A €5m helicopter belonging to property developer Seán Mulryan was destroyed in a crash after a cleaning rag had been left in its rotor.

The chopper had just been serviced at a maintenance facility owned by Ciaran Haughey, son of late taoiseach Charles Haughey, according to a report by the Air Accident Investigation Unit. A report into the accident revealed the cleaning rag had become entangled on a rotor drive-shaft, which had caused a massive malfunction in the aircraft.

The 41-year-old pilot vainly attempted to right the aircraft but it plunged to the ground and he suffered serious back injuries as a result of the crash.

The €5m helicopter was "substantially damaged" after first landing on soft ground and rolling over on to its left-hand side. The chopper had been used by developer Seán Mulryan to fly around England and Ireland to development sites, race meetings and other events.

The dramatic accident occurred last March as the pilot flew the helicopter from Celtic Heliport in Knocksedan, Dublin to Weston Airport in Lucan, West Dublin.

Not long after talking off, the pilot contacted air-traffic control, saying: "I seem to have a bit of a problem here." Almost immediately, he announced he would have to make an emergency landing and transmitted a Mayday call, the report said.

The pilot was interviewed after the accident and explained to investigators what had happened.

He tried in vain to get the chopper under control but it continued to plummet, entering a tailspin before hitting the ground.

The report says: "The pilot's next memory was lying on the ground some 10 to 15 feet from the helicopter, with rain falling on his face."