Dash 8 Q400 construction error

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 has made a thorough technical examination of the landing gear on the Dash 8 Q400 aircraft that were taken out of service after the third accident involving this aircraft type in autumn 2007. “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 per cent 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 Claus Sonberg, Executive Vice President of Corporate Communications in the SAS Group.