"The accident appears to have occurred during a sixth autorotation manoeuvre," the report states.
The helicopter crash that resulted in the deaths of two men last month seems to have happened during a training manoeuvre designed to handle engine failure.
The information comes from a preliminary report by the Air Accident Investigation Unit (AAIU) regarding the crash that took the lives of Straffan man Niall Crosby, a 46-year-old married father of two, and Antonin Kabelka, a 48-year-old Czech national, near Killucan, Co Westmeath on Tuesday, July 30.
"The accident appears to have occurred during a sixth autorotation manoeuvre," the report states.
It adds: "This exercise includes ‘autorotations’, which are manoeuvres that simulate an engine failure in flight in which the engine is disengaged from the main rotor disc and the rotor blades are driven solely by the upward flow of air through the rotor."
The initial 11-page report does not include any analysis or conclusions.
A final report will be released later as the investigation, led by Investigator in Charge Paul Farrell, continues.
The report explains that ‘autorotation’ is a part of flight training for trainee pilots, teaching them how to respond to engine failure.
An autorotative descent is a power-off manoeuvre where the engine no longer powers the main rotor.
Mr. Kabelka, a married father of three, was the helicopter instructor, and Mr. Crosby was the student pilot.
Mr. Crosby, originally from Straffan, Co Kildare, and residing in Glenageary, south Dublin, was the founder of AG Grid, a software company based in London. He had purchased the Canadian-made helicopter and was undergoing training to pilot the Bell Textron Jet Ranger X 505.