Background
The helicopter, a Robinson R44 registered G-WMCN, was built in 1997 and powered by a single Lycoming O-540-F1B5 piston engine. The pilot, aged 41, held a Private Pilot's Licence with IMC, Night, and AFI ratings and had 2,260 total flying hours, including 360 on helicopters and 31 on type. The flight was a private trip from Denham to Milton Keynes for go-cart racing, with a planned return to Denham that evening.
Weather
The pilot obtained meteorological forecasts from various sources, including a Metfax at Denham before departure. These indicated wind 190°/12 kt, good visibility, no significant weather, and a scattered cloudbase at 1,700 feet. However, one passenger recalled forecasts predicting overcast conditions with rain late in the afternoon. The Meteorological Office forecast issued at 0940 hrs indicated an occluded front from the Wash to the Isle of Wight at 1500 hrs, with general visibility 10 km and broken cloud at 2,000 feet, occasionally 6 km in rain with broken cloud at 800 feet. An aftercast for the accident time (1700 hrs) showed misty and foggy conditions with visibility 800 to 1,500 metres and cloudbase 300 to 800 feet in rain and drizzle.
Accident Flight
The flight to Milton Keynes was uneventful and conducted in reasonable weather. At about 1650 hrs, while the pilot completed after-start checks at Milton Keynes, rain began and intensified; it was dark. The rear passenger remarked on poor weather, but the pilot did not consider it a problem. The helicopter took off at 1700 hrs. The pilot reported good visibility and climbed to about 1,000 feet above Milton Keynes. The rear passenger recalled the height as 700-800 feet with an estimated visibility of two to three miles. The pilot asked the front passenger to hold a map and hand-held GPS for easy viewing, then switched on an interior light to study the map. Soon after, the front passenger exclaimed 'What's going on?' and the rear passenger saw the ground approaching. The pilot exclaimed 'What!' and attempted to level the helicopter before it struck the ground and broke up.
The pilot stated that while cruising, he lost visual contact with ground lights, assumed he entered low cloud, and attempted instrument flight while lowering the collective and descending at about 200 ft/min. At 600 feet, still in cloud, he decided to reverse course and reduce airspeed from 100 kt to 60 kt. During the turn, the helicopter struck a tree and crashed into a field, disrupting the airframe. GPS data showed a steady 100 kt for one minute, then reducing to 80 kt in the 90 seconds before impact, with a gentle 30° left turn. The final heading was 131°(M). No height data was available from the GPS.
Injuries and Evacuation
The pilot suffered lacerations to his forehead and minor fractures; he escaped the wreckage, alerted emergency services via mobile phone, and directed them to the site. The front seat passenger suffered severe internal injuries, compression fractures of the spine, broken bones, and deep cuts; he remained in intensive care for six weeks and in hospital for four additional weeks. The rear seat passenger, upon regaining consciousness, found himself propped against the tail boom; he had fractured vertebrae and was treated in hospital.
Discussion
The outbound flight was uneventful in daylight and reasonable weather. By the return departure, rain had begun and cloudbase lowered as a low-pressure centre moved southeast. This deterioration had been forecast and could have been deduced from the synoptic situation and enquiry at the destination. Upon unexpectedly entering low cloud, the pilot lost visual reference. While attempting to turn away and descend, he lost control. Factors contributing to loss of control probably included his attempt to refer to a hand-held map and GPS using interior cockpit lighting, which degraded his ability to maintain visual contact.