What happened
On October 5, 2020, a Rockwell International 112 was performing a flight from Pucón Aerodrome to Villarrica Aerodrome (SCVI) for the purpose of refueling. The flight, operated by a single pilot and accompanied by one passenger, proceeded without incident until the landing phase on runway 15.
As the aircraft touched down smoothly within the first third of the runway, the pilot noted that the landing gear unsecured light illuminated while the nose wheel was still airborne. During the landing roll, the left main landing gear retracted, causing the gear to collapse. The pilot attempted to maintain directional control, but the aircraft veered off the right side of the runway, coming to a stop approximately 524 meters from the threshold. There were no injuries to the pilot or the passenger, though the aircraft sustained structural damage to the left wing, flap, and fuselage.
The investigation
DGAC Chile investigators examined the aircraft and the site, noting that the aircraft came to rest off the runway with the left main gear collapsed. Physical inspections of the aircraft revealed that the left side step was deformed from contact with the runway surface and the left flap area had sustained damage.
While standard functional tests of the landing gear and braking systems performed at the airfield showed no external defects, a specialized inspection of the hydraulic components was conducted at a maintenance facility. This investigation focused on the left main landing gear actuator cylinder to determine why the gear failed to remain locked in the down position.
Findings
- The primary cause of the gear collapse was an internal leak within the left main landing gear actuator cylinder.
- This internal leakage was caused by the installation of an O-ring with incorrect dimensions (specifically regarding internal diameter and thickness) compared to the manufacturer's specifications.
- The internal fluid bypass created enough pressure to disengage the down-position locking pin, allowing the gear leg to retract during the landing impact.
- The aircraft's maintenance records showed that the annual inspection and 100-hour inspections were up to date, and previous inspections of the landing gear had not detected the internal component discrepancy.