What happened
On February 23, 2015, a Robin DR400-140B, registration HB-KDD, was conducting a training flight near the Yverdon-les-Bains airfield in Switzerland. After performing several takeoff and landing maneuvers on different runways, the aircraft departed from runway 05. During the initial climb, witnesses observed a significant drop in engine RPM. The aircraft entered a flight pattern involving a left turn followed by a tight right turn. While flying at an altitude of approximately 30 to 40 meters, the aircraft leveled off briefly before suddenly banking sharply to the left and plunging vertically into the ground. The impact resulted in two fatalities and the destruction of the aircraft.
The investigation
Investigators examined the aircraft's engine and accessories, finding no technical failures that could have caused the engine power drop. The investigation focused on the operational context, noting that engine power reduction exercises are commonly practiced at this airfield. The investigation also reviewed the meteorological conditions, noting high humidity and temperatures (3 °C) that were conducive to carburetor or airframe icing. While the carburetor heat control was found in the off position, investigators could not definitively confirm if the power reduction was a voluntary part of a training exercise or an unintended consequence of icing. /## Findings
- The primary cause of the accident was a loss of control at low altitude following a phase of reduced engine power shortly after takeoff.
- The takeoff was performed with a tailwind, which degraded the aircraft's takeoff and climb performance.
- Flying in weather conditions that favored carburetor or airframe icing may have contributed to the event.
- The aircraft was operating in a manner consistent with standard engine failure practice exercises, but the decision to initiate such maneuvers following a takeoff with a tailwind was inadequate.