What Caused The Explosion That Crippled Apollo 13?
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- เผยแพร่เมื่อ 30 พ.ค. 2024
- 50 Years Ago Apollo 13 was preparing to launch on a mission that would become famous for the wrong reasons, 56 Hours into the mission an oxygen tank would explode, blowing the side of the service module and leaving the command module without power. However the details on what went wrong with the oxygen tank are often overlooked by stories which like to concentrate on the astronauts and the team in mission control during the rescue.
So here's now a handful of mistakes and seemingly safe decisions turned an oxygen tank into a potential bomb, and put the mission in danger.
More references on the subject:
www.hq.nasa.gov/alsj/a13/A13_...
history.nasa.gov/afj/ap13fj/p...
history.nasa.gov/afj/ap13fj/3... - วิทยาศาสตร์และเทคโนโลยี
Recently picked up KSP and today I saw for the first time that they actually put "flying safe" into the loading screen. Just the best
I like your name as well as “stirring oxygen tanks”
That’s been there since at least 1.2 and I love it: every time I geek out a little and thank Scott for getting me into Kerbal Space Program through his videos.
The updates to the loading screen over the years have been great..Nust little Easter eggs to streamers and TH-camrs
That is the most detailed explanation I've ever heard for the Apollo 13 failure. Great job, as usual Scott.
How about one million + parts flying in close formation.. supplied by the lowest bidder 🐒
Yes. I was 9 years old when this happened and watched and covered any info that I could find at the time even though I was to young to fully understand it all.
@@puremaga17 >>> A helicopter? 😜
You should read Jim Lovell's book Lost Moon/Apollo 13.
It explains in great detail, what happened with the tank, on the ground.
Before this, I thought I knew what happened. Turns out I am not too old to learn after all.
"Sir, we dropped the highly critical module, lots of brittle components in there."
"Nah, it'll be fine."
One element to this story which is present in Lovell's book, but which you didn't mention - and is worth highlighting as it's yet another of the coincidences and minor failures that contributed to the explosion. When they were attempting to drain the tanks using the heaters whey were also monitoring the temperature within the tanks - this should have meant they would have noticed they were baking it at 500C... But they temperature sensors and monitor they were using was calibrates only to go up as high as the 27C they expected the thermostats to cut out at. So when the thermostats failed, and burned off the insulation - as far as the technicians could tell, the temperatures were precisely the 27C they were expecting - not the catastrophic 500C. If their thermometers could go higher than 27C, they'd have immediately know the tank was faulty.
Just makes me thing of the Chernobyl series - "It's ... the maximum reading on low-limit dosimeters. They gave us the number they had...."
Dave F Ouch! The law of unintended consequences.
I know.... I knew this but forgot to mention it
Always design your stuff as if it will be hacked by somebody.
The temperature monitor only went up to 80F. They knew the temperature would be a little higher because they were using the heaters to remove the O2 but yeah, if they had a wider (higher) range on the monitor, they'd have seen that something was wrong with the tank shortly after the pad test.
A good case for when testing things, choose a gauge with a range high enough to tell you if things have gone catastrophically wrong.
i feel kinda proud for the humanity that we hit a million subscribers on this channel
Thats what happens when you provide quality content !
Gradatim Ferociter is very appropriate in this case
I agree with you, although I miss the old rocket intro.
Yes !
I feel like this channel deserves at least 100 million subs for such quality content, I find the fact that it only has one million very disappointing.
Remember kids, redundancy is crucial in systems that are truly vital. Just remember to route all three of your redundant hydraulic control lines right next to each other so the occasional stray turbofan disc going trough your aircraft has a chance of slicing through all three of them in a single go!
*DC10 references intensity*
Damn, that's exactly what I thought when I read the technical data books about all this stuff ! Happy to see I'm not hte only one !
@@Cby0530 lol
@@jjohnston94 It"s not funny. Hundreds of people died because of it. Worse than 737 MAX. I worked with one of the people responsible on a later project and it didn't seem to have hurt his career much.
@@dalecomer5951 It's called gallows humor and it's funny
The official report is really interesting. Any engineer should read it to understand just how simple things can add up to a huge problem. I always tell people they should read it but it’s pretty dry. This video is an excellent summary of events!
WDE46 I love reading reports like that! Dry or not they are the true source of facts!
If you like that kind of thing, check out some of the reports for marine and air accident investigations. I've read some from most english speaking countries, and they are enjoyable for the same reason, and the writing is usually very good, if formal.
@@svchineeljunk-riggedschoon4038 Or rail accidents as well ... it's astonishing how many are just a sequence of error after error after error. Of course, what that means is that just one error fewer, and the accident wouldn't have happened.
@@KaiHenningsen The US chemical safety board have some amazing videos here, like above, it's interesting how one small thing can quickly snowball into a disaster.
SV Chineel, Junk-Rigged Schooner Sailing Hi! it’s funny your name is similar to one of the sailing channel i follow, i seem to follow a lot of sailing channels! Yes I quite often read the AAIB bulletins. The Air Safety Institute channel is very good.
I worked for the company that built that thermostat that welded. The design engineer for the thermostat line had the same picture you showed on the wall of his cube as a reminder that limits are not to be exceeded. That example was used when customers would call and ask if they could be used at higher voltages/currents. Nearly all of the people who were working at that time had retired when I started, I wish I could have gotten first hand accounts of the aftermath.
so it happened much slower then the movies shows it happening🤔🤔
But, the cryotank in Apollo 13's SM was originally installed in Apollo 10 and removed for test anomalies. When it was refurbished and installed in 13, North American Rockwell neglected to swap out the thermostat. The voltage tolerances had changed since 10.
I wonder if Lee Atwood tore that technician a new asshole.
@@dalethelander3781 if not he should have
dramatizations are like that. the movie "margin call" portays the 2008 financial crisis as if it happened overnight, when it reality it took months, I think.
It happened during 2007, there were a lot of articles detailing the house of cards that was starting to fall. It was the first time I read "trillion dollar loss"
I can’t believe fire in space look exactly the same as that in Minecraft
Where do you think Minecraft got their fire animation from?
@@privateer_am That's a stupid statement there kid.
@@CaseyFinSF
are you joking?
@@Killbayne Dont feed the troll :)
@@CaseyFinSF woosh
10:08 everyone gangsta til service module 106 gets hit by a ghast
I thought I was the only one to notice that the fire is from minecraft textures lol
8:50
"Houston, we've had a problem here"
Movie: Catastrophic explosion, shock from crew, drama
Real life: 80's freeze frame and festive steel drum flourish
Can't you go over all the changes in Apollo 14 that never gets talked about
See @11:15 - he mentions these briefly.
++Apollo
Did they redesign the CO2 filter assemblies to be the same shape and size?
@@georgeemil3618
As far as I know: No.
The Apollo hardware was a steady flow of already built hardware. You do not want to include major structural changes as long as you absolutely do need them.
A13 has shown that it is possible to build an adaptor even when in flight. If I had to make the decision, I would say: good enough.If you absoultely insist, construct a prefessional adaptor and put that on the packing list, but otherwise: don't change a working system unless there is a good reason to do so. After all this was in accident, which should not have happend in the first place.
@@kallewirsch2263 Major structural changes were made to the SM for the J missions to accomodate the SIM bay.
I can only imagine what the astronauts would have been thinking when the service module blew out! Disasters in space are scary stuff. Kudos to NASA for bringing everyone back safely! This mission is probably the most incredible point in the entire space program. Thank you Scott for explaining how it all happened in a way that's so easy to understand!
Well, their immediate response was, "Huh? What was that?" There's a few different things that can cause jolts in the spacecraft and in reality, it took them quite a while to begin recognizing the severity of this issue. They had been dealing with the problem for about 90 minutes before they realized that the command module was beyond saving and started powering up the Lunar Module.
Trumann sent north American. Rockwell a gag bill for towing the CSM back from space
There was a temperature gauge on the launch pad to display the temperature inside the O2 tank heater assembly. During the boil off process the temperature inside the tank heater got up to more than 500F but unfortunately the temperature gauge only went up to 80F. The gauge was pegged all the way up to the top at 80 and so no one realized that the temperature inside the tank heater was up so high that it was damaging the insulation on the wires.
That's something I forgot to mention
@@scottmanley Giving credit where credit is due - nice Scott👍🏼😄
I guess look on the bright side - the o2 tank could've exploded during launch to orbit instead of afterwards when it did
@@opl500 It wouldn't have exploded that early in the mission anyway. It was too early to stir the tanks. From what I've read the latest in the mission that it could have exploded and the crew might still have had a chance to survive was the beginning of powered descent. Once a sizable portion of the fuel in the LM's descent stage was used up they wouldn't have had any way to get back out of lunar orbit.
@@joevignolor4u949 I'm confused...what has the amount of fuel in the LM got to do with the O2 Service Module tank exploding???
The LOX tanks were made at a Beechcraft plant north of Boulder ,Colorado. I knew one of the engineers and he gave exactly the same explanation. Well done it is rare these days for any media to get a story right by doing their homework such as you have. Well done Sir !
Scott is a valuable human resource.
Live Safe
mVm
mVm MotoVlogMusic You mean “fly safe”
wow that was A lot of detail that I have never heard before. Great video Scott thank you and stay safe.
I was a kid, was all over ever aspect of Apollo. Kepy an eye on it over the years. I am now 60. NEVER have I heard any detailed explanation of what happened, how and why. Also. You are scary smart. You smoothly went through every engineering detail like you built the tank and system. You have filled in an important blank of what happened in my youth. Very Impressed.
One design deficiency was also that both oxygen (and hydrogen) tanks fed the fuel cells over a common manifold. No isolation valves, no check valves. You have one leak anywhere in the system, you will loose everything. If there had been the possibility to isolate the faulty tank, the outcome would've been less dangerous. Yes, the moon would've been lost. But there would've been enough oxygen in the good tank to return home. They later changed that for the J- missions and AFAIK the space shuttle not only had check valves between the tanks and the manifold, but also the possibility to switch to 'split plant' operation, i.e. feeding each FC from its 'own' tank and isolating them from each other. I still don't get why they didn't implement that in the first place. They used statistical methods to determine how often a system would fail in a given number of times, but overlooked that interconnecting independend units increases the failure rate. Strange...
You would think NASA would have learned about planning for equipment isolation after Gemini 8. That has always bothered me.
Bad teflon ruined my morning eggs so many times...no wonder they had problems with it on Apollo.
Not supposed to use metal utensils. And I’m only guessing that’s what caused it.
"But at 50+ atmospheres of pure oxygen..." yeesh
Doesn't seem like a highly unusual partial pressure for oxygen by itself. Diving equipment has a partial oxygen pressure (gas mix pressure x concentration) of 40bar when filled with air. But running electrical equipment in that environment is a different thing, of course...
@@Kenionatus Air & oxygen are not the same though.
I'm not exactly familiar with the explosive properties of pure oxygen in liquid form but I imagine it's extremely dangerous.
50+ atmospheres would not be 50+ psi but 50 x 14.7 psi, right? Somebody explain.
@@lawrencequave8691 1 atmosphere =1 BAR = 14.7 PSI
I’m surprised ground wasn’t monitoring heater current when they decided to use the heater to drain O2 tank 2. If they had been they would have seen that the heater was not cycling as it should have been, and probably caught the problem there. Alternatively, as has been mentioned elsewhere in the comment section, if the tank thermometer read above 80 degrees that most likely also would have worked to catch the problem. Of course with the benefit of hindsight it’s easy to be critical. The steps the crew and ground support took after the accident occurred were nothing short of incredible, and really spoke to how well they worked together and knew their spacecraft.
Current is not that easy to monitor when your ADCs weight at least 300 grams.
The thermostat wasn't able to read above 80.
@@TheCrackedFirebird I feel like I have heard this before but with radiation... Not great, not terrible.
@@TheCrackedFirebird Why would anyone need a thermostat to go higher in a cryogenic tank?? Of course, what's not really been said by others is that it's remarkable that the tank didn't halt and catch fire duing the draining and refilling. It's a real testimate to just how astonishingly well built the damn thing was that it managed to get as far as going into space. It's just a bummer that's the time when it choose to go kaboom. Equally astonishing is how well built the rest of the CM/SM that it survived the explosion and that it was able to be restarted after several days in a deep cold state - frankly the most frightening line in the movie after "we're venting something into space' is 'like driving a toaster through a car-wash'.
@Bobb Grimley Thanks Bobb, glad you're out there checking the internet for mistakes. Funnily enough, my spellchecker tells me that there is no such word as 'Bobb' either. Just in case you want to let the person who named you that they made a spelling mistake too.
i never thought all those years ago when i was trying to get into orbit on the free version of KSP that i would still be watching your videos in the next decade
I challenge you to find an orkier space repair job than Apollo 13.
"Oh no, vital systems of the ship blew up!"
"Don't worry, we have some cardboard, plastic bags, and duct tape! We will be fine!"
You do realize those are two separate problems they had to deal with, right?
@@yes_head I was also talking about orks. How much do you think I cared about precision in that instance?
Nazamroth oi yu dum gitz! Da air fingy blowed up! Git tha fixer tape n baggies
You must not care about "precision" at all, given you misspelled "orcs", not to mention, you have them consulting with NASA on how to fix engineering problems during spaceflight....
Lame attempt at humor...
Try again.
@@codymoe4986I believe they’re referring to the Orks in Warhammer…
I just finally watched the movie yesterday, because of you mentioning it. And I was really curious about this, of course. Excellent timing.
I already knew what caused the explosion on Apollo 13 but I also knew that I'd learn a bunch of new and interesting details by clicking on this video because it's Scott Manly!
Well, I never really understood what was the cause of the explosion. Now I know, after 20 yrs! Thank you Mr. Manley!
The cause was bloody stupid penny pinching. When the damage to the tank was discovered, it should have immediately been tagged as defective then cut apart to see what all had been affected by the impact.
I was literally just looking for more info on this yesterday. Like a video of what stirring the tanks was like.
Ya, I thought they just shook them up and down.
Lovell/Kluger's explanation of this in the book of Apollo13 is almost as complete but contained one extra titbit you didn't mention: The pressure gauge.
When the thermostats stuck shut (ohm's law - double the voltage, double the current, quadruple the power) to boil the LOx off, the pressure gauge should have alerted them that it was way high. The problem was the gauge topped out in normal use meaning the most basic way they could have detected this failure eluded them.
The lesson here stands true in anything with a gauge: Always make sure the gauge can read higher than you expect it ever to need to!
Thus endeth lesson 37 in the gospel of engineering according to me....
Lovell did also mention they duplicated the whole thing on one of the test flight articles. I hope they didn't throw away the recordings of that event.
Captain G should take an engineer to realize this tidbit. But it takes an engineer to reason his/her way out of using an overly capable gauge
So "Not bad, not terrible" strikes again.
Exactly right. Michael Crichton actually took inspiration from Apollo 13, I think, in the Jurassic Park novel: The motion sensors were programmed to make sure none of the dinosaurs had escaped so it topped out at the number there was supposed to be, but they also should’ve programmed them to make sure there weren’t more.
Let's not forget the bean counter, down stream, who gets a deal on a cheaper gauge...
Thanks, Scott. I really enjoyed the detail and clarity.
I always love the pictures/videos you're able to find to compliment what you're explaining!
Scott you're just awesome. Thanks for going into such detail and helping us forget our current situation.
I don't always test my rockets. But when I do, I do it in space.
George D. Marsack hopefully you mean in ksp
Just started watching but had to get my up vote and comment in to help you in the algos since the video is only 30 minutes old.
.... and this is one of my favorite of your videos. Love this deep dive!
Scott, thanks for this video (and all of your others) a great description of the events. Well done and easy to understand
Fantastic explanation, Scott. It's good to hear what really happened; that it wasn't just a 'spark' in the cryotank.
A spark in the cryo tank would been catastrophic?…
Най-краткото и най-точно обяснение на случилото се с Аполо 13 .
Както винаги страхотно видео .
Respect.
I have no engineering background at all and found this engaging and fascinating, not to mention well-explained. Scott, thank you for your service to the rest of us who love space (and space history) but didn’t go to MIT.
Scott, congratulations on 1 million subs, you deserve it. Thank you for this outstanding channel!
VERY well researched Scott. GOOD JOB!
when he adds the minecraft fire you know hes cultured
Ground work: Empties to 92%
History: Close enough, its not like this is rocket science.
😏
They should have replaced the tank right now and there. Who ever made the decision to proceed with that tank is a retard.
@get to the Choppaa really?!? wtf
@get to the Choppaa And the flight manager that didn"t want to bother her boss at home on a Saturday when they thought they might have a problem from the external tank foam hit on the wing of Columbia and then sleep on it over the weekend while neglecting to inform the flight crew of their concern.
The faults of man. I believe political and financial pressure on the launch had a role to play in all this. Given the incredible complexity of the build, I imagine there were only a few that could do it without damaging something else.... But then again most engineers, managers and others think those of us who turn a wrench are replaceable; "whatever you were doing can be done by somebody else" attitude. What's clear to me is someone knew there was a problem with the tank and chose to rely upon the backup procedure for the primary.
This is great thanks - feel like I’ve been waiting 50 years for a good explanation like this.
Scott, thank you for keeping me entertained in these times of isolation! Fly safe.
Thanks for the great videos in are extremely boring lockdown. fly safe people
I never really thought about the fact that the failure on the O2 tank was in fact caused by a piece of hardware that was later determined to be unnecessary.
Jason Gibbs Wrong, the fan/agitator wasn’t necessary, the heating element was still required to maintain the pressure at super critical equilibrium
Wow! Never found an explaining that was so detailed and well presented! Great job as always!
This channel might end up being my favorite channel on space and one of my top 3 channels on TH-cam in all categories. Definately the best walk thru of Apollo 13's tank issue. Thanks.
About 30 years ago, when I was working for IBM in the UK, they had an all-site meeting at a local convention center, and the guest speaker was none other than Jim Lovell, commander of Apollo 13. Whatever IBM had paid him to be there, it was money well spent. He gave an enthralling and inspiring account of the mission and the entire audience was hanging on every word.
Wait so the tank failed a test on the ground and they just said "send it"?
and even before that they were fine with using a suspected damaged ox tank
.. and it failed multiple tests. lol
Same could be said for the Challenger. These folks are under such immense pressure to launch or pure ignorance, they jeopardize everyone's lives.
VaporheadATC Yeah NASA has way too many managers in management!
It's easy to criticize in retrospect, not so much when you have an entire multi billion dollar government program and agency breathing down your neck and the eyes of the world watching your every move with bated breath.
Scott, that’s the best explanation of this event and the lead up to it. You should be really proud of your work. Many thanks
Saw the Apollo 13 capsule at Hutchinson Kansas. Absolutely insane detail
Imagine damaging life-critical equipment and then putting it into crewed space vehicle anyway. What is this, soviet union QA standards? Pretty sure they had better. Geez.
It was nothing personal, just business
EXACTLY
Imagine Apollo 1 where everyone died.
Well, Soviet Union/Russia had the same number of deadly incidents in their crewed space program with an almost order of magnitude more launches.
Ah yes, enslaved oxygen breaking free.
Thank you, for the laugh.👍
"The only thing we have to lose is our carbohydrate chains!"
Thanks Scott! This was one your most interesting videos - can't wait for the next one!
Great video Scott! I love getting ready in the morning and getting my space fix all at once!
I guess it's like aviation - fail to dot enough i's or cross enough t's and you're hating life.
but it's always the missed dot on the lower case j that causes the REAL problems
@@bumrocky Or the missed bar over the R
@@moejoe987654321 which rocket was that? I forget..
@@igvc1876 The Mariner 1, I think Sotty boy has a vid on it
Its because Tom Hanks was on that mission
I thought he was landing an airliner in the Hudson River that day.
Never put Tom Hanks on something involves flight, or you might end up stranded on a deserted island, having to land your plane on a river, getting stuck on the airport because your home country no longer exists or almost dying in outer space.
@@jackmcslay don't forget cargo ships. In fact, don't let Tom Hanks be in charge of anything.
What happens if we put Tom Hanks and Matt Damon in the same movie?? (Again?)
Wasn't he in Australia filming a movie on a corona-like virus when he caught the corona virus?
Well done! Detailed and informative with nice illustrations. Thank you, Scott.
Thanks for that Scott, superb detail as ever!
The BBC are doing a podcast series on this called ‘13 minutes to the moon’.
www.bbc.co.uk/programmes/w13xttx2/episodes/player
Cool, that will keep me occupied for a few hours, thank you!
@@621Lafayette Yes, agreed this is an excellent podcast. Season 2 is Apollo 13. Season 1 is the moon landing. Both are very good and highly recommended.
My wife is supercritical, she puts me under immense pressure...
hey, as long as there's no surface tension you're good
Check your wiring.
Scott, your video is the best technical explanation of the Apollo 13 oxygen tank failure I've ever seen. Thank you.
A great further (more detailed) insight into something I've been "studying" on & off for about a year now, out of total fascination for the Causation Factor(s) of the explosion. Thanks Scot. Great work.
I love how you say mun instead of moon.
10:10 Minecraft fire animation
I keep re-watching videos that I know I've liked, and finding that I have to like them again. All your videos too.
This was much more detailed than most other videos. Thanks!
What a coincidence, just recently watched the 90's film starring Tom Hanks about this incident.
You mean the alleged pedophile?
are you going to do all the tragedies that NASA/Roscosmos had on their respective anniversaries?
eisenklad That would be great!
Challenger is still too much for me, it makes me sad and it pisses me off because people could have been saved that day, just like Columbia ;_;
@@GoldSrc_ i was thinking of Gus Grissom/Apollo 1 . i'm not even American but that death was pure horror.
he avoided drowning when the hatch to mercury capsule blew off... only to die in the gas that keeps people alive while on the launchpad
@@eisenklad Yeah, Apollo 1 was horrible, and the capsule had lots of bad design choices, like a hatch that opens inwards and held close with latches, which made impossible to open with the higher pressure inside as well.
Thank you for bringing these details to our attention. Great job.
fantastic. i love learning about this kind of stuff. love all the photos, too. thanks for the great video!
I was in an audience with where Jim Lovell was the speaker. True or not he said that they found that someone had dropped one of the components during construction and thats what caused the problem.
John Cheresna Lots of holes lined up for the problem to occur!
So if the oxygen is in a supercritical state, how do you measure the fullness of it?
Both pressure and temperature measurements work as usual, leading to the usual routes to calculate how much gas is present.
And mass.
Methods that can measure mass is quite impractical in space I would presume. To use gas formulas would implies that one needs to measure the density directly?
Temperature and pressure are commonly used to determine operating mass even in situation where there are mixtures of vapor and liquid. Or even mixtures of differing gasses.
Yeah I got a brainfart there, totally got the ideal gas law backwards. Given a fixed volume, one DO get to calculate density directly from temperature and pressure. My thermaldynamics teacher would probably strangle me for that lol.
A very clear, enlightening video. Thanks, Scott!
Good Breakdown of the Sequence of Events that led to the Tank Failure.
Comments: 8
I can count at least 23
Prove it.
It's called caching. TH-cam doesn't keep all stats up to date for everyone equally.
First!
*second
An incredible story with the engineering details I always wanted. Scott, you are a master!
Clearest explanation of this problem I have ever heard.
In the 80’s I attended a 5 day Configuration Management course for military hardware. Th presenter was American who was a CM manager on Apollo. He claimed that the burning of the insulation was effectively a CM failure, as the tanks had been changed, but the test procedure was one version behind, and had put too much voltage in. He claimed the design change made the insulation thinner. Your explanation is much more detailed than his!
Brilliant summary Scott!
That was an excellent explanation of events. Thanks Scott!
Excellent.....no waffle, no padding....just concise, clear explanation. At the time, I listened/watched every minute of the drama. At one time, real doubts of survival were intimated, and we all held our breath. Mission Control's finest hour.
An excellent rundown that I've been waiting to hear since the words "We've got a problem" were spoken. Thank you filling that long standing gap.
this is the best explanation I've ever heard, this is amazing! Thanks Scott!!
Always great information from this channel.. thank you Scott. 😁👍
Great video with detailed explanation. Thanks!
Thank you for a great explanation of something I have wondered about my whole life. I was a little boy when it happened. Everything I have heard about it since then has left me with more questions than answers. Thank you for finally clearing things up.
Yes, that's the most comprehensive account of the catalogue of failures that led to the catastrophic explosion of that tank on Apollo13. Well presented.
Such a fascinating recount/explanation. Like any accident- there are almost always a myriad of small errors leading up to the incident. Very cool
That was so detailed and informative. Thank you!!!
Is it only me who's Scott's 'Fly safe' - really makes me comforting ;)
Great work Scott! Love your work👍🏼
Another fantastic and informative video, thanks Scott!
Great video Scott! Love your channel
Thanks a lot !
I've read a lot about the origin of this explosion but the all process remains unclear to me.
Your explainations are awesome.
Fly safe !
Always excellent videos! Thanks!
What a great story! And told in such elegant detail. Thanks, again.
another great video and so informative,well done and thanks Scott.Bill