thanks for your reply de facto!
i was flying flap 40 on a very stable air, and you know sometimes in this very nice condition, your mind and vision will freeze for a little while, but that was critical. and you know that sometimes happens when you fly for a long time.
but my question is when the aircraft bounced in the air，the landing gear struct should extend again, the air ground senser is rerurn to air mode. but when you retard the throttle, the speed brake will still deploy!