F-14: FCS roll. Slow to return to centre.
Megaf opened this issue · 9 comments
After AFCS improvements the roll channel seems to be ultra slow to return to centre after full left or right stick.
Demosntration
https://www.youtube.com/watch?v=8nXRYBN3a4E
Thanks for the report.
This made me realise that
- The moments for pitch and yaw are need to be re-examined
- Roll FCS only using the outer spoilers (bug)
- Faults in the FCS where I had used 0.5 instead of 0.05 on roll and yaw
Please retest - I've made adjustments that I think overall is an airplane that handles better - but more validation is required.
- Chaange to the FCS so that all spoilers deploy for
roll control unless DLC active - Moments for pitch, roll, yaw corrected because the
deflection angle, side/set apportionment and
therefire the coefficients needed to be reworked
to fix this - Fixes to FCS compenstators where 0.5 being used instead
of 0.05
Ok, the issue I reported is fixed. Roll self centers on stick release as expected.
Now another issue is present. There jitter in the roll,
Upon moving the stick half way for example, the aircraft starts rolling and stops then starts and stops and so on.
The roll is jittered.
Overall though, it is better.
The logic has been revised to match the F-14 FCS [1] as documented in NASA-TM-81833 - the fixes are to feed in certain values rather than allowing a jump change.
As far as I can ascertain this is as per the aircraft - however I do notice that after releasing the stick there is a small stutter depending on airspeed. Controlling the aircraft correctly (i.e. not snap releasing) mitigates this.
[1] ROLL SAS as implemented
I tested again today on commit 7aa08a3
The jitter seems to be gone.
Only issue left is, roll doesnt return to centre in one movement, it returns around halfway, tops, and then continue returning slowly.
The maximum rate limit is 36deg/second - so from a 50 degree deflection it will take at least two seconds and probably longer because of the phase lead lag controller.
1
0.05 S + 1
rate limit
36 deg/second
The 0.05 S + 1 will provide extra delay
ref:
With the changes made up to and including commit f2e1dac I now think that all of the SAS is correctly implemented
I hope this video will show a few of the issues.
https://youtu.be/W3kJr08OSSA
List of issues I tried to show here. Not in order.
- It doesn't self centre in one movement, it centres halfway, stops, continues slowly.
- Random roll when trying level flight without any stick input.
- On full side deflection, the angle of spoilers oscillated, causing the roll to be not constant.
- Rudder behaves erratically.