Accident Overview
On 8 March 2020 at approximately 1330Z, a Cessna 180 aircraft, registration ZS-TIO, departed Kitty Hawk Aerodrome (FAKT) on a private flight to Baragwanath Aerodrome (FASY) in Gauteng province. The pilot was accompanied by one passenger. During approach for Runway 13 at FASY, the aircraft's speed was about 80 mph (70 knots) with first notch flaps selected (approximately 10 degrees). The aircraft landed hard on the runway, followed by a severe vibration just before the tail wheel contacted the surface. The aircraft then veered right off the centerline onto grass, the nose contacted the ground, and it came to rest on the right edge of the runway with the left wing low and the tail lifted. Both occupants reported no injuries.
Aircraft Damage
The aircraft sustained substantial damage to the left main landing gear, left wing, propeller, fuselage, and lower engine cowling. Post-accident examination of the left main gear assembly revealed that the bolts and nuts securing the axle to the gear strut had failed. Specifically, two rear bolts were sheared and slightly bent, the third bottom nut snapped, and the fourth front top bolt was missing. The fracture surfaces were consistent with overstress failure.
Maintenance and Inspection Background
The aircraft had a valid certificate of airworthiness issued on 20 February 2019, expiring 28 February 2021. Its last 100-hour Mandatory Periodic Inspection (MPI) was conducted on 15 November 2019 at 7697.45 airframe hours. At the time of the accident, the aircraft had accumulated 7722 total airframe hours, with 24.55 hours since the last MPI. The Cessna Aircraft Service Manual requires inspection of the main landing gear spring axle attach bolt holes initially at 4000 hours or 10 years, then repeated every 1000 hours or 3 years. The inspection includes checking for rust, corrosion pits, and cracks. The maintenance organisation that performed the last inspection only visually inspected the components without non-destructive testing (NDT).
Flight Conditions and Pilot Information
The flight was conducted under visual flight rules (VFR) during daytime in visual meteorological conditions (VMC). No flight plan was filed. The pilot held a Private Pilot Licence issued 4 June 2015, valid until 30 June 2020, with a Class 2 medical certificate valid until 30 April 2020. The pilot had logged 636.5 total flight hours, including 23.4 hours on the Cessna 180 type.
Probable Cause
The aircraft landed hard on Runway 13 at FASY, resulting in the failure of the left-side main landing gear axle attachment bolts and nuts, and the subsequent separation of the main wheel and axle assembly from the left main landing gear.