What happened
On the evening of December 14, 2017, a Cessna C510 Mustang was performing an instrument approach to Friedrichhaven Airport under night conditions. The aircraft, operated by an Austrian company, was executing an ILS RWY 24 approach. During the procedure, while maneuvering to intercept the localizer, the aircraft experienced a sudden loss of altitude.
Air traffic controllers observed the aircraft fly slightly above the localizer at 4,000 ft AMSL and begin a rapid descent. The crew failed to respond to repeated communications from radar services. Shortly thereafter, the aircraft struck trees in a forested area west of Waldburg and impacted a second wooded area approximately 1,000 meters away at high speed. The impact resulted in three fatalities and the destruction of the aircraft.
The investigation
The BFU investigation focused on the sequence of events leading to the loss of control. Investigators examined the meteorological conditions, which included snowfall, moderate turbulence, and icing. The aircraft was equipped with a Garmin G-1000 avionics suite and anti-ice/de-ice systems, including pneumatic boots for the wings and tail.
Because the aircraft was not equipped with a flight data recorder or a cockpit voice recorder, the investigators could not access specific cockpit audio or flight parameters. The investigation also reviewed the pilot's credentials, noting the pilot flying had extensive experience in the type, while the copilot was in a supervision phase. The investigation also looked into the organizational structure of the flight operations, noting that the aircraft was marketed and planned by a separate entity from the aircraft owner.
Findings
- The primary cause of the accident was a sudden loss of control in flight while maneuvering in clouds during a night approach.
- The aircraft was operating in challenging weather conditions, including snowfall and likely moderate icing, which may have caused aerodynamic impairments.
- The crew was flying in darkness and through precipitation, which likely eliminated any external visual references or ground lighting as navigational aids.
- The investigation could not definitively rule out a pilot error due to spatial disorientation or a mechanical phenomenon such as an autopilot disconnection (decoupling) caused by high aerodynamic loads.
- The presence of moderate turbulence and the high approach speed likely increased the crew's workload during the critical phase of flight.