What happened
On February 25, 1968, at approximately 16:45 CET, a Beech 23 Musketeer, registration HB-EWE, was performing a sightseeing flight from Triengen airfield with three passengers. During the flight, the pilot executed a low-level pass over the airfield in the direction of runway 33. While flying at an altitude of approximately 10 to 15 meters above the ground and a speed of 120 mph, the aircraft experienced a sudden drop in altitude. This maneuver caused the right wingtip to strike a metal flagpole belonging to a nearby service station. The impact, occurring roughly 5 meters above the ground, resulted in significant damage to the leading edge of the right wing, which was dented and split. Despite the structural damage, the aircraft remained controllable, and the pilot successfully completed a circuit to land the aircraft safely on the runway without further incident.
The investigation
Investigators examined the aircraft, the pilot's credentials, and the environmental conditions at the time of the accident. The pilot held a valid license and had 252 total flight hours, including 91 hours on the HB-EWE. The aircraft was found to be in an airworthy condition and properly registered. The investigation noted that the airfield featured a 420-meter paved runway, with a service station located approximately 15 meters from the runway edge. At the time of the event, a high fog layer was present at 500–600 meters, and winds were blowing from the north-northeast (Bise).
Regarding the obstacle, the investigation identified a metal pipe, approximately 3 cm in diameter, used as a flagpole for the service station. The pole extended about 5.5 meters into the airspace but lacked any contrasting paint or visibility markings, as no company pennant was hoisted at the time. The impact was strong enough to bend the pipe and dislodge it from its relatively weak mounting.
Findings
- The pilot's reported speed of 120 mph was too high for the aircraft to have entered a stall-induced sink; however, turbulence from the prevailing winds may have contributed to the sudden loss of altitude.
- The flagpole was difficult to detect because it lacked a flag and had no high-visibility markings.
- The flight path chosen for the low-level pass placed the aircraft directly in the axis of the obstacle, which was deemed tactically disadvantageous.
- The pilot conducted a low-level pass at an altitude that was insufficient for the prevailing circumstances.