What happened
On 7 October 2001, a Cessna 177, registration ZS-NDE, was conducting a private local flight in the Upington district. During the approach to Upington aerodrome (FAUP), the pilot attempted to extend the landing gear but received no positive indication that the gear was locked down. Air Traffic Control also notified the pilot that the gear appeared to be in an unsafe position.
In an attempt to rectify the situation, the pilot activated the emergency gear extension system. However, this maneuver failed because the aircraft had lost all hydraulic pressure. The pilot proceeded to land the aircraft with the gear in an unsafe configuration. Upon touchdown, the main landing gear collapsed. The aircraft skidded on its nose wheel and tail for roughly 300 meters before coming to a stop left of runway 35. There were no fatalities or injuries, though the aircraft sustained damage to the left-hand wing-tip and the tail.
The investigation
Investigators examined the aircraft's systems to determine why the gear failed to extend and why the emergency system was ineffective. Post-accident inspections identified hydraulic fluid run-marks near the right-hand main gear wheel well. Further technical examination revealed that the left-hand rudder cable had been rubbing against a hydraulic pressure line. This continuous contact had eventually chafed through the line, creating a leak that depleted the hydraulic fluid.
Findings
- The primary cause of the incident was the left-hand rudder cable chafing through a hydraulic pressure line.
- The resulting hydraulic fluid loss caused a total failure of the hydraulic system.
- The loss of pressure rendered the emergency gear extension system inoperable.
- The aircraft was 71.3 hours past its last maintenance inspection (MPI).