What happened
On March 15, 2003, an Antonov AN-2, registration LY-KAG, was performing a VFR training flight at Samedan Airport, Switzerland. After a period of flight over the St. Moritz and Bernina regions, the aircraft landed to exchange passengers. During the subsequent takeoff, the aircraft climbed to approximately 60 meters before the flaps were retracted. At an altitude of roughly 120 to 130 meters, the engine suddenly ceased operation.
The pilot attempted to restart the engine by repeatedly manipulating the power lever to engage the accelerator pump, but the failure persisted. The pilot initiated a 180-degree turn to return to the airfield. During this maneuver, the aircraft clipped the treetops of a group of trees located near the approach path. The aircraft subsequently touched down on a snow-covered surface approximately 350 meters past the start of runway 21, about 20 meters to the right of the centerline. Upon contact with the deep snow, the aircraft overturned and came to rest on its back. All three occupants—the pilot and two passengers—remained uninjured, though the aircraft sustained heavy damage.
The investigation
Investigators examined the engine and cockpit settings following the accident. The investigation revealed that the mixture control was set 20 mm before the lean limit, and the carburetor temperature control was set to a position providing 5°C of pre-heating. A technical inspection of the engine by experts ruled out any failures in the ignition system or mechanical defects in the moving parts, housing, or aggregates that could have caused the sudden stoppage.
Administrative discrepancies were also noted, including inconsistencies in flight documentation and the absence of the aircraft's Airplane Flight Manual (AFM) on board. Additionally, the investigation found that the pilot's name was not correctly recorded on the flight notification for the specific flight in question.
Findings
- The primary cause of the accident was an engine failure during the climbing phase, occurring at an altitude insufficient to safely execute a 180-degree turn.
- Carburetor icing may have contributed to the engine failure, as the pre-heating setting was insufficient to prevent ice formation in the venturi area under the prevailing conditions.
- An incorrect mixture regulation setting may have also contributed to the engine failure, potentially causing an overly rich mixture, a condition exacerbated by the high density altitude at the accident site.
- The pilot's attempt to restart the engine via the accelerator pump may have further enriched the mixture, contributing to the power loss.