NTSB Pins September CJ4 Accident on Maintenance

Improper installation of a right main landing gear trunnion pin caused a Cessna Citation CJ4’s landing gear to collapse during rollout in September, the NTSB said in its final report. Neither pilot was injured in the accident, but the collapse punctured the right wing and caused substantial structural damage.

Investigators determined that the aft main landing gear trunnion pin for the right landing gear had not been installed far enough forward. According to the report, the right gear’s aft trunnion pin “was not installed far enough  [forward] to allow the retaining roll pin to engage and retain the trunnion pin.” Maintenance at a manufacturer’s service center, including removal and reinstallation of the trunnion pin, had been completed only 2.9 flight hours before the accident.

During the Sept. 25, 2025 repositioning flight, the flight crew felt “a bump/thud in the back of the airplane” at about 10,000 feet msl, which they initially assumed was “something falling into the aisle from the lavatory.” Immediately afterward, the landing gear’s unsafe light illuminated. The crew performed emergency and abnormal procedures, including resetting the landing gear circuit breaker. When the gear did not retract, they extended the landing gear and received three green indications.

They continued to Baton Rouge Metropolitan Airport (KBTR) with the gear down and landed the airplane. During the landing rollout, after applying moderate braking, the crew “felt the right main landing gear collapse, which then punctured the right wing and resulted in substantial damage to [the] right wing.”

Textron’s maintenance manual requires technicians to verify correct pin placement by ensuring “the aft end of the trunnion pin is at least 2.0 inches (50.8 mm) forward of the aft spar fitting.” Because the pin was not positioned far enough forward, it was not properly secured.

The NTSB referenced a similar 2018 event investigated by Spain’s CIAIAC, which resulted in Textron issuing a mandatory Service Letter SL525C-32-12 requiring inspection of aft main landing gear trunnion pins for proper installation.

The airplane had undergone an annual inspection three days earlier, and no discrepancies were noted other than the maintenance involving the trunnion pin. A contributing factor to the accident, the NTSB identified, was “the failure of maintenance personnel to follow the aircraft manufacturer’s maintenance procedures.”