What happened
On 1 May 1999, a CAP 131, registration F-GKKI, was taxiing toward a parking position at Elstree Aerodrome following a landing on Runway 26. Due to the tailwheel configuration of the aircraft, the pilot was maneuvering in a zigzag pattern along the taxiway. During this process, the pilot observed a pile of sand and bricks situated at the edge of the taxiway to the right. After executing a left turn to maintain distance from these materials, the aircraft experienced a sudden stop and pitched forward at an angle of approximately 45 degrees, resulting in the propeller making contact with the ground. The incident occurred when the left main landing gear descended into a hole located at the side of the taxiway.
The investigation
Investigators determined that the hole had been created by the airfield operator to inspect the flow of a drain. Although the site had been marked with small yellow cones—similar to those used to denote temporary no-parking zones on roads—the excavation had not yet been finalized into a permanent inspection chamber. The investigation established that while the cones were visible under standard conditions, the pilot's ability to see them was compromised. Specifically, the limited forward visibility inherent to operating a tailwheel aircraft, combined with the pilot's focus on navigating around other nearby hazards, contributed to the failure to detect the marked area.