Thrust Reverser
This is a serious problem. On 4 July 1966 an Air New Zealand DC 8 ZK>NZB was on a training flight in which simulated engine failure procedures were rehearsed.
The Check Captain rapidly retarded No.4 engine moments after lift off/rotation. This generated inertial forces that caused the associated brake thrust lever to rise and enter the reverse idle detent. Recovery was impossible before the aircraft impacted the ground about its starboard wingtip and cartwheeled several hundred metres along the Main taxiway , adjacent to the main runway, with a/c breaking up and catching fire in the process. Two of the five crew on board were killed. There were no passengers.
This accident highlighted a potentially fatal flaw in the DC8 throttle system not previously encountered during developmental or test flying, and led to subsequent modifications.
If a thrust reverser had been engaged at a critical moment in the rotation/lift off recovery may have been impossible.