AN8-15 - Textron Aviation OEM Bolt

AN8-15 – Army-Navy Specification 1/2" Drilled Head Bolt (Textron Aviation OEM Application)

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The AN8-15 is a high-strength, structural hex head bolt manufactured in strict accordance with Army-Navy (AN) aerospace standards. While manufactured to a universal military specification, the AN8-15 is the OEM-specified bolt used by Textron Aviation in numerous flight-critical applications on their Cessna and Beechcraft airframes. With a shank diameter of 1/2 inch and an overall length of 1-5/8 inches, this fastener is engineered for joints subjected to significant shear and tension loads. The hexagonal head is drilled to accept safety wire, providing the mandatory positive locking required for certified aircraft.

Every aspect of the AN8-15, from its heat-treated alloy steel composition to its superior rolled-thread manufacturing process, is tightly controlled by the AN specification. This ensures a level of strength and fatigue resistance that is impossible to achieve with commercial-grade hardware. When Textron Aviation specifies an AN8-15 in their engineering drawings, they are calling for a certified, traceable, and flight-critical structural component.

Key Features

• Army-Navy (AN) Specification Certified: Guarantees that the bolt meets the stringent material, manufacturing, and quality control requirements for aerospace use, as specified by OEMs like Textron Aviation.

• High-Strength Alloy Steel: Forged from high-grade alloy steel (typically SAE 4140 or 8740) and heat-treated to achieve a minimum tensile strength of 125,000 PSI.

• Rolled Threads for Superior Fatigue Resistance: Features UNF-3A threads that are cold-rolled, not cut, creating a continuous grain structure that dramatically increases resistance to fatigue failure from vibration and load cycling.

• Drilled Head for Positive Locking: The head is drilled to accept safety wire (e.g., MS20995), providing a secure, verifiable method of preventing rotation and ensuring the integrity of the bolted joint.

• Cadmium Plated for Corrosion Resistance: Coated with a sacrificial layer of cadmium per specification QQ-P-416, providing excellent corrosion protection in the harsh aviation environment.

Technical Specifications

• Part Number: AN8-15

• Component Type: Drilled Head Hex Bolt, Airframe

• Governing Specification: AN8

• OEM Applicability: Textron Aviation (Cessna, Beechcraft), among other major airframe manufacturers.

• Material: Heat-Treated Alloy Steel (e.g., SAE 4140 / 8740)

• Finish: Cadmium Plated per QQ-P-416, Type II, Class 3.

• Dimensions:

  • Shank Diameter: 1/2 inch (0.500 in)

  • Overall Length (from under head to end): 1-5/8 inches (1.625 in)

  • Threads: 1/2-20 UNF-3A

  • Grip Length (unthreaded portion): 25/32 inches (0.781 in)

• Minimum Tensile Strength: 125,000 PSI

Aircraft Compatibility

The AN8-15 is a standard hardware component used across all categories of certified aircraft. It is specified in numerous structural applications on Textron Aviation airframes, including Cessna Citation, Caravan, and piston models, as well as Beechcraft King Air, Baron, and Bonanza models.

Crucial Note: The correct bolt part number and, most importantly, the correct grip length for a specific application must be verified against the aircraft's Illustrated Parts Catalog (IPC) or maintenance manual.

Applications

The AN8-15 is designed for critical structural connections throughout the aircraft. Common applications on Textron and other airframes include:

• Engine Mount and Nacelle Attachments

• Landing Gear Trunnions and Strut Fittings

• Flight Control Surface Hinge Points (e.g., elevator, rudder)

• Wing Spar and Fuselage Frame Connections

Why Choose AN8-15?

Choosing a genuine, traceable AN8-15 bolt, as specified by OEMs like Textron Aviation, is a flight-critical decision. Commercial or industrial-grade bolts lack the mandatory material certifications, the superior fatigue life of rolled threads, the specified heat treatments, and the provisions for positive locking. The failure of a single structural bolt due to material defects or fatigue can have catastrophic consequences. The "AN" designation is the guarantee of quality, ensuring that the fastener has been manufactured, tested, and inspected to the highest standards of the aerospace industry.

The profound fatigue resistance of the AN8-15 bolt is a direct result of its mandatory rolled thread manufacturing process. Unlike machine-cut threads, which sever the material's grain structure and create microscopic stress risers at the thread root, rolled threads are formed by a cold-working process. A precision-ground bolt blank is forced between hardened steel dies that plastically deform the surface, causing the material to flow into the shape of the thread root and crest. This cold-working process induces a state of compressive residual stress at the critical thread root area and creates a continuous, unbroken grain flow that follows the contour of the thread. This compressed, smoothly contoured grain structure is exceptionally resistant to the initiation and propagation of fatigue cracks. As a result, a bolt with rolled threads can exhibit a fatigue life that is 50-75% greater than that of a geometrically identical bolt with cut threads, a non-negotiable engineering requirement for fasteners subjected to the constant vibration and cyclic loading inherent in aircraft operations.

Note: This is a flight-critical structural fastener. The grip length of the bolt must be carefully matched to the total thickness of the materials being joined. It must be installed with the correct mating nut (e.g., AN310 or AN365) and washer (e.g., AN960) and torqued to the value specified in the applicable aircraft maintenance manual (e.g., per AC 43.13-1B). After torquing, it must be positively secured with safety wire. Installation must be performed by a certified A&P mechanic.

Documentation

The definitive technical requirements for this component are detailed in Army-Navy specification AN8 and its modern successors (e.g., NASM8 / ASME B18.2.1). These proprietary documents must be sourced directly from the relevant standards organizations for complete engineering specifications.