ECAMS:
As I understand the FC diagrams, Alt Law has auto trim for elevators and THS, you go to manual trim in Direct law for the THS. If I am reading that wrong, please advise.
From the diagram, it appears to me that elevator trim may not be operating in Direct law, but I may be wrong on that.
Here are the words ... (from an
out of date summary of A 330 systems)
Alternate Law
• No change for
ground, take-off and flare mode compared to Normal Law.
•
Flight mode :
Pitch axis : as per Normal Law with limited pitch rate and gains depending on speed and CONF.
- Roll/yaw axes : Depending on failure :
1. The lateral control is similar to normal law (no positive spiral stability is introduced).
2. Characterized by a direct stick-to-roll surface relationship which is configuration dependent
•
Protections :
- pitch attitude : lost
- high speed : replaced by static stability
- high angle of attack : replaced by static stability
(Vc prot. Law) + aural stall warning when
α > α sw*
- low energy : lost
Direct Law
• No change for
ground mode and take-off mode compared to Normal Law.
• Flight mode : Maintained down to the ground in all three axes, direct relationship between stick and elevator/roll control surfaces which is center of gravity and configuration dependent.
•
All protections are lost
Conventional aural stall and overspeed warnings are provided as for Alternate Law.
• Main operational aspect :
- manual trimming
through trim wheel.