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F16 crosswind rudder correction is same w/speed on takeoff/landing - not real (?)


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Right now, when a crosswind is present on takeoff or landing, the amount of rudder input to maintain a path  on the runway centerline is a constant amount of rudder input - even as speed increases.
I think the rudder input for the crosswind should be LOWER as speed INCREASES.

   i.e. 60kts runway speed in 20kts crosswind = large rudder input to stay straight

   I think 160kts speed in 20kts crosswind = smaller rudder input than at 30kts speed.

This is really a problem for me when I turn OFF NWS around 100+ kts.  I have to input even more rudder to correct (yes I get that NWS helps maintain a straight track).  And some MP servers use 30hts crosswind.

Also, while flying the F16 at low speed, in my opinion the rudder input injects way too much roll. Yes, the rudder is not 90 degrees perpendicular, so some roll coupling will occur.  But it just seems too high, based on my propeller real pilot experience (including some aerobatic SEL planes).

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You're probably right about the angle of the rudder deflection.  But who knows what the FLCS does.  Often in aeronautical control systems the control gain will be inversely scaled by dynamic pressure (i.e. indicated airspeed) so the same pedal position produces a proportionally smaller deflection, but produces an equivalent effect.

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You don't have to apply rudder input.

 

In real FLCS the ARI (ailerons - rudder interconnect) makes the job.

 

FM is now WIP so may be isn't working as it should but do not get used to using rudder corrections. You don't have to do that if the FM is as real.


Edited by wizoo
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1 hour ago, wizoo said:

You don't have to apply rudder input.

 

In real FLCS the ARI (ailerons - rudder interconnect) makes the job.

 

FM is now WIP so may be isn't working as it should but do not get used to using rudder corrections. You don't have to do that if the FM is as real.

 

So steering correction during the takeoff roll is done with the stick? That's SOP?

"Subsonic is below Mach 1, supersonic is up to Mach 5. Above Mach 5 is hypersonic. And reentry from space, well, that's like Mach a lot."

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On 9/17/2021 at 6:04 PM, Machalot said:

So steering correction during the takeoff roll is done with the stick? That's SOP?

 

 

It was easy to misinterpret what he wrote, but what he meant is that in flight you don't need to touch the rudder because at slow speed the FLCS will move it for you to give you the roll response that you want at slow speed / high AoA. 

 

In a xwind landing F-16s don't touch the rudder and touch down crabbed into the wind, it's a very squirrelly aircraft to land. You can carefully use the rudder on rollout.

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You also have to account for the ground friction modeling in the sim.  I would suspect this is a global setting not specific to the Viper.  Good on you for practicing this extreme test case.

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Just FYI -  Since you mention using the rudder - I presume you are trying to decrab the viper on landing. Standard operating procedure is to NOT decrab the aircraft to align with the runway. You land crabbed. Feels weird, but actually works pretty well.

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"Just FYI -  Since you mention using the rudder - I presume you are trying to decrab the viper on landing. Standard operating procedure is to NOT decrab the aircraft to align with the runway. You land crabbed. Feels weird, but actually works pretty well. "
Hi @Deano87 - I am referring only to ON the runway use of rudder with a cross wind.  Crabbing for landing is no problem for me.

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As far as I can remember, in the other F-16 sim, landing with the F-16 requires no rudder input in crosswind conditions. You line up the flight path marker to the runway during approach. After touchdown with rear wheels, the FLCS will correct the nose direction for you automatically, so no rudder input is necessary during aerobrake, but I'm not sure about after touchdown with front wheels. It's been too long since my last time playing that sim. 

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A ground roll in a crosswind will require more rudder input to track straight when slow than when fast. If the rudder required is constant for slow and fast speeds then it is inaccurate. However I checked and it looks like the rudder input which holds track at ~80 knots is excessive at ~120 knots roll as expected.

 

The reason the "one wing low" crosswind approach method is not to be used with the F-16 is that the FLCS laws change drastically on touchdown. The particular way of crosswind approach banked into the wind but opposite rudder to align the fuselage with the runway is common in light airplanes. Using this technique in the F-16 is a problem because touching down in this way will cause the control surfaces to quickly change according to a change in how pilot inputs are converted into control surface positions. The airplane will upset despite the pilot holding constant inputs on touchdown. Instead the proscribed touchdown method is to have wings level and the fuselage not aligned with the runway.

 

 

 

 

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