What happened
On 10 January 2012, a SA341G Gazelle 1, registration G-WDEV, was conducting a private flight from a site near Bath to a landing area near an industrial estate in Salisbury, Wiltshire. During the approach to the landing site, the pilot attempted a steep approach and a stable hover in ground effect. As the pilot lowered the collective, the aircraft reached an unacceptably tail-low attitude. Upon attempting to lift the aircraft back into a hover, the pilot noticed a change in the tone of the main rotor RPM, suggesting a reduction in engine power.
While the pilot was attempting to reposition the aircraft, flames became visible behind the engine cowlings. The pilot instinctively reduced collective input, believing the RPM decay was temporary. However, the RPM continued to drop significantly, accompanied by loud popping and cracking noises. As the controls lost effectiveness, the pilot steered the descending aircraft toward the lowest available tree tops. The helicopter struck the trees and rolled onto its left side. The pilot and two passengers sustained minor injuries.
The investigation
Investigators examined the wreckage, GPS data, and eyewitness accounts. GPS analysis revealed that the aircraft flew past the intended landing site at a low altitude before turning back toward the area. The aircraft's descent through the trees showed very little forward motion.
Physical examination of the wreckage noted a tear in the aircraft skin at the base of the upper vertical fin, which contained leaves from a fir tree found at the crash site. This suggested a significant sideways motion, such as a yawing movement, during the impact. The engine was still running immediately following the accident. To suppress the fire, the pilot had used a portable fire extinguisher on the engine air intake, which subsequently caused the engine to stop.
Findings
- The accident was caused by a reduction in main rotor RPM following the onset of an engine fire.
- The pilot's instinctive reduction of collective input during the initial RPM decay contributed to the loss of altitude.
- The presence of flames behind the engine cowlings indicated an active fire in the engine compartment.
- The aircraft's descent into the trees was characterized by a lack of forward momentum and a likely yawing motion at the moment of impact.