also built the pressurised B-29 Superfortress and the 307 Stratocruiser.
I flew in a Comet flying to Mallorca for a holiday with my mum and she asked if the purser could see if could ask the flight crew if it would be possible to let me into the flight deck.
Not only did the Captain point out all the instruments and what they did (which probably increased my lifelong passion in aviation - at the time my dad was a CFI and I spent all my summer holidays flying in lots of different types of aircraft, Vernair in Liverpool had a fleet of KingAirs and they took me all around the UK and there was a pilot who had his own plane and took a shine to me so at least once or twice a week he would take me to the Isle of Man in his Mooney). Anyway, I digress. The Captain in the Comet gave me a brass badge in the shape of wings, and I was as happy as a clam!
You're lucky to be alive, the Comet has the highest loss rate and fatalities statistics of any jet airliner ever built.
@@WilhelmKarsten
Kharzeestan Krappenz DiktorBummer Jurkzxoffenz etc and co - they should note good with much awestruckness & many extreme wondermentals.
*UPDATE MORE BREAKING NEWS ETC*
*_It's interesting that some of the aircraft on the list should really have been noticeably safer than the Comet due to being a similar type but of much later design & manufacture but they definately were not safer._*
How things were back then -
*_Accident losses - % of aircraft built._*
DeHavilland Comet 4 UK 14%
DeHavilland Comet all mks 17%
Vickers VC10 UK 5%
*_The DH Comet had better safety than or similar safety to many other commercial passenger aircraft of a similar era_*
Douglas DC-1 99%
Douglas DC-2 47%
Douglas DC-3 30%
Douglas DC-4 26%
Boeing s300 72%
Boeing 307 70%
Boeing 247 48%
Boeing 707 20%
Lockheed Electra Turboprop 29%
Fairchild FH-227 30%
McDonnell Douglas DC-8 14%
Sud Aviation Caravelle 15%
Canadair CL-44 Turboprop 46%
Convair CV-580 Turboprop 22%
A comparison of more recent aircraft.
Accident losses comparison examples.
1970s - 1980s
% of total Aircraft built
Similar aircraft type, date / decade, useage, size.
Biz Jets
BAe-125-800 1.7 %
Beechcraft Beechjet 400 2.2 %
Cessna 550 Citation II 7.1 %
Learjet 35 / 36 12 %
Beechcraft 1900 6%
Dassault Falcon 10 11.5%
Aérospatiale SN.601 22.5%
Medium size jets / Turboprops.
BAe-146 5.1%
Fokker 100 6%
McDonnell Douglas DC-9-30 9.5%
Fairchild FH-227 30%
McDonnell Douglas DC-8 14%
Canadair CL-44 Turboprop 46%
Convair CV-580 Turboprop 22%
Beechcraft, Fokker, McDonnell Douglass, Learjet, Fairchild, Aerospatiale, Canadair, Convair companies defunct.
All Comets, including some Comet 1s, had full civilian use certification at some point after 1954, civilian use certification only being withdrawn after commercial flying stopped. Examples were flying until 1997 - one example did a signals research global circumnavigation flight series in 1993 via Australia virtually without a rest travelling 28000 miles, only had an ice warning indicator issue during the flights.
*The DH Comet - World Firsts.*
1st gas turbine jet powered airliner. 1st high altitude 8psi pressurised full fuselage length passenger cabin airliner, not a trivial feature as structure strength required for pressurisation considerably exceeded strength required for normal flying stress. Nobody else had done anything similar before the Comet.
The b-47 used 2 relatively small, heavily built pressurised modules (the aircraft where 6 had their wings fold up in 2 months while flying & some had their wings fall off while parked).
The 1937 Boeing piston engined airliner pressurised passenger cabin was pressurised to 2 psi only - in fact that could easily be done as the normal unpressurized fuselage cabin structure strength for flying stresses only was all that was needed to be adequate so no significant weight increase issues needed addressing.
1st all hydraulically powered flying surface controls & actuators airliner with under carriage wheel disk brakes + ABS.
1st jet airliner to cross the Atlantic.
1st jet aircraft to do a world circumnavigation flights series.
*Of course De Havilland had prior experience building many all metal construction airframe aircraft including thousands of jet powered fighter aircraft that were primarily of metal construction with pressurised cockpits & jet engines built by De-Havilland & we know the world's first all metal construction airframe airliner was built in England in the 1920s by Handley Page.*
*_De Havilland did indeed always work to better than industry standards at the time, no evidence of negligence ever being produced in relation to the DH Comet._*
The course of De Havilland & the general UK aerospace industry sector was not affected even slightly by the DH Comet.
*_Other interesting World firsts_*
_World's first turboprop aircraft._
*Vickers Viscount Turboprop Airliner 1947.*
*A 1945 Gloster Meteor Aircraft with Turboprop Gas Turbine Engine.*
They might like to answer these questions.
*Which airline has just ordered*
*60 RR England Trent XWB Engines*
*& What aircraft are the engines for?*
_Bonus question for 10 points._
Which country has the
*World's Highest Combined Per Capita*
*Nuclear + Defence + Aerospace Sector Activity?*
👍 Cheers 🙂
. .... . ... ... . .... . .... . .....
Ivxcvcxvvcxcxcvcxcvv
@@Paul-Nicer58Name a British jet aircraft still in production?
@@sandervanderkammen9230
Krappenz DiktorBummer KARZEESTAN Jurkzxoffenzstadt & co - they should all note with much awestruckness and great wonderment.
*****
*How come they can't answer simple questions - why is that?*
*****
*_DID SOMEBODY ACTUALLY SAY SOMEWHERE THAT THERE'S AIRLINER ASSEMBLY LINES OR SIMILAR IN THE UK OR IRELAND OR THAT Airbus or BOW-WING is actually British? (B-47 wings on many occasions folded up in flight or dropped off while parked)._*
Of course Brazil makes very good airliners & Brazil is 100th down list along with Indonesia for wealth per capita.
*Norway Holland Denmark Ireland Belgium - Top 20 wealth per capita - Don't make airliners - its as simple as that.*
BAe Systems & RR combined now do more Airbus work than Germany on an absolute basis & significantly more work than that on a per capita basis.
Per capita for the home nation BAe Systems is the world's largest defence contractor.
_BAe systems announced the recent £4 Billion takeover of Colorado based US based Ball Aerospace._
*BAE systems now does a significantly higher value of work for Airbus than it did when it was a major Airbus shareholder before 2005.*
*_RR now owns US Engine maker Allison for example which does classified Aerospace work for the US Govt._*
The UK has more important stuff to do these days.
_Routine simple passenger aircraft airframe assembly is becoming more of a 3rd world / trailer park area thing._
*_The DH Comet - world's first high altitude capable pressurised passenger cabin jet airliner in regular service, world's first jet airliner aircraft to cross the Atlantic, worlds first jet airliner aircraft to complete a global circumnavigation flight series._*
*They might try to sensibly answer this question - why do they believe that BAE Systems & RR (aero engines etc) & other companies, for example should be doing anything other than what they currently do & where do they get the idea from that the DH Comet had any affect at all on the progression UK aerospace sector.*
*Anybody currently flying on a widebody airliner stands a good chance of being on an aircraft powered by RR gas turbine aero engines built in England.*
📯📯📯📯
*The New RR Trent Ultrafan*
*Built In England*
*_World's Largest (see T&Cs)_*
*_Gas Turbine Aero Engine_*
📯📯📯📯
👍Manufactured by the people on a small island with less than 1% of the world's population.👍
*_A typical but small glimpse of what goes on in the very internationally orientated British aerospace sector._* -
Boeing Apache Attack Helicopter.
AH-64: *75 UK suppliers,* 7% UK content, global fleet of 1280+ aircraft.
*F35B more than 130 UK Suppliers, more than 30% UK content.*
*_F35A & F35C more than 130 UK Suppliers, more than 15% UK content._*
They might like to answer these questions.
*Which airline has just ordered*
*60 RR England Trent XWB Engines*
*& What aircraft are the engines for?*
_Bonus question for 10 extra points._
Which country has the
*World's Highest Combined Per Capita*
*Nuclear / Defence / Aerospace Sector Activity?*
👍 & 🙂 & of course 😎 indeed.
Cheers.
_Toodle_ -PIP- *Old* *_Chap._*
. ... . . .. .... . .
... . . ... . .....
ccicci vivvixxi
xxicciccixcxc
A shame some of the most important lessons in engineering are the ones that come from the worst tragedies.
If no one die, no one cares
The tragedy of the Comet Disaster is it could have been easily prevented if de Havilland had followed well-known and understood engineering standards for riveted aluminum airframes.
Prior to the Comet Disaster de Havilland was still building aircraft primarily from WOOD and was years behind in aircraft design and construction technology.
@@sandervanderkammen9230 - Which "well-known and understood engineering standards" were these? De Havilland were working on the bleeding edge of scientific knowledge regarding materials - no civil aircraft of that size had ever routinely cruised at those altitudes before. Furthermore, the DH Mosquito fighter/bomber was designed and made of wood not because DH lacked experience working with aluminium, but because the entirety of the aluminium available to the British Empire had already been requisitioned for other purposes. The whole point was that any joiner, cabinet maker or piano builder in the country could turn their hand to making parts for the Mosquito - which among other things severely pissed Hermann Goering off.
Boeing probably had the most experience building aircraft with pressurised cabins with the pre-war Stratoliner, B-29 and Stratocruiser - and when De Havilland released their data regarding metal fatigue in the wake of the investigation, Boeing's engineers freely admitted that if it hadn't happened to the Comet, it would have happened to the jetliner they were working on.
@@turricanedtc3764 Metal fatigue was not discovered by de Havilland, it was already known to aircraft manufacturers... all but de Havilland.
The Comet Disaster investigations revealed 100s of fatal flaws, design flaws, material flaws, shoddy workmanship and appalling quality control.
@@turricanedtc3764 Absolutely false, de Havilland made several unsuccessful attempts at building aircraft from aluminum alloys.
de Havilland was still building aircraft primarily from WOOD when the company went tits-up in 1958.
The industry leaders like Boeing, Douglas, Junkers and Lockheed were building all-metal, pressurized monoplane airliners before the war while de Havilland was still building wood and fabric biplanes like the Dragon Rapide!!!
Expertly well done as always, and the light-hearted tidbits and transitions are a fun touch. Bring back '...about here on a map'!
Thank you!
@@PlainlyDifficult Yeah, I miss the foam finger and the wacky variety of maps! That was a great trademark bit for the channel.
From memory, the cracks were initially started from the drilling and riveting process around the windows, work-hardening the metal resulting in it becoming brittle in those areas, further exacerbated by the pressurisation cycles and thermal stresses over time, which tragically resulted in the incidents of the planes basically popping like balloons... :(
The riveting process was the source of the trouble, because the punch method had been used…
This design was one of the simplest, yet had a timeless grace and elegance about it. I love, especially the sleek eyebrow cowling around the Rolls Royce engines. Great post.
The inlets were a fatal flaw
Indeed it's fairly clear that -
5:20 The idea that only the crew & passenger areas were pressurised is absurd obviously.
Every part of the fuselage was pressurised from the nose to the rear fuselage bulkhead including the entire cargo area.
Cheers.
Kind of unrelated, Boeing’s top test pilot of the time Tex Johnson famously rolled a 707 2 times in a row to impress potential buyers without prior ‘permission’. He was called into the office the next day and asked what exactly he thought he was doing? He said: ‘I was selling airplanes’. Apparently it worked as we found out by the end of the video.
Not as well as the bribes Boeig paid out to sell their aircraft.
Douglas may have learned something from Comets missteps but I don't think Boeing needed those lessons.
Boeing was easily the most experienced manufacturer of large pressurized aircraft, indeed lack of hands on experience of pressurising large airframe by British aircraft industry showed in Comet's design. Both Lockheed's Constellation airliner and Boeing's model 377 Stratocruiser had rounded windows (they were squarish but without sharp corners). Lockheed & Boeing had built pressurised aircrafts in WW2 and worked out kinks, De Havilland just didn't have that kind of experience.
Indeed pressurized aircraft needing rounded windows was not a unknown thing within industry at the time of Comet's construction, I often wonder why De Havilland team missed it.
How scary that must have been. Plane cracking open while 20,000 feet up.
The explosive decompression would have knocked the people out very quickly, if not instantly. Many on board were thrown headfirst into the ceiling of the fuselage by the decompression. On top of that, the shock to the lungs from the decompression would have quickly rendered them unconscious.
It would have been a very quick way to go...
was watching a video about it and saw yours on recommended and so watched this instead, great as always
Thanks for the topic, super interesting. I looked up flying back then and the cost was 5x more expensive then. I read that having an engine fall off on any plane was so common, it didn't count as an accident if the plane landed safely. Not me!
I've noticed when people complain about comfort and service in coach they try to compare it to the 50's and 60's; what they don't realize is that back then flying at all was the equivalent of first class, and if you adjust for inflation the airfrare was more expensive than an equivalent first class ticket today.
Thanks!
This video is more "plane-ly" difficult - amiright??
good one
I have seen at least 2 videos on this before but this is by far the best and most detailed look. Thanks.
It’s important to note that they didn’t immediately throw an aircraft in the water tank and start testing as you imply. There was significant pushback from both the operators and de Havilland at the time, due to the initial testing you mentioned. It was thought to be absolutely impossible, and everyone involved were incredibly stubborn, prideful, and naive, contributing to a number of needless deaths.
The Comet story is well-known, but I find it ridiculous that it’s always accompanied by the belief that it wasn’t REALLY de Havilland’s fault, due to the groundbreaking design of the aircraft. The only thing more important than not killing a bunch of people in plane crashes, is that of typical British pride and retaining their proper and polished image on the world stage.
I find the governments balancing act absolutely fascinating in this situation. They wanted to be known as the nation that pioneered commercial jet travel, but were possibly going to be remembered as the nation who crashed more jets in a given period of time than anyone in history. The British state-owned airline ie BOAC (and largest operator of the Comet, not counting the later Dan-Air) was pretty much a proxy for the government’s thoughts on this as well, which is clearly shown in their initial handling of the Comet crashes which was borderline coverup status.
In any event, by their own admission (ie they DID initially test the frames and components to check for metal fatigue and structural issues) they WERE aware of potential dangers that wear and cycles cause on aircraft. Yet, they STILL screwed up the design.
History doesn’t often give events like this a free-pass (Titanic’s design certainly didn’t - though the disaster was also due to British engineering arrogance…. weird) however unfortunately, it seems to in this case.
Do I have your consent to find your location?
"The British state-owned airline ie BOAC (and largest operator of the Comet, not counting the later Dan-Air) was pretty much a proxy for the government’s thoughts on this as well, which is clearly shown in their initial handling of the Comet crashes which was borderline coverup status. "
The consequent depth and level of accident investigation by the RAE and Cohen Committee - following the three fatal Comet hull failures - were completely revolutionary, setting the precedent for future air safety. It was a surprisingly open process.
The cutting edge of aviation history is littered with accidents and incidents. It's how people learnt, improved and adapted from experience.
"In any event, by their own admission (ie they DID initially test the frames and components to check for metal fatigue and structural issues) they WERE aware of potential dangers that wear and cycles cause on aircraft. Yet, they STILL screwed up the design."
Evidence?
Ah yes but Boeing certainly never covered up anything, Typical American arrogance eh?
@@alexwinfield9540 I’m not a Boeing fan actually, luckily their shortcomings hardly reflect the most cutting edge aerospace companies in the world (most of which do indeed reside in the US) - save for EADS/Airbus which are hands-down my favorite aerospace / defense contractor.
The Comet Disaster is the worst engineering failure in commercial jet aviation history... the real tragedy of this was it could have been easily prevented if de Havilland had simply followed well-known and understood industry standards
I'd rather fly in a plane that had disasters, and the reasons for those were identified and rectified, than on a newer plane that can possibly have hidden faults.
The same reason I absolutely REFUSE to drive a vehicle newer than 10 years old... I won't even look at it. Cutting edge tech' bring cutting edge bugs... ;o)
@@gnarthdarkanen7464
Remote hacker controlled Teslas anyone?!
@@skylined5534 As if traffic ain't a borderline clusterf*** as it is... YAY!!! Let the 10 - 13 year olds GNU open-source all they need to play GTA with REAL cars!!!
Maybe somebody should just develop an app' for that "Augmented Reality" Game!!! AND post it for public consumption... ;o)
Thank you for the excellent short-form content.
Mr. Difficult, Would K-219 be a story of interest to you? It has nuclear weapons accidents, a nuclear reactor with bent control rods, it can Cold war era boat with the incident being relatively recent. Great work as always. It is the main reason I would like to see your telling of K-219
It also has Seaman Sergei Preminin, the sailor with the biggest brass balls in the history of the Soviet navy. The channel jiveturkey actually has a great video detailing the whole incident as part of his sub-briefs series.
@@tiberiusweaver-zeman2520 Sub Brief with Jive Turkey was the first 219 documentary I had ever seen in subsequent reason for asking. His episode on finding that there were survivors on the thresher and it was just declassified 10 months ago blew my mind.
Another fine broadcast, thank you.
In my eyes possibly one of the most beautiful jet liners ever produced.
Your eyes are wrong.
@@marioxerxescastelancastro8019 your opinion is wrong.
These have to be some of my favourite content on youtube :)
Beautiful design, flawed unfortunately, but still beautiful from a designer that is still a legend in avation history.
You are my new favorite disaster channel. 😆 Seriously though, your videos are gripping.
It's worth noting that, although the stress cracks were blamed on the "square" windows, the windows were not actually square. Some of the photos in your video show how rounded the window corners were.
Decades later, a re-examination of the evidence indicated that the cracks were caused by the method of making the rivet holes around the window frames.
Thank you for covering this story.
I've yet to see the story of the Comet shown on nearly any of the air disasters type shows.
May 8, 2023 - While this video is very well made (I recommend following Plainly Difficult) I think it needs a little correction. Mentor Now! has a new video highlighting the problems of the Comet and how the "windows" being the starting point of stress fractures leading to the accidents were NOT the "square" passenger windows as assumed by the press but rather the "ADF Aerial Windows" on the roof through which the plane's antennas were mounted.
Full Video: th-cam.com/video/-DjnG74DDno/w-d-xo.html
Jump to the Time Index: th-cam.com/video/-DjnG74DDno/w-d-xo.html?t=1022
Later Comet Disaster investigations recovered wreckage that confirmed that the passenger windows were not the cause.
But the original investigation uncovered that the Comet was structurally unsound and lacked adequate materials and safety factors.
In particular the aluminum skins were fat too thin and the alloys too brittle.
And the planes lacked basic rip-stop doubler joints between panels.
The fuselage reinforcement hoops were too narrow and spaced too far apart to prevent cracks from jumping to other segments and the rivets were substandard and did not have proper quality controls.
@sandervanderkammen9230
Kharzeestan Krappenz DiktorBummer Jurkzxoffenz etc and co - they should note good with much awestruckness & many extreme wondermentals.
*UPDATE MORE BREAKING NEWS ETC*
The skin was not found to be too thin.
The original alloy used became unavailable & so an improved alloy was used.
*_It's interesting that some of the aircraft on the list should really have been noticeably safer than the Comet due to being a similar type but of much later design & manufacture but they definately were not safer._*
How things were back then -
*_Accident losses - % of aircraft built._*
DeHavilland Comet 4 UK 14%
DeHavilland Comet all mks 17%
Vickers VC10 UK 5%
*_The DH Comet had better safety than or similar safety to many other commercial passenger aircraft of a similar era_*
Douglas DC-1 99%
Douglas DC-2 47%
Douglas DC-3 30%
Douglas DC-4 26%
Boeing s300 72%
Boeing 307 70%
Boeing 247 48%
Boeing 707 20%
Lockheed Electra Turboprop 29%
Fairchild FH-227 30%
McDonnell Douglas DC-8 14%
Sud Aviation Caravelle 15%
Canadair CL-44 Turboprop 46%
Convair CV-580 Turboprop 22%
A comparison of more recent aircraft.
Accident losses comparison examples.
1970s - 1980s
% of total Aircraft built
Similar aircraft type, date / decade, useage, size.
Biz Jets
BAe-125-800 1.7 %
Beechcraft Beechjet 400 2.2 %
Cessna 550 Citation II 7.1 %
Learjet 35 / 36 12 %
Beechcraft 1900 6%
Dassault Falcon 10 11.5%
Aérospatiale SN.601 22.5%
Medium size jets / Turboprops.
BAe-146 5.1%
Fokker 100 6%
McDonnell Douglas DC-9-30 9.5%
Fairchild FH-227 30%
McDonnell Douglas DC-8 14%
Canadair CL-44 Turboprop 46%
Convair CV-580 Turboprop 22%
Beechcraft, Fokker, McDonnell Douglass, Learjet, Fairchild, Aerospatiale, Canadair, Convair companies defunct.
All Comets, including some Comet 1s, had full civilian use certification at some point after 1954, civilian use certification only being withdrawn after commercial flying stopped. Examples were flying until 1997 - one example did a signals research global circumnavigation flight series in 1993 via Australia virtually without a rest travelling 28000 miles, only had an ice warning indicator issue during the flights.
*The DH Comet - World Firsts.*
1st gas turbine jet powered airliner. 1st high altitude 8psi pressurised full fuselage length passenger cabin airliner, not a trivial feature as structure strength required for pressurisation considerably exceeded strength required for normal flying stress. Nobody else had done anything similar before the Comet.
The b-47 used 2 relatively small, heavily built pressurised modules (the aircraft where 6 had their wings fold up in 2 months while flying & some had their wings fall off while parked).
The 1937 Boeing piston engined airliner pressurised passenger cabin was pressurised to 2 psi only - in fact that could easily be done as the normal unpressurized fuselage cabin structure strength for flying stresses only was all that was needed to be adequate so no significant weight increase issues needed addressing.
1st all hydraulically powered flying surface controls & actuators airliner with under carriage wheel disk brakes + ABS.
1st jet airliner to cross the Atlantic.
1st jet aircraft to do a world circumnavigation flights series.
*Of course De Havilland had prior experience building many all metal construction airframe aircraft including thousands of jet powered fighter aircraft that were primarily of metal construction with pressurised cockpits & jet engines built by De-Havilland & we know the world's first all metal construction airframe airliner was built in England in the 1920s by Handley Page.*
*_De Havilland did indeed always work to better than industry standards at the time, no evidence of negligence ever being produced in relation to the DH Comet._*
The course of De Havilland & the general UK aerospace industry sector was not affected even slightly by the DH Comet.
*_Other interesting World firsts_*
_World's first turboprop aircraft._
*Vickers Viscount Turboprop Airliner 1947.*
*A 1945 Gloster Meteor Aircraft with Turboprop Gas Turbine Engine.*
They might like to answer these questions.
*Which airline has just ordered*
*60 RR England Trent XWB Engines*
*& What aircraft are the engines for?*
_Bonus question for 10 points._
Which country has the
*World's Highest Combined Per Capita*
*Nuclear + Defence + Aerospace Sector Activity?*
👍 Cheers 🙂 &
👍 & 🙂 & of course 😎 indeed.
Cheers etc.
_Toodle_ -PIP- *Old* *_Chap._*
. .. . ... . .... . .....
ixcxicvcixvxivx
. .... . .....,...... ... ..
Ivcxcvcxcvcccvccvvv
Career USAF here, love your work
"At the time, passenger flight were noisy and uncomfortable experiences..."
Now, we're plugged into narrow seats with no leg room with screaming children vomiting directly behind us.
But hey, you don't hear propellers or feel piston engine vibrations.
You're also paying a lot less for a ticket than what the inflation-adjusted airfare was back then.
Wow, three minutes ago? Epic! Great content bud!
Ironic how Boeing is now in similar trouble......"corporate arrogance" being the real cause.
No, no, no, no, noooo. You're wrong. It's always pilot error, or maybe, just sometimes, a bomb. Bombs are scary and stop people getting on the (money making machine) plane, not as scary though as the plane being bad and falling apart though.
So remember, PILOT ERROR. OK?
What an awesome looking design, too bad it had such a tragic flaw. I wonder if we'll ever see beautiful plains in the travel industry again.
Great video lad, always love your stuff.
What sometimes get missed with the Comet is there were actually two root causes. The shape of the windows was a major contributor. But the biggest underlying problem was the new unique and revolutionary formulation of ultra thin aluminum that the aircraft was skinned with. Which turned out to be far more brittle and prone to micro fractures than was anticipated. Boeing actually had previously discovered some of the issues later brought forth with the Comet during WW2. They had a lot of early development problems with the B-29 involving pressurization cycles and the problems they caused. Particularly those involving squared off openings in the pressure compartment skin. But pretty much everything involving the B-29 and later B-36 development was beyond classified back then. And the Comet had a much thinner skin and was introducing stresses beyond anything they had seen in the two slower bombers. The 707 didn’t just learn from seeing what happened to the Comet. It was a late in the development cycle cross conversion from a military aircraft design, so much of it was being built to the military specs, just to share common tooling. So it used the same standard aluminum thickness and formulation as the USAF required.
The reason the skin was so thin was because de Havilland wanted to use their own engines instead of more powerful ones from Rolls Royce..
de Havilland simply lacked the technical experience in designing and building aircraft from riveted aluminum.
The skins were far too thin and weak, there were too few fuselage reinforcement hoops and they were too weak, not enough rip-stop doubler joints the design and production techniques used in riveting was well below industry standards even for unpressurized aircraft.
De Havilland recieved technical data on the B-29 pressurized cabins from Boeings during WW2 but engineers at de Havilland were still building aircraft from WOOD.
De Havillands post-war jets wete made primarily from WOOD not riveted aluminum which was rhe industry standard.
@@TheJononator Rolls-Royce did not have a axial flow turbojet available when the Comet was designed..
Of course the placement of the engines was also another fatal flaw that caused several crashes.
Based on an aerodynamic theory that later proved to be completely wrong, no other airliner ever copied the flawed engine placement of the Comet.
@@sandervanderkammen9230 A lot of fighters and bombers of the era did use a somewhat similar engine placement. But they had very different needs. The big revolution of Boeing and McDonald Douglas hanging the engines on underwing pylons was less an aerodynamic leap as it was one of serviceability and cabin noise comfort. The airlines loved it because it made servicing the engines much easier.
@@andrewtaylor940 Not true at all, while some supersonic fighters have their inlets in the Wing Root none have them in the actual leading edge causing a disruption of airflow to the engines at high angles of attack and reducing wing lift, in the case of the British V-bombers there are some subtle but important differences with placement of the inlets ahead and below the leading edge line of the wing that reduce the problem but were still based on the flawed theory and a lack of good wind tunnel data.
Boeing engineer George Schairer was a member of the Von Karman Mission that discovered the Top Secret German _Luftfahrtforschungsantalt_ supersonic wind tunnel research lab in Braunschweig.
Boeing stole or copied top secret data on jet engine placement and the plans for the P.1107 which became the B-47.
The Boeing 707 Jet Stratoliner is directly based on the B-47 and the German wind tunnel data on jet engine placement.
The Comet was so badly designed and built that half of them crashed and the type was grounded in 1954 and its certificate of airworthiness was permanently revoked..
Do you have a framework video that describes why you rate things in particular ways on your Disaster and Legacy scales? I've always been curious on what goes into that rating as this disaster, which killed 21, rated 8, while other disasters you've covered which killed and injured many more rate much lower on the Disaster scale. I enjoy your breakdowns regardless, especially the technical details!
He's said a few times that the Disaster Scale is "mostly arbitrary" so I doubt there is a real process. I think he started using the Legacy Scale to differentiate between how horrifying a disaster is, and how much it actually changed things for the better.
knocked it out the park w/ this one bro
The Comet is anything but a footnote. The engineering and forensic techniques it spawned, not to mention the lessons learned from the mistakes it made, are the foundation of modern commercial air travel.
Hey, I actually knew this before you posted it, amazing.
I had a small toy plane when i was a kid that was mixed in with a pile of hotwheels cars. It was one of these planes lol
Love how much research you put into your videos I’ve seen videos on this but they are very basic not as many details
Thank you!
While the plane had historical significance and the accidents lead to breakthoughs in aircraft design, material knowledge and accident investigation rating them 8 on the disaster scale seems far fetched and higly subjective since they only lead to a total of several dozen lives lost and no lasting impacts beyond those mentioned above to anyone besides the manufacturer and the perception of flight safety among the british public. I feel the author is letting his nationality color his judgment here and that any of the radiation events or chemical spills he’s covered would rate far higher on this scale. Surely these crashes can not be more than a 3 on that scale.
The section of the test aircraft that failed now resides in the RAF Cosford museum Wolverhampton well worth a visit
The Comet still looks more elegant and futuristic than any modern passenger plane.
It does, ridiculously sleek and well shaped! It makes some airliners look comically bulky by comparison.
@@skylined5534 I mean, I know high-bypass engines are much more efficient and having the nacelles detach from the wing is much safer. So on a rational level I know today's planes are better aircraft. But that doesn't change the fact that they look cumbersome.
Excellently done!!
Comet has go to eleventy on legacy. You need an eleventy for your scale. ;)
I love it when disasters I've never heard of rank high on the PPD scales!! It means I'm about to learn something new that I should've already know about 😃
Tldr: Squarey window bad.
Bingo!
Thank you John, always interesting 😊
The Comet proved one thing: it ain't always better to be first.
Very true
Great vid, I first heard of this aircraft from the Seconds from Disaster series. Thanks for offering your take on it.
So they should have cut corners?
Yes
They should have stuck to building aircraft from wood...
This video has some BS included.
For example -
5:20 The idea that only the crew & passenger areas were pressurised is absurd obviously.
In fact every part of the fuselage was pressurised from the nose to the rear fuselage bulkhead including the entire cargo area.
Besides that.
The engine position & inlet design were not flaws or fatal flaws, there were good reasons for that design choice at the time.
Comets flew until 1997.
The Comet design had military use as a requirement. Nimrod development began at
De Havilland before 1953.
Nimrods were not withdrawn due to structure problems or other airframe issues it was entirely a significant upgrade snag & resultant basic economics & an end of line sale happening at Boeing at the same time.
We feel we can shed some light on some common misunderstandings.
At the time the Comet wasn't particularly dangerous.
Losses comparisons
How things were in those days.
DeHavilland Comet 4 UK 14%
DeHavilland Comet all mks 17%
Boeing 307 70%
Boeing 247 48%
Boeing 707 . 20%
Boeing 707 20%
Lockheed Electra Turboprop 29%
Canadair CL-44 Turboprop 46%
Convair CV-580 Turboprop 22%
Convair CV-880 (ff 1959) 27%
Convair CV-990 (ff 1961) 35%
Of course De Havilland had prior experience building many all metal construction airframe aircraft including thousands of jet powered fighter aircraft that were primarily of metal construction with pressurised cockpits & jet engines built by De-Havilland.
De Havilland carried out full stress analysis & engaged in a comprehensive & protracted testing program which is why key De Havilland people were happy to be aboard flying DH Comet aircraft.
The DH Comet was the first passenger airliner with full length fuselage pressurisation at 8psi pressure differential. Handley Page built the world's first airliner.
Of course ripstop provision was provided. The skin alloy used became unavailable at the time due to R & D at the manufacturers which resulted in the original alloy being discontinued.
The skin thickness used for the Comet was used for similar later aircraft.
Frame spacing was not found to be too large & frame width was not found to be too small.
De Havilland did indeed always work to better than industry standards at the time, used up to date knowledge for the design & construction & no evidence of negligence or criminal negligence was ever produced in relation to the DH Comet.
The DH Comet had no effect on the course of the aerospace industry in the UK. The UK now has the world's largest combined nuclear, aerospace & defence sector per capita activity.
The investigation committee did not find hundreds of fatal flaws or evidence of design defects, structural defects, defective materials or shoddy workmanship. Ripstop provision was included. Claimed incidents did not involve cracks starting from window corners.
Pretty much all changes were just in case changes or were planned development modifications & improvements that were scheduled regardless of incidents.
De Havilland designers knew all there was to know about metal fatigue at the time they designed the DH Comet.
Hope this helps.
Cheers 👍.
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@@Peppa_Wiggles23 Uhhm. Cutting corners was a joke.
@@bettyboop-xg6jo
That's right, a good joke but one of the irrelevant replies needed dealing with but indirectly.
First time on this channel. Very good video. Thanks.
“Air travel was noisy and uncomfortable “ … as compared to today?
Great video. The details of the development and initial stress testing was new to me. I remembered seeing the 1951 film “No Highway in the Sky”. The aeronautical engineer played by James Stewart goes to great lengths to prove that a new aircraft was susceptible to metal fatigue. Maybe if the DeHavilland engineers had gone to the cinema more often….
Elizabeth, you have no conception of how loud it was. I secured a flight on one of the vintage 10A Electras operated by Trans Canada Airlines. In the cabin it was bad - you had to shout to be heard. In the cockpit, in-line with the props of the twin Wasp Junior radial engines, the word "deafening" was inadequate - at take-off power the pilot and co-pilot could not communicate with each other, no matter how loud they screamed. Remember, this is with modern headsets with microphones! They communicated with hand signals until they could pull back to cruising power. So, that was an easy dig, but it minimizes how wonderful modern air transport really is.
Haha,indeed.I'd rather deal with noisy props than screaming children and drunken passenger meltdowns nowadays.The British deserve particular credit for being so radically innovative.I realize they weren't as commercially successful as their American counterparts (who were indepted to De Havilland).The Brits produced some real beauties though,the Comet,VC 10,and Vanguard.And that was a great old movie.Marlene Dietrich was so intriguing.There's also a book on the topic by Neville Shute(sp) titled Airframe.He's the author of On The Beach as well.
@@BrainScramblies Hah,a plane crash would be quieter than some.
You haven't experienced real noise until you have flown a Shackleton with four Griffons on full throttle.😵
Always well done. Nothing bugs me more than obvious mistakes, which this channel never has. Keep the great content coming John!
At the time Depressurisation was not well known during the 60’s.
It's a comet alright lol
It wasn't the cabin windows.
The failures originated at the cutouts for the ADF units on top of the fuselage. These were known as ADF "windows" which is where the confusion arises. Once the failure occurred it ripped through the thin skin of the fuselage and the plane explosively depressurised and broke up. The structure just wasn't strong enough.
Excellent comments. True, wreckage recovered proved conclusively that the passenger windows were not the cause.
Investigators found that the Comet used skins that were too thin and made from an alloy that was too brittle.
It lacked proper rip-stop doubler joints.
The fuselage reinforcement loops were too narrow and spaced too far apart and riveted joints were poorly designed and not made to a high enough standard and lacked adequate quality control.
@@sandervanderkammen9230
No evidence that the skin was too thin or too brittle etc. The particular alyminium alloy used became unavailable after being upgraded.
@sandervanderkammen9230
Kharzeestan Krappenz DiktorBummer Jurkzxoffenz etc and co - they should note good with much awestruckness & many extreme wondermentals.
*UPDATE MORE BREAKING NEWS ETC*
*_It's interesting that some of the aircraft on the list should really have been noticeably safer than the Comet due to being a similar type but of much later design & manufacture but they definately were not safer._*
How things were back then -
*_Accident losses - % of aircraft built._*
DeHavilland Comet 4 UK 14%
DeHavilland Comet all mks 17%
Vickers VC10 UK 5%
*_The DH Comet had better safety than or similar safety to many other commercial passenger aircraft of a similar era_*
Douglas DC-1 99%
Douglas DC-2 47%
Douglas DC-3 30%
Douglas DC-4 26%
Boeing s300 72%
Boeing 307 70%
Boeing 247 48%
Boeing 707 20%
Lockheed Electra Turboprop 29%
Fairchild FH-227 30%
McDonnell Douglas DC-8 14%
Sud Aviation Caravelle 15%
Canadair CL-44 Turboprop 46%
Convair CV-580 Turboprop 22%
A comparison of more recent aircraft.
Accident losses comparison examples.
1970s - 1980s
% of total Aircraft built
Similar aircraft type, date / decade, useage, size.
Biz Jets
BAe-125-800 1.7 %
Beechcraft Beechjet 400 2.2 %
Cessna 550 Citation II 7.1 %
Learjet 35 / 36 12 %
Beechcraft 1900 6%
Dassault Falcon 10 11.5%
Aérospatiale SN.601 22.5%
Medium size jets / Turboprops.
BAe-146 5.1%
Fokker 100 6%
McDonnell Douglas DC-9-30 9.5%
Fairchild FH-227 30%
McDonnell Douglas DC-8 14%
Canadair CL-44 Turboprop 46%
Convair CV-580 Turboprop 22%
Beechcraft, Fokker, McDonnell Douglass, Learjet, Fairchild, Aerospatiale, Canadair, Convair companies defunct.
All Comets, including some Comet 1s, had full civilian use certification at some point after 1954, civilian use certification only being withdrawn after commercial flying stopped. Examples were flying until 1997 - one example did a signals research global circumnavigation flight series in 1993 via Australia virtually without a rest travelling 28000 miles, only had an ice warning indicator issue during the flights.
*The DH Comet - World Firsts.*
1st gas turbine jet powered airliner. 1st high altitude 8psi pressurised full fuselage length passenger cabin airliner, not a trivial feature as structure strength required for pressurisation considerably exceeded strength required for normal flying stress. Nobody else had done anything similar before the Comet.
The b-47 used 2 relatively small, heavily built pressurised modules (the aircraft where 6 had their wings fold up in 2 months while flying & some had their wings fall off while parked).
The 1937 Boeing piston engined airliner pressurised passenger cabin was pressurised to 2 psi only - in fact that could easily be done as the normal unpressurized fuselage cabin structure strength for flying stresses only was all that was needed to be adequate so no significant weight increase issues needed addressing.
1st all hydraulically powered flying surface controls & actuators airliner with under carriage wheel disk brakes + ABS.
1st jet airliner to cross the Atlantic.
1st jet aircraft to do a world circumnavigation flights series.
*Of course De Havilland had prior experience building many all metal construction airframe aircraft including thousands of jet powered fighter aircraft that were primarily of metal construction with pressurised cockpits & jet engines built by De-Havilland & we know the world's first all metal construction airframe airliner was built in England in the 1920s by Handley Page.*
*_De Havilland did indeed always work to better than industry standards at the time, no evidence of negligence ever being produced in relation to the DH Comet._*
The course of De Havilland & the general UK aerospace industry sector was not affected even slightly by the DH Comet.
*_Other interesting World firsts_*
_World's first turboprop aircraft._
*Vickers Viscount Turboprop Airliner 1947.*
*A 1945 Gloster Meteor Aircraft with Turboprop Gas Turbine Engine.*
They might like to answer these questions.
*Which airline has just ordered*
*60 RR England Trent XWB Engines*
*& What aircraft are the engines for?*
_Bonus question for 10 points._
Which country has the
*World's Highest Combined Per Capita*
*Nuclear + Defence + Aerospace Sector Activity?*
👍 Cheers 🙂 &
👍 & 🙂 & of course 😎 indeed.
Cheers etc.
_Toodle_ -PIP- *Old* *_Chap._*
. .. . ... . .... . .....
ixcxicvcixvxivx
@@petemaly8950de Havilland used aluminum skins half the thickness or other manufacturers.
And used an inferior alloy that was too brittle
@@sandervanderkammen9230
Kharzeestan Krappenz DiktorBummer Jurkzxoffenz etc & co - they should note with much awestruckness and great wonderment.
*Wrong.*
*_Larger stressed skin pressurised passenger cabin airliners needed thicker skin simply because they were often 3 x heavier with 2 x the fuselage length & 20% higher passenger cabin diameter resulting in 20% higher pressure differential hoop stress._*
Cheers &
😎 & 🙂 & Of Course 👍 indeed.
*_Toodle_* -PIP- *Old* -Chap.-
. .... . .... . .... .
xcvxiicvxcvvv
De Havilland apparently had a reputation in the industry for building fragile aircraft.
I believe the correct word is "souls" on board not "lives" ?
I expect right off the bat putting engines in an intergrated cowling loads up maintainence time, which the military has plenty of, but not so much civil aviation?
Pedantically souls can mean already dead.
@@waggyn Thats what I understood & offered the correction in a supportive way!!!
First time I've heard of this, here in South Africa the only flight disater that gets any attention is the South African Airways Flight 295 one.
One factor that contributed to a failure to detect this problem in testing was they would do overpressure tests and THEN do pressure cycling. The overpressure work-hardened the metal which made it relatively more resistant to cycles of loading so hid how early cracks would appear.