History of the Flight
The pilot, who held a Private Pilot's Licence (Helicopters) since April 2000, intended to conduct a local flight from Sherburn-in-Elmet airfield with a family member as passenger. Earlier that day, the helicopter had been used for training flights. After a training sortie, an Assistant Flying Instructor reported an unusually rapid drop in engine rpm on throttle closure, more collective lever angle needed for lift-off, and slightly higher oil temperature. The Qualified Flying Instructor assessed the helicopter but noted no abnormalities. The accident pilot was not briefed on these reports as he did not complete pre-flight paperwork. The pilot contacted Church Fenton Approach at 1440:51 hrs, reporting departure from Sherburn. He later requested MATZ penetration to return. At 1521:23 he reported Sherburn in sight, then no further transmissions. Radar tracking ceased at 1521:26. The accident occurred near Biggin at 1526 hrs while the helicopter was tracking southwest towards the airfield. Local residents heard a 'metallic bang' followed by the engine faltering; parts fell from the helicopter, which pitched down and descended steeply. The impact was non-survivable.
Examination of the Wreckage
The helicopter lay in a field, having fallen vertically in a right-skid-low attitude with little forward speed. The left seat occupant was still in his seat; the pilot was thrown clear. Main rotor blades showed damage from ground contact but not characteristic of high RPM at impact. The tailboom had struck the ground vertically, with the tail rotor driveshaft buried. Analysis indicated a low-energy rotor strike about 0.5m aft of the fuselage attachments. Pieces of the right windscreen and door frame were found along the flightpath over 400m, indicating a low-energy main rotor strike on the canopy. In the cockpit, the magneto switch was selected to 'Left', carburettor heat control in 'Cold', mixture 'Rich'. Both plastic handgrips had detached from the cyclic control.
Subsequent Examination
The main rotor gearbox, rotor mast, freewheel clutch, and control linkages were in good condition. The engine was strip-inspected and found internally good. Both magnetos were serviceable. The carburettor air filter box showed the carburettor heat slider trapped in the 'full-hot' position, which varied from the cockpit knob position, but the slider was considered more reliable. The 'Low Rotor RPM' warning light filament showed evidence of hot stretching, indicating it was illuminated at impact. There were no signs of engine or transmission rotation at impact. The Met Office aftercast indicated a serious risk of carburettor icing at any power setting given the conditions.