What happened
On 30 April 2003, a Bell 206L Longranger, registration G-IANG, was performing a private flight near Oxenfoord Castle. After completing several commercial tasks earlier in the day, the pilot was returning to his home base with two other occupants. Due to changing weather conditions and low cloud, the pilot diverted south of his planned route to maintain visual contact with the ground.
While flying at approximately 500 feet agl, the pilot encountered low cloud at the entrance of a valley. In an attempt to avoid newly visible power cables, the pilot initiated a climb. During this maneuver, the rear of the helicopter struck a 132 kV cable. The impact caused the tail rotor/fin assembly to detach from the aircraft. The helicopter began to rotate violently to the right. The pilot attempted to enter an autorotation to manage the descent, but the aircraft ultimately performed a heavy forced landing on a grass slope.
All three occupants escaped the aircraft with minor injuries, though the helicopter was damaged beyond economic repair.
The investigation
Investigators examined the wreckage and found that the impact with the cable had stripped 15 cm from the tips of the tail rotor blades and caused the tailboom to tear away. The investigation also focused on the failure of the pilot's upper torso restraint during the impact.
Testing revealed that the stitching on the pilot's restraint failed at a load of approximately 900 lbf, which is significantly lower than the 1,500 lbf strength found on original equipment manufacturer (OEM) parts. It was discovered that the restraints in G-IANG had been replaced by a third-party company that was no longer in business, and the quality of the stitching was found to be irregular and poor.
Findings
- The pilot lost situational awareness regarding his exact geographical position relative to local hazards.
- The pilot's decision to descend to 500 feet agl to maintain visual contact with the ground placed the aircraft within the height of the power cables.
- The tail rotor/fin assembly detached due to the impact with the uppermost power cable.
- The pilot's upper torso restraint failed at a much lower load than standard OEM components due to poor manufacturing quality.