Cessna 310I N6PK accident near Sunnyside, Washington

Probable cause

The failure of the side brace lock assembly of the right main landing gear due to overstress as a result of a hard landing.

NTSB analysis

The pilot reported that while on final approach he extended the gear, and a green light illuminated signifying that the gear was down. The landing was “firm” and, shortly after touchdown, the airplane’s right main landing gear slowly collapsed, causing the right wing to drop. The airplane veered to the right, exited the runway, and came to rest in a field about 100 ft from the runway centerline. During the accident sequence, the airplane sustained substantial damage to the right horizontal stabilizer and elevator.

Postaccident examination of the right main landing gear fracture surface revealed that the side brace lock assembly likely fractured due to excessive axial compression loads that resulted in a ductile overstress fracture. Additionally, the bent side brace lock assembly attachment bolt at the lower end of the lock link also indicated that the loads associated with the failure of the attachment pin exceeded the design axial loads for the side brace lock assembly and were consistent with overload of the side brace lock assembly. The bearings and pin that attached the side brace lock to the lower end of the bellcrank, which were not recovered, were likely fractured as a result of the loads.

The damage to the gear indicated that it likely failed as a result of the hard landing.

Text from the NTSB. Open the NTSB docket for WPR23LA226 for the full record.