What happened
On 10 June 2002, a Robinson R22 Beta, registration G-BOEW, was performing aerial training maneuvers at Cranfield Airport in Bedfordshire. The flight involved a flying instructor demonstrating an 'engine off' landing technique to a student. This particular maneuver was the seventh such attempt conducted that morning.
As the helicopter approached the grass landing strip (designated 22) into the wind, the port side skid made initial contact with the edge of the strip, specifically an area marked by slightly raised, scraped earth. This contact destabilized the landing run-on. In an attempt to correct the aircraft's position, the pilot applied large control inputs while the main rotor was at a low speed. During this sequence, one of the main rotor blades struck the tail boom, resulting in the tail boom being severed and the tail rotor drive shaft being damaged.
The investigation
The investigation was based on the aircraft accident report submitted by the pilot. Investigators established that the aircraft was operating in 24-knot winds from 230°. While the pilot did not receive any immediate cockpit warnings regarding the structural damage, he noted a change in the noise of the rotor and a slight vibration. Air Traffic Control (ATC) observed the event and contacted the pilot to advise an immediate engine shutdown.
Findings
- The primary cause of the structural failure was the impact of a main rotor blade against the tail boom.
- The instability during the landing was triggered by the initial contact of the port side skid with the uneven, raised earth at the edge of the landing strip.
- The subsequent large control inputs made during the low-speed rotor state contributed to the rotor blade strike.
- There were no injuries to the two crew members on board.