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SOLVED High AoA reverses roll inputs…how?!

2,507 OrderlyHippo  1.4 years ago

Here’s a video of what I mean.

I’m so confused. My current theory is that the rear wings force the plane to yaw. This yawing of the plane causes more air to hit the vertical stabilizers, which roll the plane.
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Edit: I tried yawing against the yaw created by rolling and it seems to work. Yawing behaved more like typical roll inputs during high AoA which is neat :P
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Edit: It's because of SNAP ROLL, "a dynamic roll caused by 1 wing being completely stalled and the other wing being completely un-stalled and driving the roll round."

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    2,507 OrderlyHippo

    https://youtu.be/D1J1oUP-aKA
    You stall at a fixed indicated airspeed.
    Mass does not change the stall angle of attack. However it does change the indicated airspeed that stall occurs. So fly the plane and see what the IAS is when it stalls.

    1.3 years ago
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    2,507 OrderlyHippo

    @WNP78 What am I missing? Because if AoA determines when snap roll occurs, inverting the user’s roll input at a fixed AoA should fix the issue of inverted controls and it doesn’t seem to. Here’s evidence. How can I make the plane handle 50 deg AoA like the real one?

    1.4 years ago
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    2,507 OrderlyHippo

    @WNP78 I want a pid controller to correct for snap roll and not reduce angle of attack. I want the plane to continue pitching hard. I’m trying to make an F-35 reach the 50 deg AoA limit but I can’t and it’s driving me crazy. click me

    1.4 years ago
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    Dev WNP78

    @OrderlyHippo it's just an angle of attack. Have something show your current angle of attack and bring the plane to a stall.

    1.4 years ago
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    82.2k ReinMcDeer

    F-14 moment

    +1 1.4 years ago
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    2,507 OrderlyHippo

    @WNP78 But I'd like to know when it happens. I have to know when lift fails and drag increases. I want to know the amount of lift and drag exactly when stall occurs. I believe you're saying this ratio never changes, so don't do senseless calculations to find the angle? How do you find this ratio? Trial and error? Is a wing's stall speed not the way?

    1.4 years ago
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    Dev WNP78

    @OrderlyHippo stalling generally happens at the same angle of attack (critical angle) of the wing. Using the ailerons changes the angle of the wing and hence the angle of attack.

    1.4 years ago
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    2,507 OrderlyHippo

    @WNP78 “Snap roll!" So, that's what it is. Is it possible to know when a wing has stalled?
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    I found a function online for a wing's stall speed (google "calculate stall speed"), but it requires air density...I don't know if that's a variable that exists in SP. @Huax performed an experiment, click me, and found an approximate formula for air density: pow(2,-Altitude/5296)
    I'll probably just use that
    Edit: Weight not taken into account. Doesn’t work :(

    1.4 years ago
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    125k BaconEggs

    nice

    1.4 years ago
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    Dev WNP78

    here's a page that might explain some of the concepts: https://www.aviationsafetymagazine.com/features/stall-recovery-ailerons-or-rudder/

    Specifically the section titled "the stall":

    “Under some conditions, an aileron that is set to lift a drooping wing may actually stall that wing and drop it viciously,”

    Essentially, trying to roll left, you're using the right aileron to "lift" the right wing up. If that wing is just on the verge of stalling, the extra lifting is too much to ask of the wing, causing it to stall and lose even more lift, making it fall instead of rise.

    +5 1.4 years ago
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    it's more of an uncommanded roll than a commanded roll which got inverted
    could be airfoil issues
    could be lift issues

    but yeah some planes have this effect

    1.4 years ago