I literally dropped an RB211 off of a 747-400 (no injuries except to pride) everything was being done to the book as it was 1st eng removal at a new facility (I had done them before) all equipment was new, guess what, the manufacturer of the equipment had fitted a 737 rated gearbox to the winching gear, guess what, it gave way and engine hit the floor from about 6 ft. How does that saying go, it happened before and it will happen again! So much for quality control!