What happened
On August 16, 1986, at approximately 18:36 local time, a Piper PA-22-108 "Colt" aircraft registered HB-ORR was involved in an accident near the Dittingen aerodrome in Switzerland. The pilot had arrived earlier that day for an airshow and, after the event concluded, intended to conduct practice approaches and go-arounds before flying back to Basel with a passenger.
The pilot took off from runway 11 and maneuvered into a final approach for runway 29. During the second attempt, he found himself too high and executed a slip to lose altitude, flaring only 1 to 3 meters above the ground just before crossing a road over the runway. Immediately after leveling out, the pilot applied full power to initiate a go-around.
However, due to the low altitude and the aircraft's limited climb performance, it failed to gain sufficient height. The aircraft climbed at a steep angle but collided with the tops of trees located approximately 550 meters northwest of the runway threshold. The impact caused the plane to crash into the forest below. Both occupants survived without injury, though the aircraft was destroyed and minor damage occurred to the surrounding woods.
The investigation
The Swiss Transportation Safety Investigation Board (STSB) examined the flight dynamics, aircraft condition, and operational context. The investigation confirmed that the Piper PA-22-108 was airworthy, with no mechanical failures detected in the engine, fuel system, or ignition. Weight and balance were within limits.
The aerodrome at Dittingen has a grass runway with a significant slope; runway 29 starts significantly lower than runway 11. Operational rules prohibited takeoffs from runway 29 due to obstacles, though go-arounds were theoretically possible if initiated at a safe altitude. The pilot was not authorized for local flights but had been permitted to attend the airshow.
Weather conditions were favorable with good visibility and light winds. Performance calculations based on the aircraft's manual indicated that even under optimal conditions, the Piper Colt could not have cleared the 60-meter elevation gain required to reach the tree line from the point where the go-around was initiated.
Findings
The accident was caused by a combination of operational errors and physical limitations:
- Late Go-around Initiation: The pilot initiated the go-around too late, having descended to an unsafe altitude (1-3 meters) during the slip.
- Inappropriate Flight Technique: Executing a slip to lose altitude in a light aircraft with low power margins is risky. The pilot chose to turn right toward rising terrain rather than left, where obstacles and parked aircraft were present.
- Performance Limitations: The Piper PA-22-108 lacks the climb gradient necessary to clear the tree line from such a low altitude at that weight and density altitude. Even with maximum power, the aircraft could not have reached the required height in time.
- Regulatory Non-compliance: The pilot was operating outside the aerodrome's restricted local flight rules, having only permission for the airshow visit.
Safety action
The report highlights the critical importance of adhering to go-around decision heights and understanding the performance limitations of light aircraft. It underscores that tactical decisions, such as using slips to lose height in low-power planes, must account for the available climb performance after power application. No specific new safety recommendations were issued beyond the standard findings regarding operational discipline and aerodrome usage rules.