What happened
On August 6, 2018, a Piper PA-42 Cheyenne III, registration OB-1714, operated by Servicios Aéreos Tarapoto E.I.R.L., was performing a passenger flight from Pucallpa International Airport to Contamana Aerodrome. After landing at 12:29 local time, the aircraft traveled approximately 712 meters down the runway.
As the crew attempted a 180-degree turn on the left main gear axis to head toward the parking apron, the aircraft experienced a sudden vibration followed by an abrupt tilt to the left. This movement caused the left propeller to strike the runway, creating a loud impact and friction noise. The crew immediately shut down both engines and cut the fuel valves. The passengers and crew were evacuated through the rear door without injury.
The investigation
The investigation conducted by the CIAA focused on the structural failure of the landing gear. Examination of the wreckage revealed that the left main gear had collapsed due to a fracture and partial detachment of the shock strut housing assembly.
Laboratory analysis of the components determined that the fracture in the housing assembly originated at the bottom of the component, specifically below the attachment lugs of the side brace. This fatigue crack was accelerated by high-stress tension and vibrations experienced during landing. The investigation also noted that the aircraft frequently performs forced 180-degree turns at this location, using the left main gear as a pivot point while engine power is applied, which places significant concentrated stress on the gear structure. Additionally, minor deformations in the runway surface were noted, which can contribute to landing gear fatigue.
Findings
- The primary cause was the fracture and partial detachment of the left main gear shock strut housing assembly during the landing roll and subsequent turn.
- Service Bulletin (SB) No. 969 was found to be insufficient, as it did not define the specific inspection area on the upper part of the housing and failed to require inspections of the lower area where the fatigue actually initiated.
- The necessity of performing forced 180-degree turns to clear the runway subjects the landing gear to high-intensity loads.
- The presence of runway surface irregularities contributes to increased vibrations and structural fatigue.