What happened
On January 25, 2019, a Piper L-4 (registration HB-ODZ) was conducting training maneuvers at Birrfeld Airport (LSZF). The flight, operated for training purposes under Visual Flight Rules (VFR), was intended to help a pilot gain tailwheel endorsement. The crew, consisting of a flight instructor and a student pilot, performed a three-point landing on the grass runway 26 without initial incident.
During the subsequent braking phase on the runway, the instructor noticed an abnormal noise originating from the rear of the fuselage, accompanied by a significant loss of lateral maneuverability. Once the aircraft had come to a complete stop, the crew inspected the airframe and discovered that the tailwheel had detached from the fuselage.
The investigation
Investigators examined the mechanical assembly of the tailwheel, which is attached to the rear of the fuselage via three leaf springs that function as shock absorbers. This assembly is further connected to the rudder through a system of chains and springs. The investigation reviewed the aircraft's maintenance history, noting that the tailwheel had been last inspected during a 100-hour inspection. The aircraft, a 1944 model, had accumulated over 4,220 flight hours and 5,555 total landings.
Findings
The separation of the tailwheel was caused by the failure of the leaf springs used to mount the component to the fuselage. The investigation concluded that the high number of landings performed by the aircraft was a significant contributing factor to the structural failure of these components.