Why Fighter Jets Can Be Too Unstable

  • Published on Aug 17, 2019
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    Writer/Narrator: Brian McManus
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Comments • 1 880

  • Real Engineering
    Real Engineering  29 days ago +673

    Notebooks are available here. Feels cool to create merch that is actually useful. standard.tv/re-notebook

    • Zbigniew Modrzejewski
      Zbigniew Modrzejewski 16 days ago +1

      The Future of Flight : quantumantigravity.wordpress.com/

    • 015A
      015A 17 days ago

      hi i'm in my freshman year of high school now i would have bought and contributed to the sale of the note books but unfortunately i only use and need binder paper but i'm gonna buy it because i'm taking industry technology classes and auto cad and solid works sucks for making a simple idea drawing of something that might not work so i'm gonna beg my parents to get me another note book and only this one so i can make simple drawings to just get the basics of what i want to use

    • James Metz
      James Metz 20 days ago

      Thanks so much for these notebooks, I needed some for school this semester but was disappointed by similar versions, if you keep these in stock that would be amazing

    • Nxdav
      Nxdav 21 day ago

      Literally bought one the second I saw it.. this is gonna be really helpful! Thank you!!

    • Seimen Veldt
      Seimen Veldt 23 days ago

      What kind of grid is it? We EU students need 1cm grid notebooks..

  • Phillip Keane
    Phillip Keane Day ago

    They're not "too unstable". You're talking like this is an accident of design. They're exactly as unstable as they need to be.

  • lr21643
    lr21643 Day ago

    Pretty sure the c.g. of that Cessna at around 3:20 would actually be much further aft. If memory and the internet serve, the datum on a C-172 is the firewall, and the c.g. is supposed to be between 3 and 4 feet behind that.

    Furthermore, the term center of lift can be misleading, at least as usually used. It's probably ok if you're just taking off or cruising around. However, consider a plane in a vertical dive. The wing, in most cases, is still trying to pitch the aircraft "down". For the center of lift to do that, it would have to be infinitely far away.

    The horizontal stabilizer doesn't actually have to push down, depending on how the airplane is loaded, the size of the horizontal stab, and how far back it is. On certain indoor model airplanes, like EZB's, you can sometimes see the lift of the tail bend the tailboom up. If you don't know what an EZB is, check this out:
    Notice how large and far back the horizontal stabilizer is. The c.g. on a model like this may be behind the trailing edge of the wing.

    • lr21643
      lr21643 Day ago

      BTW, downwash effects on the tail REDUCE pitch stability. Consider that, in level flight, the plane has to have lift equal to the weight. At high speeds, a lot of air is going past the wing, so, in order to get enough lift, it only has to direct that air down a little bit. At lower speeds, that air has to be directed down at a greater angle and velocity. So the downwash varies oppositely to what you'd like.
      Fortunately, the dominant effect is the changing angles of attack of the horizontal stab and the wing. But I don't really have the energy to explain that now. Probably most aircraft aerodynamics textbooks would explain it.

  • FPV Stealth rc
    FPV Stealth rc 3 days ago

    Thank you very much for your sharing I have subscribed excellent videos sub 2M

  • Chris Sanchez
    Chris Sanchez 6 days ago

    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.

  • Daniel Kron
    Daniel Kron 8 days ago +2

    Apparently there is no planes in the world. Only in US

  • Damion Richter
    Damion Richter 8 days ago


  • Rzr2ffe
    Rzr2ffe 8 days ago

    Your center of gravity for the Cessna is too far forward

  • Meister Kaos
    Meister Kaos 10 days ago +1

    It's because fighter jets don't talk about their emotional problems with their peers until it's too late, and one day they just drop out of the sky.

  • Zemani
    Zemani 10 days ago

    Future engineers where u at?

  • Anders Backman
    Anders Backman 11 days ago

    Are the graph paper millimeter / 5 mm / 1 cm or some weird US / British grid?

  • shubham temak
    shubham temak 11 days ago

    I'm doing aircraft maintenance engineering and I cleared aerodynamics exam ur vid helped thx

  • Tanner Denny
    Tanner Denny 12 days ago

    Knocked up by a gust of wind... isn’t that how Jesus got made borned?

  • David Niegowski
    David Niegowski 12 days ago

    Hey Brian, I’m making a jet engine for one of my engineering classes and I realized I might be a bit overambitious, but I’m committed. Would it be possible to DM you some simple questions on twitter occasionally?

  • Kate Russell
    Kate Russell 13 days ago

    So is this why the new 737 aircraft pitch differently because the engines are located more up and forward?

  • Kingdom of Osea
    Kingdom of Osea 14 days ago +1


  • Yoda Yoda
    Yoda Yoda 15 days ago +1

    Funny fact. I learned all of this via kerbal space program

  • Jayakrishna Balaji
    Jayakrishna Balaji 16 days ago +1

    Can you please take time explain about the #B737-Max8 air crash in light with MCAS?

  • Zbigniew Modrzejewski
    Zbigniew Modrzejewski 16 days ago +1

    The Future of Flight : quantumantigravity.wordpress.com/

  • Julio
    Julio 18 days ago

    SPEED IS KEY!!!!

  • Cameron Harper
    Cameron Harper 18 days ago

    Can you stop posting porn for Wendover Production???

  • MrManiac3
    MrManiac3 19 days ago

    Below. Oh. Oh.

  • Miami Kasabian
    Miami Kasabian 20 days ago

    Best you've done yet, you should be lecturing stability! It only took me three months of flight mechanics to still not really get it ...

  • Jordan Teo
    Jordan Teo 20 days ago

    sorry, this may be too much from me to ask but could you go over the superbottle and electric motors from tesla? or how electric aircraft may happen in the future

    • Jordan Teo
      Jordan Teo 20 days ago

      love the dedication and simple animations w/ explanations

    • Jordan Teo
      Jordan Teo 20 days ago

      also, how can tesla shink the amount of wiring needed from a couple thousand meters of wiring to couple hundred?

    • Jordan Teo
      Jordan Teo 20 days ago

      there was a recent discussion with Sandy Munro from Munro & associates inc. (tvclip.biz/video/i93VJ1PEp6o/video.html 47:50) he shares some things many being important when considering tesla's future, one of them was the superbottle. I was very intrigued by how one small thing can be a substitute (or combining. I'm not how it fits in the whole system) three major (cooling and heating) systems

  • Dev Shah
    Dev Shah 20 days ago

    Make a video on the future of NANO MATERIALS

  • Luis
    Luis 20 days ago +1

    Very interesting explanation about horizontal stabilizers. What about a delta wing? How does that works? Could you make a video about it?

  • Frank Nakamo
    Frank Nakamo 21 day ago

    Airplanes can not scientifically fly, they using telekinesis to make airplanes lift, airplanes all are too heavy and not capable of self sustaining in air.

  • Yves Cartieaux
    Yves Cartieaux 21 day ago

    Nice pictures but too many inaccuracies, it is not relevant to speak about stability without speaking of neutral point. Stability is not directly linked to the empennage type : aircraft with canard could be stable or unstable…. and what about tailless configuration (F-106, Mirage 2000...) ?
    This documentary is definitely not something to show for stability explanation.

  • Andrew Egan
    Andrew Egan 21 day ago

    Congrats on two mil

  • Colin Woodall
    Colin Woodall 21 day ago

    I didn't like what was available so I made my own - engineer's motto? lol

  • Mark Zaikov
    Mark Zaikov 22 days ago

    5:00 AM binge watching science.

  • SillieWous
    SillieWous 22 days ago +1

    Something is either stable or unstable. It may be difficult to control, but it is either of the two not in between.

  • InDieTasten Development

    I have a question regarding 5:50. Angle of attack is the angle of the surface against the current direction of travel. If the plane pitches down, it will also descend, so the direction of travel goes down as well. In the animation, the angle the wing surface against an arbitrary horizontal line. So how does this work exactly?
    In the previous example of downwash, it was explained, that the difference is caused by speed of travel, which makes sense for the same reason, that the second example with the wing outside the wash doesn't make sense. What part am I missing?

  • burningSHADOW42
    burningSHADOW42 22 days ago

    How does the Eurofighter fit into all of this. To my knowledge it is designed to be extremely unstable.
    I heard at some point that the aerodynamically stable position for a Eurofighter is upside down.

  • Karel Kédl
    Karel Kédl 22 days ago

    I think you should break this topic down to elements and explain all about stability and mention both static and dynamic stability. Because you are mixing these two together here.

  • DFX2KX
    DFX2KX 22 days ago

    Anyone who thinks 'the more unstable the better needs to get X-plane (any version), and try making a dynamically unstable aircraft that's actually flyable. getting the control curves dialed in right is hard enough when the plane is only *mildly* fidgety. There's a demo aircraft in version 10 called 'Deathtrap' it's a flying wing with forward sweep. How the hell it flies as good as it does, I don't know, but it'll end up going backwards if you so much as look at it funny.

    • DFX2KX
      DFX2KX 22 days ago

      I say X-plane because the tool to do this comes with the game/sim. Plane Maker

  • K G
    K G 22 days ago

    I like turtles

  • DumbledoreMcCracken
    DumbledoreMcCracken 22 days ago

    I don't like these videos. If the audience is lay, then I think they don't really know what the words mean. The audience of authorities wouldn't be informed?

  • anka 098
    anka 098 22 days ago

    that channel made me realize that I love engineering, my collage did the opposite.

    • anka 098
      anka 098 20 days ago

      @X-ray Scott they dont give us answers for our basic simple questions .. most doctors treat thier students like these stupids will never understand im just gonna give them some exams and they should memorise whatever is written in the note.. so that students study for the exam and delete evry thing they studied after exams.. also the practical side is ignored in my college and that is the sadiest thing .. that was in my first and seconed year .. after that i realized that its all about self teaching ..

    • X-ray Scott
      X-ray Scott 20 days ago +1

      What did you make a collage of that made you hate engineering?

  • anka 098
    anka 098 22 days ago

    watching this for enhancing my planes in KSP :^

  • Fully_Retractable
    Fully_Retractable 22 days ago

    Came here for the educational value, and left with a notebook, as soon as you said it was graph paper, I was sold!

  • Ocotillodavid
    Ocotillodavid 23 days ago

    Too many self-certified experts. The post is a big YAWN!

  • Y Tho
    Y Tho 23 days ago

    2/5 of those comments were pretty obviously jokes. like, "involuntary hypermobility" clearly isn't a good thing, because it's "involuntary", and the first one read like a joke as well. you should use skillshare to learn how to pick examples that better support your argument using their course on writing an effective essay.

  • Isaac L-L
    Isaac L-L 23 days ago

    Important note about why the cG is so far back for the X-29. Jets have a lot of weight in the back because of where the engine is (same reason that your C172 has its cG far up), and therefore you can get the wings further back.

  • DexMaster881
    DexMaster881 23 days ago

    Meanwhile In Soviet Russia:
    Physics.exe has been paused on demand by Commrade Stalin

  • Ty White
    Ty White 23 days ago

    The lines at 3:40 gave me a big "AHHA" moment. I have wondered before how the relatively small elevators in the back could be able to adjust the pitch of the wings, when the wings are so much larger. It seems the larger wings would deflect more air than the smaller elevator, and over power the elevator. I see now the elevators can control the pitch because of greater leverage in relation to the center of gravity :) hope everything I said is logical.

  • KerazyJoe
    KerazyJoe 23 days ago

    If the The Den was still on, you would have done a feature.

  • Ben Knisley
    Ben Knisley 24 days ago

    Yo selling moleskine style notebook for your channel is brilliant!

  • deldote
    deldote 24 days ago +2

    I'm sorry dude, but you got this one wrong, or at least you oversimplified the explanation to the point where it does not give the right message.
    I am both a physicist and a glider pilot, and I spent a lot of time trying to make sense of the stability of airplanes, since the way I was taught it in flight school (which was sort of similar to what you say in this video) did not make sense to me. In your explanation, you give the impression that the instability comes from the canards being in front of the CoM. This is not the case, as one can make perfectly stable planes with canards. One can even make planes with two 'main' wings.
    The 'standard' explanation about the changing AoA on the tailplane does not really work, since changes in pitch affect the AoA of both the tailplane and the main wing equally. If the torques are balanced in level flight and we double the AoA so that lift of both the tailplane and the wing will double, the torques will remain perfectly balanced. There is gonna be no restoring torque to provide stability.
    What makes a plane stable is the difference in AoA between the tailplane and the main wing, this is called 'decalage'. If the back wing has a lower AoA than the front wing in level flight, a change in pitch will relatively affect the back wing more than the front one, so that a net restoring torque is generated. This can be done with canards to. It does not matter if both wings are behind the CoM or if one is in front of it, all that matters is that the back wing has less AoA than the front one.
    Read chapter 6.1 of this book for a more detailed analysis, for me it was really enlightening www.av8n.com/how/.
    I hope i don't sound too critical, I just write this because i got stuck with the same problem some time ago and finally managed to get a clear picture. I love your channel, and thank you for making great content!

  • Gulfam Anjum
    Gulfam Anjum 24 days ago

    Is not the area of Plan design belongs to the Civil Engineering? I felt in the video some thing mine [architectural].

  • Gulfam Anjum
    Gulfam Anjum 24 days ago

    You are blessed with truly clear spoken English style; selection of the words was so simple that I could not feel that the English is not my native language. Thank you very much.

  • Sotos
    Sotos 24 days ago +1

    Am I the only one who noticed Thessaloniki at 3:50? Happy to see my hometown in one of your videos!

  • Daniel Bd
    Daniel Bd 24 days ago

    Can you make a video about Von Braun space station and if now is the right time to build it?

  • Flikz
    Flikz 24 days ago


  • Alessandro Esposito
    Alessandro Esposito 24 days ago

    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.

  • 4G12
    4G12 24 days ago

    This actually relates very well to automotive handling stability as well. The fastest possible setup in terms of qualifying laptimes is one of mild oversteer overall, but it is more cognitively expensive for most drivers to control and perform consistently than a setup with mild understeer overall which although slower over a single lap, is much easier to perform consistently over the entire length of the race distance.
    That said, some of the best drivers are so skilled at car control they prefer neutral to mild understeer setups, since their car control is no longer conscious but instead, as instinctive as walking and running.

  • Nighthawk
    Nighthawk 24 days ago +1

    "Handles like a dream..."
    *_cue epic guitar solo_*

  • Maverick
    Maverick 24 days ago

    Great explanation

  • Rushank Sarade
    Rushank Sarade 24 days ago

    What would happen if we lose AMAZON RAINFOREST? Can we rebuild the forest again?

  • Rocketry 1000
    Rocketry 1000 24 days ago

    I don’t enjoy how Static Stability was used in the place of Positive Stability or the fact that downforce was not explained properly, the camber of the horizontal stability creates downforce in the same manner as a wing creates lift. Side note the CF-18 crash in this video was caused by asymmetric thrust due to the loss of the starboard engine not due to the instability of the aircraft.