Just a few thoughts on trim.
I've never flown even the 'Bus simulator, but I have studied the systems. (Does the Caravelle simulator count?
) I'm a retired Naval Aviator and both old and bold.
Yes, the THS is a 500 pound gorilla that can overpower the elevator position.
The THS is controlled by the Prim computers, theoretically any one of the three Prims can do it. Without Prims, it won't move except by manual input.
Recently, I was attempting to clarify some issues regarding THS manual trim (in the last thread), and asked the question, "
How does the system know the pilots are done applying manual trim?" Apparently, once it senses the crew playing with manual trim, it gives up and says "Your trim for the rest of the flight." In a normal flight context, this is bad since the THS can overpower the elevator and cause potentially dangerous loss of control or interfere with proper functioning of protections.
The airlines/training establishments apparently consider this to be a very serious safety problem and they apply draconian penalties for touching the trim wheel. As a result, aircrews fly the majority of their careers without touching the manual trim wheel after it is set for takeoff. They almost forget it is there once airborne.
The trim wheel moves as the aircraft trims itself. There are marks alongside the trim wheel indicating its position, and these marks are illuminated so that they are visible at night in a dark cockpit, but it appears aircrews are not even thinking about looking at the wheel for information.
Part of the problem seems to be that the aircraft does not have the ability to resume automatic control of the trim once the microswitch that senses manual override is activated. As a result, crews are taught to keep their paws off the thing. That would result in bad training habits. (Real Airbus guys feel free to correct these statements.)
Next issue. The trim running up to 13 degrees makes sense due to the prolonged nose up stick input. Once a high AOA was achieved, however, the AOA readings and airspeeds were considered invalid (due to airspeed below 30 knots). The PRIMS could not have liked that and were no doubt all 3 disabled by that point. Once the PF started making nose down inputs, the Prims were still disabled and thus the THS did not move from its 13 degree position.. The crew did not get the proper feedback from their nose down control inputs (the stall warning actually came back) and they never saw the trim position due to their past training.
The only way to have saved the day was to get the trim rolled down manually to get the plane flying again.
Apparently the A330 pitching moments were not so bad as to prevent a stall recovery with proper control inputs.