History of the Flight
The accident occurred on 15 September 2007 at 1505 UTC near Lanark, Scotland, during a short private flight. The pilot had flown from his home to a farm near Larkhall earlier that day, accompanied by an adult male friend and two children: the pilot's five-year-old son and a six-year-old friend. After less than an hour on the ground, the helicopter departed at 1500 UTC for the return journey. An automotive gearbox had been loaded into the rear compartment.
Witnesses observed the helicopter approaching Lanark from the west before turning and descending into the Mouse Water valley, which runs past the pilot's home. The helicopter was described as flying faster than normal, in a banked, nose-low attitude. No one witnessed the actual impact.
Accident Site and Wreckage
The helicopter crashed into steep, heavily wooded ground on the south bank of the Mouse Water valley, approximately 150 metres from the intended landing point. The initial impact occurred with the upper branches of two substantial trees. The left side of the rotor disc struck a fir tree, dislodging a complete main rotor blade, which landed about 150 metres beyond. The main gearbox was torn from its mountings. The tail boom separated into two sections. The cabin and engine struck rising ground, coming to rest inverted about 45 metres from the initial impact point. A severe post-crash fire destroyed much of the cabin structure.
Examination of the fir tree revealed a broad, horizontal scar consistent with a single main rotor blade strike. The orientation of the scar and wreckage suggested the helicopter struck the trees in an upright attitude with little bank angle and a nominally level pitch. The impact speed was relatively high. The engine was delivering power at impact.
Witness Accounts
Twenty witnesses reported seeing the helicopter during the flight. Several in Lanark described its final maneuver as unusual, involving a steep left bank and descent at high speed. Two witnesses had seen a similar maneuver before and were not concerned. The helicopter was not reported to be in obvious difficulty, and no smoke, flames, or falling objects were observed. Most witnesses described the engine sound as normal.
The wind at the accident site was estimated at 23 to 28 knots from 240 degrees at 500 feet above the site, increasing slightly with altitude. Weather conditions were generally good with scattered cloud at 3,200 feet. No significant mountain wave activity was present.
Investigation and Cause
The AAIB investigation did not positively determine the cause of the accident. No technical reason was found to explain the crash, although a technical fault could not be entirely ruled out. The investigation considered it more likely that the pilot attempted a turning maneuver at low height, during which the helicopter deviated from the intended flight path. This may have resulted from handling difficulties, misjudgment, spatial disorientation, distraction, or a combination of factors. Evidence suggested the pilot began a recovery, but there was insufficient height to complete it before the helicopter struck trees.