Overview
On 19 November 2009, at approximately 19:55 local time, a Schweizer 269C helicopter, registered HB-XYI, experienced a loss of control during a night external landing in Unterbärgetal, municipality of Burgdorf/BE, Switzerland. The helicopter subsequently collided with terrain. The two occupants, a flight instructor and a student pilot, were uninjured. The helicopter sustained severe damage.
History of the Flight
The flight was a night VFR training flight. The crew met at Bern-Belp airport for a pre-flight briefing. The flight instructor had prepared and refuelled the helicopter. Flight planning was divided between the pilots. The general planning was done by the instructor, who noted a take-off mass of 1879 lb, a HOGE power calculation of 2000 ft, and planned fuel of 40 U.S. gallons. Weather information indicated visibility over 10 km and wind at 5000 ft AMSL from 230° at 20 kt. The crew discussed high atmospheric humidity, forecast temperatures, and poor light conditions. They agreed that each pilot could make a 'no go' decision at any time.
The crew took off from Bern-Belp at 19:12, heading towards Kirchberg. After leaving air traffic control at 19:19, they proceeded to the first planned landing site. In the Krauchthal area, the instructor took controls and flew towards Unterbärgetal to show the trainee the second landing site. A reconnaissance circuit was flown at about 3500 ft AMSL, and the instructor demonstrated the approach, initiating a go-around at about 2500 ft AMSL. After climbing, the trainee took controls and performed three landings near Kirchberg, which were satisfactory.
At 19:42, the instructor contacted Bern-Belp to inform them of the intention to overnight the helicopter on the Längenberg, near Zimmerwald. The instructor again took controls to demonstrate an approach to the landing area in Unterbärgetal. The approach was initiated from about 4000 ft AMSL, descending over the Glööri ridge. At about 3000 ft AMSL, vehicle headlights were visible on the main road in the Unterbärgetal valley. The planned landing area was perceived as a black meadow. The highest obstacles in the approach area were at 644 m AMSL. The fixed landing light was switched on during the base leg but produced intense reflections due to high humidity, so it was turned off. The crew continued the approach. The trainee pilot began to have doubts about the impending approach due to unfamiliarity and marginal conditions. Shortly after, the loss of control occurred.
Cause and Contributing Factors
The accident is attributable to a loss of control during a night external landing, after which the helicopter collided with the terrain. The following factors contributed to the accident:
- Unsuitable choice of a night external landing site in relation to the prevailing conditions.
- Low night flying experience of the crew.
- Inappropriate approach procedures for a night external landing.
- Marginal technical equipment of the helicopter for night external landings.
- Minimal definition of training steps, prerequisites, and conditions for the activity as a flight instructor on night flights in the flight school's training manual.
Damage and Injuries
The helicopter was severely damaged. Both the flight instructor and the student pilot were uninjured.
Location and Time
Unterbärgetal, municipality of Burgdorf/BE, Switzerland. Date: 19 November 2009, time: approximately 19:55 local time (CET).