Qantas has accelerated a programme to modify its Rolls-Royce RB211-524G/H-T engines that power part of its Boeing 747-400 fleet, after experiencing five high-pressure compressor stage-one blade failures. However, the airline does not expect to have its 84 installed engines modified until early 2010.
The airline is statistically likely to encounter another such failure before the fleet modification is completed, according to an Australian Transport Safety Bureau report into a February 2007 incident in which a Qantas 747-400 on a flight between Sydney and Los Angeles was forced to return to Sydney after such a failure.
Qantas is one of only two operators to have experienced the problem, with an unnamed operator suffering 11 failures, including seven on 747 freighters. Three of the Qantas incidents happened on the same aircraft at different installation times and different wing locations.
R-R issued a service bulletin in 2006 to address the problem, which is caused by complex vibration, induced by asymmetric blade tip rubbing around the HPC stage one rotor path. The tip rubbing is believed to be due to distortion of the HP module 41 case. R-R is undertaking further testing and research into the failures, says the ATSB.
Source: Flight International
