MS21073L4 - Textron Aviation OEM Nutplate

MS21073L4 – Textron Aviation OEM Nutplate

Available now on the Airparts.aero Marketplace.

Overview

The MS21073L4 is a military-standard, two-lug, low-height, self-locking, floating anchor nut, commonly known as a nutplate. This versatile fastener is an essential component in airframe construction and repair, designed to provide a strong, permanent, and serviceable threaded receptacle in a location where access to the backside is limited or impossible. The "floating" design allows the threaded nut element to move slightly within the cage, compensating for minor misalignment between the screw hole and the nutplate itself. This feature drastically simplifies panel installation and prevents thread cross-threading.

Key Features

• Floating Nut Element: The threaded nut is captured within a cage but is allowed to "float" radially. This compensates for slight hole misalignments during panel assembly, making screw installation significantly easier and faster.
• Self-Locking Design: The "L" designation indicates a self-locking feature, typically a deformed thread or a nylon insert. This provides prevailing torque, which resists the loosening of the mating screw under vibration, eliminating the need for safety wire or lock washers in many applications.
• Low-Height Profile: Engineered with a low-profile design, making it ideal for use in space-constrained areas or where a minimal protrusion on the backside of a panel is required.
• Two-Lug Mounting: Features two mounting lugs with rivet holes, allowing it to be securely riveted to the airframe structure, creating a strong and permanent threaded attachment point.
• MS Certified Standard: Manufactured in strict accordance with the MS21073 specification, this nutplate guarantees the material, dimensions, locking torque, and performance characteristics required for certified aviation use.

Technical Specifications

• Standard: MS21073 (Nut, Self-Locking, Plate, Two Lug, Low Height, Steel)
• Full Part Number: MS21073L4
• Component Type: Floating Anchor Nut (Nutplate)
• Material: Carbon Steel
• Finish: Cadmium Plated
• Locking Feature (L): Yes, prevailing torque self-locking
• Thread Specification: 4-40 UNC-3B
  • Nominal Diameter: #4 (0.112 inches)
  • Threads Per Inch: 40 (Coarse Thread)
• Rivet Hole Spacing: 0.688 inches (center-to-center)
• Recommended Rivet: MS20426AD3 or AN426AD3 (3/32" countersunk rivet)

Aircraft Compatibility

The MS21073L4 is a fundamental airframe component used universally across all types of aircraft, including those manufactured by Textron Aviation (Cessna, Beechcraft). It is specified anywhere a strong, serviceable, and misalignment-tolerant #4-40 threaded receptacle is needed.

• Common Applications:
  • Inspection Panels & Access Doors: Providing the threaded points for securing frequently removed panels.
  • Avionics & Instrument Mounting: Used to mount instrument panels, avionics racks, and individual components.
  • Fairings & Cowlings: Attaching non-structural or secondary structural fairings and engine cowlings.
  • Systems Installation: Securing brackets, clamps, and other system hardware to the airframe structure.

Applications

This nutplate is the engineered solution for creating durable, reliable, and easy-to-use threaded attachments:

• Blind Assemblies: The primary method for creating a threaded hole where there is no access to install a traditional nut.
• Rapid Assembly & Maintenance: The floating feature significantly speeds up the process of installing multi-screw panels by forgiving minor hole alignment errors.
• High-Vibration Environments: The self-locking feature ensures that the mating screw remains secure without additional locking components, even in areas of high airframe vibration.

Why Choose MS21073L4?

A properly installed MS21073L4 nutplate provides a superior fastening solution compared to a simple tapped thread in thin sheet metal. It distributes the load over a wider area via its riveted footprint and provides a reusable, self-locking thread that won't wear out or strip easily. Using a genuine MS-standard nutplate ensures that the fastener has the correct material strength, locking properties, and dimensional tolerances required for a professional and airworthy repair or modification. For building and maintaining aircraft structures, it is an indispensable piece of hardware.

Order Your MS21073L4 Nutplates Now

Simplify your panel installations and ensure a secure, serviceable connection with certified MS-standard hardware. Visit Airparts.aero to order your MS21073L4 floating nutplates today.

The MS21073L4 floating anchor nut is an elegant engineering solution to a common assembly problem. The nut element is securely crimped within the basket or cage, which is then riveted to the structure. This design allows the nut to move within a defined radial range, creating a "forgiveness factor." When a screw is inserted through a panel into the floating nutplate, it can effectively "pull" the nut into perfect alignment with the hole, preventing cross-threading and binding. This is especially valuable when installing large panels with dozens of screws, as it is nearly impossible to drill all holes with perfect alignment. The self-locking feature is achieved by subtly deforming the upper threads of the nut into a slightly elliptical shape, which creates a friction grip on the mating screw.

Applicable Textron Aircraft

• Beechjet 400/400A
• Citation CJ1 or CJ1+
• Citation CJ2 or CJ2+
• Citation CJ3 or CJ3+
• Citation CJ4
• Citation III, VI or VII
• Citation Longitude
• Citation M2
• Citation Mustang
• Citation Sovereign or Sovereign+
• Citation V, Ultra, Encore or Encore+
• Citation X
• Citation X+
• Citation XLS, XLS+ or XLS Gen2
• King Air 350 or 350C FM-1 to FM-35
• King Air B200, B200T, B200C or B200CT
• King Air B200GT or B200CGT
• King Air C90GTi Series
• Skyhawk
• Stationair

List not comprehensive, may be applicable on other models.

Note: Installation requires drilling two rivet holes and one center screw hole to the correct dimensions and spacing. The nutplate is then secured using two solid aircraft rivets (typically MS20426AD3). Proper rivet installation is critical to the strength of the nutplate assembly.