Lonewolf_50
Retired F4
As caveated by our contributor, the scenario might not have been similar enough to have triggered a "this is one of those situations" responses from the crew.
What I was trying to get at (damping and pitch rate limiting functions considered) is that I think the pitch rates would be a little faster (you'd have to wait less time) if you moved the THS with the wheels (even when auto trim is functioning, which it should in Alt 2) rather than wait for the elevator THS linkage to induce THS nose down (THS actually up a bit) commands.
But if one doesn't train it, one probably doesn't resort to such actionns when things get hairy in the cockpit.
Iīm fully with you at that, but:
I wanted to make it clear, that i couldnīt find a reference in the valid publications for aircrew (FCOM, FTCOM) and maintenance (LTTM), which even would give a hint to use manual trim in such cases.
So how should the crew know about it?
Why should it have been trained?
Did anybody knew it before AF447?
On what basis would it be trained now?
We had the manual trim discussion before on the older thread, but there everybody asssumed direct law, where only manual trim is available.
We even dont know, how the system will behave after manual trim has been applied despite autotrim still active.
(Ref. LTTM)
Operation/Control and Indicating
When you turn the handwheel installed in the cockpit center pedestal the chain and cable loop move the input shaft. The input shaft moves the mechanical servoloop mechanism through an override mechanism. The override mechanism, which is installed adjacent to the Pitch Trim Actuator (PTA), makes sure that the mechanical control cancels the electrical control.
Operation of the Override Mechanism
Operation of the Mechanical Control
The input shaft turns.
A cam in the shape of a V turns.
The cam moves a roller which disconnects the internal microteeth from the
output shaft of the PTA.
At the same time a piston is pushed to operate the three override mechanism microswitches.
The mechanical control now comes on before the electrical control.
Release of the Mechanical Control
The input shaft stops.
The cam in the PTA is released.
The internal springs connect the internal microteeth to the output shaft of
the PTA.
At the same time the piston moves back from the microswitches.
The mechanism is now set in the electrical control position.
MECHANICAL INPUT SHAFT
The Mechanical input shaft connects the mechanical control loop and theTHS
actuator. The shaft has a flange which is connected to the mechanical input of the THS actuator. The other end of the shaft has a sprocket. The mechanical control-loop chain is installed on the sprocket
What happens after release (which i interpret as not turning the wheel any more)? I couldnīt find anything in the manuals.
Point is: We know now, that trimming the THS manually would have helped to bring the nose down. But we dont know consequences in other circumstances, as there seems to be no documentation concerning such a usage. So how can one train for it without documentation?