What happened
On 20 October 2005, a Bolkow Bo 209 Monsun, registration G-AZRA, was performing a private flight approaching a private airstrip near Miserden, Gloucester. The pilot, intending to land on runway 13, noted a wind report from nearby Kemble indicating a wind of 230 degrees at 11 knots. Based on this information, the pilot determined that landing on the longer, downslope runway (direction 22) would result in a tailwind of approximately 11 knots, whereas the shorter runway (direction 13) would involve a crosswind component.
The aircraft touched down approximately 80 metres beyond the threshold of the 390-metre runway. Upon attempting to decelerate, the pilot applied firm braking; however, the wheels locked, causing the aircraft to slide across the wet grass with minimal deceleration. With only 100 metres of runway remaining, the pilot applied full left rudder to avoid a stone wall at the end of the strip. This maneuver caused the aircraft to deviate left and slide toward the right, eventually colliding with a post and wire fence. The impact caused a dented spinner, a cracked fiberglass cowling, and a dented wing leading edge. There were no injuries to the pilot.
The investigation
The investigation examined the runway conditions and the performance requirements for the aircraft. The airstrip featured two landing areas: a 450-metre downslope runway and a 390-metre level runway. At the time of the accident, the grass on runway 13 was wet and approximately 3 to 4 inches in height.
Technical data from the aircraft's owner's manual was reviewed, which specifies a landing distance of approximately 440 metres from a 50-foot approach, including a 240-metre ground roll, assuming dry hard surfaces. The investigation also referenced Safety-Sense Leaflet 7c, which provides multipliers for non-standard conditions. For wet grass, the required landing distance should be increased by 35%, and for very short/wet grass, by as much as 60%.