What happened
On February 8, 2009, a Mooney M20R, registered as N401AC, crashed into the forested terrain of the Jura mountains near Rotlachen, Switzerland. The flight originated from Freiburg im Breisgau, Germany, with the intention of reaching Sion, Switzerland, for a recreational trip.
While flying under Visual Flight Rules (VFR), the pilot diverted from the original flight plan to fly directly toward the Grenchen VOR. As the aircraft approached the Jura ridges, the pilot encountered increasing snowfall and a milky sky, which significantly reduced visual references. Despite the deteriorating conditions, the pilot continued the flight at a constant altitude of 4000 ft QNH. The aircraft eventually struck trees on the slope of the Matzendörfer Stierenberg at a shallow angle. The impact was severe enough that the engine separated from the airframe. The pilot sustained serious injuries, specifically an elbow fracture, while the passenger remained uninjured.
The investigation
Investigators examined radar plots, engine monitoring data, radio communications, and the aircraft wreckage. The investigation established that the aircraft was in a high-speed cruise of approximately 170 knots at the time of impact. The investigation also reviewed the pilot's flight planning, which had utilized various meteorological tools, though the pilot's assessment of the weather was found to be overly optimistic.
Data from the engine monitoring system confirmed that radar contact was lost at approximately the same time as the accident. The investigation also noted that the emergency locator transmitter (ELT) failed to activate upon impact, and the pilot was unable to activate it manually due to his injuries. The search and rescue operation was eventually aided by the pilot's ability to contact a relative via mobile phone, which helped direct rescue helicopters to the site.
Findings
- The primary cause of the accident was the continued flight in the absence of sufficient visual references.
- The pilot maintained a high-precision manual flight at 4000 ft QNH, which consumed significant cognitive resources, leaving little mental capacity for navigation or transitioning to Instrument Flight Rules (IFR).
- There was an overly optimistic assessment of the evolving weather conditions.
- The pilot's situational awareness regarding the local terrain and the specific responsibilities of air traffic control was insufficient.
- The pilot was experiencing significant personal and professional stress at the time of the accident.
- The pilot mistakenly believed that air traffic control would ensure terrain clearance, whereas the controller's role in this context did not include such responsibility.