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S1450-4H24-125 – Textron Aviation OEM Steel Cadmium Washer
Available now through the AirParts Aero marketplace.
Overview Section
The Textron Aviation S1450-4H24-125 is a high-strength, precision-engineered Specialty Steel Washer utilized across the Cessna and Beechcraft product lines. Unlike standard utility washers, the S1450 series is designed for specific structural and mechanical interfaces where exact thickness and material hardness are required to maintain fastener preload.
The "-125" suffix typically denotes a specific thickness (0.125 inches), making this a "thick" or "spacer-grade" washer. It is manufactured from high-grade carbon steel and finished with a Yellow Cadmium plating, providing the necessary corrosion resistance for use in engine compartments, landing gear bays, and primary structural joints.1
Key Features Section
High-Tensile Steel Construction: Machined from heat-treated steel to prevent "dishing" or deformation under the high clamping loads of structural bolts.
Yellow Cadmium Plating: Coated per QQ-P-416 Type II standards to provide superior protection against moisture and galvanic corrosion when in contact with aluminum skins.
Precision Thickness (0.125"): Acts as a critical spacer to ensure correct "grip length" for bolts, preventing threads from entering a shear plane.
Controlled Parallelism: Manufactured with extremely tight tolerances on surface flatness to ensure uniform pressure distribution across the mating surface.
OEM Specification: Authentic Textron hardware ensuring compliance with the original type certificate and stress analysis of the airframe.
Chamfered Inner Diameter: Features a slight internal radius to accommodate the fillet found under the head of high-strength aerospace bolts (like the NAS or AN series).
Technical Specifications Section
| Specification | Detail |
| Part Number | S1450-4H24-125 |
| Manufacturer | Textron Aviation (Cessna / Beechcraft) |
| Material | Carbon Steel (Heat Treated) |
| Finish | Yellow Cadmium Plate (Type II) |
| Inside Diameter (ID) | Sized for #4 or 1/4" Fasteners (Verify per IPC) |
| Thickness | 0.125 inches |
| Hardness | Aerospace Structural Grade |
Aircraft Compatibility Section
The S1450-4H24-125 is a specialized fastener found in critical locations on the following airframes:
Beechcraft King Air: Often used in Engine Mount assemblies and landing gear drag-link attachments for the 90, 200, and 300 series.
Cessna Citation: Utilized in the mounting of heavy avionics racks and environmental system components.
Beechcraft Baron/Bonanza: Found in wing-bolt installations or stabilizer attachment points where specific spacing is required.
Cessna 208 Caravan: Used in the cargo pod mounting hardware and strut-to-wing interfaces.
Technical Applications & Safety
In aerospace engineering, the washer is rarely just a "spacer." For a thick washer like the S1450-4H24-125, its primary job is to ensure that the Grip of the bolt (the unthreaded portion) extends through the entire thickness of the material being fastened, without the nut "bottoming out" on the threads.
Safety Warning: Never substitute this OEM washer with a standard AN960 or commercial washer. The S1450 is often heat-treated to a specific hardness; using a softer washer in a high-load application can cause the washer to "sink" over time, leading to a loss of bolt tension and potential structural fatigue.
Technical Engineering Insight
The engineering value of the S1450-4H24-125 lies in its Load Concentration Management. By providing a 0.125" thick steel interface, this washer prevents "point loading" on aluminum structures. It effectively spreads the force from the bolt head across a wider area, reducing the risk of stress cracks in the surrounding airframe.
By sourcing this part through AirParts Aero, you ensure the Cadmium plating is applied with the correct bake-relief process to prevent Hydrogen Embrittlement. This is critical for high-strength steel hardware, as improper plating can cause the washer to shatter under load without warning.
Installation & Maintenance Addendum
Facing: If the washer has a chamfered (beveled) side on the inner diameter, that side must face the head of the bolt to clear the bolt's radius.
Corrosion Check: During annual inspections, look for "white powder" (zinc/cadmium oxide) around the washer, which indicates it is doing its job as a sacrificial anode. If the steel core becomes visible (rust), replace the washer.
No Stacking: Whenever possible, use one S1450-4H24-125 rather than stacking multiple thin washers, as a single thick washer provides superior structural rigidity and more consistent torque readings.
