On landing, with the main landing gear touched down, the spoilers will deploy if thrust levers are idle or is reverse is selected on 2 engines (one each side).
There are circumstances when just one main landing has touched down, this will still deploy spoilers, but only partially, reverse has to be selected on 2 engines (one either side again). The theory is that this will slightly decrease the lift to bring the other main landing gear to the ground more gently than by deploying full spoilers. Normal spoiler deployment sequence continues when both gear is down.
As for deploying reverse thrust straight from the A340 manual:
"Deployment requires :
— one FADEC channel operating with its associated throttle reverse signal
— aircraft on ground from at least one LGCIU
— TLA (thrust lever angle) reverse signal from PRIM 1 (FLT CTL
PRIMARY COMPUTER 1) or associated PRIM
— switch reverse signal from associated EIU
Before the transit completion of the blocker doors, the FADEC sets reverse idle thrust."
As for deploying just the inboard reversers, when pulling the levers, I have personally found the inboard to immediately deploy, the outer ones follow almost immediately after, must be something to do with the interlock mechanism. Another note/possibility is that I have often flown with an outboard thrust reverser MEL..so the opposite outboard thrust reverser is interlocked, so it cannot supply reverse thrust, only idle reverse.
In Cathay, our procedures are to pull the thrust reverser levers immediately after touchdown.
Hope that helps
[Edited 2008-09-09 08:52:19]
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