AFCS Altitude Hold Transonic bug.

[CF104]

Hello,

While in Altitude Hold and accelerating through the transonic region, the autopilot doesn't react according to the IRL F-4E flight manual. At 0.9 Mach there is a slight altitude fluctuation that the AFCS handles as the initial shock wave passes the pitot boom static port. Passing through Mach 1.0 causes a quick increase in indicated altitude accompanied by a violent pitch down by the AFCS followed by an AFCS auto disconnect. This is contrary to the real life flight manual stating that there will be fluctuations but not violent. It would appear that the static pressure shock wave influence may be overdone? Applicable TO 1F-4E-1 reference and flight track file attached. 

F-4E testing AFCS ALT HOLD.trk

[Cat107]

I think that our altitude error is pretty accurate, but the current autopilot response is a bit too violent, we are already investigating the issue and we will try to adjust the autopliot to better handle that, thanks for your input 

 

Edited June 12, 2024 by Cat107