I fly the Airbus A320/21 so I can only tell you about that. I understand that a similar logic applies to the rest of the Airbus
family. The ground spoilers automatically extend when both main gears are compressed and:
1. Both throttles are at forward idle if ground spoilers
are armed,
or;
2. Reverse thrust is slected on a least one egine with other thrust lever at idle if ground spoilers
are not armed.
However, just to complicate things further, the spoilers will deploy partially (10 degrees) if:
1. Reverse thrust is selected on at least one engine with the other thrust lever at idle
and;
2. At least one main gear strut is compressed.
This takes care of the single engine case. Hope this helps?!
LOC
