What happened
On 9 September 2021, a Piper PA-24-260 Comanche, registration ZS-EFF, departed Rand Aerodrome (FAGM) for a local flight. The aircraft was occupied by a pilot and an aircraft maintenance engineer (AME) who was monitoring the instrumentation following a period of inactivity. During the flight, the crew observed significant fluctuations in battery voltage, with the system discharging and a red discharge light illuminating.
In response to the electrical instability, the crew decided to return to Rand Aerodrome. During the final approach, the pilot extended the flaps and landing gear. As a precaution, the AME utilized the manual emergency gear extension lever. Despite these efforts, the green down-and-lock indicator failed to illuminate. Upon touchdown on Runway 11, the aircraft traveled approximately 60 meters before the landing gear collapsed. The propeller struck the runway, and the aircraft slid on its belly before exiting the runway onto the grass. There were 0 fatalities and 0 injuries.
The investigation
SACAA AIID examined the aircraft and its maintenance history. Post-accident inspections of the landing gear assembly, motor, and transmission revealed no external damage or mechanical defects in the hardware itself. However, a subsequent investigation into the electrical system identified that a screw securing a cable ring lug to the master switch had become loose, causing the cable controlling the charging system to detach. This disconnection prevented the alternator from maintaining proper voltage levels.
Furthermore, the investigation reviewed the aircraft's 100-hour mandatory periodic inspection (MPI) completed earlier that year. It was determined that the master switch area had not been inspected for cable security, which was a required task under the manufacturer's maintenance checklist.
Findings
- The landing gear failed to lock into position prior to touchdown, likely because the manual extension was performed while the electric motor remained operative, preventing the mechanism from fully engaging.
- An electrical failure occurred because a disconnected cable at the master switch prevented the charging system from maintaining stable battery and buss voltage.
- The 100-hour MPI was not performed in accordance with manufacturer instructions, as the maintenance personnel failed to inspect the condition and security of the electrical cables in the master switch area.