What happened
On the evening of 24 June 2007, an Agusta Westland Merlin HC. Mk 3 helicopter, registration ZJ 137, was departing from a static display park at the Promenade in Salthill, Co. Galway. As the aircraft, operated by the Royal Air Force, began its lift-off and transitioned away from the display area, an emergency egress door became detached from the airframe at an altitude of roughly 150 feet.
The falling door struck the ground, resulting in 3 minor injuries to individuals on the ground who were attempting to avoid the falling component. The aircraft sustained slight impact damage to the area of the emergency egress door following the separation.
The investigation
The investigation focused on determining why the door separated from the aircraft while in flight. Investigators examined the door and its associated locking mechanism, concluding that both were fully airworthy and functional prior to the incident. No mechanical or technical failure was identified as the cause of the separation.
Review of digital video and various camera recordings established that the emergency egress door-locking handle was set to the "Jettison" (unlocked) position as the helicopter commenced its departure.
Findings
Investigators determined that the door separated because the locking handle had been left in the unlocked position. Evidence suggests that members of the public likely tampered with the handle while the helicopter was parked for viewing at the static display.
Furthermore, the flight crew did not identify the incorrect handle position during their pre-flight inspection. The investigation characterizes the event not as a deliberate act of malice, but rather as an act of mischief by a member of the public.