four engine jock
I've read that the engines on the B727 can be used in-flight - but not recommended!
The Trident (or more affectionally known as the "Ground-gripper" within British Airways) routinely used reverse thrust in the air and could achieve a rate of descent of around 10 to 15000 fpm. Reversers were routinely used during the landing flare; however, they weren't to be deployed without the implicit order from the handling pilot; otherwise the pitch-change came as a big surprise!
A captain (an ex Trident man) who I used to fly with whilst on the L1011 was recounting those days when he flew the Ground-gripper. One day when he was asked if he had enough height and speed to continue his approach he replied (in his Yorkshire accent) "Aye, ave got'n abundance of both"!
TCF