What aircraft was involved and where did it happen?

The accident on 2012-10-16 involved a AS350B2 Ecureuil, registration G-BXGA, at 1.5 nm south of Kettlewell, Yorkshire, GB.

What was the probable cause of the accident?

The lifting sling struck the tail rotor blades due to a combination of high airspeed, a nose-up descent attitude, and turbulence, which caused the sheathed sling to swing into the rotor path.

Tail rotor damage during aerial work in Yorkshire

An AS350B2 helicopter sustained damage to its tail rotor blades after a lifting sling struck the blades during an approach near Kettlewell.

What happened

On 16 October 2012, an AS350B2 helicopter, registration G-BXGA, was performing aerial work near Kettlewell, Yorkshire. The mission involved transporting power line poles from a field site to a construction area approximately 15 km away. After completing several successful trips, the pilot was descending toward a field site at a speed between 75 and 80 knots.

During this approach, a 7-meter long chain lifting sling, which was suspended beneath the aircraft and covered in a cloth sheath, struck the tail rotor blades. The impact produced a loud bang and high-frequency vibrations within the cockpit. Despite the vibration, all cockpit instruments continued to show normal readings. The pilot notified the ground crew of the incident via radio and jettisoned the empty sling before performing a minimum power landing. The aircraft sustained impact damage to the tail rotor blades, the port horizontal stabiliser, and the tail rotor driveshaft cover, but there were no injuries to the crew.

The investigation

The investigation examined the flight conditions and the equipment involved. At the time of the accident, the weather was generally good, though a westerly wind of 25 knots, gusting to 35 knots, was present, causing some turbulence near the hills. The investigators also reviewed a previous, similar incident involving another AS350B2, registration G-ORKY, which had occurred one week earlier.

Findings

The primary cause of the incident was the chain lifting sling making contact with the tail rotor blades.
The sling, which featured a cloth sheath, was found to angle further back during flight than unsheathed slings.
The incident was likely caused by the sling entering the tail rotor area due to high airspeed and a nose-up descent attitude.
Turbulence contributed to the movement of the sling into the rotor path.

Safety action

Following a flight trial, the operator determined that the cloth sheath caused the sling to hang at an angle that increased the risk of contact. Consequently, the operator increased the sling length to 10 meters and removed the cloth sheaths from most of the sling. A safety bulletin was distributed to all pilots and ground personnel, emphasizing the importance of maintaining a speed limit of 80 knots and being prepared to reduce speed during descents or in poor weather.