The helicopter may have experienced a build-up of unburnt fuel in the exhaust system, which ignited while in flight, near Ledbury, Herefordshire, 2 April 2021
The helicopter, a Rotorway Executive 162F (G-JDHN), was in a stable cruise when the pilot heard a very loud noise which may have been caused by unburnt fuel igniting in the exhaust.
This resulted in the helicopter reacting in a way that the pilot could not rationalise in the short time available, so he successfully autorotated to land in a field. At the end of the ground run, the left skid caught on uneven ground and the helicopter rolled over onto its left side. Both the pilot and passenger managed to escape with minor injuries.
It is suspected that defects in the cylinder 3 exhaust valve sealing may have been the cause of unburnt fuel in the exhaust system