SP90C8 – Textron Aviation OEM 1/16" x 1/2" CRES Cotter Pin (MS24665-151)
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Overview
The SP90C8 is a genuine Textron Aviation Original Equipment Manufacturer (OEM) split cotter pin, conforming to the military standard MS24665-151. This is a flight-critical piece of hardware whose sole purpose is to provide a positive, mechanical lock for fasteners, most commonly a castellated nut on a drilled-shank bolt. It is an essential component for ensuring the integrity of some of the most critical assemblies on an aircraft, including flight control linkages and landing gear systems.
This cotter pin is manufactured from Corrosion Resistant Steel (CRES), which provides excellent protection against rust and corrosion in the harsh aerospace environment. As a genuine Textron OEM part, it is guaranteed to be manufactured from the correct material with the proper temper and to the precise dimensions of the MS24665 standard, ensuring a perfect fit and reliable performance.
Key Features
Genuine Textron Aviation OEM Part: Guarantees the part is the factory-specified and fully certified component, ensuring airworthiness and full traceability.
Positive Mechanical Lock: When installed correctly, it provides an infallible physical barrier that prevents a castellated nut from backing off its bolt, even with a complete loss of torque.
Corrosion Resistant Steel (CRES): Fabricated from a 300-series stainless steel alloy, offering superior, long-term resistance to environmental corrosion.
MS24665 Standard Compliance: Manufactured and tested in strict accordance with the military standard for split cotter pins, guaranteeing material properties and dimensional accuracy.
Single-Use Safety Device: Engineered for a single installation to ensure the tines have the required ductility for a proper bend and the full strength to perform their locking function.
Technical Specifications
Part Number: SP90C8
Cross-Reference Standard: MS24665-151
Component Type: Split Cotter Pin
OEM Authority: Textron Aviation
Governing Specification: MS24665
Material: Corrosion Resistant Steel (CRES), 300-Series (passivated).
Nominal Diameter: 1/16 inch (0.062 inches)
Length (measured under the head to the end of the short tine): 1/2 inch (0.500 inches)
Aircraft Compatibility
The SP90C8 (MS24665-151) is a universal hardware item used on virtually all Textron aircraft and across the entire aviation industry wherever this size of cotter pin is specified by an engineering drawing.
Primary Textron Aviation Platforms:
Cessna Piston Aircraft (100, 200, 300, 400 Series)
Beechcraft Piston Aircraft (Bonanza, Baron)
Cessna and Beechcraft Turboprops (Caravan, King Air)
Cessna Citation Business Jets
Hawker Business Jets
Note: Verification of applicability is the responsibility of the installer. Always consult the current version of the aircraft's Illustrated Parts Catalog (IPC) or maintenance manual to confirm the correct cotter pin part number for a specific fastener assembly.
Applications
Sole Application: To secure castellated nuts (e.g., AN310, MS17825) on drilled-shank bolts (e.g., AN3-AN20 series) and other types of fasteners with provisions for a cotter pin.
Ubiquitous in primary flight control systems, landing gear assemblies, engine control systems, and powerplant installations.
Why Choose SP90C8?
A cotter pin is one of the most fundamental safety devices on an aircraft. Its failure can lead to the catastrophic failure of a primary flight control or landing gear component. The genuine Textron OEM SP90C8 guarantees that the pin is made from the correct, certified CRES material with the proper ductility to be bent without fracturing, yet with the required shear strength to perform its locking function. Using a generic hardware store pin made of an unknown or brittle material introduces an unacceptable risk of in-flight failure.
The engineering principle of a split cotter pin is to function as a pure shear-based locking device. It is designed to carry no tensile load. When installed through the castellations of a nut and the hole in a bolt, the two tines of the pin are placed in double shear. The pin's sole purpose is to physically obstruct the nut from rotating. The required shear strength of the pin is therefore a critical design parameter. The MS24665 standard ensures that the 300-series CRES material of the SP90C8 is properly processed to provide a minimum shear strength (for a 1/16" pin, this is approximately 230 pounds). This strength is far in excess of any residual rotational torque that might act on a properly installed nut, providing a nearly infallible mechanical lock as long as the pin is present and its material integrity has not been compromised by corrosion or fatigue.
Note: This is a flight-critical, single-use component. A new cotter pin must be used every time a castellated nut is installed or re-installed. The pin must be the correct diameter to ensure a snug fit in the hole and bolt. The tines must be bent in accordance with standard practices (e.g., as detailed in FAA Advisory Circular AC 43.13-1B, Chapter 7) to properly secure it. Never reuse a cotter pin, as bending the tines work-hardens the material, and attempting to re-bend them can cause fracture.
Documentation
The military standard governing this part is publicly available through the Department of Defense ASSIST database.
ASSIST Document Summary Page for MS24665: http://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=42654