SAS Group, which last year grounded its Bombardier Q400 fleet following three landing-gear incidents, issued a very bold statement this morning.Clearly not mincing words, SAS says that, following a thorough technical examination of the turboprops' landing gear, it found problems in 63% of the SSV valves on the inspected aircraft, and cannot be blamed for the undetected error that caused the first two accidents in the course of its maintenance work.
What does Bombardier have to say about all of this?
"There is no new evidence published by any investigation authority that alters the conclusions reached by the DAIB [Danish Accident Investigation Board] in its preliminary report, and the EASA in its statements, with respect to the cause of the O-ring blockage that prevented the main landing gear actuator from fully extending," says the manufacturer.
"While investigations into Q400 main landing gear incidents continue, Bombardier will not comment or speculate on specific issues in isolation, such as the SSV valve, without the context of the final reports."
Meanwhile, here is the full statement from SAS:
“We are waiting for the Accident Investigation Board’s final conclusion, and don’t want to speculate about the reason behind the third accident. We can confirm, however, that our technical department has found problems in 63% of the SSV valves on the inspected aircraft that we have permanently grounded after the accidents last autumn. SAS had no possibility of – and cannot be blamed for not – discovering these problems, or the undetected error that caused the first two accidents, in the course of its maintenance work," says executive VP of corporate communications Claus Sonberg.
SAS adds: "The Danish Accident Investigation Board has previously concluded that a construction error in the actuators was the cause of the first two accidents involving a Dash 8 Q400. The Accident Investigation Board has not presented any conclusion on the reason behind the third accident, but has in a provisional report stated that the most likely reason is that an O ring came loose from the SSV valve in the hydraulics system in combination with the following fault-tracing. The SSV valve also has a construction error and is currently being modified by the supplier."
SAS previously requested $77 million in compensation from Bombardier for costs and lost income associated with the accidents.
(Photo from Bombardier's Q400 web page - which it might want to consider updating: http://www.q400.com/q400/en/operators.jsp )
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Please see Flight's article:
The company says its technical department has checked the Q400 fleet and found problems in 63% of the door sequence solenoid valves it inspected after the grounding.
Danish accident investigation commission HCL said last November that an O-ring had migrated from the valve and blocked an orifice in the landing-gear actuator assembly. This blockage prevented the starboard main landing-gear from deploying, forcing the Q400 to land at Copenhagen with the gear retracted.
SAS Group says it is waiting for HCL’s findings, but insists: “SAS had no possibility of – and cannot be blamed for not – discovering these problems…in the course of its maintenance work.”
HCL says a loose O-ring could not normally have migrated to the landing-gear because certain components in the aircraft, notably a mechanical sequence valve, prevented passage.
But SAS technicians replaced both the door sequence solenoid valve and the mechanical sequence valve on the aircraft in question just days before the accident.
HCL has suggested that, during the replacement, the rogue O-ring was unwittingly transferred – perhaps in one of the unions – to a position within the aircraft from which it could freely travel to the landing-gear assembly.
SAS Group claims that the door sequence solenoid valve has a “construction error” and that the component is being modified.
I was a passenger on a Bombardier Q400 that was forced to make an emergency landing in Munich (diverted from Florence, Italy) last year because the nose gear did not deploy. (Story here: http://blog.flightstory.net/307/dash8-q400-incident-at-munich-picture/ ) It was one of the most frightening experiences of my life. Fortunately, no one was injured due to one hell of a job by the crew. However, when I came home and did some research on the plane I was incensed. The number of landing gear issues should give pause to anyone thinking of getting on one of these planes. Personally, I will not be flying on the Bombardier Q400 again until I read that the landing gear problems have been resolved.
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