What happened
On 23 February 2003, an Aerospatiale AS350B1 Ecureuil, registration G-BVJE, was performing aerial work involving forest firefighting near Kyle of Lochsh, Scotland. The aircraft was utilizing a 'Bambi Bucket' to collect water from a hill loch. During the thirteenth approach to the water, the pilot was monitoring the underslung load via a mirror when the aircraft experienced an unexpectedly high rate of descent at approximately 100 feet.
To correct the descent, the pilot applied significant power, which stabilized the aircraft into a low hover. While the pilot noted no immediate mechanical issues or unusual engine temperatures, the aircraft's tail rotor blades subsequently struck the surface of the loch. Approximately two minutes later, while transitioning away from the water, a chip caption light illuminated in the tail rotor gearbox. The pilot then landed the aircraft at a nearby village playing field.
The investigation
Investigators examined the aircraft following the incident and discovered metal particles on the tail rotor gearbox chip detector. Physical inspection of the Aerospatiale AS350B1 Ecureuil revealed that the tail rotor blades had sustained damage consistent with an impact with the water surface. The investigation also considered the environmental conditions, noting that the loch surface was partially frozen and situated in the lee of a steep hill, which could mask turbulent wind conditions.
Findings
- The tail rotor blades struck the surface of the water during the descent phase of the approach.
- The tail rotor striking the water surface was the primary cause of the mechanical damage.
- The presence of a partially frozen loch surface likely obscured the pilot's awareness of gusty or turbulent wind conditions.
- The high rate of descent may have been caused by a momentary lapse in concentration or a localized downdraft.