The exact cause of the ‘loss of control’ of a helicopter at a Bucks aerodrome could not be identified, report says.
The aircraft, a Westland Scout AH1, was lifting off after refuelling at Turweston Aerodrome when the pilot lost control, according to the report published by the Air Accidents Investigation Branch.
The helicopter was carrying its owner and an instructor, with the report saying that the two people on board suffered ‘minor’ injuries.
After refuelling, the instructor advised a vertical take-off to avoid affecting a nearby parked aircraft with rotor downwash.
According to the report, the owner initially lifted the helicopter into a hover without incident.
To provide greater clearance from the nearby aircraft, the instructor then took control and manoeuvred the helicopter slowly to the left before beginning a turn into wind.
However, as the instructor applied left pedal to initiate the turn, the helicopter unexpectedly began rotating rapidly to the right.
Despite applying full opposite yaw control, the rotation continued to increase.
Thinking there was a problem with the tail rotor he closed the throttle and as the helicopter settled, he raised the collective to cushion the landing.
Read more:
Dramatic moment armed police surround car in Wycombe as gym goes on lockdown
Firefighters rush to three-storey flat block after kitchen fire
Three casualties after car collides with building on Bucks High Street
However, the aircraft suffered some damage upon landing.
The report reads: “The helicopter landed heavily damaging the skids and causing the main rotors to droop whilst rotating and strike the tail boom.
“This resulted in significant disruption to the tail rotor drive system shafts and support bearings.”
Following the incident, the aircraft was examined onsite, with the report saying the ‘extensive damage’ to the structure surrounding the tail rotor drive shafts and transmission system was indicative of the main rotor blades striking the tail boom.
“It was also found that the tail rotor blades had also contacted the ground sustaining damage during the landing, shock loading and further damaging the drive train.
“There was no evidence of pre-existent faults or malfunctions that could have contributed to this accident.
“Foreign object or an external control restriction was also considered but no evidence was found,” reads the report.
With the absence of a technical malfunction and taking into account the calm conditions and simplicity of the manoeuvre, the report found there to be no clear obvious cause.
The report concluded: “The helicopter was being flown within its capabilities in unchallenging conditions when the loss of control occurred.
“In the absence of a technical fault or malfunction, the exact cause of the loss of control could not be identified.
“However, it appeared to demonstrate the characteristics of a loss of tail rotor effectiveness, but this was considered to have been unusual in this type of helicopter.
“Similarly the concept of tail rotor breakaway was also considered but could not be positively determined.”
