What happened
On 14 November 1999, a Piper PA-28-151, registration G-BTIH, was conducting a private flight from Blackbushe Airport to Belle Vue Farm, Devon. After picking up two additional passengers, the pilot attempted a takeoff from a 625-metre grass runway at Belle Vue Farm. The surface was damp at the time of the departure.
The pilot initially perceived the takeoff as normal, with the aircraft becoming airborne approximately two-thirds of the way down the strip. While attempting to accelerate at an altitude of 20 to 25 feet to clear a hedge at the end of the runway, the aircraft dropped back onto the ground. Realizing a stop was impossible, the pilot applied heavy back pressure to clear the hedge, clipping a fence post in the process. The aircraft then struck an earth bank and a hedgeruna, causing the fuselage to break into two distinct sections. All four persons on board sustained serious injuries and required extraction from the wreckage.
The investigation
The investigation examined the aircraft's performance capabilities against the actual runway conditions. While the aircraft was likely near its maximum takeoff weight, the investigation noted that the manufacturer's performance data was based on dry, paved runways. Applying corrections for the damp grass surface increased the required takeoff distance to 50 feet to approximately 2,590 feet. Furthermore, applying a recommended safety factor of 1.33 would have increased the required distance to 3,450 feet, which exceeded the available runway length.
The investigators also looked into why the aircraft dropped during the acceleration phase. Two possibilities were considered: the aircraft may have climbed out of ground effect, causing a sudden increase in induced drag, or the aircraft may have encountered a localized downdraft or tailwind caused by the nearby hangar.
Findings
- The takeoff distance required to clear a 50-foot obstacle, when accounting for the damp grass surface and safety margins, exceeded the available runway length.
- The aircraft dropped back to the ground during the acceleration phase, potentially due to exiting ground effect or encountering unfavorable wind conditions.
- The occupants were wearing only lap restraints, as shoulder harnesses were not utilized in the rear seats.