Lance Cole (Flight International, 13-19 January) cites the stall/crash of a Lufthansa Boeing 747 at Nairobi in 1974 in his valid criticism of last year's Singapore Airlines (SIA) tail cutaway. The 747 accident was due to the pneumatic-powered leading-edge flaps being retracted when flap extension was commanded, due to no duct pressure being available, as bleed valves were closed to facilitate engine start and the leading edges were not incorporated into the take-off configuration warning system. This was an accident waiting to happen and many 747s had taken off with leading-edge flaps retracted. Nairobi proved too hot and high for luck to hold.
Lumping this in with the "Olympian incompetence" exhibited by the SIA crew is a little bit disingenuous. To parallel this, one would have to cite the almost identical Delta Air Lines Boeing 727 incident at Dallas/Fort Worth in August 1988 when it collided with the instrument landing system localiser. Why? Take-off with all flaps retracted due to crew indiscipline and faulty configuration warning.
The parallels with SIA are haunting: continuing a vain attempt to extract lift from the wing after the onset of the stick-shaker to the point of tailscrape. No increase in thrust or call for such. Luckily for SIA, the engines didn't surge.
David Connolly Brussels, Belgium
Source: Flight International
