What happened
On November 28, 2013, a Jodel D113, registration F-PNUH, was performing circuit training at the Clermont-Ferrand Auvergne aerodrome. The flight was a dual instruction session involving an instructor and a student pilot. The weather conditions were favorable, with calm winds, visibility exceeding 10 km, and a temperature of 2 °C.
During the third takeoff-and-landing cycle, the instructor noted that the landings were being executed as smooth "three-point" landings. However, during the landing phase, a scraping noise was heard coming from the rear of the aircraft. The aircraft initially veered to the right, and although the pilot attempted to correct the yaw, the aircraft drifted to the left and exited the runway. The impact of the excursion caused the main landing gear to break, resulting in heavy damage to the aircraft.
The investigation
Technical examinations focused on the tailwheel assembly. Investigators determined that the tailwheel attachment bolt had failed due to a fatigue cracking process. While the exact origin and initiation point of the crack could not be determined because the complete bolted assembly was no longer intact, the failure was clearly linked to fatigue.
Maintenance records showed that the aircraft was maintained by the club's approved workshop under a maintenance program established in 2003. This program required checking the condition and free rotation of the tailwheel and performing lubrication during every 50-hour inspection, but it did not mandate the replacement of the bolt. The most recent 50-hour inspection had been completed in August 2013, and the aircraft had flown 23.5 hours since that service. No anomalies regarding the tailwheel had been noted during that inspection.
Findings
- The runway excursion was caused by the fatigue failure of the tailwheel attachment bolt.
- The maintenance program for the aircraft did not include a scheduled replacement interval for the tailwheel bolt, only inspections and lubrication.
- Following the accident, the operator updated its maintenance program to include the replacement of the tailwheel attachment bolt every 500 flight hours.