Trent 900 engine checks continue after Qantas incident

Qantas is still scheduled to take delivery by year's end of two new Rolls-Royce Trent 900-powered Airbus A380s, even though the carrier’s operations were severely compromised in November when a major uncontained engine failure led to the grounding of its six-strong fleet of Superjumbos. Another two A380s are scheduled for delivery by March 2011.

13th Dec 2010


Qantas is still scheduled to take delivery by year's end of two new Rolls-Royce Trent 900-powered Airbus A380s, even though the carrier’s operations were severely compromised in November when a major uncontained engine failure led to the grounding of its six-strong fleet of Superjumbos. Another two A380s are scheduled for delivery by March 2011.

The incident involved the carrier's flag-ship A380 (registration VH-OQA) as it climbed out of Singapore, bound for Sydney on 4 November. Flawed welding of oil pipes within the high-pressure/intermediate-pressure (HP/IP) structure of No 2 engine reportedly led to the leakage of oil that then ignited. The fire led to the failure of a turbine disc, which is thought to have split into two or three pieces before causing major damage to the wing, including leading-edge slats, the front spar, and adjacent systems.
The A380 lost one of its two main hydraulic systems, while punctured tanks leaked fuel. The compromised systems triggered more than 50 cockpit-warning messages and prevented the crew from shutting down No 1 engine after the landing, during which three tyres burst.

Reportedly, the five-man crew (which included two training captains performing checks) could not properly jettison fuel, nor transfer it between the aircraft’s tailplane and main wing tanks, which ultimately led to instability that forced the crew to land at a high weight.

Qantas resumed A380 services on the Sydney-London ‘kangaroo’ route on 27 November, using one of two aircraft returned to operations after intensive engine inspections had been performed in consultation with Australia's Civil Aviation Safety Authority (CASA), Airbus and Rolls-Royce. Power was voluntarily limited by Qantas to about 70,000lb thrust initially, although the Trent 900's 72,000lb maximum certificated engine thrust remained available if required.

The carrier expects to reintroduce its remaining A380 services "progressively", with the last likely to be Melbourne-Los Angeles, a route which routinely requires full thrust. The pace of reintroduction is being dictated by the accumulation of experience with modified Trent 900s and the possible need for "additional changes to engines".

Meanwhile, the A380 involved in the 4 November incident, which had logged about 8,165 flight hours and 831 flights since delivery in September 2008, remained in Singapore undergoing investigation as Asian Aviation went to press.

A380s normally account for 50 of Qantas’s 613 weekly departures. With all six on the ground – one was in Hamburg undergoing a maintenance C check with Lufthansa Technik – the Australian operator maintained international operations using some of its 26 Boeing 747-400s on European and US long-haul routes. The airline's 14 Airbus A330s were used to cover for the 747s and Boeing 767s were added to the regular A330 routes.

An initial European Aviation Safety Agency (EASA) airworthiness directive (AD) ordered repetitive inspections of all Trent 900s, including those on Lufthansa and Singapore Airlines A380s "before next flight" – or within an initial ten flights if installed on-wing – then after every 20. Qantas reported finding oil leaks "beyond normal tolerances" on three of its six A380s.

Operators had to check low-pressure turbine (LPT) first-stage blades, the HP/ IP structure air-buffer cavity and oil service tubes. On 23 November, this requirement was superseded by a second AD (still regarded as only an interim mandate), which removed the need to inspect LPT blades. EASA expected to consider further requirements if a terminating action were identified that would obviate the need for repetitive inspections.

Rolls-Royce was criticised in many quarters for its conservative response to the Qantas incident and its share price dropped almost 10 percent in two days. On 12 November, the engine maker confirmed it had identified an unspecified faulty part that had triggered the failure. The engine company then began a programme to replace parts, or whole engines, on the 20 aircraft flown by Singapore Airlines, Qantas, and Lufthansa.
Airbus says incorporating Trent 900 changes could delay some A380 deliveries in 2011 and that it might seek compensation from the engine manufacturer. Some units were returned from Airbus to Rolls-Royce for use as replacements in the active fleet. Three of the four A380s still to be delivered this year are understood to have Trent 900 engines.

Initial engine checks by Rolls-Royce included a "rigorous" examination of data evidence, analysis of recovered material, and interrogation of the Trent 900 fleet history. The manufacturer drew two key conclusions: the issue was specific to the Trent 900 and the failure was confined to a specific component in the turbine area.

In late November, there were conflicting reports about what relevant knowledge Rolls-Royce might have had before the uncontained engine failure. In its interim statement on 12 November, Rolls-Royce predicted a small reduction in previous estimates of underlying profit-growth, partly attributed to the Trent 900 incident.
 

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