What happened
On the evening of June 3, 1988, a Piper PA-38 Tomahawk HB-PIF, operated by the Ausserschwyz Flying Club (ASFG), was involved in an incident at Môtiers Aerodrome in the canton of Neuchâtel. The aircraft had arrived earlier that day from Wangen-Lachen with the pilot and his wife on board. Upon landing, the pilot noted that the grass runway was wet and heavy due to recent light rain.
Around 19:00 local time, the pilot prepared for the return flight to Wangen-Lachen. He inspected approximately one-third of the 508-meter grass runway and determined it was suitable for departure. After warming up the engine and completing pre-flight checks, he applied full power with the flaps in the takeoff position. The pilot reported that the aircraft struggled to gain altitude during the roll. As speed increased, the stall warning horn began to sound intermittently whenever control inputs were made.
The aircraft finally lifted off near the end of the runway, where a slight upward slope acted as a ramp. It crossed low over the road bordering the aerodrome to the west and struck the ground in the middle of an adjacent football field. The pilot cut the engine immediately upon impact. The aircraft bounced once before coming to rest about thirty meters later in a nearby fish farm pond after hitting a fence separating the field from the water. All occupants were uninjured, though the aircraft was severely damaged.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) examined the operational, meteorological, and technical factors surrounding the event. The pilot held a valid private pilot license with all experience gained on the Piper PA-38 type. He was in good health, and the aircraft possessed valid airworthiness certificates. Maintenance records were compliant, and the weight and center of gravity were within limits. Visual inspection of the wreckage revealed no pre-existing technical defects, and the pilot confirmed the engine functioned normally throughout the takeoff roll.
Meteorological data from Geneva indicated variable winds of 2–5 knots, visibility of 20 km, and temperatures around 18–19°C. Rainfall in the area prior to the accident was minimal (less than 1 mm), but the grass runway height was approximately 5 cm, contributing to heavy ground conditions. The aerodrome is a private field requiring Prior Permission Required (PPR) status due to its marshy location and lack of permanent staff.
The pilot stated he attempted to call for PPR authorization and runway condition updates on both the previous day and the morning of the accident but received no answer. Consequently, he proceeded without explicit confirmation of current conditions.
Findings
The investigation concluded that the accident resulted from a failed takeoff due to insufficient runway length for the prevailing conditions. Performance calculations indicated that while the theoretical ground roll for a Piper PA-38 at maximum weight was approximately 330–465 meters on dry pavement, the wet grass surface required an additional margin of at least 40%. This raised the necessary takeoff distance to between 460 and 650 meters. With only 508 meters available, the runway was critically short.
Contributing factors included:
- Wet and heavy runway conditions which significantly increased ground roll.
- Poor estimation of aircraft performance by the pilot regarding the specific aerodrome conditions.
- Inadequate information in the flight manual, which lacked precise data for takeoff distances on grass runways.
- Variable wind which may have had an unfavorable effect on acceleration.
The SUST noted that while the pilot’s decision to cut power after clearing the immediate obstacles was prudent, it was too late to prevent the collision. The incident highlighted the critical importance of the PPR system; had the pilot received current information regarding the runway's poor condition, he likely would have aborted the flight or adjusted his weight.
Safety action
The report emphasized that the PPR requirement exists to allow aerodrome managers to inform pilots of temporary usage conditions. The failure to reach the aerodrome management by phone left the pilot without crucial safety data. The SUST recommended that pilots, when in doubt about runway performance due to surface conditions, should conduct a test takeoff with reduced weight (without passengers) to verify safety margins before committing to a full-weight departure.
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