Remember a mate sending me some pics a few years back, of a far eastern carrier 74 classic, (poss air china) that had landed in Germany. They had been operating a revenue sector carrying a large number of pax, whilst operating on 3engs only from the start. The u/s engine had, had the blades secured with pax seat belts to stop the windmilling effect - obviously pre departure. Whatsmore, was that there was severe fan blade damage to one of the remaining so called good engines. If I recall correctly German Aviation Authority grounded the a/c immediatly and ordered that at least 3 engines were replaced before it would be aloud to fly again.