Printed headline: Inspire Cleanliness
The Australian Transport Safety Bureau (ATSB) recently released an investigative report involving an engine occurrence that led to a European Aviation Safety Agency airworthiness directive mandating the replacement of corrosion-inducing cleaning processes for Rolls-Royce blades.
In May 2017, an Airbus A380 operated by Qantas Airways departed Los Angeles destined for Melbourne. The crew turned back 2 hr. into the flight after hearing a loud bang followed by unusual vibration and what turned out to be a false fire warning.
After an uneventful landing, the initial inspection found no breach of the No. 4 engine casing and minor damage to the right flap due to exiting debris. A subsequent teardown found fatigue cracking due to internally corroded low-pressure turbine blades, which had resulted in blade debris and downstream damage through the engine. The corrosion was attributed to a chemical residue in the hollow blades left after a July 2015 cleaning operation.
In response to the occurrence, the manufacturer modified its blade-cleaning instructions to include best practices for the removal of process solutions and chemical residues. The revised procedures—which include flushing of aerofoil cavities and modifying the orientation and support of the blades while cleaning—were adopted at all applicable Trent 900 Stage 2 low-pressure turbine blade maintenance facilities. An internal manufacture safety alert also was distributed to raise awareness of the issue and its potential impact on other engine types.