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EB9025-14 – Bell Helicopter OEM Self-Locking Floating Plate Nut
Available now on the Airparts.aero Marketplace.
Overview
The Bell Helicopter EB9025-14 is a flight-critical, OEM, self-locking, two-lug floating plate nut. This is a highly engineered piece of hardware, cross-referencing to the military standard MS21060L4, and is specified by Bell for use in structurally demanding, high-temperature applications where fastener misalignment is a factor. Unlike a fixed plate nut, the EB9025-14 features a nut basket that can "float" radially within its cage. This design is critical as it accommodates manufacturing tolerances and slight misalignments between a panel and the airframe structure, which prevents cross-threading and the inducement of stress during fastener installation.
This nut is fabricated from A-286, a high-temperature, corrosion-resistant steel (CRES) superalloy, and is rated for service up to 450°F, making it ideal for use on firewalls and in the engine and transmission compartments of helicopters. It features an all-metal, prevailing torque locking mechanism and is silver-plated to prevent galling. For the high-vibration, high-temperature, and high-stress environment of a helicopter, this certified Bell OEM floating plate nut is a non-negotiable component for airworthy assembly and repair.
Key Features
Genuine Bell Helicopter OEM Part: A factory-specified part, guaranteeing full conformity with the material and performance requirements for Bell rotorcraft.
Direct Cross-Reference to MS21060L4: Manufactured to the stringent military standard for a floating, high-temperature plate nut.
Floating Nut Design: The nut basket floats within the base to accommodate fastener misalignment, which eases assembly, prevents cross-threading, and eliminates stress on the joint.
A-286 CRES Superalloy Construction: The "L" designation specifies A-286, a precipitation-hardenable superalloy that provides exceptional strength at elevated temperatures.
450°F Service Rating: Certified for continuous service in high-temperature environments.
All-Metal Prevailing Torque Lock: An integrally formed locking feature provides consistent, reliable self-locking performance that is not degraded by temperature or contaminants.
Silver Plating for Anti-Galling: Silver plated to act as a high-temperature solid lubricant, preventing the nut and bolt threads from seizing.
Technical Specifications
Bell Part Number: EB9025-14
Military Standard P/N: MS21060L4
Component Type: Nut, Self-Locking, Plate, Two Lug, Floating
Thread Size (-4): 1/4-28 UNF-3B
Material / Temp Code (L): A-286 Corrosion-Resistant Steel (CRES), rated for 450°F (232°C).
Finish: Silver Plated per QQ-S-365.
Governing Specification: MS21060 / NASM21060.
Aircraft Compatibility
Bell Helicopter: This is a standard hardware component used across the Bell rotorcraft family where a high-temperature, 1/4-28 floating plate nut is required. Applicable models include, but are not limited to:
Bell 206 Series, 407 Series, 412 Series, 212, UH-1 Series.
Note: The correct nut for any application must be verified against the aircraft's specific Illustrated Parts Catalog (IPC) or maintenance manual.
Applications
Engine Cowlings & Firewalls: The ideal fastener for securing engine cowlings, heat shields, and inspection panels in high-temperature zones where precise alignment can be difficult.
Transmission Decks & Access Panels: Used extensively on transmission cowlings and structural access panels.
Component Mounting: Attaching components and brackets in areas where tolerance stack-up requires a misaligning nutplate.
Why Choose EB9025-14?
In the extreme vibration environment of a helicopter, using the correct, certified hardware is a matter of life and death. The Bell EB9025-14 is the specified OEM part. Substituting a fixed plate nut where a floating nut is required can induce dangerous stress into the airframe and make proper torquing of the bolt impossible. Using a nut made from an incorrect, low-temperature material will cause a loss of strength and locking ability, leading to fastener failure. As a genuine Bell part, the EB9025-14 guarantees the correct material, the critical floating design, and the quality control required for the unique demands of rotorcraft flight.
The engineering principle that makes the EB9025-14 (MS21060) indispensable is its ability to compensate for tolerance stack-up. In any complex airframe assembly, each component has a manufacturing tolerance (e.g., ±0.010"). Across a large panel with multiple holes, these individual tolerances can accumulate, or "stack up," resulting in a significant misalignment between a bolt hole in the panel and its corresponding nut plate on the substructure. A fixed nut would require forcing the bolt, inducing preload stress, or time-consuming reaming of the hole. The MS21060's floating basket design provides a zone of radial compliance (typically ±0.030" or more). This allows the nut to shift and perfectly align with the bolt's axis, absorbing the tolerance stack-up. This ensures a stress-free installation and guarantees that the clamp load from the torqued bolt is applied purely axially, which is critical for achieving the designed strength and fatigue life of the joint.
Note: The EB9025-14 must be installed using two appropriate structural rivets. These are prevailing torque nuts and have a limited reusability life; they should be checked for minimum prevailing torque before reuse, in accordance with the aircraft maintenance manual. Installation must be performed by a certified A&P/IA mechanic.
Documentation
NASM21060 (Standard): The current standard for these plate nuts is a controlled document. However, the legacy MS21060 specification sheet, which defines the core dimensional, material, and performance requirements, is often available through online mil-spec libraries.
