Accident investigators have been unable to establish the reason for a Mayday call made from a helicopter shortly before it crashed killing both people on board, including a man from Chorley.

Flying student Philip Charles Gray, 45, of Mawdesley and instructor Steven Edward Lewis, 38, died when the Schweizer aircraft crashed on the east bank of the River Wyre, near Stalmine, Lancashire, on the morning of September 22 last year.

The pilot had made a Mayday transmission 20 minutes into the flight from Blackpool airport.

Received at Blackpool, the transmission mentioned the word “failure” but the requested further transmission a few seconds later consisted mainly of background noise, a report by the Air Accidents Investigation Branch (AAIB) said.

The report said: “Transmission of the Mayday indicates that the instructor had identified an emergency situation and, although it was not possible to determine what this was, the Mayday itself was delivered in a voice that, according to family members, sounded calm and held no sense of panic.

“Analysis of the final transmission, however, suggests that the helicopter was by then no longer in controlled flight.”

The AAIB said examination of the helicopter revealed that the main rotor was turning at low speed on impact, “but the reason for this could not be established”.

The AAIB said the most likely cause of the accident was “a loss of control during an attempted forced landing downwind”.

Mr Lewis was from Rainhill, Merseyside.