correct as is FBW Pushing Nose Down with Greater than 11 Degrees AoA in Landing Gains Making It Difficult Hold 13 AoA on Approach Causing Pitch Occilations

[Hawkeye91]

There seems to be a new thing occurring with the FBW that didn't seem to occur prior to the flight model update where the F16 keeps want to pitch the nose down if your AoA goes above 11 degrees. This makes it difficult to do short field style approaches where its recommended to hold 13 degrees AoA on final for a minimum distance landing.

I managed to do a decent job in this trackfile holding the 13 AoA but I felt like I was fighting the tendency of the nose to drop to 11 degrees the whole time making the approach feel very unstable from a control standpoint. From what I understand from reading the public manuals, in landing gains, above 10 degrees AoA the FBW pitch system goes into a combined AoA Command and Pitch Rate Mode, I'm not sure how exactly this should translate to how our control inputs should feel, but right now it feels like unless you hold a constant backpressure against the FBW it wants to pitch the nose down to lower the AoA.

I'm using realsim's FSSB and I have the force settings set at 13 lbs of force for max pitch deflection allowing me to make really fine grain adjustments on final and right now the FBW feels really unstable with the pitch down tendency.

Should the FBW above 10 degrees AoA require you to hold against the nose down tendency to maintain a 13 degree AoA?

F16 Approach Pitch Occilationstrk.trk

Edited July 14, 2022 by Hawkeye91

[BIGNEWY]

Hi, the team have checked, and it is working as intended.

FLCS works as AoA/pitch rate command system above 10 degrees of AoA in to/landing gains. This means that FLCS will reduce any stick input above 10 degrees of AoA, so you will need to pull-up on the stick more and hold it to maintain 13 degrees AoA on approach or trim to it. 

thank you

 

[Yaga]

On 7/13/2022 at 2:20 PM, Hawkeye91 said:

There seems to be a new thing occurring with the FBW that didn't seem to occur prior to the flight model update where the F16 keeps want to pitch the nose down if your AoA goes above 11 degrees. This makes it difficult to do short field style approaches where its recommended to hold 13 degrees AoA on final for a minimum distance landing.

I managed to do a decent job in this trackfile holding the 13 AoA but I felt like I was fighting the tendency of the nose to drop to 11 degrees the whole time making the approach feel very unstable from a control standpoint. From what I understand from reading the public manuals, in landing gains, above 10 degrees AoA the FBW pitch system goes into a combined AoA Command and Pitch Rate Mode, I'm not sure how exactly this should translate to how our control inputs should feel, but right now it feels like unless you hold a constant backpressure against the FBW it wants to pitch the nose down to lower the AoA.

I'm using realsim's FSSB and I have the force settings set at 13 lbs of force for max pitch deflection allowing me to make really fine grain adjustments on final and right now the FBW feels really unstable with the pitch down tendency.

Should the FBW above 10 degrees AoA require you to hold against the nose down tendency to maintain a 13 degree AoA?

F16 Approach Pitch Occilationstrk.trk 4.09 MB · 3 downloads

 

No, there's definitely something weird going on. I also use the FSSB and absolutely know the unstable wobble you're describing. Also seems to happen during AAR on occasion. 

In the comment above, it's suggested to correct with pitch rate trim. That's a bit odd and seems like a symptom that something else isn't quite right. . 

Reduction above 10deg AoA might be too aggressive. The opposite might be true under 10deg AoA. This could make your nose feel heavy at 11deg AoA and light at 9deg AoA with extremely unstable response to input as it transitions between. 

It does feel a lot like a feedback loop. An induced oscillation from a far too negative curve. 

As far as FSSB settings, I found that reducing the max pitch force helped a bit. 

 

Edited July 17, 2022 by Yaga

[RuskyV]

I'm a user of the FSSB and something that has helped me is reducing the pitch curvature to 78, the remaining 22 percent seems to have no input into the flight model, this was observed by conventional joystick users when pulling the stick all the way back and finding that last percentage was having no impact on pitch at all. (There is a thread somewhere that discusses this).

interesting that the last 22 percent has no impact on commanded pitch rate, but I guess that's not really the topic of this thread...

anyhow give it a shot and see if it helps