2002 Robin DR400-180R accident at Morgetegrat (HB-EUW)

Overview and Aircraft Details On 15 June 2002, a Robin DR400-180R with registration HB-EUW was destroyed in a terrain collision at Morgetegrat in the Gantrisch area, municipality of Rüschegg, Canton of Bern, Switzerland. The aircraft was owned and operated by Segelfluggruppe Bern. It was a single-engine, four-seat low-wing aircraft of wooden construction, serial number 855, built in 1973, and powered by a Lycoming O-360-A3A engine. The aircraft was certified for VFR day operations and glider towing. ## Flight and Accident Sequence The pilot, a Swiss citizen born in 1946, held a restricted private pilot licence (RPPL) and had 290 total flight hours, including 83 on the accident type. He had been scheduled to conduct towing flights that day. At 14:32 local time, he took off to tow a single-seat glider into the Gantrisch area. The climb and tow proceeded normally. At 2,300 m AMSL, the glider pilot requested a course correction, which was made but not acknowledged. The glider then released. After release, the tow aircraft briefly continued climbing, then entered a steeply banked turn and pitched down. Witnesses described the aircraft as performing erratic manoeuvres, with high speed and engine power. The aircraft struck the mountainside of Morgetegrat at a near right angle, with high speed and bank, and the engine operating at high power. The pilot was fatally injured. ## Investigation Findings The wreckage was severely damaged, with a main debris field of approximately 8 m by 6 m. Rock particles were found welded to the propeller, and the crankshaft was broken, indicating high engine power at impact. The tachometer indicated 3,050 RPM at impact, exceeding the maximum allowable 2,700 RPM. The tow winch was torn from the fuselage, and the tow cable remained fully extended, indicating the pilot had not reeled it in after release. Comparison flights conducted on 22 August 2002 with the same aircraft type showed that when the control stick was released after a simulated release, the aircraft followed a flight path comparable to the accident flight. Without pilot input, the throttle would need to be reduced within 10 to 80 seconds to avoid exceeding the maximum engine RPM. ## Medical and Technical Assessment The pilot's autopsy revealed severe narrowing of the coronary arteries, which could lead to arrhythmia or sudden cardiac death under stress or oxygen deprivation. However, the forensic examination could not confirm that a medical condition caused incapacitation at the time of the accident. No alcohol, drugs, or medication were detected in the pilot's blood. The investigation found no evidence of pre-existing technical defects contributing to the accident. The possibility that an object blocked the control stick was considered but ruled out based on the flight path and comparison tests. ## Probable Cause The accident was caused by a collision with terrain because the tow aircraft was very probably no longer being controlled after the glider released.