Markus Casey of Salthill in Galway was killed instantly when the plane plummeted into a field at Kilmovee and John Dunphy, a senior engineer with Wicklow County Council, was injured.
Just seven minutes after taking off from Knock Airport for Weston aerodrome on May 11, Mr Casey reported “limited power and being unable to hold altitude and then attempted a forced landing in difficult terrain”, according to a preliminary air accident report.
Department of Transport investigator Paddy Judge said witnesses described a labouring engine, which stopped, restarted for a couple of seconds and stopped again some seconds prior to the noise of impact.
The plane was destroyed and Mr Judge said an inspection of the wreckage did not show signs the propeller was turning when it crashed.
The engine was stripped and examined at the air accident investigation unit’s facility in Gormanston, Co Meath.
Two inlet valves showed cracks and a valve segment was found in another engine cylinder.
Mr Judge said the cause of the cracking has “yet to be determined” and further research is required before a final report.