The Danish investigation board has released a preliminary report on the SAS Dash 8-400 (Q400) accident from September 9th at AAL.
Apparently corrosion in the Actuator Piston has been hold responsible for this accident.
The technical investigation was focused on the right main landing gear assembly. Significant fracture damage to the right main landing gear was observed.
During the investigation, it was observed that the rod end of the right main landing gear retraction/extension actuator had separated from its piston rod.
The main landing gear retraction/extension actuator, the actuator rod end, and stabilizer brace assembly were removed from the aircraft for further examination.
Examination of the internal threads of the retraction/extension actuator piston revealed the presence of corrosion, which led to separation of the rod end from the piston. The separation contributed to the landing gear collapse.
The regulatory authorities were apprised of the situation and have subsequently issued an airworthiness directive which requires immediate action by the operators.
The investigation continues.
History of flight
The accident flight was a scheduled domestic passenger flight from Copenhagen International Airport, Kastrup (EKCH) to Aalborg Airport (EKYT).
The flight from EKCH until the approach to EKYT was uneventful.
On approach to EKYT, the landing gear was selected down. When the landing gear extension sequence was completed, the cockpit indication for the landing gear indicated two green lights and one red light. The two green lights indicated that the left main landing gear and the nose landing gear were down and locked (safe). The red light indicated that the right main landing gear was not locked (unsafe). A go-around was initiated.
An alternate landing gear extension procedure was conducted but the cockpit indication for the right main landing gear remained unsafe.
A visual inspection of the landing gear was performed.
The cabin was prepared for an emergency landing and the passengers were briefed.
The aircraft touched down on the left main landing gear, followed by the right main landing gear, and shortly thereafter the right main landing gear collapsed. The aircraft then departed the runway to the right and came to rest on the lower fuselage and right wing tip.
The aircraft was substantially damaged.
Some passengers sustained minor injuries.
The accident took place during daylight hours and visual meteorological conditions.