Abstract: A dereefing cutting includes a knife actuated by a spring which is held in a preloaded condition by a latch mechanism. The latch includes a detent which is held in place by a timer mechanism. Upon partial opening of the canopy, the timer mechanism is actuated and, after a predetermined delay, releases the detent. The knife is urged by the preloaded spring to cut the reefing line and fully release the parachute canopy.