What happened
On 30 March 2021, a Rotorway 162F helicopter, registration G-OHOV, was performing the final low-level hover test of a series intended to bed-in newly installed transmission drive belts. The flight was being conducted as a private operation at Street Farm, Takeley, Essex.
While the aircraft was hover taxiing at approximately 10 feet and a speed of 10 knots, the pilot experienced a sudden loss of engine power. The pilot responded by initiating a run-on landing, managing to settle the aircraft onto the ground at a walking pace. However, the landing surface consisted of soft, rutted earth. The skids dug into the ground rather than sliding, causing the helicopter to tip forward. During this movement, the rotating main rotor blades struck the ground, which violently overturned the aircraft onto its side. The impact caused extensive damage to the tail boom, tail rotor, and main rotor blades. The pilot was uninjured.
The investigation
The AAIB examined the engine control system, which utilizes a Fully Automated Digital Electronic Control (FADEC) setup consisting of two separate Engine Control Units (ECU). Investigators downloaded and analyzed data from both FADEC 1 (the primary controller) and FADEC 2 (the secondary controller).
While FADEC 1 showed no faults or warnings, the data from FADEC 2 revealed a CPU error code and erratic throttle position data during the final seconds of the flight. Investigators also noted a significant, unexplained discrepancy in the data time stamps between the two units, making it difficult to confirm if both units recorded the same flight period. Additionally, the investigation looked into a fuel pump issue reported by the pilot during start-up, but the pump was found to be functioning correctly following the accident.
Findings
- The primary cause of the structural damage to the Rotorway 162F was the aircraft tipping forward and the main rotor blades contacting the ground.
- An uncommanded loss of engine power occurred, though the specific mechanical or electronic cause could not be definitively identified.
- A CPU fault and erratic throttle data were recorded by the secondary engine controller (FADEC 2).
- The soft and rutted nature of the landing site prevented the skids from sliding, contributing to the forward tip.