Accident Overview
On 1 December 2005 at 0915 UTC, a Robinson R44 Raven, registration G-ODHG, was destroyed during a hover maneuver at Sywell Airfield, Northants. The sole occupant, the pilot, was uninjured. The aircraft was a 2001 model equipped with a single Lycoming O-540-F1B5 piston engine.
Flight History
The pilot, aged 59, held a Private Pilot’s Licence and had 104 total flying hours, with 11 hours on the R44 type (3.2 as pilot-in-command). The previous day, he had flown a Robinson R22 from Ireland to Cannock but abandoned his flight to Sywell due to bad weather. On the accident day, he planned to fly G-ODHG to Cannock with an instructor to recover the R22.
The Accident Sequence
The pilot intended to hover taxi G-ODHG to the eastern side of the airfield to collect the instructor. The surface wind was from 200° at 10 kt, visibility 8 km, and cloudbase 800–1,000 ft. The helicopter was fuelled to full in both main and auxiliary tanks and parked adjacent to another R44 and an R22.
After completing pre-flight checks, the pilot raised the collective lever. The helicopter yawed left and the nose pitched up. He lowered the collective and corrected with right pedal, causing the helicopter to settle back down. G-ODHG was then facing the other R44.
He again raised the collective to lift into hover and moved the cyclic aft to avoid drifting toward the parked aircraft. The helicopter yawed left and nose pitched up again. As he continued raising collective and attempting corrections, the helicopter pivoted around the rear of the left skid landing gear, rolled left, and the main rotor blades struck the ground. It came to rest on its right side. The pilot released himself through the front left door; the Airfield Fire and Rescue Service attended immediately.
Weight and Balance
The weight and CG calculation for the accident flight:
- Basic Weight: 1,460 lb at arm 106.1 in (moment 154,890 in/lb)
- Pilot: 155 lb at arm 49.5 in (7,672.5 in/lb)
- Auxiliary Fuel: 110 lb at arm 102 in (11,220 in/lb)
- Main Fuel: 184 lb at arm 106 in (19,504 in/lb)
- Total: 1,909 lb, moment 193,286.5 in/lb, CG 101.25 inches aft of datum
The CG envelope at 1,909 lb ranges from 92 to 102.5 inches aft of datum, placing the CG close to the aft limit.
Pilot Experience
The pilot learned on the R22 (92.4 hours total, 16.4 as PIC) and converted to the R44 (11.6 hours total, 3.2 as PIC). All flying was from the right front seat. He had not flown the R44 solo with a full fuel load before this flight.
Analysis
The accident flight was the first time the pilot flew the R44 solo with full fuel. Consequently, the CG was close to the aft limit but within limits for the all-up weight. Given the proximity to other aircraft, the pilot wanted to avoid drifting toward them.
It is possible that on the first lift attempt he applied too much left tail rotor pedal, causing the marked left yaw. On the second lift, the combination of aft CG, left pedal, and increased aft cyclic caused the left yaw and high nose-up attitude. The pilot had not experienced such attitudes before and could not prevent the main rotor blades from striking the ground.
Conclusions
The pilot considered that the aft CG was a major factor in the accident. To address the issue, he now places 56 lb of ballast in the left front seat when flying solo with full fuel, moving the CG forward to 99.7 inches and reducing the need to counter nose-up pitch when lifting into the hover.