Accident Overview
The accident occurred on 23 February 2015 at approximately 15:00 local time, 1.2 km northeast of the Yverdon-les-Bains aerodrome in Switzerland. The aircraft, a Robin DR400-140B registered as HB-KDD, was destroyed upon impact. Both occupants, an instructor and a pilot, sustained fatal injuries. No fire broke out.
Flight History
The flight was a Visual Flight Rules (VFR) training session. Before the accident flight, the instructor and pilot had planned to use a Piper Cub L-4 but switched to the Robin DR400-140B because the grass runway for the Cub was not serviceable. The aircraft departed runway 23 around 14:15. Witnesses observed the aircraft perform two or three touch-and-go landings on runway 23 before stopping. It then took off from runway 05 and conducted one more touch-and-go. During initial climb, near a riding school, several witnesses noted a significant reduction in engine power. The aircraft entered a glide and began a left turn, followed by a sharp right turn. While flying south at an estimated height of 30–40 m, the aircraft stopped the turn, flew straight briefly, then abruptly rolled to the left, nosedived vertically, and struck the ground shortly before 15:00. Total flight duration was approximately 48 minutes.
Meteorological Conditions
A low-pressure system west of Scotland influenced a frontal band from France across central Europe. In the morning, freezing rain mixed with ice crystals fell over the plateau. By early afternoon, a warm front lay just west of the Jura. At the accident site, dry weather prevailed between Lake Bienne and Lake Geneva. The western edge of a rain zone moved along the Broye valley. A moderate wind from the south with gusts up to 15 kt was present. Clouds were 5/8–7/8 at about 1000 ft AGL, with several more compact layers above. Visibility exceeded 10 km. Wind at the surface was 190° / 3–6 kt, temperature and dew point both 3 °C, QNH 1004 hPa. Moderate turbulence and the risk of carburetor icing were noted. A mechanic observed ice accumulation on propeller leading edges and wings earlier in the day. Witnesses reported light rain and light wind at the time of the accident.
Aircraft Information
The Robin DR400-140B is a single-engine, four-seat, low-wing aircraft with a fixed tricycle landing gear, constructed of wood and fabric. It was built in 1992 by Avions Pierre Robin. The engine was a Lycoming O-320-D2A, four-cylinder, producing 160 HP at 2700 RPM, driving a two-blade fixed-pitch metal propeller. Airframe total time was 8340:53 hours since new; engine time since new was 5733:23 hours, with 1275:53 hours since overhaul. The estimated takeoff mass was 834 kg, with the center of gravity within limits.
Cause and Contributing Factors
The investigation determined that the accident was due to the aircraft colliding with terrain as a result of a loss of control at low altitude, following a phase of reduced engine power shortly after takeoff. A contributing factor was the takeoff with a tailwind, which reduced takeoff and climb performance. Additionally, the flight occurred in weather conditions that may have been conducive to carburetor or airframe icing.