What happened
On 25 January 2002, a Piper PA34-200T Seneca, registration ZK-SFC, was conducting an air ambulance mission from Hamilton to Gisborne. The flight carried a pilot, a non-flying pilot, and a patient. While approaching Gisborne Aerodrome, the pilot attempted to extend the undercarriage but found the nose gear remained in the retracted position, indicated by an "undercarriage unsafe" light.
After several attempts to resolve the issue using both standard and emergency extension procedures, the pilot decided to divert to Hastings Aerodrome, where technical support was available. To minimize the risk of the aircraft tipping over, the pilot elected to perform a full wheels-up landing. The aircraft slid along the runway, resulting in minor damage to the lower skin, antennas, and propellers, but all three occupants escaped without injury.
The investigation
Investigators examined the nose undercarriage assembly and discovered that the steering ball on the nose oleo strut had exited its intended track. The ball had traveled along the outside of the steering channel and become lodged, preventing the gear from locking down.
Testing revealed that the steering and track assembly channels were misaligned. While the aircraft had been maintained according to schedule, the misalignment was difficult to detect during standard 100-hour inspections because a vertical view of the channels typically requires removing the aircraft's lower panel. The investigation considered that the misalignment could have been caused by exceeding towing limits or performing tight turns on rough ground.
Findings
- The misalignment of the steering and track assembly channels was the primary factor that allowed the steering ball to exit the channel and jam the nose gear.
- This misalignment may have developed over time due to improper towing or heavy rudder inputs while taxiing on uneven surfaces.
- The pilot's decision to land with the gear retracted was appropriate and prevented more serious injury or a potential aircraft overturn.
Safety action
Following the investigation, the Commission recommended that operators and maintenance personnel for the Piper PA34-200T Seneca adhere strictly to aircraft towing limitations and perform thorough, regular inspections of the nose undercarriage assembly to ensure correct alignment.