Originally Posted by roulishollandais
two very different situations :
- The flight AA587 [...]conventional aerodynamic forces.
- In the both cases with Yaw damper failure [...] Dutch roll
Dozy,
It seems that my text was unclear : the both cases were Miami and Bubbers44's B727 flight and did not correspond to the two situations.
In my post I suspected a dutch roll as possible, in the Miami flight, and in Bubbers44's B727 flight (avoided by Bubbers44 aerobatics experience), and not in the AA587 flight.
The connexion I am asserting, between AA587 and dutch roll, is that AA587 used a unfounded and dangerous method, created against Learjet's dutch roll generalized to other oscillations too, as nobody worried about dutch roll and other oscillations. Telling about PIO experiences has during a long time been considered as totaly taboo (not sure it is finished).
In any situation that rudder pedaling is dangerous.
edit : add that PS : If you have a dutch roll, accept the yaw damper outputs as they are (adapted or failing, you can do nothing, only the ground), but only the pilot's input on stick and pedals can - and must - be modified and adapted to stop increasing that crazy oscillation (and high negative Vz) and stop the oscillation and stabilize attitude and path so much as possible (once more inertial data HUD may help).