Incident Overview
On October 7, 2019, at approximately 0830 eastern daylight time, a Honda HA-420, registration H166HJ, operating as a Title 14 Code of Federal Regulations Part 91 executive/corporate flight by Pro by Air, experienced a landing gear malfunction during approach to Charleston, South Carolina. The airline transport pilot and four passengers were not injured. The aircraft sustained substantial damage to the fuselage and pressure vessel.
Sequence of Events
The pilot reported that during the landing approach, he selected the landing gear handle to the DOWN position. The main landing gear indicators showed green, but the nose landing gear indicator displayed yellow, followed by an unsafe audible alarm. The pilot aborted the approach and requested a tower flyby. During the flyby, tower personnel reported that the “doors did not look right.” The pilot attempted to cycle the gear twice without success. Subsequently, he declared an emergency and performed the emergency gear extension checklist. After completion, the main landing gear indicated green and locked, while the nose landing gear indicator showed red. The pilot also received a warning message regarding the gear doors. He conducted a normal approach and landing; the airplane slid to a stop on the runway. The pilot and passengers deplaned on the runway and awaited emergency services.
Examination and Findings
An FAA inspector examined the aircraft and found substantial damage to the fuselage, with the pressure vessel damaged as a result of the gear-up landing. The airplane was recovered to a hangar for further examination by the FAA and representatives of the Honda Aircraft Company. During the examination, a towbar adapter lug was discovered inside the nose wheel axle assembly. The lug, bearing part number P228, was removed and its dimensions recorded. Comparison with the original equipment manufacturer (OEM) chart from Brackett Aircraft Company Inc. revealed that the adapter lug was neither a Honda Aircraft part nor the OEM-specified lug for this aircraft.
A witness mark was found on the top surface of the nose landing gear door and at the bottom of the nose landing gear bay. Without the adapter lug inserted, the clearance between the nose landing gear door and the nose landing gear axle measured approximately 11/16 inch. When the lug was reinserted into the nose wheel gear axle assembly with about 1.5 inches extending, a considerable negative clearance existed between the fuselage and the lug.
A representative of the fixed base operator (FBO) that performed ground handling on the airplane stated that pin adapters are used when connecting the nose wheel to the towbar because the wheel hubs are too small for the universal towbar hookup. The presence of the non-standard lug in the axle assembly is noted as a contributing factor to the gear malfunction.