An Air Accident Investigation Report into a helicopter crash, which claimed the lives of an instructor and student, has found that the accident was caused by the aircraft hitting disused power lines 30ft above the ground.
The pilot, 34-year-old instructor Colm Clancy from Co Donegal, and his student, 24-year-old Dermot Sheridan from Co Clare, were killed in the crash on 1 April 2009 at Kilshanchoe, Co Kildare.
The report criticised the pilot for engaging in low-level flying exercises below the minimum height in an undesignated area.
The flying school he was employed by, the European Helicopter Academy, was criticised for its level of instructor oversight.
The helicopter had left Weston Aerodrome just after 4pm 1 April and headed south of Enfield.
Radar tracked the aircraft as it made a series of wide turns over a large tract of bog before engaging in a number of descents and climbs.
At around 4.33pm the helicopter crashed into disused power cables but the alarm was not raised until the following morning by members of the instructor's family.
The aircraft had disintegrated in the crash with pieces of the cockpit found 66m away from the helicopter.
The report said the crash was not survivable and the deaths were due to multiple injuries.
An examination of the rotor blades clearly indicated that they had hit the power lines. The report states that the instructor was probably training his student in auto-rotation, where the engine does not power the rotors, simulating an engine failure.
Normally this is done between 1,000 and 2,000 ft while advanced training is done close to airfields in case of accidents.
The minimum height for flying in Ireland is 500ft. The power lines were 30ft high.
The visibility of cables is frequently extremely difficult, according to the report, and the area where the accident happened is such that it would have been extremely difficult for the pilot or student to see the cables.
The report concludes that the helicopter was flying below the minimum height and that it collided with power lines while travelling at speed, probably coming out of a controlled descent.
The investigation has made one safety recommendation, which has been accepted by the Irish Aviation Authority relating to increased awareness of cable strikes.
