The **AN320-4 castle nut** is a critical piece of standard aircraft hardware, identified by its AN (Army-Navy) specification, which signifies it as a non-self-locking, castellated nut. This particular part number, AN320-4, directly supersedes older specifications while being frequently cross-referenced with its modern MS (Military Standard) equivalent, the MS21045-4.
Aircraft Compatibility
This AN320-4 nut is specifically applicable to the Beechcraft T-34 Mentor series of aircraft, including but not limited to:
- Beechcraft T-34A Mentor
- Beechcraft T-34B Mentor
- Beechcraft T-34C Turbo Mentor (select applications where AN320-4 hardware is specified in the IPC)
It is widely used throughout various systems of the T-34 Mentor, including flight control linkages, landing gear components, engine mount attachments, and other critical structural assemblies where a positive locking mechanism is required. Owners, A&P mechanics, and FBO maintenance shops working on the T-34 Mentor will frequently encounter the AN320-4 in parts manuals and during routine maintenance.
Overview
The AN320-4 is a standard aircraft castle nut, designed for secure fastening applications within aircraft systems. Its primary role is to provide a robust mechanical joint when mated with a corresponding bolt, typically in a 1/4-28 UNF configuration. Unlike self-locking nuts, the AN320-4 relies on its castellated design to accommodate a cotter pin, which passes through a hole in the bolt and the nut's castellations, preventing the nut from rotating loose under vibration or load. This positive locking feature is paramount in ensuring the integrity of critical airframe components and systems.
- Stock: Out of Stock - On Backorder
- Manufacturer Part #: AN320-4
- Part#: AN320-4
Aircraft Fitment Finder
Returns & refund summary
- 30-day return window — with prior return authorization, unopened in original packaging.
- Restocking fee: 20% on unopened items, 30% on open-box items.
- Refund processing fee: 5.51% applies to all refunds (returns, cancellations, core-fee refunds) regardless of reason.
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- Non-returnable categories: installed/used parts, special-order or rebuilt items, programmed items (incl. ELTs), batteries, AOG-priority orders, international orders.
Full terms: Return Policy.
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All parts sold by American Aviation Parts are genuine factory products sourced through authorized distribution channels. Our authorization status varies by brand — for some brands we are a direct authorized dealer; for others we are an independent reseller through authorized distribution. Either way, the part you receive is the same factory product, with standard documentation available on request.
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Need traceability paperwork?
If your installation requires FAA Form 8130-3, manufacturer Certificate of Conformance, or other traceability documentation, please call 1-877-722-8727 or email [email protected] before placing the order so we can confirm what is available for this part.
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