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High AOA

276 elliotjuk  1.1 years ago

Hello all,
I was just wondering if there was any advice yall can give me on how to make an aircraft thats good at high angle of attack manuveurs.
My main issue is that roll reverses at high aoa (and I know i'm not meant to use ailerons as such), but is there any way to prevent this?
In addition, are tricks like LERX modelled ingame, or are they simply only there to make an aircraft more unstable?
Thanks

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    276 elliotjuk

    @ToeTips
    @Nerfaddict
    I also just posted a new HARV if you want to have some experiments with it. Link is here.

    edit: wrong link

    1.1 years ago
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    276 elliotjuk

    For people that stumble onto this post in the future, I can conclude that:

    • The more unstable a plane, the less alpha it can pull as all it will want to do is backflip
    • There is a balance for each plane for pulling high alpha - it depends on your thrust to weight ratio, leading edge slats/flaps and wing loading.
    • A higher wing loading means you can induce the alpha at a higher speed, but this comes at the cost of overall stability as you have less wing
    • A lower wing loading means the plane will stall less at lower speeds, but you'll never be able to pull alpha as either the insane thrust to weight will keep it airborne or just the sheer amount of lift will prevent a stall (which is needed for alpha.)
    • Having front control surfaces such as canards will help alot for stability, and using a bit of coding magic you can make the process automatic
    • It is better to use PitchRate for slats, and pitch/vtol for flaps. This is because the slats slow down the pitch rate until you either run out of deflection or you have reached the stop point. Flaps do the opposite, they induce the alpha.
    • Instability will make the plane rapidly pitch up, which can be nice for instantaneous turns but not for sustained alpha. You will need to make the plane more stable by either moving the landing gear or adding weight in the front.
    • Too much instability will be way too hard to control as the more you increase the code's sensitivity, the more it will shake the control surfaces, making it less precise
    1.1 years ago
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    276 elliotjuk

    I just posted a high alpha research vehicle here

    1.1 years ago
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    276 elliotjuk

    @ReinMcDeer yeah, i just needed to do more research
    i originally thought LERX was just vortex controlling, but its more than that
    the LERX causes the root of the wing to have a bigger chord, which delays the stall as the centre of pressure is far futher forward

    +1 1.1 years ago
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    94.0k ReinMcDeer

    LERX does work but it needs to be made using the default wings (you can also make them hidden)

    1.1 years ago
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    276 elliotjuk

    @ToeTips not jet 13, that one just demonstrates what i've managed to accomplish with 'canards'. Take the Llama instead

    1.1 years ago
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    26.6k ToeTips

    @elliotjuk
    So should I modify that airframe or?

    1.1 years ago
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    29.8k Nerfaddict

    @elliotjuk here's a demonstration craft I made that uses all the points me and baconeggs mentioned

    1.1 years ago
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    276 elliotjuk

    In short, I want an airframe that is unstable enough for instantaneous turns, but is easy to control and has PSM capability with raw aerodynamics (similar to the 'Jet 13' I just uploaded), while having a realistic G limit and a lack of canards

    1.1 years ago
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    276 elliotjuk

    @BaconEggs @Nerfaddict
    Shouldn't higher wing loadings increase speed (not modelled in SP unless you use fuselage wings), but decrease agility + manuverability?
    And also, I found having the primary wings generate lift ahead of the centre of mass and using the horizontal stabilisers to well... stabilise the aircraft works well for instantanous turns (but it comes at a lack of AOA because it wants to pull up constantly after they stall)

    1.1 years ago
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    276 elliotjuk

    @ToeTips Sure. I have one currently on my profile (not the AOA one, but still pretty good)
    I'll upload it in a minute
    I'm reasonable at making unstable aircraft, just not giving it the high AOA capability, unlike another one which i'm also going to upload (it has canards, which is likely why its more manuverable)

    1.1 years ago
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    29.8k Nerfaddict

    @elliotjuk I've made innumerable PSM Capable aircraft and here's what I found works best:
    |
    -"Flat Bottom" Airfoils have the smoothest stall curve meaning plenty of control even past 30°AOA check here for more info
    |
    -Having a wing loading between 200kg/m² and 300kg/m² works great and still leaves loads of agility, but 350kg/m² and higher is kinda pushing it as from my experiences it makes the aircraft feel quite sluggish
    |
    Basically, higher wing loadings increase manueverability, but decrease agility and vice verse
    |
    -CoL should be close to the CoM but still behind it, the closer the better
    |
    -FBW works wonders, but is completely optional due to complexity

    +1 1.1 years ago
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    137k BaconEggs

    flat bottom and nacaprop airfoils, keep center of lift slightly behind center of gravity *depending on the configuration

    +1 1.1 years ago
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    26.6k ToeTips

    @elliotjuk
    I see
    Can I see the plane? I'm a action is better than words type guy

    1.1 years ago
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    276 elliotjuk

    @ToeTips As much as I would like to, I want to design a plane that doesn't need them compared to others - I've been partly successful with forward swept wings, but thrust vectoring on the same design feels like cheating

    1.1 years ago
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    26.6k ToeTips

    Use canards. They are bit like front wheel steering on cars. The offer more nose authority on planes.

    1.1 years ago