Textron Aviation Inc 525C N361MB accident near Baton Rouge, Louisiana

Probable cause

The improper installation of the trunnion pin, which resulted in a failure of the right main landing gear. Contributing to the accident was the failure of maintenance personnel to follow the aircraft manufacturer’s maintenance procedures.

NTSB analysis

About 10,000 ft mean sea level during a repositioning flight, the flight crew felt a bump/thud in the back of the airplane, which they thought was caused by something falling into the aisle from the lavatory. The flight crew observed that the landing gear unsafe light was illuminated. The flight crew stated that they followed emergency/abnormal airplane checklist items and reset the landing circuit breaker, which did not retract the landing gear. Then, the crew lowered the landing gear, which resulted in three green landing gear position lights. They continued the flight to the destination with the landing gear extended where they landed the airplane. During landing rollout and after applying moderate braking, they felt the right main landing gear collapse, which then punctured the right wing and resulted in substantial damage to right wing.

Postaccident examination revealed the aft main landing gear trunnion pin for the right main landing gear was not properly installed during the recent maintenance as the aft trunnion pin was not installed far enough to allow the retaining roll pin to engage and retain the trunnion pin. The pilot reported and maintenance records showed that maintenance performed by the aircraft manufacturer’s service center, which included the reinstallation of the main landing gear trunnion pin, occurred 2.9 hours before the accident.

According to the manufacturer’s maintenance manual installation procedures, maintenance personnel are required to make sure the aft end of the trunnion pin is at least 2.0 inches (50.8 mm) forward of the aft spar fitting to verify proper installation.

The Civil Aviation Accident and Incident Investigation Commission (CIAIAC) of Spain investigated a similar accident that occurred on May 4, 2018, as documented in CIAIAC Report A-012/2018. As a result of the investigation, the aircraft manufacturer published a mandatory service letter (SL525C-32-12) to do an inspection of the aft main landing trunnion pins for proper installation.

Text from the NTSB. Open the NTSB docket for CEN25LA402 for the full record.