Accident Overview
On March 10, 2024, at about 2330 Pacific daylight time, a Beechcraft 60 (registration N167U) was substantially damaged during a landing accident near Chino, California. The airplane was operating as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot and five passengers were not injured.
Pilot Actions
According to the pilot, he extended the landing gear about five miles from the destination airport and observed that the left main landing gear green annunciator light was off. He cycled the landing gear but the light remained off. During the flight, he changed the left landing gear annunciator light bulb, but the annunciator light still did not illuminate. The pilot then overflew the airport while attempting to manually extend the landing gear using the hand crank, but was unable to extend the left main landing gear. He subsequently landed with the left main landing gear retracted, resulting in substantial damage to the left wing.
Postaccident Examination
A postaccident gear swing revealed that the landing gear system retracted and extended normally except for 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. Additionally, 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, along with the left landing gear retract rod assembly and pressure boot.
Metallurgical Findings
Metallurgical examination of the retained parts showed 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.
Maintenance History
According to the airplane’s maintenance logbooks, the most recent annual inspection was completed seven months before the accident. The inspection included compliance with FAR 43 appendix D checklist, inspection and greasing of wheel bearings, servicing of brake reservoir, and testing of landing gear and systems with the airplane on jacks, reporting no defects. A review of logbooks from 2001 to the accident date did not reveal any adjustments or modifications to the retraction linkage. The landing gear motor was replaced in 2006, but the maintenance excerpt did not include any adjustments to the retract assembly. The manufacturer’s 100-hour/annual inspection guidance does not specify criteria for inspecting main landing gear linkages, though Appendix D to 14 CFR Part 43 requires inspection of linkages, trusses, and members for undue or excessive wear fatigue and distortion, as well as inspection of the retraction and locking mechanism for improper operation.