Danish investigations into the Scandinavian Airlines Bombardier Q400 gear-up landing in Copenhagen during the last weekend of October have discovered that a blockage in a retraction actuator prevented the right-hand landing-gear extending.
The finding supports initial suggestions that the 27 October event was unrelated to the two gear-collapse accidents involving Scandinavian Airlines Q400s at Aalborg and Vilnius on 9 and 12 September.
Danish investigation authority HCL says the right-hand main landing-gear only partially deployed during the approach to Copenhagen, and attempts to recycle the gear and use alternative extension procedures failed to resolve the problem.
Corroded retraction actuators, which had then disconnected, had been found on the Q400s involved in the earlier accidents but HCL says the actuator on the Copenhagen aircraft was found to be intact and still connected to the undercarriage.
But it states that further examination identified a blocked orifice within the actuator assembly which prevented the complete extension of the right main gear.
“This finding is not related to the two previous accidents,” says HCL. “The source of the blockage is unknown at this time and the investigation continues.”
HCL’s discovery appears to back manufacturer Bombardier’s earlier claim that this latest event was unconnected to those last month.
SAS Group grounded all Q400s after the first two accidents in order to replace appropriate landing-gear components on its entire fleet, and the aircraft had only been back in service for a few days when the Copenhagen event occurred. The event has prompted SAS to ground its Q400s again and permanently withdraw them from service.