What happened
On 14 October 1999, an Auster J4/100, registration G-AIJT, was performing a standard 3-point landing on the grass runway at Whiterashes Airfield, Aberdeen. During the landing sequence, the leaf spring of the tailwheel failed, causing the tailwheel assembly to detach from the aircraft. Despite the separation, the fractured portion of the spring functioned as a tailskid, preventing the rear fuselage from contacting the ground and allowing the pilot to maintain effective control of the aircraft. The departing components moved upward into the lower edge of the rudder, resulting in localized deformation to the rudder structure.
There were no injuries to the two occupants on board during the occurrence.
The investigation
The investigation focused on the mechanical failure of the tailwheel leaf spring. The pilot reported that the fracture occurred near the lower end of the spring, close to where the castering tailwheel unit attaches to the airframe. Physical examination of the fracture surface revealed two lobes of clean metal, while the remainder of the surface showed signs of oxidation.
Detailed inspection and photographic evidence indicated that the failure occurred through the third and final section of the three-leaf spring. Specifically, the break was located where the second leaf ends and the third leaf extends toward the tailwheel attachment point.