What happened
On 11 November 2021, a student pilot was conducting solo training maneuvers at Wonderboom Aerodrome (FAWB) in Gauteng. The flight began with several successful touch-and-go landings performed with an instructor on board. After the instructor disembarked, the student pilot continued the session alone, completing one successful circuit.
During the second solo touch-and-go attempt, the pilot experienced a violent shimmy in the nose wheel while attempting to apply power for takeoff. This instability caused the pilot to lose directional control, leading the Piper PA28-180 Cherokee, registration ZS-CZU, to veer left off the runway. The aircraft exited the asphalt surface, causing the nose landing gear steering tube assembly to break. The propeller subsequently struck the ground, and the aircraft came to a stop approximately 15 meters from the runway edge. There were no injuries to the pilot, though the aircraft suffered substantial damage.
The investigation
Investigators examined the aircraft's maintenance history and flight records. While the aircraft's flight folio showed no outstanding defects regarding braking or steering, a similar incident involving the same aircraft had occurred on 14 September 2021. In that previous instance, a different student pilot also experienced nose wheel shimmying; however, that defect was not recorded in the aircraft's official defect report.
Post-accident inspections of ZS-CZU revealed significant mechanical damage, including a destroyed propeller, a bent engine cradle, and a broken oleo collar. The nose gear oleo outer steering tube was found to have been torn out of the engine cradle. The investigation also noted that the engine required a shock load inspection due to the force of the impact.
Findings
- The primary cause of the excursion was an unstable approach to landing, which resulted in the aircraft impacting the runway surface too heavily on the nose gear.
- The heavy impact caused the nose gear steering tube to fail, which likely triggered the violent shimmying felt by the pilot.
- A previous similar occurrence involving the same aircraft had not been properly documented in the maintenance logs, meaning no repairs were performed on the nose gear prior to this accident.
- The aircraft had flown approximately 96 hours since its last mandatory periodic inspection.