History of the Flight
On 21 July 2008, at approximately 1230 UTC, a Robinson R44 Astro helicopter (registration G-YIIK) was involved in an accident at Delph, near Oldham, Lancashire. The pilot, who held a Private Pilot's Licence and had 360 hours total flying experience (21 hours on type), was returning to a private landing site outside his house. The site, situated in a valley at about 885 ft amsl, was approached from the north-east. During the approach, the pilot observed from a windsock that the wind was from the north-north-west at approximately 20 kt. He flew downwind for about half a nautical mile before turning into wind and approaching on a north-easterly heading, his normal approach for a northerly wind.
Just after entering the hover over the landing site at approximately 30 ft, the pilot noticed the windsock point vertically upward, and the helicopter began to rotate clockwise. He applied full left pedal, but the rotation continued. The helicopter began to drift downwind toward trees while still rotating, so the pilot raised the collective lever fully to increase height. At about 200 ft agl, the rotation stopped and the helicopter was flying downwind with zero indicated airspeed. The pilot pushed forward on the cyclic to increase IAS, but the low main rotor rpm (Nr) warning sounded (Nr less than 97%). He then lowered the collective to try to increase Nr, resulting in a rapid descent.
The pilot elected to land on a relatively flat area in a field below rather than risk a steep area further downwind. Just prior to touchdown, he raised the collective to cushion the landing. The helicopter landed heavily in an upright attitude before rolling onto its left side. The pilot was seriously injured and was able to turn off the engine and fuel supply. Paramedics from an air ambulance removed him from the helicopter about ten minutes after the accident and transported him to hospital. The helicopter was damaged beyond economic repair.
Pilot's Comments
The pilot commented that landings can be 'tricky' with a north-westerly wind because the wind tends to 'shift a lot.' He also felt that he was slow in applying left rudder pedal and did not check the Nr after the low Nr warning sounded, so the amount of Nr decay was unknown.
Weather
A Met Office aftercast indicated that at the time of the accident, the wind at 1,000 ft amsl was likely from 340° at 25-32 kt, and the surface wind from 320° at 15-25 kt. The surrounding terrain could have caused localized rapid changes in wind speed and direction.
Discussion
The helicopter entered the hover, out of ground effect, with the wind from the 10 o'clock direction and was subjected to a large wind shift. As a result, the pilot lost directional control, possibly due to loss of tail rotor effectiveness (LTE). The pilot applied full left rudder and raised the collective, which over-pitched the main rotor blades, reducing Nr. At approximately 200 ft agl, the helicopter was in the avoid curve with low Nr. After lowering the collective to regain Nr, the pilot was committed to landing due to the high rate of descent and insufficient height to recover to normal flight.