The pilot of the Just Aircraft Highlander had completed 11 takeoffs and landings to a full stop at the airport in Brasstown, North Carolina.
During a subsequent takeoff, he saw that the left main landing gear wheel was wobbling. He returned to the turf airstrip and landed at the slowest possible speed, however the left main landing gear wheel separated, and the airplane came to rest inverted on the runway.
Examination of the wreckage by an FAA inspector revealed substantial damage to the right wing and vertical stabilizer. The pilot sustained minor injuries in the crash.
Three lock nuts that secured the wheel were missing and not recovered. Additionally, there was no damage or stripping on the threads of the respective studs.
The pilot could not see the three nuts during preflight inspection as they were concealed by a hubcap.
The mechanic who completed a condition inspection about two months before the accident stated that the three missing nuts were light locknuts, made of an alloy. The mechanic removed the hubcap during the inspection as he had to lubricate the wheel bearing. At that time, he could see that the three nuts were secure however, since they were already set to a torque, he did not attempt to tighten them.
Probable Cause: Failure of the left main landing gear wheel lock nuts, which resulted in a wheel separation and nose over during landing.
To download the final report. Click here. This will trigger a PDF download to your device.
This August 2021 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
How did the mechanic know they were “set to a torque”????
it is common to use a paint marking pen, to mark a line on the side of the nut to the part, in this case the wheel half. If the line does not match between the nut and the part, the nut has rotated, usually to a loosened condition, indicating a loss of torque on the nut.
I don’t know of any AN stop nut that is aluminum. The Cleveland parts list shows a cad plated AN365 steel stop nut to hold the wheel halves together.
I’d guess that being an experimental aircraft, owner/pilots can use whatever they want.
This choice was not a good idea.!
If the owner is also the manufacture and has repair/maint authority, then you are right on both accounts. And this shows how some people do not understand why certain bolts, nuts and washers are used for exhaust, landing gear, valve covers, water pumps, etc, etc. Safety wire? What’s that and why do you do those fancy threading? And then there is the electrical system and loading…. sigh.