Why Fighter Jets Can Be Too Unstable

  • Published on Aug 17, 2019
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Comments • 1 996

  • Real Engineering
    Real Engineering  5 months ago +736

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

    • PugsOP
      PugsOP 23 days ago


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      015A 5 months ago

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    • James Metz
      James Metz 5 months ago

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    • Nxdav
      Nxdav 5 months ago

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

    • Seimen Veldt
      Seimen Veldt 5 months ago

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

  • ChimeraArts
    ChimeraArts Day ago

    I thought almost all fighter jets are unstable and need computer controls to help stabilize it or am I wrong?

  • The Vortex
    The Vortex 2 days ago

    Would an aerospace engineer need to make an unstable space ship to make rolling into orbit easier on the ship?

  • Max Jones
    Max Jones 11 days ago

    So basically fighter jets have adhd, so it's easier for them to notice things and do things but harder for them to focus without intense input telling them to do so. Source? me, as a spectrum individual.

  • Kevlar
    Kevlar 13 days ago

    That feeling when you're scared of turbulence not because of a fear of flying, but rather because of a fear of motion sickness induced nausea.

  • Ben G Vegas
    Ben G Vegas 14 days ago

    9:11 my city

  • Dark Angel
    Dark Angel 18 days ago

    Bernoulli’s principle is inverted in supersonic flight compared to subsonic flight

  • Simon
    Simon 18 days ago

    Can you please do a video about the issues of the Boing 737 max. Is the problem there related to the stability you describe in this video?

  • VicPapefu
    VicPapefu 20 days ago

    I was a fighter jet pilot and flew different configurations supersonic planes. More unstable jet planes, which in general have small close to triangle wings, usually require more speed to land them, and for us that is an issue mostly if you need to land in a very short landing place; and that's why you have a parachute in the rear of the tail. If the wings are too short, for instance MiG-21, and you want to land as short as possible, you can learn how you push the parachute button when still like 6 feet over the ground, though you need to know in that case how to handle the nose of the plane.

  • Jaromír Anděl
    Jaromír Anděl 21 day ago

    And I thought it depends mainly on position of CG and CL.
    When the CL is behind the CG and let's say the nose is going up: the AoA is increased->lift is increased->aircraft is moved back to stable position.
    When the CG is behind the CL and let's say the nose is going up: the AoA is increased->lift is increased->rate of attitude change is increasing.

  • gonzalo moreno andonaegui

    Real Engineering If T-tail configuration is so advantageous, why most commercial aircraft don't use them ? Why it is used mostly in heavy cargo aircraft ?

  • Faybie
    Faybie 27 days ago

    Your explanation was not faulty, people on the internet want to interpret things differently than they are intended because they want to create turmoil for fun. Your x-29 video was next to flawless and you have nothing explain.

    VLNOW 29 days ago

    Been binge watching your channel lately. Thanks for your work and your clear explanations.

  • Trung Le N.Q
    Trung Le N.Q Month ago

    $15 for a notebook, boi you over-rated

  • clipside
    clipside Month ago

    real engineering putting these expert wannabe commenters in their place with real science...

  • Harrys Kydon
    Harrys Kydon Month ago

    Hey dear real engineering can you make a video on variable sweep wing?

  • Christopher Andersen

    I know u want to make money but watching 2 mins of commercials just to have you spouting ur sponsor is a complete turn off

  • The Rcproject
    The Rcproject Month ago

    what about a video about wing design and how it may effect flight envelope by looking at different aircraft

  • Jesse Lima
    Jesse Lima Month ago

    The best explaination!

  • awf2512
    awf2512 Month ago

    Huge respect to you,having just passed my principles of flight exam you made the stability chapter more "understandable" and logical.Thanks a lot.

  • Hugo Amkreutz
    Hugo Amkreutz Month ago

    that will be in the description be-below. did anyone else hear that at the end?

  • sabin_playsroblox YT

    The straight wings made planes extremely agile in the second world war but sweapt wings causes less stability just like the ball and valley pronlem

  • Shalabh Saxena
    Shalabh Saxena 2 months ago +1

    8:19 a typical Ryanair landing

  • Marcus MIDI
    Marcus MIDI 2 months ago

    Amazing :)

  • A Winner
    A Winner 2 months ago +1

    8:17 that plane was a lot lower than I expected

    • A Winner
      A Winner Month ago

      To the person that liked this. How did you find this comment after a month?

  • Lilly Anne Serrelio
    Lilly Anne Serrelio 2 months ago +1

    I just learned more about aerodynamics in 12 min from this video then I did from an entire week in my high school physics class.

  • Recruit Lucier
    Recruit Lucier 2 months ago

    8:15 code brown code brown let's get me some new pants

  • Kid Genius
    Kid Genius 2 months ago

    thank. That's all I can say: Thank you. I have always wanted to understand more about aerodynamics and the forces behind it. (Btw, I'm not sure if aerodynamics is the right word) Now I understand... I think. Correct me if I'm wrong. Fighter plane wings are straight to make it purposely unstable, compared to airliners and even the F-4 Phantom,k right? If I'm right, that's because of you, Real Engineering. Thanks.

  • Nitrocide
    Nitrocide 2 months ago +7

    Commenter: *incorrect comment*
    Real Engineering: *YOU DARE OPPOSE ME MORTAL*

  • EXL Playz
    EXL Playz 2 months ago

    Speak English. Not “I LIKE PLANES”-ish.

  • EXL Playz
    EXL Playz 2 months ago

    What if in the valley, the valley has to much friction (grass). The ball might be stuck on the hill...

  • Vagelis Axarides
    Vagelis Axarides 2 months ago

    @3:55 what a beautiful shot of my city

  • evolboost
    evolboost 2 months ago

    If only we could apply these stability lessons to girls...

  • Ryan Smith
    Ryan Smith 2 months ago

    I mean.... a fighter is really just a rectangular box with an engine. Good thing for thrust vectoring tho

  • El Game'o Cammando
    El Game'o Cammando 2 months ago

    people actually thought more is good? lol you would think you'd know too much of anything ia bad.

    • El Game'o Cammando
      El Game'o Cammando 2 months ago

      Too little too nice, Perfectly balanced as all things should be.

  • athanasios koukoulis
    athanasios koukoulis 2 months ago

    Students pilots watching your video also!

  • Bhavi Rathore
    Bhavi Rathore 2 months ago

    2:39 the side view not being in line with front view really is discomforting for me.

  • a nonymous
    a nonymous 2 months ago

    The Harrier family of aircraft were well known for their Anhedral wings allowing for incredible maneuverability when rolling, when this was considered unsafe the british government mandated that a system be put in place to reduce the risk of instability, the royal air forces solution was to install the system, but not actually attach it to the aircraft mechanics and avionics, thereby obeying the law but maintaining the effectiveness of the harrier. (Or so I have been told)

  • Max sucks at games
    Max sucks at games 2 months ago

    All I learned Is that Cessena 172 was designed by a smart dude and that fighter jet designers are murderous monsters

  • RSGTomcat
    RSGTomcat 2 months ago

    As an aerospace engineer, I just wanted clarify one detail:
    Downwash is not really a substantial factor in the static stability and control of an aircraft in the sense that you described. It has an impact on the tail aerodynamics, yes... But it's affect is accounted for in the angle of incidence of the horizontal stabilizer during the design phase of the plane. That's why it's impact doesn't really affect the stability as substantially the way the video implied. The downwash vector stays about the same with constant AoA and increasing speed. It does change with varying wing AoA, but that's more of a dynamic issue than a static one. If the designer wants an effective AoA on the h-stab of -2° and the wing downwash produces -1° of effective AoA in the local free stream airflow around the tail, then the H-stab will intentionally be placed at -1° from the fuselage centerline because that is -2° from the local free stream air at the tail. Lift is a function of AoA and speed. The angle of incidence acts as a constant AoA of the h-stab (including accounting for downwash) relative to the velocity vector of the plane. The velocity changes with altitude as the attitude goes from upwards pitch to climb and slow down, to downwards pitch to descend and speed up.
    Everything else was spot on.

  • Zaspany Flegmatyk
    Zaspany Flegmatyk 2 months ago

    Thanks, I actually study control engineering and I really found it inspirational :D

  • asdasd aasfdsf
    asdasd aasfdsf 2 months ago


  • Weston Harris
    Weston Harris 2 months ago

    - sees name of video -
    - has flashbacks of every plane every built in KSP -
    Literally though, I spent ya. About half a day trying to fix a fighter jet that I have no clue what the problem is.

  • Ilias C
    Ilias C 3 months ago

    3:54 Thessaloniki Greece

  • Aroop Roelofs
    Aroop Roelofs 3 months ago

    With this knowledge, I managed to build an airplane in KSP that isn't hypermobile :>

  • Airguardian
    Airguardian 3 months ago +1

    There's many misleading things on this video. First and foremost, the unstability of a FSW design like the X-29 or Su-47 doesn't come inherently from the planform design of the wings but rather from the placement of CG relative to center of lift. A forward swept wing aircraft can perfectly be designed to be stable. Then, the video of the hornet crashing at 8:10 has NOTHING to do with the topic of stability. In fact that plane was designed to be statically stable if I recall correctly. That accident happened because of an engine flameout during a high-alpha pass inducing too heavy of a yaw-rolling coupled moment for the pilot to compensate. Then you hint that the energy that needs to be spent on control surfaces to recover back to 'balance' when maneuvering is much higher than what it is in practicality for unstable designs while not mentioning or accounting for the fact that 'stable' designs also pay for their stability with 'trim drag' energy bleed. You are also referring to plane trajectories with regard to stability in a way that only makes sense for trimmed aircraft with the control surfaces being fixed without pilot input, not for planes with computers running them... Usually your videos are great, but this one didn't reach your usual quality standards. Not sure if you rushed it or just don't have enough grasp on the subject. :'(

  • Amir Alavi
    Amir Alavi 3 months ago

    Boy you are an F-15 fan. No complaints tho, it's a nice bird!

  • Peter Smythe
    Peter Smythe 3 months ago

    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.

  • Peter Smythe
    Peter Smythe 3 months ago

    Static stability implies STRAIGHT flight. But not level. A lawn dart is excessively statically stable, but will plow itself straight into the ground even with a rocket motor attached to it.

  • Gehtdi anschasau
    Gehtdi anschasau 3 months ago

    7:04 It might be a flawed concept, but making this wings adjust that fast and still withstand air resistance at fighter jet speed is amazing.

  • Stormy Campbell
    Stormy Campbell 3 months ago

    As an engineering student in high school, and aspiring pilot, I sometimes question if aviation is really the route I want to go in life. Then I find myself on youtube and end up finding new ways to fall in love with the industry all over again.

  • Christyandi K
    Christyandi K 3 months ago

    I too can be (emotionally) unstable

  • Jeffrey Stroman
    Jeffrey Stroman 3 months ago

    This is an excellent video, thanks

    JOSEF BORG 3 months ago

    I think your idea and use of 'automatically' is very flawed, no aircraft designed will return to or maintain a stable flight without input from the pilot... This is for large passenger planes, commuter planes that are smaller and fighter jets.
    There are many factors behind this reason and it would take a proper understanding of flight physics to explain it for clearly, however it should suffice for you to understand there is a reason and aircraft has controlled surfaces and that is primarily to keep the aircraft in a stable and purposeful flight path.
    All aircraft left to themselves will roll and crash!

  • RageAlert47 Of The Ragers
    RageAlert47 Of The Ragers 3 months ago +20

    Normal people: But
    Real Engineering: *_Bot_*

  • Everythingman
    Everythingman 3 months ago

    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.

  • Sukacita Yeremia
    Sukacita Yeremia 3 months ago

    OK, now, is it possible to make a plane that are unstable changing to both directions?

  • Bryce McCormick
    Bryce McCormick 3 months ago

    Gotta keep those poles in the open left hand plane!!!

  • Jim Jam
    Jim Jam 3 months ago

    I'll have to watch this multiple times.. but I'll be back. Cheers

  • Ankur Vashishtha
    Ankur Vashishtha 3 months ago

    Real Engineering to comment section:- How do you like them apples?