Aircraft crashes no mystery

I am writing in reference to Neil Winton's article Air safety is better, but skies are not all clear (July 29, page 7).

As a person who worked in the aircraft industry I must comment on respect of the "mystery crashes" referred to in this article, i.e. U.S. Air Boeing 1994 and United Airlines 1991, both 737 aircraft.

It was generally considered in the industry that these crashes and several mystery events in flight were caused by a "rouge" fault in the power control unit (P.C.U.) which operates the aircraft rudder.

I believe Boeing have issued a modification to this unit as well as an extensive program for old units. The fault was difficult to replicate but was not a mystery in the true sense. The 737 is still the world's best selling aircraft and very reliable.

TONY DOYLE

Jakarta