Sydney: Australian officials investigating the mid-air disintegration of an engine on a Qantas superjumbo said on Thursday they identified a potential manufacturing defect in Rolls-Royce engines used in 20 A380s worldwide that could cause engine failure.
The Australian Transport Safety Bureau (ATSB) said it recommended a new round of safety checks for planes fitted with the engines, and that Rolls-Royce, affected airlines and other safety regulators were taking action to ensure the A380s involved were safe to fly.
The ATSB has been leading the investigation into the disintegration of a Trent 900 on a Qantas A380 shortly it took off from Singapore on November 04. Shrapnel speared through the wing, caused structural and other damage that set off a cascade of problems for the pilots before they made a safe emergency landing in Singapore.
Three airlines using Trent 900 engines have conducted extensive checks and modified some parts since European regulators issued a safety directive following the November 04 blowout — the most serious problem for the world`s largest and newest jetliner.
But ATSB safety bureau chief commissioner Martin Dolan said Thursday`s safety recommendation was based on a conclusion reached only a day earlier, in conjunction with Rolls-Royce, as investigators prepared to release their preliminary report into the Qantas incident.
"We considered it was a sufficiently significant safety issue that we should immediately release it to parties who were operating with these engines," Dolan said on Thursday.
In a statement, the ATSB said there is "a potential manufacturing defect" with an oil tube connection in the Trent 900 engine.
"The problem relates to the potential for misaligned oil pipe counter-boring, which could lead to fatigue cracking, oil leakage and potential engine failure from an oil fire," the statement said.
It recommended close inspection of engines "and the removal from service of any engine which displays the counter-boring problem”.
The European Aviation Safety Authority issued an emergency order on November 11 requiring airlines to re-examine their Trent 900s and ground any planes with suspicious oil leaks. It said a preliminary probe showed an oil fire broke out in the section housing the turbines — shafts that power the engine when they are spun at great speeds by combusting jet fuel. An oil pump and network of tubes lubricate and cool the turbines.
EASA said the blaze may have caused the breakup of the intermediate pressure turbine disc, a heavy metal plate that holds the blades of the middle of three turbines.
Turbine engines are known to generate vibrations that can cause parts to wear prematurely. The EASA order indicated that oil tubes may have fractured as a result of such vibrations and spewed oil in an extremely hot section of the engine, causing a fire. The resulting heat could have caused the rotor to which the turbine blades are attached to expand, bringing the turbine blades into contact with the casing that encloses the engine.
The ATSB statement refers to the same part of the engine as the European directive, and goes further than the EASA`s directive by attributing the problem to a likely manufacturing defect.
Qantas grounded its fleet of six superjumbos immediately after the Nov. 4 incident while it conducted exhaustive checks and modifications, including replacing 16 Trent 900 engines. The Australian airline returned two A380s to service last weekend.
The airline said on Thursday it would conduct detailed one-off inspections as a result of the ATSB recommendation.
But Qantas spokesman Simon Rushton said the airline was not pulling its A380s from service and the latest checks were not expected to interrupt services.
Two other airlines use Trent 900 engines on their A380s — Singapore Airlines, which has 11 of the superjumbos, and Germany`s Lufthansa, which has three.