What happened
On March 14, 1964, a Beech 65-80, registration HB-GBE, was conducting a visual flight rules (VFR) flight from Liège, Belgium, to Linz, Austria. While cruising at approximately 8,000 feet near Büchel, the aircraft entered an uncontrolled flight state. During this period of instability, the horizontal stabilizer suffered a structural failure. The aircraft subsequently entered a flat spin, descending through a low cloud layer before impacting the roof of a residential and commercial building in Kehrig, Germany. The accident resulted in three fatalities among the passengers and one serious injury to the pilot. The aircraft was destroyed, and moderate damage was sustained by the building.
The investigation
The investigation, conducted by the German Luftfahrt-Bundesamt with technical assistance from the aircraft manufacturer and the Technical University of Braunschweig, examined the structural integrity of the wreckage. Metallurgical testing of the horizontal stabilizer spar fragments was performed to identify potential material defects or manufacturing errors. The investigation also reviewed the pilot's flight experience, the aircraft's maintenance history, and the prevailing meteorological conditions along the flight path.
Findings
- The investigation determined that the failure of the horizontal stabilizer was a force-induced fracture caused by loads exceeding the structural limits of the component.
- There were no evidence of material defects, manufacturing flaws, or pre-existing fatigue cracks in the stabilizer spars.
- The pilot was flying under VFR but encountered weather conditions that did not meet minimum visibility or ceiling requirements for visual flight.
- The pilot did not hold the necessary instrument rating to legally continue the flight under instrument flight rules (IFR).
- The transition from stable cruise to an uncontrolled flight state likely occurred as the pilot attempted to navigate through instrument meteorological conditions (IMC), leading to aerodynamic loads that overstressed the tail unit.
- While the autopilot was engaged at the onset of the instability, it could only be considered a contributing factor if a malfunction occurred, as the pilot was responsible for monitoring its operation.