N167U

On March 10, 2024, about 2330 Pacific daylight time, a Beechcraft 60, N167U, was substantially damaged when it was involved in an accident near Chino, California. The pilot and five passengers were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

According to the pilot, he extended the landing gear about five miles from his destination airport and noticed that the left main landing gear green annunciator light was OFF. He cycled the landing gear, but observed the same result. The pilot also changed the left landing gear annunciator light bulb during the accident flight, but the annunciator light remained OFF. He then overflew the airport while he attempted to manually extend the landing gear with the hand crank, but was still unable to extend the left main landing gear. He then landed with the left main landing gear retracted, which resulted in substantial damage to the left wing.

A postaccident gear swing revealed that the landing gear system retracted and extended normally with exception of the left main landing gear, which had a broken main gear retract rod assembly. The examination also found that the left main landing gear retract rod had punctured the gearbox case. In addition, the uplock cable was severed at the wheel well. The emergency gear extension functioned normally when tested. The broken cable was isolated at both ends and retained for metallurgical examination as was the left landing gear retract rod assembly and the pressure boot.

A metallurgical examination of the retained parts revealed that the left main landing gear retract rod exhibited fracture features consistent with ductile overstress. The overall deformation and fracture pattern was consistent with buckling from compression loading. The bushing for the pressure boot was located outboard of the outboard fracture in the retract rod and did not move under hand forces. The retract rod displayed a yellowish-green coating, consistent with primer, at the inboard end. The outboard end had white paint covering the yellowish-green coating. A portion of the retract rod on either side of the pressure boot bushing had a green coating, also consistent with primer. Rub marks were observed on the green primer, which exposed bare metal, and sliding contact marks were observed inboard of the bushing. The remaining green primer was substantially bubbled and flaked away from oxidation of the underlying surface.

The uplock cable fracture surfaces exhibited contact damage from another object at the fracture location, and the wires were thinned consistent with ductile overstress fracture. No evidence of a progressive mechanism such as fatigue was observed.

According to the manufacturer, the rod assembly is attached to the gear motor and serves as the linkage for the gear retraction process. The maintenance manual states,

“The landing gear motor is controlled by the gear extension switch located on the left subpanel. The larger upper arms and the lower arm of the actuator, in conjunction with rod assemblies and linkage, control extension and retraction of the main and nose landing gear. Rod assemblies attached to the smaller upper actuator arms operate the inboard main landing gear doors.”

The manufacturer’s 100 hour/annual inspection guidance does not include any specific criteria to inspect the main landing gear linkages; however, Appendix D to 14 Code of Federal Regulations Part 43 does require that “each person performing an annual or 100-hour inspection shall inspect…linkages, trusses, and members for undue or excessive wear fatigue and distortion.” The regulation also requires an inspection of the retraction and locking mechanism for improper operation.

According to the airplane’s maintenance logbooks, the most recent annual inspection, completed seven months before the accident,

“Inspected this aircraft FAR 43 appendix D checklist for Annual inspection…inspected and greased all wheel bearings, serviced brake’s reservoir, tested landing gear and systems with airplane on jacks, no defects found.”

A review of the airplane logbooks from 2001 to present did not reveal any adjustments or modifications to the retraction linkage. The landing gear motor was replaced in 2006; however, the maintenance excerpt did not include any adjustments to the retract assembly.