Aircraft and Pilot Information
The accident involved a Robinson R44 II, registration G-OPDG, serial number 11815, manufactured in 2007. It was powered by a single Lycoming IO-540-AE1A5 piston engine. The helicopter had flown six hours since a 50-hour maintenance check in April 2021, with no reported defects. The pilot, aged 34, held a Private Pilot’s Licence and had 79 hours total flying experience, including 18 hours on type. His recent flying included 10 hours in the last 90 days and 4 hours in the last 28 days.
Flight History
The flight was a private evaluation by a potential buyer. The pilot planned to fly from the owner’s private site near Dromore to another private site at Maghera, County Londonderry. The landing area was a grassed patch approximately 30 m by 30 m, surrounded by a 1.5 m tall wooden fence, with a low-rise building adjacent. A large tree stump was present near one corner. The pilot had previously landed at the same site in a Robinson R22.
The helicopter took off at 2003 UTC. The VFR flight to Maghera and the initial approach were uneventful. The pilot performed an orbit to check the landing site was clear. The weather was dry with visibility over 9 km, no reported cloud, temperature 21°C, and a 2 kt wind from 220°. The helicopter’s total takeoff weight was 905 kg, including 155 kg of fuel.
Accident Sequence
On final approach, at about 150 ft agl and 40 kt, the helicopter was established onto an into-wind heading of 230°. The descent rate was approximately 500 fpm, with airspeed gradually reducing. At about 30 ft agl and 15 kt, the pilot began raising the collective lever and increasing aft cyclic to slow the helicopter and arrest the descent. Data showed that during the next four seconds, the descent was arrested at about 10 ft agl, with airspeed at 10 kt, and the helicopter within a few metres of the landing site.
However, the pilot reported that during this manoeuvre, the low rotor rpm warning horn sounded and the low rpm warning light illuminated (activated when rotor rpm falls below 97%). The helicopter started to yaw right and descend. The pilot stated this happened very quickly. Aware of the nearby tree stump, he recalled overriding the governor to increase the throttle and may have lowered the collective while manoeuvring to touch down on the grass.
As the helicopter touched down, its tail boom struck the adjacent fence, causing the helicopter to yaw right toward the building. The main rotors subsequently struck the building before the helicopter came to a stop. The pilot, uninjured, shut down the helicopter. The aircraft was damaged beyond economic repair.
Comments
The pilot attempted to recover the low rotor rpm when close to the ground but lost control while avoiding the tree stump. The reason for the rotor rpm decay was not established. Although the pilot had landed uneventfully at the same location before, the site had several obstacles that increased the risk of contact if a problem occurred near the ground. The pilot stated that he would look to reduce this risk in the future by reviewing his landing site selection criteria.