Bloody great. As an aircraft maintenance engineer ( Airframe / propulsion ) I really enjoyed this video. I had no problem when studying this subject which we called the theory of flight in training. I enjoyed anything like this and also theory of flight in helicopters. A subject young man you might like to add one fine day. I should point out that the training I am talking about was in the late 60's early 70's. Then we had no graphic video tools like this, and a lot of our training was done using models, illustrated drawings, but most important the retired aircraft that occupied our training hanger. These included several Hawker Hunters, a couple of De Havilland Chipmunks, the whole tail section of a Hardley Page Victor bomber, and a Westland Whirlwind. As I said, it was a long time ago.
An Airbus is flying 30,000 feet in the air at 200,000 mph. Suddenly a eurofighter jet pulls up and slows down beside it and radioes it. “Boring flight, huh, Airbus? Watch this!” The fighter proceeds to flip upside down and speed up, breaking the sound barrier before corkscrewing to skim the ocean, and coming up back beside the Airbus. “What’d you think?” The Airbus pilot replies, “Not bad, but look at this.” The Airbus proceeds to fly straight for the next five minutes before the pilot comes on the radio again. “See?” The fighter pilot is perturbed. “I don’t get it, what did you do?” “I got up, stretched my legs, went to the bathroom and got a cinnamon bun.”
Or just fuck it, and add Vernor thrusters everywhere makes look more badass when maneuvering, and can also maneuver in high atmosphere, or even vacuum because why not ?
Or dihedral angle, this naturally levels the aircraft. I built an F-104 Starfighter in KSP, the short and low wing design made it very unstable (in terms of stability). I usually use longer wings with winglets pointed up for stability
Being an aerospace engineer myself I don't like how this vid mixes up static and dynamic stability issues without a proper explanation of both, which results in a vague, undefined "stability" being used. It's a lot more to digest though, considering a ~12 min production. Worth to notice is that statically stable aircraft might be dynamically unstable. Other than that, as always, great work. Keep it up. ;)
imizia pretty sure no plane is designed to only be statically stable, and that no design is truly “dynamically stable.” Planes are designed to be stable at expected accelerations
@@FoxtrotGolfLima Not entirely true. Yes, stability and control analysis is based on flight envelope and sizing data, because the product still needs to fly and be fit for certification. Certification specifications (at least for airliners, I don't work with military) allow for the spiralling motion to be dynamically unstable provided that time constant is sufficiently big (meaning the response is not abrupt).
@imizia Nice to see a colleague here, greetings from the Czech Republic!🙋♂️ I had exactly the same reaction to the ‘static’ stability thing. Another ‘oh dear’ came along with the explanation of how the stabilizer works. At first I was intrigued - I never considered downwash to be a significant factor in static stability (qualitatively speaking) and was looking forward to some eye-opening revelation - but sadly nothing came of it. Still really good and informative video though.
To those who are interested in the stabilizer explanation: Increase of angle of attack (AOA) of the airplane causes increase of AOA of the wing as well as of the stabilizer. Regardless of the empennage design. Classical, cruciform, T-tail - doesn’t matter all that much. The trick is that the stabilizer is set in such a way (by negative angle of incidence and/or upside-down airfoil) that in the usual range of airplane AOA it produces negative lift (downforce). When airplane AOA increases, it increases lift of the wing as well as of the stabilizer - but since the stabilizer lift is negative, its increase manifests itself as decrease of the downforce. Thus, letting the airplane pitch down - against the increase of airplane AOA. When airplane AOA decreases, the same happens, only in reverse. About the downwash - it affects AOA of the stabilizer, always. The airflow is affected by the wing pretty far from the wing itself in all directions (at subsonic speeds), so you don’t get rid of the influence by putting the stabilizer on top of the fin, that’s not far enough. When AOA of the wing increases, the downwash angle increases as well, which reduces AOA of the stabilizer - therefore the increase of AOA of the stabilizer will be smaller than the increase of AOA of the wing. An example: L 410 UVP-E airplane with high-wing and cruciform tail gets about 0.55 degree of stabilizer AOA per 1 degree of wing AOA, while L 610 G airplane with high-wing and T-tail gets about 0.7 degree of stabilizer AOA per 1 degree of wing AOA. So, the effect of downwash is significantly weaker with T-tail, but it definitely isn’t eliminated. And as long as increase of wing AOA doesn’t cause decrease of stabilizer AOA (which might be physically impossible), the described principle works and provides static stability in the pitch axis.
Oh and the center of gravity (CG) position is also pretty painful for any aviator out there 😁 Explanation for those interested: A conventional airplane (like that in the picture) will usually have the CG aft of the wing lift, not forward. Usually both wing lift and stabilizer downforce pitch the airplane up, they don’t wrestle each other. What causes the airplane to pitch down then? It’s the part of the pitching moment that is not caused by lift and downforce. It’s pretty much always present and pretty much always pushes the airplane to pitch down. Most of it is caused by the wing due to its nonsymmetrical up-cambered airfoil.
The eurofighter is like a aerodynamically insane aircraft. It’s controlled by so much processing power that is make Linus Tech tips setups look like a celerons
Within a few points, Yes On most of the European Delta canards (Typhoon, Gripen, Rafale) the deflection of the canards is what makes them so unstable The airflow disturbance over the top skin of the wing radically changes the centre of lift It is why in high speed maneuvers the Typhoon's canards can actually lock in place
Yeah. I read somewhere that the canards are also computer controlled so that their radar cross section can be reduced, but I don't know if that claim is true.
This is very interesting. As someone who flys models, we move the cg to adjust pitch sensitivity. A forward cg, typically 15% of the wings chord, makes the model very stable and easy to fly. An aft cg, typically 25-30%, gives high maneuverability but at the cost of stability. Any further back and the model becomes impossible to fly as a tail heavy plane will attempt to to a backflip if you look at it funny. This is different to what you maneuverability as we can easily move the cg of a model with weights but a full size aircraft has its cg set by it's payload and design. Thanks for the in depth video and awesome graphics 😁
@@fenrir834 I only run far aft cg (30%) on my crazy tiny stunt plane, everything else is about 20% which gives a good mix between stable and high maneuverability.
@@doctaflo it doesn't need a comma. Comment section is the noun. That's just like saying "Don't think you're smarter than me Kyle." You don't need a pause.
That's a bit of disservice from the engineers who designed it with far less digital tools than today. The X29 was more of an experiement on supermaneuverability. The control system was successful but it proved that due to the extra stress on the wings due to the forward swept design, it had to be heavier. A later plane, the x31, proved that thrust vectoring could contribute to agility so it was used in the F22.
hi O F D... ' american was first made pretty plane X-29 with the single jetmotor... later ussr russia copy steal to make su-47 with 2 jetmotors from X-29
@@shaider1982 F-22 tails move faster than the nozzles, so not more agile. It uses thrust vectoring largely for supersonic trim drag reduction. The nozzles help maneuverability, but it is plenty maneuverable and agile without their pitch assistance.
I just found this channel last week, and the timing is perfect. My son is just off to college to start a dual major in MechE and Aero, and I've advised him to watch as many of these as possible. If that weren't lucky enough, I've also become interested in developing some motion graphics and technical animation skills, and this channel is a perfect example of what I'd like to be able to do.
Wait until your aerodynamics classes an then you notice that you know nothing hehehehe, but if you do understand the aero classes , you'll have to understand the stability and controll classes too hauahaua. Good luck and I hope you become a great aeronautical engineering too
@@tadferd4340 that's actually possible in KSP, I have a design that can pitch 90 degrees at 900ms without losing wings, but pulling off such stunt means knocking out Jeb and losing most of the speed
Hey, I have been wondering about how engineers go about Optimising existing technologies. I would love if you could compare two generations of piston engines and show where more power and efficiency is produced, that would be awesome.
Take your pick and google it. Going from flathead which was easy to produce to OHV which had better flow and was less prone to overheating. Going from OHV to DOHC which allowed engines to flow even better and allowed for higher revs so small engines could produce lots of power as well as be fuel efficient when driven lightly. The introduction of direct fuel injection which allows carefully controlled lean burn which produces more power for far less fuel.
@@Bartonovich52 but wasnt the disadvantages of DOHC is got less torque to produce than OHV ? Thus makes them equal in technologies but different in purpose ?
@@megimargareth4015 no, DOHC doesnt make less torque than single ohc or pushrod engines, its just a trend that manufacturers who value the pros of developing DOHC dont value torque
I always love this channel as you bring forward the knowledge of aviation that has never been shared to the public unless they became pilots or areo engineers because it seems too daunting!
Always love the ball and hill analogy. It's such an easy and fun way to visualize concepts, whether it'd be kinetic and potential energy or stability problems like in this video.
@@jahedali1127 Don't forget what lay beyond that wall, Lest they trap you when you fall. Don't give up your life and balance, This be a warning to help your stance.
@@martijn9568 Exactly. Plus the engine failure isn't even the immediate cause of the uncontrollable stall - it's the loss of airspeed. And the loss of airspeed is of course caused by the engine failure, probably combined with hard maneuver (near-stall, high drag situation requiring a substantial amount of thrust to push through).
The angle of attack explanation at 5:32 doesn't seem right to me: angle of attack is defined relative to airflow, not the ground. If the plane were to descend through still air (in relation to the ground) then the angle of attack is would be the same as if we were flying level with the ground. Thus there should be no stabilizing force in relation to the ground. Am I missing something?
A bit oversimplified. Pitch attitude and angle of attack can be mistaken. For example, in straight and level flight you can be at lower AOA than in descent in landing configuration. In climb you can have lower AOA than during descent depending on configuration and what you do with an aircraft.
The explanation is incomplete. The speed is what affects the angle of attack. As the plane drops in speed the wings produce less lift, making gravity a more significant component, increasing the wing's the angle of attack, and lowering the angle of attack on the horizontal stabilizer.
You are correct, although there is the lagging effect of the velocity climbing as you pitch down that he is describing that would be technically correct, but not nearly as important as the angle of attack immediately after a gust of wind or some other force pushes the attitude of the plane off center. A much better analogy is an arrow and the quivers, or a shuttlecock in badminton.
According to a Grumman engineer who worked on the program the X-29's instability came from it's canards, not the forward swept wing. It was quite safe too with both analog and digital slight control systems. And for unstable aircraft the tail produces lift to push the nose down, not downforce to push it up.
Nicolas Sousa they were retired by the US Navy in 2006 I’m pretty sure, so no. They destroyed most all of them except for a few non-airworthy examples to prevent parts from being smuggled to Iran
@@furinick No longer, in fact, the plane that replaced the F-14 (F/A-18A/B/C) are slowly getting replaced by F/A-18E/F and/or F-35. The F-14 are basically two generations behind the top US naval fighters, and US military don't really keep plane that old for long, with the exception of B-52 and U-2.
Everytime I see your video I relate to my graduation Mechanical Engineering course and it feels good to be able to relate it! Particular to this video studied this topic of gyroscopic and aerodynamic stabilization in Design of Machine Elements 😊 Edit : Thank you to you too @Real Engineering for making learning interesting! 😃
This was the first time I've ever purchased something from an intra-video TH-cam ad. Those double sided moleskin graph paper pages are EXACTLY what I've been looking for in notebooks for years. I immediately bought two. If you do consider doing a reprinting, please look into offering a native left-handed option. I usually start notebooks writing from the back in order to make it more ergonomical, but that means page numbers are upside down and count backwards. However, I'm probably only one of maybe a dozen people that do this, so it's understandable if it doesn't make economic sense to create a whole print of left handed notebooks.
I am currently a ATPL flight student, and this was such a great revision of the Principle of Flight topic Stability! Thanks a lot! Keep it up with videos like this or the one before! 👍🏼
As a child, we had dime store balsa airplanes, that we flew by throwing them into the air. They consisted of 5 pieces--- the fuselage, the wing, the stabilizer, the tail, and a metal clip. The first four were simple...put them together, and you have your plane, or what looks like one. BUT, that metal clip was necessary. It was thick, and had weight. I now know it gave the plane a center of gravity where you put it. The plane behaved differently when placed in different places. As I recall, when placed forward, it would do great loops. Which was great. Placed more centrally, it would fly nice and level and go a long way --- boring, plus you had to go get it.
great video. I'll throw in some bonus facts about the F-16 since i've flown some flight sims in it (bit i am not a pilot). Because of the issues an aerodynamically unstable (or "relaxed stability aircraft") aircraft has with the center of lift moving forward as the Angle of Attack (AoA) increases, this creates a feedback loop where as the AoA increases, upward pitch increases which increases the AoA. This quickly gets out of hand to the degree that no pilot can reasonably control. To deal with this the F-16 makes use of a Fly-by-wire system. Unlike other aircraft (F-15, F/A-18) the F-16 is purely fly-by-wire, there are no cables nor hydraulic backups for manual control should the system go down, or the aircraft lose power. This is because again, there's a basically zero percent chance of a pilot controlling the aircraft without the flight stability systems. Being a single-engine aircraft this is naturally of some concern since loss of engine would mean loss of power and absolute loss of aircraft control. To alleviate this the F-16 has an APU which lasts about 10 minutes to provide power to the controls. In event of a minor engine loss where the engine may be able to be re-started, the F-16 actually can restart the engine with its internal starter (a fairly uncommon feature in US aircraft at least). While this fly-by-wire system is needed to be able to fly the aircraft at all, it also had a huge benefit of doing most of the work of flying the aircraft for the pilot. In flight sims i was able to take off in the F-16 (unladen) on my first try after watching a video tutorial, and reading a manual. The landing was iffy and i ended up going off the end of the runway because i touched down late, but the aircraft can only do so much for the pilot. One of the biggest advantages of the flight systems is how they prevent the aircraft from entering a stall -- supposedly a pilot is more likely to damage the control stick than they are to induce a stall from turning the aircraft. Finally, the flight stick is somewhat unique in that it originally did not move at all (with the more modern ones moving very slightly). The Control stick registers the force applied and uses that for control inputs. This is much faster than a joystick using potentiometers and a spring to return it.
Also the F-16 put the flight stick on the side of the aircraft to make it easier to control, the F-16 pioneered many things, intentional instability, full fly by wire, and flight sticks to the right side instead of the center.
This was an awesome video. Actually explains the phrase told to us in ground school "moving the CG aft increases performance." Although now that I think about that more, that was in relation to fuel economy, so maybe not. Oh well, great video.
That plug for the notebook was smooth! But honestly I did use your vid on the X29 and swept wings to write a 20,000 word research report, including some wind tunnel testing. Thank you so much for referencing your sources in the description! It may seem pointless but it gave me many sources of inspiration to start, and save me a ton of time! You're amazing!
@@UnicaLuce Nope, if CoL is in front of the CoM when flying forwards, then it's behind it when flying backwards. If you have >1 TWR, you can use this to stabilize the fall and land on your tail.
I have designed multiple aircraft. The Center of Gravity is NOT in front of the wing. Typical location of the CG is about 0.3 to 0.4 of the average chord position behind the leading edge of the wing. Placing the CG too far forward (such as your video indicates by putting it in front of the wing) causes a huge loss of efficiency because the horizontal stabilizer and the elevator needs to generate a huge downward moment thus creating a great deal of unnecessary induced drag which wastes fuel. If the CG is in the 0.3 position we get an ideal situation where the horizontal stabilizer / elevator combination is in neutral position for level flight thus requiring minimal drag to fly. If the CG is moved further back, less command authority is necessary to control the plane but also makes the job of the pilot harder. The CG should never be put back more than 0.4 without a fly by wire system as the plane would be uncontrollable by manual means. You might want to do a video about the quest of fuel efficiency leading to a very famous accident in a DC10 cargo plane where the tail surfaces were trimmed smaller so as to achieve greater fuel efficiency but this led to not enough command authority at slower speeds during landing. In this particular case, the DC10 bounced 3 times then broke up because it was landing at too slow a speed. The size of the tail is often a tradeoff between low drag at high speed (when you have plenty of command authority even with very small tail surfaces) and the need for command authority at low speeds (where command authority is low and there is a need for larger tail surfaces). As with many things, environmentalism comes with a price in human lives. Things that save fuel and energy is often paid for by the loss of human life. Another place you may want to look is at the Reno Air Race where P51 D Mustangs from WWII are typically used with tail surfaces trimmed smaller in order to reduce drag at the risk of too little command authority during landing.
Actually Boeing does build an intentionally aerodynamically unstable airliner and it's not the MAX it's the 777 this video is wrong they exist and it's not unsafe
This is like commercial, every day cars vs super cars or race cars. Your everyday car will have the wheel alignment “toe-in” to make the car more stable (it will correct itself to drive in a straight line),while race cars usually have it “toe-out” to increase cornering performance.
Excellent and simple explanation. The term typically used is “relaxed stability” since many fighters do have static stability, just not what is required for safe and controlled flight. That is, the design will return it to straight and level with light maneuvering, but rapid maneuvering would cause the aircraft to tumble before the stabilizing forces could act. Another thing you touched on is roll stability. There is no pure roll stability because an aircraft has no idea which way is down. Roll stability is based on slipping the airplane and is called “slip-roll” coupling. The idea is that when the aircraft is knocked askew by a wind gust, it results in a slip and that rights the aircraft. Well... it has an opposite effect in a skid (using excessive bottom or pro-roll rudder rather than top rudder). So an aircraft that had tons of roll stability will actually be more maneuverable in roll than one that doesn’t. This is most evident in the snap roll or flick roll... where the rudder is used to induce a massive rolling force in combination with the elevators stalling the down-going wing which produces phenomenal roll rates in rather pedestrian aircraft.
Amazing video, I’m very inspired to learn more about this topic. Also a request if you see this, can you make a video describing the aerodynamics of the Space Shuttle & the pros & cons of a delta wing aircraft??
You explained more about stability and control for aircrafts in 10 mins than my profs in undergrad did in a whole semester. Stability and control is my specialization now. I gotta say, well researched
Ok a couple things: 1. Aircraft have a center of pressure, not lift. Drag, lift, and downforce are all pressure forces on the aircraft. 2. It's perfectly possible for a poorly trimmed but statically stable aircraft to automatically pull itself into a power-on stall.
nice vid, easy to understand, thanks for this very educative vid. wish you added the Su-27, but don't know if it was more unstable than the X-29. also one thing though about the people who thought instability is a good thing, they forgot about the human factor, well though it can just be left without saying.
The Su-27 Flanker is a pretty conventional aircraft. Probably no more unstable than the F-15 or F-16. The Su-47, however, was within the same ballpark of instability that the X-29 is in, since it's a similar design.
Given that any level of intability is impossible to control by a human and all jets with relaxed stability rely on a fly-by-wire system to artificially stabilize them, the human factor isn't really... well, a factor in this discussion. It's only about how easily the flight controls are able to bring the plane back to straight and level flight
I forget occasionally that you actually know what you're talking about! Was hoping to hear about stability and control margins. Oh well. Excellent overview at any rate.
The F-16 featured relaxed stability. It wasn't completely unstable. It was the first US fighter to feature a computer assisted digital fly by wire system to mitigate against the loss of control of the aircraft.
As a cessna mechanic I can tell you that your representation of the location of the c of g is miles out. The c of g on all low speed, pleasure aircraft is located as close to the centre of lift as possible. The location you show for c of g is actually the datum point for c of g measurements.
aa guns dont have tracking capabilities tho so chances of hitting are significantly less and they have somewhat limited range too (tldr there are only useful if the aircraft is flying at a very low altitude)
Most modern AAA are radar guided (heck even technology from last century). Aiming manually at long-distance high-speed aircraft is almost an exercise in vain.
Love the video. One little note: while talking about the Embraer EMB 120 Hor. Stabilizer it is technically wrong to say that it has a negative “AoA” since AoA is defined with respect to wind flow. But yes, it has a negative geometric angle with respect to it’s body horizontal axis.
Super interesting. I am interested in flying for a while and not too long ago I booked a flight with a pilot in a small plane. Once we started and we were in the air out of nowhere the pilot let me fly it by myself without any real instructions (beforehand we just covered basic lift and weather concepts an such). It was a cloudy day and so a lot of thermic force was put on the plane and the plane was tossed around. At first I tried to counteract the turbulences, but I soon figured out on my own that I did not have to do it, because the plane got stable on its own and I could metaphorically speaking ride the turbulence like a surfer can a wave. Great day. And thanks for covering the physics behind it.
"Alexa, please turn the AC on, this TH-cam comment on my phone made me uncomfortable. Also, please turn the desktop on and order another batch of high concentrate lemon juice, salt, sugar and cachaça. I am hopping into the Tesla so it will drive me to the psychologist and ask him for ideas."
The missile knows where it is at all times. It knows this because it knows where it isn't. By subtracting where it is from where it isn't, or where it isn't from where it is - whichever is greater - it obtains a difference or deviation. The guidance subsystem uses deviations to generate corrective commands to drive the missile from a position where it is to a position where it isn't, and arriving at a position that it wasn't, it now is. Consequently, the position where it is is now the position that it wasn't, and if follows that the position that it was is now the position that it isn't. In the event that the position that it is in is not the position that it wasn't, the system has acquired a variation. The variation being the difference between where the missile is and where it wasn't. If variation is considered to be a significant factor, it too may be corrected by the GEA. However, the missile must also know where it was. The missile guidance computer scenario works as follows: Because a variation has modified some of the information that the missile has obtained, it is not sure just where it is. However, it is sure where it isn't, within reason, and it know where it was. It now subtracts where it should be from where it wasn't, or vice versa. And by differentiating this from the algebraic sum of where it shouldn't be and where it was, it is able to obtain the deviation and its variation, which is called error.
2:27 The ball in a valley and ball on a hill analogy reminds me a lot of the chemical engineering principle of stable and unstable steady state. Stable steady state is a reaction condition that neither generates nor consumes more energy than put into the system. It takes energy to move the chemical materials out of the stable steady state(similar to the ball in the valley). An _unstable_ steady state likewise neither consumes more or less energy than put in, but unlike the stable system, a single shift up or down in temperature would make the reaction move away from the steady state with more energy than put in(similar to the ball on a hill).
4:39 I'm pretty sure downwash is only a function of angle of attack of the wing, not speed. Sure the higher the speed the higher the force induced by the downwash is, but so are all the aerodynamic forces. To look at it relatively to the other forces acting on the aircraft, you need to remove the dynamic pressure and just look at the coefficients.
Nah, Betty was yelling. "Altitude... Altitude... PULL UP! PULL UP!" while the radar altimeter was screaming. That said, was a really unfortunate crash. Pilot lost an engine while already at low energy for an airshow display. Yaw caused a spin and was too low to recover. Was at Lethbridge Air Show.
I sometimes just didn't understand WHY my boat sometimes wants to head upwind or downwind when pulling in the sheet, but now I know! It's due to the centre of lift changing position, which is obvious, but I completely overlooked that the angle of attack moves the centre of lift relative to the sail Thanks a lot!!! Instead of steering with the rudder, I try my best to steer with other things to minimize drag. There's a few ways to steer without the rudder: with heel angle and trim, which can be broken down into a lot of different components. One of them is changing the angle of attack of the sail. The centre of lift moves around the mast, so pulling in the sheet means it shifts back and to the centre of the boat. As you say, the change in angle of attack means the centre of lift moves as well. This effect counteracts the change in position and orientation of the sail to a degree. In different conditions and using different sails, one of these two effects is dominant, and the boat has either the tendency to head upwind or downwind. Most often, the rotation of the sail around the mast has more effect than the angle of attack shift. Though there are moments where the other is dominant. Increasing the angle of attack and then decreasing the angle of attack a lot causes the centre of lift to shift forward, followed by an almost complete loss of pressure. Since the sail loses pressure in the back part easier, and the wind comes in at the front of the sail first, the centre of lift shifts forward even more. All of that means the boat wants to head downwind
Wait... The center of gravity should be around 30% of the wing width from the wing nose to be self leveling... Made a lot of rc models and this detail is crucial...!
@Fedor Djogani I constructed airplanes by myself, gliders, motor planes, acro, 3d, speed and slow flyer... If everything I know would be wrong... they would not fly but they did, actually mostly pretty good...
So if I'm understanding correctly, the X-29 was/is essentially too unstable, while aircraft like the F-16, F/A-18, etc. are still unstable but not as unstable to the point of inefficiency?
The thing is there's a limit to what you can do with manned aircraft anyways. Not much point in taking them beyond a survivable performance capability, if the intent is to have the pilot onboard. Pretty much all the top tier 4th and 5th generation fighters have the flight envelope software-limited to keep the pilot from blacking out. (There are ways to turn that off, but from what I understand is that it also has a tattle-tail system so doing it is usually frowned upon outside of actual combat. Not just increased risk to the pilot, but airframe stress and other things that would require extra checks later on.) And one could only imagine the performance they could get if they could manage a robotic control system proficient enough to do the job, and plan with an airframe and flight envelope that could well exceed any human capability to survive the forces involved.
I spoke to an Viper (F-16) pilot about this very issue. Same with a Raptor (F-22) pilot and Super Hornet F/A-18 F pilot. The differences in the explanations were very interesting and diverse.
Haha, okay. I have heard the "unstable is good in fighter planes" thing before, but this makes a lot of sense. You want to avoid stability that would resist manoeuvring, but that doesn't mean you actively want to go in the other direction. Makes sense that something close to static stability is a good thing, so you can quickly start a roll, but also quickly stop it :D
@@reid1283 turn on mass and lift overlay. The blue lift ball should be behind the yellow mass ball. The mass is further towards the nose than lift. If that doesn't help then try press T for SAS (stability control)
I feel like you either oversimplified the topic or misunderstood it. Having multiple sets of wings producing lift like a canard layout or a flying tailplane does not make an aircraft unstable. Burt Rutan's VeryEasy and LongEasy designs are proof of this, as well as the Quickie tandem wing and I think some cargo planes. The one thing that makes a plane inherently stable or unstable is the location of the center of lift in relation to the center of mass. If the center of lift is in front of the center of mass, the plane wants to fly backwards, and you need a computer to convince it otherwise via fly-by-wire magic. If your center of lift is behind your center of mass, the plane just wants to do a gentle nosedive, which is easily trimmed out. This is why weight and balance are so important for planes, especially small ones. Roll stability is a lot easier. Having either a rearward sweep or dihedral increases stability, and having anhedral or a forward sweep decreases it. Hanging most of your weight below the wing helps too, which is why low-wing planes have much more dihedral than high wing planes to achieve the same stability.
The F104 isn't all that interesting. Maybe ti's enough for a 5 minute video? Unless you want to talk about roll coupling, which is a scary and difficult thing to describe. The rest of the plane is really very conventional. (save the blown flaps..) It's just a very fast airplane. The short chord of the wing means the CoL doesn't change much as you get through mach. The big horizontal stabilizer means you're never at a lack of pitch control.. unless you're deep into stall where the wings can put the tail in a wind shadow. But those aren't really "f104" things.
This is the rare ‘Real engineering’ videos I actually understand pretty well. I always thought planes had to have their centre of lift behind there centre of mass, however he proved me wrong and I understood how! What a shocker
After finding out you made notebooks, I immediately bought one and I love it! It’s a perfect size for travel and made exceptionally! The moleskin, bookmark, and the elastic band are good touches too.
Notebooks are available here. Feels cool to create merch that is actually useful. standard.tv/re-notebook
Hi
Great stuff
I was looking actively for this notebook type, but couldn't find any locally, as I was giving up you posted this video :) Thanks man
Nabbed one immediately; I absolutely love Moleskine notebooks, I have way too many already but I'll be happy to add this one to the collection :P
You’re probably one of the first to actually have a reason to buy the merch
I wish my life was designed with some static stability.
Same
Well, if you just lie down and stay like that, you are basically in the most statically stable configuration for the human body.
Social services and security measures have that purpose and are proven to be helpful.
@@nazamroth8427 if you are "locked sideways" that is.. so you do not swallow your tounge etc etc.
Same
"Speed is life. Altitude is life insurance."
L and then there’s mcas...
Underrated
@@airwipe1639 Unless you're a Boeing 737 MAX that is!
@@airwipe1639 MCAS which likes to nullify your life.
Very true, tho with todays jets a missile will get you whether your high or low, fast or slow..
The only youtuber whose merch is graph paper notebooks
Ik its late but thats like one of the only merch products id actually buy since i can use it in school.
That’s so awesome
1:45 Real Engineering just casually roasts his viewers LOL
239 likes yet no comments
@@dylanisaac1017 yes
Lmao
lol
Then he poceeds to demonstrate that they were right o_O
Bloody great. As an aircraft maintenance engineer ( Airframe / propulsion ) I really enjoyed this video. I had no problem when studying this subject which we called the theory of flight in training. I enjoyed anything like this and also theory of flight in helicopters. A subject young man you might like to add one fine day. I should point out that the training I am talking about was in the late 60's early 70's. Then we had no graphic video tools like this, and a lot of our training was done using models, illustrated drawings, but most important the retired aircraft that occupied our training hanger. These included several Hawker Hunters, a couple of De Havilland Chipmunks, the whole tail section of a Hardley Page Victor bomber, and a Westland Whirlwind. As I said, it was a long time ago.
This is how Real Engineering assert dominance over the people of his comments section
Kun Feng he put those people on blast and educated tf outa them 😂😂😂 i love it
@@filipjackowski1066 I probably should have blurred the names.....
Real Engineering I think it was good to leave the names. It’s pretty satisfying and they can’t deny facts
@@RealEngineering na, shame them. They need to be put down on their but.
@@jonathanpalmer228
Two "t"s pal... two "t"s
An Airbus is flying 30,000 feet in the air at 200,000 mph. Suddenly a eurofighter jet pulls up and slows down beside it and radioes it.
“Boring flight, huh, Airbus? Watch this!” The fighter proceeds to flip upside down and speed up, breaking the sound barrier before corkscrewing to skim the ocean, and coming up back beside the Airbus. “What’d you think?”
The Airbus pilot replies, “Not bad, but look at this.” The Airbus proceeds to fly straight for the next five minutes before the pilot comes on the radio again. “See?”
The fighter pilot is perturbed. “I don’t get it, what did you do?”
“I got up, stretched my legs, went to the bathroom and got a cinnamon bun.”
"200,000 mph" LOL
WOW! I didn't know Airbuses could fly at 0.03% the speed of light! That's amazing.
@@Crowbars2 you're gonna have to add a couple more zeros in front of that three.
Fly the P-8 Poseidon, bring a coffee maker on every flight. Pisses off all of the fighter pilots on base
@@tommylee2894 You're wrong. Google "200000 miles per hour / c in percent".
KSP has taught me that you just need to add more reaction wheels
Or just hide control surfaces inside the fuselage so it doesn't look wrong.
Or just fuck it, and add Vernor thrusters everywhere
makes look more badass when maneuvering, and can also maneuver in high atmosphere, or even vacuum
because why not ?
Or dihedral angle, this naturally levels the aircraft. I built an F-104 Starfighter in KSP, the short and low wing design made it very unstable (in terms of stability). I usually use longer wings with winglets pointed up for stability
and struts to hold the massive control surfaces stable
Anything with enough thrust and control surfaces will fly
Commenter: *incorrect comment*
Real Engineering: *YOU DARE OPPOSE ME MORTAL*
*cough*
cough
coff
one of them were satirical though lol. Real Engineering got woooshed hard.
A god of Olympus
Being an aerospace engineer myself I don't like how this vid mixes up static and dynamic stability issues without a proper explanation of both, which results in a vague, undefined "stability" being used. It's a lot more to digest though, considering a ~12 min production.
Worth to notice is that statically stable aircraft might be dynamically unstable.
Other than that, as always, great work. Keep it up. ;)
imizia pretty sure no plane is designed to only be statically stable, and that no design is truly “dynamically stable.” Planes are designed to be stable at expected accelerations
@@FoxtrotGolfLima Not entirely true. Yes, stability and control analysis is based on flight envelope and sizing data, because the product still needs to fly and be fit for certification.
Certification specifications (at least for airliners, I don't work with military) allow for the spiralling motion to be dynamically unstable provided that time constant is sufficiently big (meaning the response is not abrupt).
@imizia Nice to see a colleague here, greetings from the Czech Republic!🙋♂️ I had exactly the same reaction to the ‘static’ stability thing. Another ‘oh dear’ came along with the explanation of how the stabilizer works. At first I was intrigued - I never considered downwash to be a significant factor in static stability (qualitatively speaking) and was looking forward to some eye-opening revelation - but sadly nothing came of it.
Still really good and informative video though.
To those who are interested in the stabilizer explanation:
Increase of angle of attack (AOA) of the airplane causes increase of AOA of the wing as well as of the stabilizer. Regardless of the empennage design. Classical, cruciform, T-tail - doesn’t matter all that much. The trick is that the stabilizer is set in such a way (by negative angle of incidence and/or upside-down airfoil) that in the usual range of airplane AOA it produces negative lift (downforce). When airplane AOA increases, it increases lift of the wing as well as of the stabilizer - but since the stabilizer lift is negative, its increase manifests itself as decrease of the downforce. Thus, letting the airplane pitch down - against the increase of airplane AOA. When airplane AOA decreases, the same happens, only in reverse.
About the downwash - it affects AOA of the stabilizer, always. The airflow is affected by the wing pretty far from the wing itself in all directions (at subsonic speeds), so you don’t get rid of the influence by putting the stabilizer on top of the fin, that’s not far enough. When AOA of the wing increases, the downwash angle increases as well, which reduces AOA of the stabilizer - therefore the increase of AOA of the stabilizer will be smaller than the increase of AOA of the wing. An example: L 410 UVP-E airplane with high-wing and cruciform tail gets about 0.55 degree of stabilizer AOA per 1 degree of wing AOA, while L 610 G airplane with high-wing and T-tail gets about 0.7 degree of stabilizer AOA per 1 degree of wing AOA. So, the effect of downwash is significantly weaker with T-tail, but it definitely isn’t eliminated. And as long as increase of wing AOA doesn’t cause decrease of stabilizer AOA (which might be physically impossible), the described principle works and provides static stability in the pitch axis.
Oh and the center of gravity (CG) position is also pretty painful for any aviator out there 😁
Explanation for those interested:
A conventional airplane (like that in the picture) will usually have the CG aft of the wing lift, not forward. Usually both wing lift and stabilizer downforce pitch the airplane up, they don’t wrestle each other. What causes the airplane to pitch down then? It’s the part of the pitching moment that is not caused by lift and downforce. It’s pretty much always present and pretty much always pushes the airplane to pitch down. Most of it is caused by the wing due to its nonsymmetrical up-cambered airfoil.
The eurofighter is like a aerodynamically insane aircraft. It’s controlled by so much processing power that is make Linus Tech tips setups look like a celerons
Within a few points, Yes
On most of the European Delta canards (Typhoon, Gripen, Rafale) the deflection of the canards is what makes them so unstable
The airflow disturbance over the top skin of the wing radically changes the centre of lift
It is why in high speed maneuvers the Typhoon's canards can actually lock in place
Nice to meet you here, Matt!.
F-35 hold my invisible cola
*Laughs in b2 stealth bomber*
Yeah. I read somewhere that the canards are also computer controlled so that their radar cross section can be reduced, but I don't know if that claim is true.
This is very interesting. As someone who flys models, we move the cg to adjust pitch sensitivity. A forward cg, typically 15% of the wings chord, makes the model very stable and easy to fly. An aft cg, typically 25-30%, gives high maneuverability but at the cost of stability. Any further back and the model becomes impossible to fly as a tail heavy plane will attempt to to a backflip if you look at it funny. This is different to what you maneuverability as we can easily move the cg of a model with weights but a full size aircraft has its cg set by it's payload and design. Thanks for the in depth video and awesome graphics 😁
Thank you that was interesting & informative - much better than many comments ;-)
imo CG at 20% is really manoeuvrable.
@@fenrir834 I only run far aft cg (30%) on my crazy tiny stunt plane, everything else is about 20% which gives a good mix between stable and high maneuverability.
My ex is unstable in all 3 aspects of yaw, roll and b_tch.
B. M. You get the Internet comment of the day!
Nice
ROFL! 🤣 😂 😅
Hehe. Mine blasted off after looping around me 3 times, yelling something in her native tongue I don't understand.
@@rostislavsvoboda7013 was it? lululululululululul!!!!
" Here is a picture of me hating my life " xD
The good old days going into a lecture understanding less after the lecture.
Real world aerodynamics: **exists**
Ace Combat Planes: **visible disgust**
Nothing that Belkan witchcraft can’t fix
Ace Combat UAVs: *Laughs in immediate 90° turns.* 😭
@@reid1283 dr Schroeder is that you?
Osher Benahron
“That’s right, I’m belkan. Born and Raised”
@@Viviana088 at Mach, no less.
Fighter jets do tend to be more unstable when there is a missile flying towards it
Huh thats weird
Make sure you don't put yourself to sleep lol
Top comment
They can become even *more* unstable after the missile hits, too
Helpful
“The missile knows where it is from where it isn’t...”
Huh?
Ah, I remember this one well.
Lol
@@nicholasrussellgriffith9650 th-cam.com/video/bZe5J8SVCYQ/w-d-xo.html
Oh god not this again
The last words in this video were too unstable-able-able.
Below-oh-oh xD
He was imitating Max headroom....
@@FSEVENMAN don't you say it it it...
He didn't have enough energy left to stabilise his voice.
I was hoping someone would say this 😂
11:25 "you can find the links to bel-ow-ow-ow"
This is gonna be a sick beat.
Underrated comment
i replayed it like 4 times to make sure my FBI agent wasnt playing jokes on me.
"Speed is life" - yes, but there is second part to this:
"Altitude is life insurance" :D
Fighter jets tend to be unstable as it’s hard to give an aircraft therapy
Especially if an aircraft had a difficult childhood.
The Comedy Butchers they have to live with ptsd of beeps, and missiles. I can’t blame them for being so unstable.
Those wild Weasles man. The second they hear a beep they’re just jinking left and right....
Especially the ww2 and Vietnam vet aircrafts,they sure struggle :(
#fighterJetsMatter
Alternative title: don’t think you’re smarter than me comment section
*KNOW YOUR FUCKING PLACE TRASH*
I love this comment enough to be bothered by the missing comma after "me."
“This causes instability”
It’s not instability, it’s supermaneuverability!
“Did I fucking stutter?”
@@Kay_213_ I mean, you're right.
@@doctaflo it doesn't need a comma. Comment section is the noun. That's just like saying "Don't think you're smarter than me Kyle." You don't need a pause.
The x29 engineers clearly didn't use skillshare to make a better design
That's a bit of disservice from the engineers who designed it with far less digital tools than today. The X29 was more of an experiement on supermaneuverability. The control system was successful but it proved that due to the extra stress on the wings due to the forward swept design, it had to be heavier. A later plane, the x31, proved that thrust vectoring could contribute to agility so it was used in the F22.
hi O F D...
'
american was first made pretty plane X-29 with the single jetmotor...
later ussr russia copy steal to make su-47 with 2 jetmotors from X-29
@@shaider1982 Pretty sure that OP was making a joke about video sponsorship.
@@ericgulseth74 yeah, I guess.
@@shaider1982 F-22 tails move faster than the nozzles, so not more agile. It uses thrust vectoring largely for supersonic trim drag reduction. The nozzles help maneuverability, but it is plenty maneuverable and agile without their pitch assistance.
I just found this channel last week, and the timing is perfect. My son is just off to college to start a dual major in MechE and Aero, and I've advised him to watch as many of these as possible. If that weren't lucky enough, I've also become interested in developing some motion graphics and technical animation skills, and this channel is a perfect example of what I'd like to be able to do.
General audience: 🤷♂️
Aeronautical engineers: *slow claps*
I'm 13 and this is my favorite channel and I kinda understand this stuff.....I even made an essay all from this channel knowledge
@@4rsh193 good 👍
Wait until your aerodynamics classes an then you notice that you know nothing hehehehe, but if you do understand the aero classes , you'll have to understand the stability and controll classes too hauahaua. Good luck and I hope you become a great aeronautical engineering too
your university based knowledge is no match for my KSP experience
Your bird intelligence is no match for my people intelligence.
Turns out pitching up 90 degrees at mach 3 is a bad idea. You don't need those wing, right Jeb?
@@chlorine5795 Big brain.
@@tadferd4340 that's actually possible in KSP, I have a design that can pitch 90 degrees at 900ms without losing wings, but pulling off such stunt means knocking out Jeb and losing most of the speed
@@tadferd4340 oof, IRL it would just vaporize...
"Which you can find the links to below-ow-ow"
ow ow ow ow
I was looking for this comment xD
@@joelmulder ahaha same, i went ctrl+f "link".. i knew someone would have commented on this ahahah
OwO
Stubbed his toe perhaps?
Hey, I have been wondering about how engineers go about Optimising existing technologies. I would love if you could compare two generations of piston engines and show where more power and efficiency is produced, that would be awesome.
Take your pick and google it.
Going from flathead which was easy to produce to OHV which had better flow and was less prone to overheating.
Going from OHV to DOHC which allowed engines to flow even better and allowed for higher revs so small engines could produce lots of power as well as be fuel efficient when driven lightly.
The introduction of direct fuel injection which allows carefully controlled lean burn which produces more power for far less fuel.
@@Bartonovich52 but wasnt the disadvantages of DOHC is got less torque to produce than OHV ?
Thus makes them equal in technologies but different in purpose ?
@@megimargareth4015 no, DOHC doesnt make less torque than single ohc or pushrod engines, its just a trend that manufacturers who value the pros of developing DOHC dont value torque
I always love this channel as you bring forward the knowledge of aviation that has never been shared to the public unless they became pilots or areo engineers because it seems too daunting!
Always love the ball and hill analogy. It's such an easy and fun way to visualize concepts, whether it'd be kinetic and potential energy or stability problems like in this video.
*Bold of you to assume we're either students or Engineers.*
I mean... I am.
im not but i would like to be one
If only he knew how many hours I spend farming karma on Reddit
@@jahedali1127 Don't forget what lay beyond that wall,
Lest they trap you when you fall.
Don't give up your life and balance,
This be a warning to help your stance.
@@garret1930 i dont know what you mean?
CF-18 crashing at 8:15 at the Lethbridge Air Show in 2010 in Canada. Cause of accident was engine failure.
Glad someone else noticed. Unfortunately, this channel does not accurately explain or research topics or videos.
It was about an unrecoverable situation, which is what the clip shows.
@@martijn9568 Exactly. Plus the engine failure isn't even the immediate cause of the uncontrollable stall - it's the loss of airspeed. And the loss of airspeed is of course caused by the engine failure, probably combined with hard maneuver (near-stall, high drag situation requiring a substantial amount of thrust to push through).
@@brendanreed3378 It's just background footage. It's to fill out the video with relevant content whilst the dialogue is the focus.
@@brendanreed3378 a stable plane glides for far longer than a fighter with a damaged engine. the video was fine to show.
The angle of attack explanation at 5:32 doesn't seem right to me: angle of attack is defined relative to airflow, not the ground. If the plane were to descend through still air (in relation to the ground) then the angle of attack is would be the same as if we were flying level with the ground. Thus there should be no stabilizing force in relation to the ground. Am I missing something?
his reference frame in the video is probably the airflow and not the ground
A bit oversimplified. Pitch attitude and angle of attack can be mistaken. For example, in straight and level flight you can be at lower AOA than in descent in landing configuration. In climb you can have lower AOA than during descent depending on configuration and what you do with an aircraft.
The explanation is incomplete. The speed is what affects the angle of attack. As the plane drops in speed the wings produce less lift, making gravity a more significant component, increasing the wing's the angle of attack, and lowering the angle of attack on the horizontal stabilizer.
I see how that segment could cause confusion. The animation definitely was with reference to the ground and not the relative wind.
You are correct, although there is the lagging effect of the velocity climbing as you pitch down that he is describing that would be technically correct, but not nearly as important as the angle of attack immediately after a gust of wind or some other force pushes the attitude of the plane off center. A much better analogy is an arrow and the quivers, or a shuttlecock in badminton.
According to a Grumman engineer who worked on the program the X-29's instability came from it's canards, not the forward swept wing. It was quite safe too with both analog and digital slight control systems. And for unstable aircraft the tail produces lift to push the nose down, not downforce to push it up.
11:25
Real Engineering: "...which you can find the links to below-oh-oh."
Me: Wow! That's some pretty bad voice turbulence!"
Last Time I was this early, the F-14 was still in service.
The f-14 is still in service just in Iran.
Out of all places
Don't some us carriers have a few?
they have one in Macross oh well...
Nicolas Sousa they were retired by the US Navy in 2006 I’m pretty sure, so no. They destroyed most all of them except for a few non-airworthy examples to prevent parts from being smuggled to Iran
@@furinick
No longer, in fact, the plane that replaced the F-14 (F/A-18A/B/C) are slowly getting replaced by F/A-18E/F and/or F-35. The F-14 are basically two generations behind the top US naval fighters, and US military don't really keep plane that old for long, with the exception of B-52 and U-2.
Everytime I see your video I relate to my graduation Mechanical Engineering course and it feels good to be able to relate it! Particular to this video studied this topic of gyroscopic and aerodynamic stabilization in Design of Machine Elements 😊
Edit : Thank you to you too @Real Engineering for making learning interesting! 😃
I got my thesis next year, I'm interested in thermo and fluids so hopefully will do something in those fields
@@mika1998125 Amazing streams to work in... All the best 👍
Huge respect to you,having just passed my principles of flight exam you made the stability chapter more "understandable" and logical.Thanks a lot.
This was the first time I've ever purchased something from an intra-video TH-cam ad. Those double sided moleskin graph paper pages are EXACTLY what I've been looking for in notebooks for years. I immediately bought two.
If you do consider doing a reprinting, please look into offering a native left-handed option. I usually start notebooks writing from the back in order to make it more ergonomical, but that means page numbers are upside down and count backwards. However, I'm probably only one of maybe a dozen people that do this, so it's understandable if it doesn't make economic sense to create a whole print of left handed notebooks.
At 11:26 their seems to be a recording or editing area. Unless that was an attempt to emphasize that the links are below.
Links are bel lo lo lo low
I am currently a ATPL flight student, and this was such a great revision of the Principle of Flight topic Stability! Thanks a lot! Keep it up with videos like this or the one before! 👍🏼
Did you mean version, or maybe reiteration? :-)
Could you make an episode like this discussion the pros and cons of the “double delta” wing of the Saab J-35 Draken?
As a child, we had dime store balsa airplanes, that we flew by throwing them into the air.
They consisted of 5 pieces--- the fuselage, the wing, the stabilizer, the tail, and a metal clip.
The first four were simple...put them together, and you have your plane, or what looks like one.
BUT, that metal clip was necessary. It was thick, and had weight. I now know it gave the plane a center of gravity where you put it.
The plane behaved differently when placed in different places. As I recall, when placed forward, it would do great loops. Which was great. Placed more centrally, it would fly nice and level and go a long way --- boring, plus you had to go get it.
Those erasable gel pens showed at 10:57 are the best! The feel of a pen with better erasing then a pencil.
the clicker version is better imo
I’m just waiting for Wendover to leave a comment that promotes his own channel.
Just mention logistics or timetables and he'll be here in a pinch.
Can’t tell if this is an insult or not
real engineering will engineer a door for him to see himself out with
@@lmao.3661 It's banter mate.
Ah well then fuck me
*The Ace Combat 4 thumbnail made me hit "like" before even watching the video.*
It does look similar to Ace Combat 4.
It's real life not ace combat
Williamhughjones Will look at the thumbnail and then look at the cover of Ace Combat 4.
I was going to comment the same thing lol. Looks like this might be the orginal photo and AC edited the original. It's identical otherwise.
great video. I'll throw in some bonus facts about the F-16 since i've flown some flight sims in it (bit i am not a pilot). Because of the issues an aerodynamically unstable (or "relaxed stability aircraft") aircraft has with the center of lift moving forward as the Angle of Attack (AoA) increases, this creates a feedback loop where as the AoA increases, upward pitch increases which increases the AoA. This quickly gets out of hand to the degree that no pilot can reasonably control. To deal with this the F-16 makes use of a Fly-by-wire system. Unlike other aircraft (F-15, F/A-18) the F-16 is purely fly-by-wire, there are no cables nor hydraulic backups for manual control should the system go down, or the aircraft lose power. This is because again, there's a basically zero percent chance of a pilot controlling the aircraft without the flight stability systems. Being a single-engine aircraft this is naturally of some concern since loss of engine would mean loss of power and absolute loss of aircraft control. To alleviate this the F-16 has an APU which lasts about 10 minutes to provide power to the controls. In event of a minor engine loss where the engine may be able to be re-started, the F-16 actually can restart the engine with its internal starter (a fairly uncommon feature in US aircraft at least).
While this fly-by-wire system is needed to be able to fly the aircraft at all, it also had a huge benefit of doing most of the work of flying the aircraft for the pilot. In flight sims i was able to take off in the F-16 (unladen) on my first try after watching a video tutorial, and reading a manual. The landing was iffy and i ended up going off the end of the runway because i touched down late, but the aircraft can only do so much for the pilot.
One of the biggest advantages of the flight systems is how they prevent the aircraft from entering a stall -- supposedly a pilot is more likely to damage the control stick than they are to induce a stall from turning the aircraft.
Finally, the flight stick is somewhat unique in that it originally did not move at all (with the more modern ones moving very slightly). The Control stick registers the force applied and uses that for control inputs. This is much faster than a joystick using potentiometers and a spring to return it.
Also the F-16 put the flight stick on the side of the aircraft to make it easier to control, the F-16 pioneered many things, intentional instability, full fly by wire, and flight sticks to the right side instead of the center.
This was an awesome video. Actually explains the phrase told to us in ground school "moving the CG aft increases performance." Although now that I think about that more, that was in relation to fuel economy, so maybe not.
Oh well, great video.
That plug for the notebook was smooth! But honestly I did use your vid on the X29 and swept wings to write a 20,000 word research report, including some wind tunnel testing. Thank you so much for referencing your sources in the description! It may seem pointless but it gave me many sources of inspiration to start, and save me a ton of time! You're amazing!
Anyone who has played KSP knows about planes that are "too unstable" x)
They are perfectly stable, just in the opposite direction :D
@@wojtek4p4 yeah towards the ground.
@@UnicaLuce Nope, if CoL is in front of the CoM when flying forwards, then it's behind it when flying backwards.
If you have >1 TWR, you can use this to stabilize the fall and land on your tail.
harder to design planes than rockets in ksp.
oh man its hard to recover from stalls in these planes isnt it
I have designed multiple aircraft. The Center of Gravity is NOT in front of the wing. Typical location of the CG is about 0.3 to 0.4 of the average chord position behind the leading edge of the wing. Placing the CG too far forward (such as your video indicates by putting it in front of the wing) causes a huge loss of efficiency because the horizontal stabilizer and the elevator needs to generate a huge downward moment thus creating a great deal of unnecessary induced drag which wastes fuel. If the CG is in the 0.3 position we get an ideal situation where the horizontal stabilizer / elevator combination is in neutral position for level flight thus requiring minimal drag to fly. If the CG is moved further back, less command authority is necessary to control the plane but also makes the job of the pilot harder. The CG should never be put back more than 0.4 without a fly by wire system as the plane would be uncontrollable by manual means. You might want to do a video about the quest of fuel efficiency leading to a very famous accident in a DC10 cargo plane where the tail surfaces were trimmed smaller so as to achieve greater fuel efficiency but this led to not enough command authority at slower speeds during landing. In this particular case, the DC10 bounced 3 times then broke up because it was landing at too slow a speed. The size of the tail is often a tradeoff between low drag at high speed (when you have plenty of command authority even with very small tail surfaces) and the need for command authority at low speeds (where command authority is low and there is a need for larger tail surfaces). As with many things, environmentalism comes with a price in human lives. Things that save fuel and energy is often paid for by the loss of human life. Another place you may want to look is at the Reno Air Race where P51 D Mustangs from WWII are typically used with tail surfaces trimmed smaller in order to reduce drag at the risk of too little command authority during landing.
Oh, I know, I know!
Let's build an unstable
commercial airliner to save fuel.
Oh wait...
Do these engines make my pitch look fat?
Actually Boeing does build an intentionally aerodynamically unstable airliner and it's not the MAX it's the 777 this video is wrong they exist and it's not unsafe
@@PabloGonzalez-hv3td Oh no, the 777 isn't unstable. Just look at the thing with its giant tail
This is like commercial, every day cars vs super cars or race cars.
Your everyday car will have the wheel alignment “toe-in” to make the car more stable (it will correct itself to drive in a straight line),while race cars usually have it “toe-out” to increase cornering performance.
Excellent and simple explanation.
The term typically used is “relaxed stability” since many fighters do have static stability, just not what is required for safe and controlled flight. That is, the design will return it to straight and level with light maneuvering, but rapid maneuvering would cause the aircraft to tumble before the stabilizing forces could act.
Another thing you touched on is roll stability. There is no pure roll stability because an aircraft has no idea which way is down. Roll stability is based on slipping the airplane and is called “slip-roll” coupling. The idea is that when the aircraft is knocked askew by a wind gust, it results in a slip and that rights the aircraft.
Well... it has an opposite effect in a skid (using excessive bottom or pro-roll rudder rather than top rudder). So an aircraft that had tons of roll stability will actually be more maneuverable in roll than one that doesn’t. This is most evident in the snap roll or flick roll... where the rudder is used to induce a massive rolling force in combination with the elevators stalling the down-going wing which produces phenomenal roll rates in rather pedestrian aircraft.
Amazing video, I’m very inspired to learn more about this topic. Also a request if you see this, can you make a video describing the aerodynamics of the Space Shuttle & the pros & cons of a delta wing aircraft??
You know which engine is reliable?
A Toyota Corolla engine
Napoleon I Bonaparte wrong channel bud
@@williamthebutcherssonprodu227 he's not wrong tho
The rest are just endless money pits.
I’m pretty sure turbine engines are more reliable than gas car engines.
nah...cant beat a corolla engine
I love the thumbnail. I like F-22s. It's the first reason why I clicked as soon I saw it.
Combat performances and technical capabilities aside, I personally like its sleek look. A true representative of a modern day jet fighter.
You explained more about stability and control for aircrafts in 10 mins than my profs in undergrad did in a whole semester. Stability and control is my specialization now. I gotta say, well researched
Ok a couple things:
1. Aircraft have a center of pressure, not lift. Drag, lift, and downforce are all pressure forces on the aircraft.
2. It's perfectly possible for a poorly trimmed but statically stable aircraft to automatically pull itself into a power-on stall.
nice vid, easy to understand, thanks for this very educative vid. wish you added the Su-27, but don't know if it was more unstable than the X-29.
also one thing though about the people who thought instability is a good thing, they forgot about the human factor, well though it can just be left without saying.
The Su-27 Flanker is a pretty conventional aircraft. Probably no more unstable than the F-15 or F-16. The Su-47, however, was within the same ballpark of instability that the X-29 is in, since it's a similar design.
Given that any level of intability is impossible to control by a human and all jets with relaxed stability rely on a fly-by-wire system to artificially stabilize them, the human factor isn't really... well, a factor in this discussion. It's only about how easily the flight controls are able to bring the plane back to straight and level flight
Are the gridlines in metric or imperial for the notebook?
probably metric
centi-smoots
@@tachy1801 exactly lol
I forget occasionally that you actually know what you're talking about! Was hoping to hear about stability and control margins. Oh well. Excellent overview at any rate.
The F-16 featured relaxed stability. It wasn't completely unstable. It was the first US fighter to feature a computer assisted digital fly by wire system to mitigate against the loss of control of the aircraft.
As a cessna mechanic I can tell you that your representation of the location of the c of g is miles out. The c of g on all low speed, pleasure aircraft is located as close to the centre of lift as possible. The location you show for c of g is actually the datum point for c of g measurements.
Thanks for this video. It was really clear and I learnt a lot
Remember how you mentioned that the computer can adjust for instability? Thats the case in the f16 and its not exactly staticly neutral
Anti-Air gun see plane: let's make you more unstable
Plane: Must be a SAM
AA Gun:Chaff and flares won't work on me
aa guns dont have tracking capabilities tho so chances of hitting are significantly less and they have somewhat limited range too (tldr there are only useful if the aircraft is flying at a very low altitude)
@@teddytatyo Depends on what platform they are on.
Modern SPAAGs often have radar and tracking.
Usually gonna have radar tracking.
Most modern AAA are radar guided (heck even technology from last century). Aiming manually at long-distance high-speed aircraft is almost an exercise in vain.
Gaijin pls nerf AAA. To op!!
Love the video. One little note: while talking about the Embraer EMB 120 Hor. Stabilizer it is technically wrong to say that it has a negative “AoA” since AoA is defined with respect to wind flow. But yes, it has a negative geometric angle with respect to it’s body horizontal axis.
Super interesting. I am interested in flying for a while and not too long ago I booked a flight with a pilot in a small plane. Once we started and we were in the air out of nowhere the pilot let me fly it by myself without any real instructions (beforehand we just covered basic lift and weather concepts an such). It was a cloudy day and so a lot of thermic force was put on the plane and the plane was tossed around. At first I tried to counteract the turbulences, but I soon figured out on my own that I did not have to do it, because the plane got stable on its own and I could metaphorically speaking ride the turbulence like a surfer can a wave. Great day. And thanks for covering the physics behind it.
I’m a senior in aerospace engineering and I commented about the X-29
Yeah bud and I work for The pope as his majestys pimp
@@e141-f2n that got him, i agree
Imagine having multiple computers to make sure you're stable.
Desktop, Laptop, Tablet and Phone all working together right now
very relatable
"Alexa, please turn the AC on, this TH-cam comment on my phone made me uncomfortable. Also, please turn the desktop on and order another batch of high concentrate lemon juice, salt, sugar and cachaça. I am hopping into the Tesla so it will drive me to the psychologist and ask him for ideas."
The missile knows where it is at all times. It knows this because it knows where it isn't. By subtracting where it is from where it isn't, or where it isn't from where it is - whichever is greater - it obtains a difference or deviation. The guidance subsystem uses deviations to generate corrective commands to drive the missile from a position where it is to a position where it isn't, and arriving at a position that it wasn't, it now is. Consequently, the position where it is is now the position that it wasn't, and if follows that the position that it was is now the position that it isn't. In the event that the position that it is in is not the position that it wasn't, the system has acquired a variation. The variation being the difference between where the missile is and where it wasn't. If variation is considered to be a significant factor, it too may be corrected by the GEA. However, the missile must also know where it was. The missile guidance computer scenario works as follows: Because a variation has modified some of the information that the missile has obtained, it is not sure just where it is. However, it is sure where it isn't, within reason, and it know where it was. It now subtracts where it should be from where it wasn't, or vice versa. And by differentiating this from the algebraic sum of where it shouldn't be and where it was, it is able to obtain the deviation and its variation, which is called error.
You cheeky fucker.
I think you're a enginner or something coz what u said just flew above me
2:27 The ball in a valley and ball on a hill analogy reminds me a lot of the chemical engineering principle of stable and unstable steady state. Stable steady state is a reaction condition that neither generates nor consumes more energy than put into the system. It takes energy to move the chemical materials out of the stable steady state(similar to the ball in the valley). An _unstable_ steady state likewise neither consumes more or less energy than put in, but unlike the stable system, a single shift up or down in temperature would make the reaction move away from the steady state with more energy than put in(similar to the ball on a hill).
4:39 I'm pretty sure downwash is only a function of angle of attack of the wing, not speed. Sure the higher the speed the higher the force induced by the downwash is, but so are all the aerodynamic forces. To look at it relatively to the other forces acting on the aircraft, you need to remove the dynamic pressure and just look at the coefficients.
For the record, I'm not an Engineer, I'm a physicist.
I’m curious, what do you do as a physicist?
@@psun256 As in what do physicists do? Or what field of physics to do I study?
for the record, i am a medical student. I doubt that plane engineering will ever help me with ophthalmology patients, but you never know.
@@TheBoredPhysicist Think he meant what *you* do i.e. your work/field of study.
8:10
Flight computer: *STALL WARNING* *STALL WARNING*
Nah, Betty was yelling. "Altitude... Altitude... PULL UP! PULL UP!" while the radar altimeter was screaming.
That said, was a really unfortunate crash. Pilot lost an engine while already at low energy for an airshow display. Yaw caused a spin and was too low to recover. Was at Lethbridge Air Show.
"Speed is life."
and altitude is life insurance.
8:09 That happened in my city not too long ago during the Airshow. Got to see it up close. Very dope.
I sometimes just didn't understand WHY my boat sometimes wants to head upwind or downwind when pulling in the sheet, but now I know!
It's due to the centre of lift changing position, which is obvious, but I completely overlooked that the angle of attack moves the centre of lift relative to the sail
Thanks a lot!!!
Instead of steering with the rudder, I try my best to steer with other things to minimize drag. There's a few ways to steer without the rudder: with heel angle and trim, which can be broken down into a lot of different components. One of them is changing the angle of attack of the sail. The centre of lift moves around the mast, so pulling in the sheet means it shifts back and to the centre of the boat. As you say, the change in angle of attack means the centre of lift moves as well. This effect counteracts the change in position and orientation of the sail to a degree. In different conditions and using different sails, one of these two effects is dominant, and the boat has either the tendency to head upwind or downwind.
Most often, the rotation of the sail around the mast has more effect than the angle of attack shift. Though there are moments where the other is dominant.
Increasing the angle of attack and then decreasing the angle of attack a lot causes the centre of lift to shift forward, followed by an almost complete loss of pressure. Since the sail loses pressure in the back part easier, and the wind comes in at the front of the sail first, the centre of lift shifts forward even more. All of that means the boat wants to head downwind
Wait... The center of gravity should be around 30% of the wing width from the wing nose to be self leveling... Made a lot of rc models and this detail is crucial...!
@Fedor Djogani 😂
@Fedor Djogani I constructed airplanes by myself, gliders, motor planes, acro, 3d, speed and slow flyer... If everything I know would be wrong... they would not fly but they did, actually mostly pretty good...
"Handles like a dream..."
_ssshwooooosh!_
*_cue epic guitar solo_*
So if I'm understanding correctly, the X-29 was/is essentially too unstable, while aircraft like the F-16, F/A-18, etc. are still unstable but not as unstable to the point of inefficiency?
Correct. Russian Sukhoi Su-47 faced the same exact problem as well.
The thing is there's a limit to what you can do with manned aircraft anyways. Not much point in taking them beyond a survivable performance capability, if the intent is to have the pilot onboard. Pretty much all the top tier 4th and 5th generation fighters have the flight envelope software-limited to keep the pilot from blacking out. (There are ways to turn that off, but from what I understand is that it also has a tattle-tail system so doing it is usually frowned upon outside of actual combat. Not just increased risk to the pilot, but airframe stress and other things that would require extra checks later on.) And one could only imagine the performance they could get if they could manage a robotic control system proficient enough to do the job, and plan with an airframe and flight envelope that could well exceed any human capability to survive the forces involved.
8:13 that last-second escape is the most impressive thing i’ve ever seen.
Me: builds a paper model of a fighter plane.
Plane: is unstable.
Me: surprised engineer picachu face.
You can make most of them fly in a straight line if you shift the cg forward. They don't really need to do maneuvers anyway
stIck some plasticine on the nose, thank me later
"Speed is life, altitude is life insurance"
3:11 Center or centre ? PICK ONE AND STICK TO IT
jk you do amazing videos, keep up the good work ! :)
Its autogenrated
I spoke to an Viper (F-16) pilot about this very issue. Same with a Raptor (F-22) pilot and Super Hornet F/A-18 F pilot. The differences in the explanations were very interesting and diverse.
Haha, okay. I have heard the "unstable is good in fighter planes" thing before, but this makes a lot of sense. You want to avoid stability that would resist manoeuvring, but that doesn't mean you actively want to go in the other direction. Makes sense that something close to static stability is a good thing, so you can quickly start a roll, but also quickly stop it :D
“Involuntary hyper mobility” that one had me laughing for a while
More like involuntary crash
@@myusername3689 Rapid unscheduled disassembly
"Just let me know on twitter or Instagram, which you can find the links to bellow ow ow"
If you want to learn basic aerodynamics, just play Kerbal Space Program
Just make sure to install a mod called Ferrum Aerospace if you want actual aerodynamics
You will also learn basic landing gear position lol
How to get gud stabilitie
1. Thrust
2.????
@@reid1283 turn on mass and lift overlay. The blue lift ball should be behind the yellow mass ball. The mass is further towards the nose than lift. If that doesn't help then try press T for SAS (stability control)
Am I the only one who noticed Thessaloniki at 3:50? Happy to see my hometown in one of your videos!
I must say that this is one of the few youtube channels that i watch every singel video from, you are doing a really good job plz keep it up
I feel like you either oversimplified the topic or misunderstood it. Having multiple sets of wings producing lift like a canard layout or a flying tailplane does not make an aircraft unstable. Burt Rutan's VeryEasy and LongEasy designs are proof of this, as well as the Quickie tandem wing and I think some cargo planes. The one thing that makes a plane inherently stable or unstable is the location of the center of lift in relation to the center of mass. If the center of lift is in front of the center of mass, the plane wants to fly backwards, and you need a computer to convince it otherwise via fly-by-wire magic. If your center of lift is behind your center of mass, the plane just wants to do a gentle nosedive, which is easily trimmed out. This is why weight and balance are so important for planes, especially small ones. Roll stability is a lot easier. Having either a rearward sweep or dihedral increases stability, and having anhedral or a forward sweep decreases it. Hanging most of your weight below the wing helps too, which is why low-wing planes have much more dihedral than high wing planes to achieve the same stability.
Do a video on the F-104
The F104 isn't all that interesting. Maybe ti's enough for a 5 minute video?
Unless you want to talk about roll coupling, which is a scary and difficult thing to describe. The rest of the plane is really very conventional. (save the blown flaps..) It's just a very fast airplane. The short chord of the wing means the CoL doesn't change much as you get through mach. The big horizontal stabilizer means you're never at a lack of pitch control.. unless you're deep into stall where the wings can put the tail in a wind shadow. But those aren't really "f104" things.
Nobody:
Real Engineering's 11 min. vid: I'm about to end this youtube commentor's whole career.
This is the rare ‘Real engineering’ videos I actually understand pretty well. I always thought planes had to have their centre of lift behind there centre of mass, however he proved me wrong and I understood how! What a shocker
Only when they go in reverse.
After finding out you made notebooks, I immediately bought one and I love it! It’s a perfect size for travel and made exceptionally! The moleskin, bookmark, and the elastic band are good touches too.