What happened
On 26 July 2007, a Cessna 177A, registration ZS-FJY, was conducting a private flight departing from and returning to Bethlehem Aerodrome. While on final approach for runway 29, the pilot experienced a sudden and total loss of elevator response.
To manage the emergency, the pilot diverted the approach to runway 31, which featured a grass surface. Without elevator control, the pilot attempted to manage the aircraft's pitch by modulating engine power. During the landing sequence, the aircraft bounced three times before coming to a halt. The impact caused the nose landing gear to collapse, resulting in damage to the propeller and both the nose and main landing gear. There were no injuries to the pilot or the two passengers on board.
The investigation
Investigators examined the aircraft's mechanical systems and maintenance history. The inspection focused on the flight control mechanisms and the aircraft's recent maintenance records. The investigation looked into the condition of the control cables and the routing of the battery vent system. Additionally, the team reviewed previous audits conducted by the airworthiness department and the recent inspections performed by the Approved Maintenance Organisation (AMO).
Findings
- The primary cause of the flight control failure was the corrosion of the right-hand elevator control cable.
- This corrosion was triggered by the leakage of battery acid onto the cable where it passes through a fairlead in the rear fuselage.
- The battery's overboard vent-pipe was found to be directing fluids into the fuselage rather than venting them outside the aircraft.
- Although the control cables had been inspected by the AMO as part of recent maintenance, the corrosion had not been detected.
- Weather conditions at the time of the accident were clear with excellent visibility.
Safety action
Following the discovery that the recent inspection failed to identify the degrading cable, it was recommended that the AMO undergo an audit regarding its maintenance practices, specifically concerning the scope of work and inspection effectiveness.