Landing gear collapse caused by foreign object debris at Port Alfred

Casualties unknown • Runway 25 Port Alfred Aerodrome, Eastern Cape, ZA

A Piper Seneca II experienced a left main gear collapse during an emergency landing at Port Alfred Aerodrome due to a dislodged rivet.

What happened

On 1 May 2021, a Piper Seneca II PA 3-4, registration ZS-PBV, was performing circuit training at Port Alfred Aerodrome in the Eastern Cape. The flight, which was being conducted under Part 141 training regulations, included an instructor and a student pilot. After completing five successful circuits, the crew noticed that the green indicator light for the left-side main landing gear failed to illuminate during the base leg of the sixth circuit.

Upon noticing the indication error, the instructor initiated a go-around and requested the tower to visually inspect the gear. Air traffic control confirmed that the left main gear had not fully extended to its locked position. The instructor subsequently declared an emergency landing on Runway 25. As a precautionary measure during the final approach, the pilot shut down and feathered the left engine. During the landing roll, the left main gear collapsed, causing the aircraft to veer left and come to a stop off the runway. There were 0 fatalities and 0 injuries among the two occupants, though the aircraft sustained minor damage.

The investigation

Following the incident, an aircraft maintenance organization inspected the left main landing gear assembly. The inspection identified a piece of foreign object debris (FOD) consisting of a CherryMAX rivet. This rivet had become lodged in the grease between the machined faces of the truss and the link assembly. This obstruction prevented the gear down lock from properly engaging. It is believed that the rivet had detached from the nacelle and migrated into the landing gear mechanism.

Findings

  • The primary cause of the gear collapse was the presence of foreign object debris (FOD) within the landing gear mechanism.
  • A dislodged rivet prevented the left main gear down lock from engaging correctly.
  • The rivet likely originated from the engine nacelle area.

Safety action

Following the removal of the debris, the dislodged rivet was replaced, and the landing gear underwent serviceability testing in accordance with the Piper Maintenance Manual. Maintenance organizations are encouraged to maintain strict housekeeping standards during and after maintenance procedures to mitigate the risk of introducing debris into critical flight components.

Probable cause

A dislodged rivet acting as foreign object debris (FOD) became trapped in the grease of the left main gear assembly, preventing the down lock mechanism from engaging and leading to a gear collapse upon landing.

Frequently asked questions

What happened in the 2021-05-01 Piper Seneca II PA 34 accident near Runway 25 Port Alfred Aerodrome, Eastern Cape, ZA?

A Piper Seneca II experienced a left main gear collapse during an emergency landing at Port Alfred Aerodrome due to a dislodged rivet.

What aircraft was involved and where did it happen?

The accident on 2021-05-01 involved a Piper Seneca II PA 34, registration ZS-PBV, at Runway 25 Port Alfred Aerodrome, Eastern Cape, ZA.

What was the probable cause of the accident?

A dislodged rivet acting as foreign object debris (FOD) became trapped in the grease of the left main gear assembly, preventing the down lock mechanism from engaging and leading to a gear collapse upon landing.

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