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Qantas is expected to disclose its plans this afternoon to bring four of its six giant A380s back into service later in the week.

The one in Singapore with the holes in its wing, a shredded engine, and a “drowned” second engine, will take somewhat longer, while there is another one in Frankfurt having a scheduled airframe overhaul — called a C check — performed by a Lufthansa subsidiary.

So, why should we be frightened by the Qantas A380 incident involving QF 32 from Singapore to Sydney last week?

Because Qantas is frightened. Qantas CEO Alan Joyce made this abundantly clear with his decision to ground the A380 fleet and in his many interviews related to it.

This is officially the scariest thing ever to happen to Qantas since a money-saving instruction not to use full reverse thrust on 747s resulted in QF 1 to London ploughing into a golf course at the old Don Muang airport at Bangkok on September 23, 1999.

What made this incident scarier than other Qantas engine failures, including the one on a 747-400 trying to bring the A380 passengers to Sydney from Singapore the following day?

Parts of the No.2 (inboard) Rolls-Royce Trent 900 engine blasted through the wing with sufficient force to cause damage that appears to have been near to or have directly affected fuel lines or even a fuel wing tank.

The fragments of engine took out half the hydraulic controls of the jet and interfered with wiring near the leading edge of the wing, preventing the pilots from shutting down the outboard No.1 engine after a landing that blew several tyres, requiring it to be extinguished by fire engines.

The wheels of the jet were gravity dropped into the lock-down for landing position instead of powered down.

We will known the exact extent of the damage done by this “uncontained” engine failure when the ATSB lead investigation produces an interim factual report.

Why aren’t jet engines designed to prevent “uncontained” engine failures?

They are. Rolls-Royce screwed up badly. While there is no way to fully contain a turbine disk or other heavy rotating part failure from breaching the casing of a jet engine, the Rolls-Royce design was supposed to conform to a set of certification requirement preventing things ever getting this bad.

Rolls-Royce is also under the pump over an uncontained engine explosion in the related Trent 1000 engine it has built for the Boeing 787 Dreamliner, but which blew up in a engine test cell in the UK in August, creating a new series of delays for that much-delayed plastic jet.

An earlier series Rolls-Royce engine, from the RB-211 family, also had an uncontained failure on a Qantas 747-400 shortly after it left San Francisco on August 30. It was an RB-211 engine that failed but was contained on the relief Qantas 747-400 bringing passengers who had been on the A380 back to Sydney from Singapore the following night. Those passengers have finally arrived on a successful third Qantas flight, which has completed their epic QF 32 service from London to Sydney via Singapore.

Is there any obvious reason why Qantas should be the only Rolls-Royce-powered A380 operator to experience such serious problems with the engine?

No. There are two other operators with Rolls-Royce engines A380s, Singapore Airlines, which has nearly twice as many as Qantas and has been flying them for much longer, and Lufthansa, which has only this year started services. Each has reported one routine engine shut down in flight incident, and nothing like the Qantas incident. Both airlines have also made the additional inspections of the engines required by Rolls-Royce following Qantas incident last week. Since then Qantas has found potentially serious issues with three of the Trent 900 engines it has inspected, summarised by Alan Joyce on radio this morning as “oil in places where it shouldn’t be”.

Does the decision by Singapore Airlines and Lufthansa to continue A380s services after those inspections make them less safe than Qantas.

No, all it means is that they have not discovered the same problems that are of such clear concern to Qantas. The grounding decision by Qantas was unavoidable, given the seriousness of the events that occurred in the QF 32 incident, and has been received with admiration in the airline industry.

Qantas simply cannot risk a similar incident on another A380. Singapore Airlines and Lufthansa have not had such an incident, but since QF 32 occurred they, like Qantas, have been given very demanding inspection requirements for their Rolls-Royce engines, and if they turn out “clean” they fly.

Could it be that Qantas did something “wrong” with its A380 engines?

Maybe. But there is no evidence to support that being the case. It had complied with earlier airworthiness directives requiring other inspections of these engines. The “clustering” of the Rolls-Royce Trent 900 issues on the Qantas fleet defies explanation at this stage, but raises the possibility that defective materials in its engines have in failing, revealed a vulnerability or defect in the engine design.

If, stress “if”, this is found to be the case, Rolls-Royce and its customers are going to have to modify or replace their engines.

Passing current engines as fit for flight is one thing, but finding and fixing the underlying cause or causes of the faults Qantas has uncovered is a long-term and critical safety matter.

Why has Qantas been so unlucky in terms of flight scares lately?

It has in fact been incredibly lucky, as well as fortunate in having outstandingly good pilots. It was the quality of its pilots that calmly brought QF 32 to a safe stop in Singapore. It was luck, as in the spinning of a turbine disc rather than roulette wheel, that spat the sharp blade from the disintegrating engine through the wing where it did instead of right through the main wing tank, or through the wall or floor of the cabin, or back into contact with the horizontal stabiliser on the tail.

All more deadly places for it to have hit, yet purely by chance, to have missed.