New engine, new airplane, new jumbo-sized worries

A380 arrives in New York 2008

It is dramatic and it plays hell with how comfortable passengers feel with the airplane, but the short-term grounding of the super jumbo Airbus A380 was a good thing. Its not about the size of the airplane or the number of people it carries. It is about finding out what caused the apparently unprompted deconstruction of the Rolls Royce Trent 900 engine on a Qantas flight from Singapore last Thursday.

New engine, new airplane, new worries about whether there's some design flaw and the disaster-that-didn't-happen is the free pass investigators get to figure it out without anybody having to die.

But wait, its not entirely about the engines either. Pilots train for engine-out emergencies so losing one isn't that big of a deal, especially considering that the A380 has four, and the flight wasn't that far out over water when the bang happened, scaring the beejeebies out of the 466 people aboard.

The bigger story concerns what happened after the engine spewed its innards outwards. Once the inboard left engine died, pilots were unable to change the thrust of the outboard engine. So while they didn't literally lose two engines, they effectively lost control of the second.

"This airplane is a magic airplane," John Darbo told me. John is a pilot, a controller, a safety expert and a fellow member of the International Society of Air Safety Investigators and he doesn't speak Jargon.  "Magic" is how he describes the highly-digitized airplanes Airbus is famous for. "If, in that system, the engine is designed to stay where it is in a failure, and it just stays there, that will be a point in the investigation, not only the failure of the engine but the consequences to the system as a whole."

"There was no possibility to influence engine number one after the rupture of the electrical line due to the engine pieces flying into the wing," Jörg Handwerg a pilot for Lufthansa, which has four A380s in its fleet told me via skype this evening. We'd been talking about this event since it happened, when Jörg, a reader of my blog who also happens to be the spokesman for his union was in New York. He and I were sitting around wondering why the certification standards on this airplane allowed a reduction in hydraulic system redundancy. Most airliners, even other Airbus models have three. The A380 has two. Which leads us to the second item on the list of worrisome factors in the Qantas chain of events.

The damage to the leading edge of the wing seems to have severed one of those two hydraulic system lines to some flight controls. This is apparent from the videos shot by passengers on the Qantas flight. (If you're wondering why their hands weren't already occupied with worry and/or rosary beads check out the various videos on You Tube. The flight and the captain were the very essence of calm.)

But despite the outward show, Capt. Richard Champion de Crespigny and First Officer Matt Hicks had good reason to be concerned.  Jörg said, "The hydraulic lines are in the front of the wing behind the slats. As exactly this part was cut through by the engine part during the kinetic explosion, the green system appears to be without pressure after the engine damage. Only every second ground spoiler came up. Additionally the gear doors of the front wheel did not close after extraction of the gear."

This photograph is reproduced with the permission of
Rolls-Royce plc, copyright © Rolls-Royce plc 2010

Uncontained engine failure is an aviation bugaboo. Not unheard of but far from trivial. Which is why engine manufacturers go to great lengths to analyze what is likely to be the trajectory of their disintegrating products so that plane makers provide enough protection for the critical bits that could get caught in the cross fire.  


All of which is to say that while the news story seems to be about Roll Royce engines, this Qantas event will certainly command a more expansive investigation perhaps even leading to a review of the  presumptions used in the design of the world's largest airliner.