What happened
On 17 January 2004, a Robinson R22 Beta, registration G-UESY, was engaged in a training flight at Elstree Aerodrome, Hertfordshire. The flight involved an instructor and a student pilot practicing takeoff and landing maneuvers on a section of the airfield consisting of uneven, waterlogged, and soft grass.
During the initial stages of the session, the student performed a controlled but firm landing. During the first takeoff attempt, the aircraft rocked forward because the rotor disc was not positioned correctly. Following a mid-air briefing by the instructor regarding corrective cyclic inputs, a second takeoff was attempted. As the helicopter became light on its skids, the aircraft again rocked forward. In an attempt to prevent the helicopter from tipping, the instructor applied a slight rearward cyclic correction. This action caused the helicopter to roll rapidly to the left. The rotor blades struck the ground, and the aircraft yawed to the right, impacting the ground on its left side. The two crew members escaped through the broken windscreen with no injuries.
The investigation
The investigation examined the ground conditions and the aircraft's behavior during the takeoff sequence. Investigators noted that the terrain was undulating and soft. Marks in the earth suggested that the rear of the left skid may have dug into the soft ground during a previous landing. Additionally, the uneven nature of the surface meant the left skid was positioned lower than the right skid prior to the takeoff attempt. The investigation also considered the impact of the rotor disc attitude and a light quartering tailwind.
Findings
- The aircraft sustained moderate damage to the cockpit area and rotor blades.
- The primary cause of the accident was a dynamic rollover event.
- The rollover was triggered by the instructor's rearward cyclic correction, which was exacerbated by the uneven, waterlogged ground and an incorrect rotor disc attitude.