What happened
On March 17, 1990, a Cessna F-172 G aircraft registered as HB-CND was conducting private parachute drop operations at the Luzern-Beromünster airfield. The pilot had already completed one successful sortie earlier that day. At approximately 17:20 local time, he initiated a second takeoff with three skydivers aboard, utilizing tandem equipment.
The aircraft accelerated along runway 34 but failed to gain adequate speed on the wet, soft grass surface. After traveling roughly 300 meters, the plane briefly lifted off before settling back onto the ground. The pilot decided to abort the takeoff. As the aircraft rolled into the northern, unusable section of the runway where the terrain was significantly softer, the nose wheel encountered high resistance. This caused the aircraft to slow rapidly and overturn almost immediately.
The investigation
The Eidgenössische Flugunfall-Untersuchungskommission (EFUK) examined the flight data, weather conditions, and aircraft status. The pilot held a valid commercial license with over 1,800 total flight hours. The aircraft was airworthy, with its last 100-hour inspection completed in early March 1990.
Weather reports indicated high pressure, visibility of 3–5 km, and a light variable wind around 3 knots. The critical factor was the runway surface: while dry grass requires standard calculations, wet and soft turf demands additional distance not explicitly noted in the flight manual for this specific condition. The aircraft's takeoff weight was approximately 1,040 kg, very close to its maximum limit of 1,043 kg.
Findings
The investigation determined that the primary cause was the insufficient acceleration on a wet, soft grass runway combined with a high takeoff weight. Contributing factors included:
- Underestimation of the required ground roll distance for grass runways in wet conditions.
- Execution of a "rolling takeoff" by accelerating immediately upon entering the runway without stopping first to build momentum.
- Potential tailwind component affecting performance.
- The nose wheel digging into the soft earth of the unusable runway section due to reduced aerodynamic lift from the elevator as speed decreased, leading to blockage and overturning.
Safety action
The pilot's decision to abort after the second touchdown was deemed appropriate. However, the incident highlights the risks of operating heavy aircraft on short, soft grass strips without accounting for moisture-induced drag increases.