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Trent 900 Oil Leaks Prompt More A380 Groundings, Engine Swaps

A380 damage
Pieces of the failed turbine disc punctured a fuel tank and cut hydraulic and engine control lines.

A380 damage
A portion of the Intermediate Pressure turbine disc was found on an Indonesian island.

November 11, 2010 — The European Aviation Safety Agency (EASA) has issued an Airworthiness Directive (AD) that requires Rolls-Royce Trent 900 engines to be inspected every 20 cycles for oil leaks. Following the recent in-flight failure of an engine on QF32 Nancy, a Qantas A380, Singapore and Lufthansa airlines have begun swapping out engines on A380s in which oil staining has been found inside a key section of the engine. As investigators continue to search for a technical explanation, some Qantas employees say the airline bucked superstition by naming the plane after a living person - Australian aviation legend Nancy Bird Walton, who has since died. One Qantas employee told EAA that Nancy has been “haunted” with mechanical problems ever since.

Engineers believe excessive vibration when higher takeoff power settings have been used may be causing oil leaks due to cracked oil lines, which have led to fires on two engines: one airborne and one on a test stand. Singapore had grounded all 11 aircraft in its A380 fleet to inspect the engines but have returned eight to service and is in the process of replacing engines on the remaining three. Lufthansa also made an engine change on one of its A380s, saying it was unrelated but on the advice of Rolls-Royce. Qantas’ entire A380 fleet remains grounded.

A Qantas employee that spoke with EAA says mechanics have been complaining about “off-shore” maintenance on Nancy ever since the aircraft returned from Germany after its first inspection by Lufthansa, which was contracted to provide heavy maintenance for the Qantas A380 fleet.

The Australian reported that leaking and pooled oil has been found in other Trent 900 engines in the same area where the turbine disc failed on QF32’s engine. During the test of a Trent 1000, a variant of the 900, an oil fire began in the same area of the engine, eventually leading to an uncontained failure.

The focus is likely to continue to center around both the design limits of the engine and Qantas’ operational procedures. Qantas uses higher takeoff power settings than Lufthansa and Singapore airlines, but they are reportedly still below the maximum limits for the engine during this phase of flight. The long-haul nature of Qantas’ operations (some flights are 15 hours) demand the higher takeoff power settings due to higher weights.

Read Mac McClellan’s blog about how the certification process produces aircraft that minimize the impact on safety when a malfunction occurs

The disintegration of the No. 2 engine sent debris up into the wing, causing hydraulic lines to be cut and a puncture of fuel tank No. 2. Former Qantas Chief Pilot John Jensen, EAA 515397, said in an e-mail to EAA that the fuel tanks were relatively full, which lessened the chance for fuel vapors to ignite when the engine fragments punctured the tank.

“The crew [was] faced with a slew of problems caused by broken hydraulic lines, leading edge flap damage, and lack of control of No. 1 engine,” Jensen said. “In my time, Rich (the captain on QF32) was always a dab hand and did a good job, it seems.”

Cascading failures soon followed as the No. 1 engine reverted to flight idle when its control circuits were cut. Now with only two operating engines (only on the right side), fuel was dumped to lessen the weight in the event of a go-around. The hydraulic damage forced the crew to lower the main gear with a secondary system. Although the nose gear and brakes were not affected, the thrust reversers were not available. Aircraft of this size can stop effectively with just brakes; however, the leading edge damage left the slats inoperative, which usually necessitates a higher approach speed.

Read a great discussion about why the Trent 900 is good example of how society places too many demands on technology to deliver competing objectives

Qantas Chief Executive Alan Joyce said that the A380s would not return to the air unless the airline was 100 percent sure that its operations were safe.

Full video of flight crew’s passenger announcement and landing. Stock footage at the beginning.

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