CH149 Cormorant Epilogue

The accident aircraft, call sign “Outcast 903”, with a crew of six, was scheduled for a training mission flying out of 9 Wing located at Gander International Airport (CYQX), N.L. The training mission was primarily focused on overland Search and Rescue evolutions for the Flight Engineer Under Training.

At the end of the mission, the crew conducted hover work in the vicinity of the intersection of Runway 31 and Runway 21. During the final clockwise hover turn sequence, the pilot flying’s seat unexpectedly descended to its lowest position. As the seat rapidly descended, the collective position moved downward abruptly and was quickly brought back up near its original position. For approximately 2 seconds, the aircraft was subject to severe vertical vibration (bouncing), during which time small cyclic movements were made and full left pedal was applied. The aircraft flight vector reversed from the previous clockwise rotation to an accelerated counterclockwise left yaw about the aircraft vertical axis (i.e. the mast). The aircraft rotated through approximately 400° and as the right rolling moment intensified, the right outboard wheel, the right horizontal stabilizer, and the main rotor blades impacted the runway near simultaneously. The impact occurred at 15:43 L. There was no post-crash fire. The aircraft was destroyed. Four of the six occupants sustained minor injuries while two occupants sustained serious injuries.

The investigation determined that a combination of factors, including seat non conformances and the horizontal position that was maladjusted, allowed the seat to be in a false lock condition. When the seat dropped, the loss of outside visual references in combination with the severe vertical vibration resulted in an unrecognized spatial disorientation of the pilot flying. This caused the pilot flying to incorrectly perceive a right yaw and apply full left pedal input; this led to a severe left yaw and contributed to the change in roll attitude that likely rendered the helicopter unrecoverable.

Multiple special inspections and aircrew information files were issued to address the seat non-conformances and avoid false lock conditions. Additional preventive measures have been identified to address deficiencies in fire fighting services, egress and tracking of armament as highlighted during this investigation.