A330 ALT LAW without Auto-trim?

[stabilator]

Hello all, finally decided to join the forum, i've got a question for the Airbus pilots

I was reading the QF72 report and noticed the A330 reverted to alternate law without auto-trim (like in abnormal attitude ALT law) and it states the crew had to manually trim the aircraft. I'm curious as to how the aircraft would have behaved in this configuration.

As I understand it, the elevators are used by the auto trim for short term inputs, and the THS then moves to fair them. So would the lack of autotrim mean just the THS is frozen with the elevators still providing the flight path stability in ALT law (with manual trim just to fair the elevator)? or would it have had more conventional behavior, with neither elevator nor THS providing flight path stability, requiring manual trim for speed and config changes?

The report doesn't go into much further detail but I was left asking questions about how the load factor demand in ALT law works when the autotrim function is not doing its thing.

I am not a transport pilot so this question is purely out of interest, if any airbus pilots could chip in with their two cents it would be greatly appreciated.

Thanks

[BEL1000]

Flying a let's say A320 in Alternate Law with no auto trim would mean that you have to obviously trim airplane yourself. Which for example means if you want to ascend at 1000 FT/MIN then you need to have a slight pushback pressure on the sidestick all the time until reaching desired altitude. If auto trim exists and you want to let's say climb at the same rate of climb which we said would be 1000 FT/MIN then you need to apply slight pushback pressure on the sidesticks for a few seconds or shorter until climbing at 1000 FT/MIN then you need to release sidestick for it to come to the neutral (Center) position and let autotrim adjust it and let it keep climbing at a constant 1000 FT/MIN.

Or just trim to ascend at 1000 FT/MIN if in Alternate Law with no Auto Trim available.

Auto trim is good and does not require you to keep sidestick in a certain position when climbing or descending and keeps that descent/climb rate it stopped at when releasing sidestick.

[C_Star]

I'd say alternate law/load factor demand work the same as in normal flight - i.e. the airplane is stable and flt controls behavior is unchanged - no trim required to fly the plane. The only difference would be that the elevator stays permanently deflected to maintain commanded path. A manual input on the trim wheel is only required to zero the elevator deflection.

Here's an excerpt from the FCOM:

F/CTL STAB CTL FAULT Applicable to: MSN ***

Ident.: PRO-ABN-27-L-00010373.0001001 / 05 AUG 10

MAN PITCH TRIM........................................................ ...........................................................C HECK L2The force needed on the pitch trim wheel may be higher than usual (pre-takeoff manual setting). L1 IF MAN TRIM AVAIL: TRIM FOR NEUTRAL ELEV L2 If man pitch trim is available, trim to maintain elevator at zero position (indications on F/CTL SD page). To improve the longitudinal control of the aircraft, it is recommended to disconnect the autothrust.

L1 IF TRIM LOCKED > 8 UP: MAX SPEED....................................................... ............................................................ ...180 KT L2 If trim is locked above 8 ° up, pitch down authority may not be sufficient for speed above 180 kt. Select configuration as appropriate - Fuel consumption is increased.

L1

ASSOCIATED PROCEDURES

F/CTL ALTN LAW (PROT LOST) MAX SPEED....................................................... ............................................................ ..........330/.82

[stabilator]

Thanks for the responses fella's, perfectly answers my question.

Cheers