What happened
On the afternoon of 1 April 2009, a Schweizer 269C-1 helicopter, registration EI-CZL, departed Weston Airport for a flight training session. On board were an instructor and a student pilot. After communicating their intention to operate south of Enfield between 1,000 and 2,000 feet, the aircraft transitioned into uncontrolled airspace.
Radar tracking showed the helicopter performing maneuvers over bogland at various altitudes. During the flight, the aircraft performed a series of descents. At approximately 16:33 hrs, the helicopter descended to a height of roughly 30 feet, where it struck disused electrical power lines near Kilshanchoe, Co. Kildare. The impact was not survivable, and both occupants were killed. The wreckage was discovered the following morning by an Irish Coast Guard helicopter after family members raised an alarm.
The investigation
The AAIU examined the flight history, maintenance records, and radar data. The investigation found that the flight training organization had not recorded the specific details of this accident flight on its Flight Authorisation Sheet. Furthermore, because the flight training school's office had closed earlier that evening, no alert was raised by Weston Air Traffic Services when the aircraft failed to return as expected.
Investigators also reviewed witness accounts. Several individuals in the vicinity observed the helicopter performing low-level maneuvers, including what appeared to be an autorotation exercise. One witness noted the aircraft descending to a low altitude before disappearing behind trees. The investigation also looked into the visibility conditions, noting that a low sun angle and glare from surface water may have contributed to the difficulty in spotting the wires.
Findings
- The primary cause of the accident was the collision with disused electrical power lines during a low-level flight phase.
- The aircraft was performing training maneuvers, including a probable low-level transition following an autorotation.
- The flight training organization's failure to document the flight on the authorization sheet meant there was no internal record of the intended mission.
- The lack of an immediate alert from Weston ATS was due to the operations office being closed and the absence of a formal abbreviated flight plan for the specific flight.
- Environmental factors, such as low sun elevation and glare, may have hindered the crew's ability to identify the wires.