An uncontained engine failure on board Qantas Boeing 747-400 VH-OJP earlier this week could be linked to a recently issued FAA Airworthiness Directive (AD) which was issued following the discovery of cracks in the low pressure turbine of a number of Rolls-Royce RB211 engines.
The AD, which takes effect from September 27, calls for the inspection of blades in the low pressure turbine for cracks initiating from corrosion pits during the next scheduled maintenance visit.
“Several low pressure turbine (LPT) shafts have been found with cracks originating from the rear cooling air holes,” the AD reads. “The cracks were found at normal component overhaul, by the standard magnetic particle inspection (MPI) technique defined in the associated engine manual. The cracks have been found to initiate from corrosion pits. Propagation of a crack from the rear cooling air holes may result in shaft failure and subsequently in an uncontained low pressure turbine failure. For the reasons stated above, this AD requires the inspection of the affected engines’ LPT shafts and replacement of the shaft, as necessary.”
Qantas says that it had been “fully compliant” with the directive, and that VH-OJP’s affected engine had been inspected in July and was not yet due for its next maintenance visit where the AD inspection would be carried out.
A replacement engine has been despatched to San Francisco on another Qantas 747-400’s fifth engine pod mount (similar to as in this photo).