Uncontained consequences

Pictures of Indonesian police struggling to carry the piece underscore its danger to aircraft and passengers.

If the turbine disc had punctured the fuselage, lives could have been lost and if the A380 had been higher a major decompression incident could have occurred.

As it was the pilots had to grapple with 54 error messages and multiple failures but fortunately an airport was close.

With the discovery that the intermediate pressure turbine disc had failed focus immediately swung to a catastrophic failure of a Rolls Royce Trent 1000 at derby in August which resulted in further delays to the 787 program.

While Rolls Royce is tight lipped about that failure industry sources reported to trade journal Aviation Week that an oil fire broke out within the engine during high-power test runs and the heating is believed to have softened the intermediate pressure shaft which subsequently failed.

The unconstrained turbine then reached an over-speed condition and ultimately disintegrated with parts thrown loose penetrating the engine casing.

Three days after the crash as Australian Aviation went to press Qantas confirmed at least three engines were required before it grounded A380 fleet would be airborne again, while Singapore Airlines and Lufthansa were each performing at least one engine change each.
Uncontained engine failures, are extremely rare but they have cost lives.

The most tragic was the disintegration of the front fan of a United Airlines DC-10-10 on July 19, 1989, which required an emergency landing a Sioux Gateway Airport, Sioux City in the US.

United Flt 232 was on a flight from Denver to Philadelphia and an hour into the flight the number 2 centre engine suffered a massive failure of the Stage 1 fan disk caused by a fatigue crack originating from a previously undetected metallurgical defect located in a critical area of the disk.

Subsequently five other Stage 1 fan disks were found to have cracks.

The DC-10 was almost uncontrollable and cartwheeled on landing killing 111 of the 296 aboard.

And in Australia there have been a number of uncontained failures.

One of the most serious involved an Ansett, 727-277, VH-ANA in July 1992 at Brisbane Airport.

According to the Flight Safety Foundation the aircraft with 105 aboard had just lifted off when the crew heard a loud bang emanate from the rear of the aircraft.

This was followed by cockpit indications of a fire in and a loss of thrust from, the centre engine.

Ground witnesses saw large flames streaming from the rear of the aircraft.

The crew shut down the engine, completed the engine-fire checklist, and flew a circuit for a landing on the same runway.

During the landing roll, the crew was advised that there were still signs of fire around the centre engine, so a decision was taken by the aircraft captain to evacuate the aircraft.

In the evacuation, two passengers received minor injuries.

The investigation revealed that a fatigue failure had occurred in the first-stage compressor fan disc of the no. 2 engine leading to disruption of the engine.

The fire resulted when a section of engine disc severed the main fuel line to the engine.

More recently in December 2002 an Air New Zealand 767-219ER suffered an uncontained engine failure after take-off from Brisbane on route to Auckland.

NZ132 with 190 passengers and 10 crew had reached 11,000 feet when there was a bang and the engine failed and was shut down.

According to the Flight Safety Foundation Examination of the left engine revealed a large rupture of the outboard core cowl and severe gouging and scoring of the outboard side of the engine strut above the cowl damage.

The leading edge flap panel above the strut was extensively damaged over approximately 40cm and there was damage to fairings behind the engine.

It was found that the first-stage high-pressure turbine disk had failed and released a large segment of the disk rim and outer web.

The engine casing around the disk had been completely severed and the central shaft fractured between the stage-one and stage-two high-pressure turbine disks.

Fortunately the debris exited away from the fuselage and at an altitude where decompression would not have been an issue.

Mercifully uncontained engine failures are extremely rare but as engines get bigger and more powerful the consequences of “rare failure” become greater.

Maybe the A380 Trent 900 failure is a wakeup call to re-examine tolerances and failure protection in large jet engines.