?unique=a259673)
416-633 – Piper Aircraft OEM Flat Countersunk Machine Screw
Available now on the Airparts.aero Marketplace.
Overview
The Piper 416-633 is a genuine OEM, non-structural machine screw used to attach fairings, access panels, and other non-primary-structural components on a wide range of Piper aircraft. This fastener is a 100-degree flat countersunk head screw, designed to sit flush with the aircraft's skin for a smooth, aerodynamic finish.
This part is a direct cross-reference to the military standard (mil-spec) part number MS24693-S273. It is manufactured from high-strength alloy steel and plated with cadmium for exceptional corrosion resistance. The 100-degree head is the standard for aerospace, and the Phillips drive allows for easy and reliable installation. This screw is most commonly found in the wheel fairing (wheel pant) assemblies of the Piper PA-28 series.
Key Features
Genuine Piper Aircraft OEM Part: A factory-specified part, guaranteeing correct material, fit, and performance.
Mil-Spec Cross-Reference: Directly equivalent to MS24693-S273, ensuring certified quality and traceability.
100° Flat Countersunk Head: The standard aerospace countersunk head, designed to install flush with the skin for minimal aerodynamic drag.
Alloy Steel Construction: Fabricated from high-strength alloy steel for durability and shear strength.
Superior Corrosion Protection: Cadmium plated in accordance with QQ-P-416, Type II, Class 3 (Yellow Chromate) to resist rust and environmental degradation.
Technical Specifications
Part Number: 416-633
Mil-Spec Equivalent: MS24693-S273 (supersedes AN507-1032R10)
Component Type: Machine Screw, 100° Flat Countersunk Head
OEM Manufacturer: Piper Aircraft, Inc.
Material: Alloy Steel
Finish: Cadmium Plated, Type II (Yellow Chromate)
Thread Size: #10-32 UNF-3A
Nominal Length: 5/8" (0.625 inches)
Drive Type: Phillips Recess
Aircraft Compatibility
This screw is a common hardware item used on numerous Piper aircraft. It is specifically called out in the parts catalog for:
Piper PA-28-236: Dakota (used for wheel fairing/pant installation)
Piper PA-28 Series: Likely used on other PA-28 models (Cherokee, Warrior, Archer) for similar fairing and panel applications.
Note: This compatibility list is for general reference. The specific aircraft Illustrated Parts Catalog (IPC) for a given serial number is the final and absolute authority for determining part applicability.
Applications
Wheel Fairings (Wheel Pants): The most common documented application, used to secure the main gear fairings to the attachment brackets.
Access Panels & Inspection Covers: Used in various non-structural locations where a flush-head fastener is required.
Interior Components: May be used for attaching non-structural interior panels and fittings.
Why Choose 416-633?
Using a genuine Piper or certified mil-spec screw is critical for ensuring airworthiness, even in non-structural applications. The 416-633 is guaranteed to be made from the correct, high-strength alloy steel and to have the proper cadmium plating to prevent corrosion and seizing. Using a non-certified or commercial-grade hardware store screw introduces a significant risk, as it will lack the required strength, vibration resistance, and corrosion protection, leading to component loss, rust, and potential damage to the surrounding structure.
The engineering significance of the MS24693 cross-reference is its design as a structural machine screw. Unlike common hardware, this fastener features a Class 3A thread fit, which is the tightest tolerance for aerospace screws. This tight fit minimizes "play" between the screw and the nut plate, providing a more rigid joint that is highly resistant to loosening under the constant, high-frequency vibration experienced on a landing gear fairing. The 100-degree head angle (as opposed to the 82-degree industrial standard) provides a wider, more gradual bearing surface, which better distributes the clamp load onto the thin aluminum or fiberglass fairing, reducing the risk of cracking or dimpling the material.
Note: The 416-633 is a non-structural fastener. It must be installed by a certified A&P mechanic. It is typically installed into a nut plate (e.g., MS21047 or similar) and should not be over-torqued, as this can damage the fairing or the nut plate. Always verify the correct part number and length for the specific application in the aircraft's parts catalog.
Documentation
MS24693: The military standard sheet defines all dimensional, material, and performance requirements for this series of screws and is publicly available through various online mil-spec libraries.
Piper PA-28-236 Parts Catalog: This document (e.g., P/N 761-680) lists the 416-633 as a component of the wheel fairing assembly.
