Design fault causing Qantas engine failures

[Greg McDonald]

From NEWS.COM.AU:

QANTAS is being plagued by engine failures caused by a "design" problem that may not be fixed until 2010, a report says.
The airline has told investigators examining an engine failure during a 2007 flight from Sydney to Los Angeles - in which "loud bangs" were heard before the pilot turned the plane around - that it had experienced four similar incidents in the past five years.

The airline also said three of the five "blade failures" inside its engines happened on a single plane and engineers have since sped up its service program for the fleet.

In a report released today, investigators from the Australian Transport Safety Bureau (ATSB) concluded that the Los Angeles-bound plane's problem was caused by cracked engine parts.

Investigators said there was a "statistical probability" that there would be a similar engine failure within the next two years, but the airline was not being blamed for the problems.

"It was not possible to identify failure precursors or predict potential (engine) failures," investigators said in the report.

"The completion of modification to the operator's entire fleet of engines is not expected until 2010… there is a statistical probability of another failure within the operator's fleet before the entire fleet modification program is completed."

Qantas engineering general manager David *** said problems stemmed from a design issue and were not related to maintenance procedures.

"The issues raised are an industry wide matter," Mr *** said.

The ATSB report said another international airline had experienced seven similar engine failures.

According to the report, soon after the Los Angeles-bound 747 took off from Sydney Airport on February 3, 2007, crew members heard "several loud bangs and felt vibration through the aircraft structure".

The pilot shut down the engine and dumped excess fuel before returning to the airport.

"Immediately after the event, Qantas launched its own investigation and instituted a program to mitigate the issues involved," Mr *** said.

The manufacturer of the engines involved told investigators that it had been aware of the failures, which were believed to have been caused by vibrations.

[Philip Argy]

Here's the text of the abstract from the ATSB Report:

At 1200 Eastern Standard Time, on 3 February 2007, after departing Sydney Airport and while in a climb at approximately 4,000 ft above ground level, the flight crew of a Boeing 747-438 aircraft, registered VH-OJM, heard several loud bangs and felt vibration through the aircraft structure. Observing an increase in the exhaust gas temperature indication for the number-3 engine, the crew following the non-normal checklist, shut down the engine, dumped excess fuel and returned the aircraft to Sydney Airport.

A subsequent examination of the engine found that it had sustained a high pressure compressor (HPC), stage 1, blade failure. The mode of failure was known to the engine manufacturer, who had attributed it to blade tip rubbing, due to distortion of the engines high pressure case (module 41). To address the problem, the engine manufacturer had introduced service bulletin (SB), SB72-F002. The number-3 engine did not have the service bulletin embodied at the time of the failure.

Although the exact time of the blade tip rubbing and subsequent cracking could not be determined, the engine manufacturer believed that crack initiation to blade failure took approximately 50 cycles.

During the investigation, the aircraft operator experienced a subsequent failure, bringing the total number of failures of this type for the operator to five. Similar failures were reported by another aircraft operator, with 16 similar failures reported in total.

As a result of the incident, the operator accelerated its modification embodiment program and expects to have all installed engines modified by early 2010

[Brenden S]

Wasnt that the flight where our own Will Tidmarsh was on the flight?

[Daniel G]

Originally Posted by Brenden S

Wasnt that the flight where our own Will Tidmarsh was on the flight?

Nope, it was our Chris Roope!

[Sarah C]

I love it how they won't mention who the 'manufacturer' is - it is no secret which one it is!

[Philip Argy]

The ATSB report is public, and it reports the manufacturer to be Rolls Royce and the engines in question are RB211-524 (–T) engines. The report also notes that another engine that utilises the same HPC stage 1 blades as the RB211 (-T) had experienced identical blade root failure.

In all cases the blade failure was attributable to "complex vibration, induced by asymmetric blade tip rubbing around the HPC stage 1 rotor path. The tip rubbing was believed to be the result of distortion of the HP module 41 case, and was associated with high casing loads".

Qantas has addressed the issue by ensuring that the clearance between the blade tips and the casing is at its maximum tolerance on its 21 aircraft fitted with these engines.

The full report is at:
http://www.atsb.gov.au/publications/...700356_001.pdf

[Raymond Rowe]

Originally Posted by Brenden S

Wasnt that the flight where our own Will Tidmarsh was on the flight?

During our last spotting weekend. a few board mebers were quoted by journo's in the reports on the radio and papers.