What happened
On April 1, 2010, a Sikorsky S-92A, registration LN-OQE, operated by CHC Helicopter Service AS, was conducting an offshore flight to the Gullfaks B platform in the North Sea. During the approach at approximately 500 feet, the captain attempted to adjust his seat position for landing. During this movement, the seat detached from its mounting rails.
To prevent the seat from falling further and potentially jamming the collective or cyclic controls, the captain was forced to grab the overhead handles and remain anchored to them. Because the captain could not release the handles, he was unable to assist the pilot flying during the remainder of the approach. The co-pilot managed to complete a normal landing at the platform without further complications.
The investigation
The investigation revealed that the aircraft had undergone a nose landing gear inspection less than a week prior to the event. During this maintenance, the cockpit seats—which were non-standard "High Comfort Crew Seats"—had been removed and reinstalled by two apprentices. Upon inspection after the incident, investigators found that the forward slide stop mechanism was missing from the captain's seat, and several locking pins were absent from both the captain's and co-pilot's seats.
Further investigation into the operator's maintenance practices showed that while the company had implemented several changes following the 2010 incident, a similar event occurred in December 2013 involving another Sikorsky S-92A, registration LN-OQG, where the captain's seat also detached due to missing locking components.
Findings
- The primary cause of the incident was the omission of locking pins and slide stop brackets during the reinstallation of the seats following maintenance.
- The use of non-standard seating required specific installation procedures that were not adequately captured in the existing maintenance documentation.
- Communication between the responsible technician and the apprentices performing the task was insufficient.
- The investigation noted that the effectiveness of the corrective actions taken after the first incident was inadequate, as evidenced by the recurrence of the failure in 2013.