June 27, 2013Australian safety regulators have issued a final report on the Qantas A380 engine failure and emergency landing on Nov. 4, 2010, including more details about the incident and a review of manufacturing failings at engine-maker Rolls-Royce.
The incident saw flight QF32 return to Singapore’s Changi Airport shortly after takeoff due to an uncontained failure in one of its Trent 900 engines. The cause has already been traced to an oil fire in the engine, resulting from a cracked oil feed pipe in the high pressure/intermediate pressure (HP/IP) hub assembly. The wall width of some oil feed pipes –including the one that cracked on the Qantas aircraft – was found to be thinner than design specifications due to a misaligned bore.
The Australian Transport Safety Bureau (ATSB) says in its final report that the crack in the oil pipe resulted from fatigue, and “developed over some time.” The crack became wide enough to allow oil to be released into the buffer space between the bearing chamber and the hot air surrounding the IP turbine disc. The oil was released as an atomized spray, and the air within the buffer space was hot enough for the oil to ignite.
The resulting fire eventually affected the IP turbine disc drive arm, resulting in the separation of the disc from the drive shaft. “Following the separation of the disc, the engine behaved in a manner different to that anticipated by the manufacturer during engine design and testing,” the ATSB says. The disc accelerated to a speed “in excess of its structural capacity” and burst into three main segments, which punctured the engine case.
Regarding Rolls-Royce, the ATSB found that the misalignment of the counter bores in the feed pipes “was the result of movement within the HP/IP bearing support assembly during manufacture and that a number of opportunities existed during the design and manufacture processes where the misaligned oil feed stub pipe counter bores could have been identified and managed.” According to the final report, “those opportunities were missed for a number of reasons, but generally because of ambiguities within the manufacturer’s procedures and the non-adherence by a number of the manufacturing staff to those procedures.”
The factors that led to the mistakes occurred over a number of years, and “highlighted the importance of manufacturers providing clear procedures and of personnel complying with those procedures,” the ATSB says. The safety agency says it has worked with the aircraft and engine manufacturers “to ensure that any identified safety issues were addressed and actions taken to prevent a similar occurrence.”
Responding to the final report, Rolls-Royce says it “supports the conclusions” of the ATSB. “This was a serious and rare event which we very much regret,” says Colin Smith, the manufacturer’s director for engineering and technology. “At Rolls-Royce we continually strive to meet the high standards of safety, quality and reliability that our customers and their passengers are entitled to expect. On this occasion we clearly fell short.”
Smith says Rolls-Royce has “already applied the lessons learned throughout our engineering, manufacturing and quality assurance procedures to prevent this type of event from happening again.” The company says it has also carried out its own investigations to understand and address what went wrong.
But back to the present, the process of stripping down the Qantas A380 that made an emergency return to Singapore’s Changi airport on November 4, has made significant progress as you can see in this photo from the Australian Transportation Safety Board. The board is reporting that the massive number 2 engine was removed from the wing and is being progressively dismantled at an engine shop in Singapore. But that’s not all.
“A number of wing and body fairing panels have been removed from the aircraft to facilitate the examination of the underlying structure and systems affected by the engine failure,” the board announced on Wednesday.
Now here we are, barely beyond 3 years past the first passenger flight of the A380 and the question being asked is whether the damage wrought by the spinning-out-of-control number 2 engine is so great that Qantas will have to write off the $300 million plane. There’s a huge emotional cost to the term “hull loss”. Nobody wants that less than Airbus, which spent roughly $14 billion developing the A380 and has firm orders to build 234 of them.
But the list of items that went wrong on the airplane is making lots of folks queasy, and I’m not talking about the passengers here. Airline executives and financiers, along with Rolls Royce and Airbus engineers have been sleeping fitfully for the past 14 days.
I call your attention to the blog Plane Talking. Blogger Ben Sandilands has scooped everyone with the publication of a PowerPoint presentation by Thomas Montagne, the technical services manager of Airbus. Complete with dramatic photos and graphics, the presentation confirms some of damage to the airplane from shedding pieces of the engine. (Ben adds interesting commentary about the wisdom of engine manufacturer-supplied maintenance, and questions whether there is an inherent conflict of interest when engine suppliers also provide engine service.)
The graphic illustration of the damage to the airplane adds weight to the speculation of folks who have been basing their opinions on passenger videos, news clips and publicly available images of the airplane. My guess is that Ben’s blog stats are going to go stratospheric from the clicks of armchair investigators and aviation enthusiasts.
In the meantime, the Australian newspaper Herald Sun published a list of airplane failures including the loss of one of two hydraulic systems, the loss of control of the left outboard engine, fuel leaks in the left wing tanks and loss of fire control in that same area. The article also suggests that fuel from a tail tank could not be transferred forward. Whether this caused the pilots to moderate how much fuel they dumped from the wings, or if they even had control over the wing tanks isn’t known.
A Boeing 747 pilot explained the problem to me recently by saying, “The big deal is if the tail tank won’t transfer, you have a CG problem. You have to keep fuel in the most-forward fuel tank,” he explained, to balance the aft weight. Clearly the men in the cockpit of Qantas Flight 32 were in a dilemma; land heavy and risk not being able to stop the plane in time, or land tail heavy and risk tank rupture and subsequent fire. Where’s the good choice there?
Dealing with the weight distribution was far from their only problem. My 747-flying friend added, “multiple failures get confusing very fast. You have one or two components fail which cause other components to fail. You’ve got these messages coming up. If you get a couple of those multiple messages its hard to sort out what the real problem is among a blizzard.”
Captain Richard de Crespigny, first officer Matt Hicks and Mark Johnson are to be hailed for finding their way through the storm of malfunctions and bringing that airplane to a safe landing in Singapore. Now its the investigators who find themselves with a blizzard of information. They can be thankful for that. More information should be better than less. If they are conscientious, if they sort it out, and make the right decisions about what needs to be fixed on the engine and on the airplane, air travelers will have something else to be thankful for.