fixed differential stabilator and rudder behavior in a Deep Stall with MPO engaged

DummyCatz · December 17, 2022

Hi,

Found two control logic bugs. One is related to the stabilators, and the other is related to the rudder.

First the stabilators. In my recent deep stall experiences with MPO engaged, I noticed that when the stick is released, the fully-deflected stabs would first return to neutral position upon MPO engagement, which is correct. But then the stabs slowly returned to full nose-down position, as if the pitch integrator was not disconnected, which I considered a bug.

In case of a yaw departure and subsequent spin, holding MPO but bot touching the stick is very useful as the differential stabs would help to generate extra yawing moment to negate the spin. If the stabs are fully deflected, we cannot make use of the differential mechanism anymore.

The second bug is about the rudder. In a deep stall condition, the rudder would also act to negate any yawing motion, using purely yaw-rate sensor inputs. This is independent of the AOS (angle of sideslip) feedback that could help to increase departure resistance, as elaborated in the dash-1 manual, 'AOS feedback function' and also 'yaw rate limiter' paragraphs in the FLCS section. Holding MPO switch would disconnect the AOS feedback so we only got yaw-rate feedback here.

But in DCS, what I noticed is that the rudder is deflected against the yaw half-way through the yaw motion, but then is deflected into the yaw again, as if the AOS feedback is still there and not disabled by MPO. This is highlighted with slow motion in the track.

Thanks.

F16 deep stall behavior of rudder and diff stab.trk

Edited December 17, 2022 by DummyCatz