Incident Overview
On 20 July 2015, a serious incident involving a near collision occurred approximately 1 nautical mile southwest of Samedan Airport (LSZS). The aircraft were an AgustaWestland AW109SP helicopter, registration HB-ZRR, operated by Swiss Air-Ambulance AG, and a Grob G 109 B motor glider, registration HB-2088. The helicopter was on an approach while the motor glider was taking off. The two aircraft approached each other dangerously without the crews establishing visual contact.
Causes
According to the Swiss Transportation Safety Investigation Board (STSB), the serious incident was directly caused by the failure of the helicopter crew and the motor glider crew to establish visual contact during the approach and takeoff phases, respectively, leading to a dangerous proximity between the two aircraft.
Contributing Factors
Several factors played a role in the incident. The flight information service at the aerodrome did not provide traffic information to either crew. Additional direct factors included the helicopter's high approach speed and descent rate, the limited effect of the helicopter's collision warning system on the crew, the motor glider crew not perceiving their collision warning indications, the motor glider crew not activating the transponder, and the motor glider's collision warning system being inadequately configured. A systemic factor was that the helicopter approach procedure used carried inherent risks.
Systemic Risk Factor
While not directly causal, the STSB identified that the helicopter approach procedure used was not published, posing a systemic risk.
Investigation
The investigation was conducted by the STSB. No information on injuries or damage was provided in the source.