What happened
On 21 April 2006, a DR 107 One Design, registration G-IIID, was involved in an incident at Tatenhill, Staffordshire. Following the occurrence, the pilot conducted an inspection of the aircraft and discovered that a pin used to secure the tailwheel assembly to the spring was missing.
The investigation
The AAIB examined the aircraft's tailwheel assembly to determine how the component had been lost. The assembly is designed with a round, cross-section spring. A vertical hole is drilled through both the tailwheel unit and this spring, into which a pin is driven to create an interference fit. The investigation noted that the ends of this pin are flush with the tailwheel unit, meaning there is no mechanical locking mechanism to prevent the pin from migrating out of position, other than the friction of the interference fit itself.
While the pilot attempted to locate the missing pin, the search was unsuccessful, and the specific reason for its loss could not be determined. A post-incident photograph provided by the pilot showed the tailwheel held in place by a temporary pin, and an inspection of the assembly revealed no deformation around the hole that would indicate why the original pin had departed.
Findings
- The tailwheel assembly was secured to the spring via a pin using an interference fit.
- The design of the original unit lacked a secondary locking mechanism, such as a split pin, to ensure the pin remained seated.
- The loss of the securing pin could not be established due to the failure to recover the component.