MS21045L3 - Textron Aviation OEM Hexagon Self Locking Nut

MS21045L3 – Textron Aviation OEM 10-32 Self-Locking Nut (Nyloc)

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Overview

The MS21045L3 is a lightweight, hexagon, self-locking nut, supplied with the full certification and traceability of Textron Aviation as an Original Equipment Manufacturer (OEM) component. This fastener is manufactured to the rigorous Military Standard MS21045 and is the modern, lighter-weight successor to the legacy AN365 series fiber locknut. Its self-locking capability is derived from a captive nylon collar that provides a consistent prevailing torque, making it the industry standard for securing #10-32 UNF bolts (such as the AN3 series) in general airframe applications.

Constructed from cadmium-plated steel, this nut is designed for reliable performance in a vast number of structural and non-structural joints. Its most critical design parameter is its operational temperature limit of 250°F (121°C), dictated by its nylon locking element. As a genuine Textron Aviation part, it is the factory-specified hardware for countless connections on Cessna, Beechcraft, and Hawker aircraft.

Key Features

• Textron Aviation OEM Certified: Guarantees the component is a factory-approved, fully traceable part for the Textron Aviation family of aircraft.

• Nylon Insert Self-Locking: Features a captive nylon collar that grips the bolt threads, providing a consistent prevailing torque that offers excellent resistance to loosening from vibration.

• 250°F Temperature Rating: Certified for use in the vast majority of airframe, interior, and systems applications where temperatures will not exceed 250°F (121°C).

• Lightweight Hexagon Design: Manufactured to the MS21045 standard for a reduced height and weight profile compared to the legacy AN365 nut it replaces.

• Cadmium-Plated Steel: The nut body is fabricated from high-strength steel and plated with cadmium per QQ-P-416 for durability and superior corrosion resistance.

• Supersedes AN365 Nuts: The MS21045 is the modern, approved replacement for the older AN365 series nut in most applications.

Technical Specifications

• Part Number: MS21045L3

• Legacy Part Number: AN365-1032

• Component Type: Self-Locking Hex Nut (Nylon Insert)

• OEM Authority: Textron Aviation

• Governing Specification: MS21045 / NASM21045

• Material: Steel, Cadmium Plated

• Locking Element: Nylon Insert

• Thread Specification: #10-32 UNF-3B

• Maximum Operating Temperature: 250°F (121°C)

Aircraft Compatibility

As a Textron Aviation OEM part, this nut is the specified component for an immense number of applications across their entire product line.

• Primary Textron Aviation Platforms:

  • Cessna Piston Aircraft (172, 182, 206, etc.)

  • Beechcraft Piston Aircraft (Bonanza, Baron)

  • Cessna and Beechcraft Turboprops (Caravan, King Air)

  • Cessna Citation Business Jets

  • Hawker Business Jets

• General Aerospace Usage: The most common self-locking nut for #10-32 bolts in ambient temperature locations on virtually all certified aircraft.

Note: Verification of applicability is the responsibility of the installer. Always consult the current version of the aircraft's Illustrated Parts Catalog (IPC) and maintenance manual to confirm part number eligibility and the correct temperature rating for a specific location.

Applications

• The standard locking nut for AN3-XXA series bolts.

• Used for securing inspection panels, fairings, brackets, clamps, and systems hardware.

• For assembly of interior components, avionics trays, and secondary structures.

• Not for use in high-temperature areas such as firewall forward, engine compartments, or near bleed air ducts.

Why Choose this MS21045L3?

Using the correct temperature-rated hardware is a flight-critical safety requirement. The MS21045L3 is the standard, specified nut for the majority of airframe connections. Choosing the genuine Textron Aviation OEM part guarantees you are installing a fully certified component that meets both the MS standard and the airframe manufacturer's quality requirements. This eliminates the risk of using an incorrect or unapproved part, particularly the catastrophic error of installing a 250°F nylon-insert nut in a high-temperature application where an all-metal nut (like the MS21044N3) is required.

The self-locking function of the MS21045L3 is based on the principle of a friction-interference fit. The integrated nylon collar has a precisely controlled internal diameter that is smaller than the major diameter of the mating bolt's threads. As the bolt is threaded into the nut, it enters the nylon element, which must elastically deform to allow passage. This deformation creates a powerful, uniform 360-degree radial compressive force that grips the bolt's threads. This sustained radial load results in a high-friction state between the nylon and the steel bolt threads, creating a consistent "prevailing torque" that resists the loosening effects of vibration. In addition to providing the locking force, the resilient nylon collar also helps to damp high-frequency vibrations, which can contribute to improved fatigue life of the bolted joint.

Note: This is a flight-critical hardware component. The 250°F (121°C) temperature limitation must be strictly observed. Installation must be performed by a certified mechanic using a calibrated torque wrench. This nut is reusable for a limited number of cycles; however, if it can be run down to the threads by hand, it has lost its locking capability and must be replaced. Always consult the maintenance manual for specific reuse criteria.

Documentation

The military standard governing this part is publicly available through the Department of Defense ASSIST database.

• ASSIST Document Summary Page for MS21045: http://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=36977