The US Federal Aviation Administration has re-issued an emergency airworthiness directive (AD) reducing the time allowed for replacing the engine/ pylon fuse pins on General Electric- and Pratt & Whitney- powered Boeing 747s.
The action follows the discovery of a fractured forward fuse pin on an unidentified aircraft. The pin, which had accumulated 7,750 flight cycles and 42,027 flight hours, had cracked because of metal fatigue, says the FAA. The failed pin was located in the inboard strut at the forward end of the upper link.
"This is a re-issue of an earlier AD," says Boeing which adds that the new timetable "-tightens up the interval of inspections and allows the pin replacement to be completed sooner".
The original AD, which was issued in March 1995, followed the losses of a China Airlines 747-200F in December 1991 near Taipei, and an El Al 747-200F near Amsterdam's Schiphol Airport in October 1992, because of an in-flight engine separations.
As well as the replacement of all fuse pins, the subsequent modification effort involves adding two extra mountings made from corrosion-resistant steel, which are bolted to a new midspar attachment on the underside of the wing.
Source: Flight International
