What happened
The aircraft touched down on the runway with the nose gear fully retracted rather than extended. Upon landing, the aircraft sustained damage consistent with a nose-gear-up touchdown.
The investigation
Post-accident examination of the airframe revealed that the nose gear assembly was stuck in the wheel well. The root cause was identified as an incorrect fastener installation on the nose gear centering spring assembly. Specifically, an AN4-12 bolt was found wedged within the gear door linkage mechanism.
Records indicated that an annual inspection had been performed 20 hours prior to the accident. During this maintenance event, bolts and bushings on the shimmy damper were replaced. However, the mechanic did not follow the Piper PA-34 Maintenance Manual specifications for the centering spring bolt. The manual requires an AN24-20A bolt installed with the head pointing down and secured by a MS20364-428C lock nut.
Instead, the bolt in question was installed with the head facing up and secured using a castle nut and cotter key. This orientation allowed the bolt to catch on the linkage when the gear attempted to retract. Piper Service Letter 852, issued in September 1978, addressed this specific issue and noted that improper installation could restrict nose gear operation in the up position. The service letter also announced a placard to remind mechanics of the correct method. This non-mandatory advisory had not been complied with on N4886T.
Findings
The investigation concluded that the failure was mechanical, stemming from a maintenance error. The use of an incorrect bolt type and orientation violated the manufacturer's instructions. Furthermore, the lack of compliance with Piper Service Letter 852 contributed to the oversight, as the letter specifically warned mechanics about this potential restriction in gear operation.
Safety message
Maintenance personnel must strictly adhere to manufacturer maintenance manuals and comply with relevant service letters, even when they are non-mandatory. Critical fasteners, particularly those involved in landing gear systems, require precise installation methods to ensure proper function and prevent mechanical interference.