What happened
On the evening of 5 September 2021, a Cessna 172M, registration ZS-SSB, departed Wonderboom Aerodrome (FAWB) for a private sightseeing flight. The aircraft was carrying a pilot and three passengers, intending to view the city lights of Pretoria and Johannesburg.
During the flight, the aircraft descended to an altitude of approximately 50 to 100 feet above the ground while following a roadway. As the pilot activated the landing light to alert oncoming traffic, the propeller made contact with an overhead powerline crossing the M35 road. The impact caused the aircraft to shudder and produced a bright flash of light and a loud bang. Following the strike, the pilot performed a check of the flight controls and engine performance before deciding to return to the aerodrome.
The investigation
An investigation into the incident revealed that while the pilot initially believed the vibration was caused by an air pocket, a subsequent inspection of the aircraft uncovered physical evidence of a wire strike. Specifically, the propeller blade showed a distinct nick, and wire markings were found on both the exhaust and the lower left main gear strut.
Investigators also reviewed the aircraft's weight and balance documentation. The actual takeoff mass was found to be 2,427 lbs, which exceeded the maximum takeoff weight of 2,300 lbs by approximately 5.5%. Additionally, the pilot failed to record the damage in the aircraft's flight folio following the occurrence.
Findings
- The primary cause of the incident was the propeller striking a powerline while the aircraft was operating at an extremely low altitude.
- The pilot operated the aircraft below the minimum required height for non-congested areas, violating safety regulations.
- The aircraft was operated in an overweight condition, exceeding its maximum takeoff weight.
- The pilot's low-level maneuvering over the roadway endangered the safety of the occupants and property on the ground.