F-16 level turn vs oblique turn at corner velocity.

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saberrider

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Unread post01 Sep 2017, 12:38

When you pull 9g in a level turn AoA limiter is @15 .But if you are rolled 45 degrees left/right and pull 9g limiter is the same? I ask this because when you bank for level turn AoA is higher even if you want to fly in a straight line and rudder is deflected upward.
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Unread post01 Sep 2017, 13:45

Short answer, yes it will be the same.

Long answer, you are confusing total nose angle relative to velocity vector with AoA (alpha) and sideslip (beta). If you roll 45 degrees and hold everything else the same the horizontal component of that 1G will see you turn, while the fact that the vertical component is now less than 1G means you will also start to lose altitude. You correct this by applying yaw to pull the nose toward the up-side wing. You have now generated sideslip and its force has a vertical component to assist the vertical component from the AoA but its horizontal component COUNTERS the horizontal component of the AoA. So that covers the straight line bank.

One thing to remember is that aerodynamically the plane does not care about its orientation. If you pull 9G at 90degree bank while at the CAT-I limiter you will be at 15 AoA and losing altitude. To not lose altitude you need a bank of 84-86 degrees. I can't remember exactly right now and I haven't had enough coffee to calculate it. You need a vertical component of the Aero force to counter gravity. If you are at 45 degrees of bank on a CAT-I 9G pull you will have a LOT of vertical force to counter gravity but less horizontal force so you will accelerate UP but you will have reduced lateral acceleration relative to a "level" turn, but you will still be at the same 15 AoA.

This is all academic of course, as the Viper cannot sustain energy while riding the CAT-I limiter at 9G and it will slow down and thus have reducing G and increasing AoA.
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saberrider

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Unread post01 Sep 2017, 19:49

Thank you ! But if you ad some roll how you not overshoot AOA!!
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Unread post01 Sep 2017, 20:19

saberrider wrote:Thank you ! But if you ad some roll how you not overshoot AOA!!

Excellent question! The answer is that you cannot roll with a 9G/Max AoA input. If you try and roll it reduces your G by some amount. I think this is something johnwill knows more about.
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Unread post01 Sep 2017, 20:46

There is no FCC function to reduce g when applying roll command. Roll limitations are pilot observed limits, at least at normal airspeeds. I think there are some added roll limitations at very low airpeed, high AoA conditions. If flying at 9g and applying roll, the airplane will roll, possibly over loading some airplane component like wing, horizontal tail, or vertical tail. That is why the limit is there.

There are some low altitude conditions where the F-16 ( at least some blocks) can sustain 9g. Ask Gums, been there.

The equation for bank angle required for level flight g is

Cos (BA) = 1/g
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Unread post01 Sep 2017, 21:00

johnwill wrote:There is no FCC function to reduce g when applying roll command. Roll limitations are pilot observed limits, at least at normal airspeeds. I think there are some added roll limitations at very low airpeed, high AoA conditions. If flying at 9g and applying roll, the airplane will roll, possibly over loading some airplane component like wing, horizontal tail, or vertical tail. That is why the limit is there.

There are some low altitude conditions where the F-16 ( at least some blocks) can sustain 9g. Ask Gums, been there.

The equation for bank angle required for level flight g is

Cos (BA) = 1/g

I forgot it was up to the pilot in the F-16. And I wasn't saying it couldn't sustain 9G, just not 9G at 15 AoA as that only occurs at the top right of the plateau (extremely specific point I know) and if you could sustain that... well... Thanks for the info and the equation johnwill! I owe you a drink. You don't happen to be in Phoenix are you?

See, saberrider? I told you johnwill would know more than I do.
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Unread post01 Sep 2017, 23:11

How about next time you are in DFW? I don't travel around as much as earlier days.
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Unread post01 Sep 2017, 23:18

johnwill wrote:How about next time you are in DFW? I don't travel around as much as earlier days.

If I find myself heading that way I will let you know!
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saberrider

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Unread post02 Sep 2017, 06:52

I believe that roll limit is due wings twist at high speed and aerodynamic efficiency of flaperons .After some point flaperons deflection DON'T count much because stalling point of them, so are not at max .deflection just dif. horizontal tail make the difference . Thanks to all of you for info.
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saberrider

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Unread post26 May 2018, 13:21

If one barrel roll's he will get the same amount of G's in roll or downside of rolling add one G in the HUD ,because of gravitational force pushing down?
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Unread post26 May 2018, 16:50

G displayed on the HUD is aircraft centric, not planetary centric. If you are inverted and level the HUD will read -1G.
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