What happened
On March 26, 2002, a Kamov KA-32A12 helicopter, registration HB-XKE, departed from Bern-Belp airport for a type rating flight. The crew, which included a pilot, a flight instructor, and an observer from the Federal Office of Civil Aviation, was performing maneuvers in the area of Schwarzenburg, Laupen, and Grosses Moos.
During the return leg of the flight, the flight instructor began performing manipulations for a technical engine test. During this process, both engines shut down almost simultaneously. The pilot immediately initiated an autorotation procedure, which was successfully executed. However, upon landing in a field near Neuenegg, the helicopter tipped onto its right side, resulting in heavy damage to the aircraft. There were no injuries among the occupants.
The investigation
The investigation focused on the simultaneous failure of both powerplants and the cockpit environment. Investigators examined the cockpit layout, specifically the placement and ergonomics of the engine control switches. The investigation also reviewed the aircraft's maintenance history, noting that a 100-hour inspection had been completed just one day prior to the accident. Technical analysis of the engine governor systems and the possibility of accidental activation of test sequences during flight were also scrutinized.
Findings
- The primary cause of the accident was the simultaneous shutdown of both engines caused by the accidental activation of the wrong switch.
- The pilot mistakenly operated the free turbine overspeed test switch instead of the engine electronic governor (EEG) switch for the right engine.
- Both switches were located in the same column, slightly offset from one another, and lacked distinct markings or safety guards.
- The flight was a combination of a type rating flight and a technical maintenance flight, which increased the complexity of the cockpit tasks.
- There were no technical safety nets in place to prevent the activation of the overspeed test sequence while in flight.
Safety action
Following the investigation, safety recommendations were issued to the Federal Office of Civil Aviation (BAZL) and EASA. The recommendations called for a review of the function, risk analysis, and ergonomics of the overspeed and gas generator test switches, specifically regarding their color-coding and physical security. In response, the operator implemented interim modifications to mark and secure the relevant switches.