1201C10-031A – S-TEC / Genesys Aerosystems Plain Flat Cadmium Steel Washer
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The 1201C10-031A is a precision-engineered, aerospace-grade flat washer specifically utilized in the installation and maintenance of S-TEC (Genesys Aerosystems) Autopilot Systems. Unlike general-purpose industrial washers, this component is manufactured to high-tolerance aircraft standards to provide a stable bearing surface for fasteners within sensitive electromechanical flight control servos and mounting brackets. The 1201C10-031A is critical for distributing the clamping load of a bolt or screw over a larger area, preventing the localized crushing or "brinelling" of the soft aluminum or composite airframe structures and autopilot mounting plates.
Constructed from high-tensile carbon steel and finished with Type II Cadmium plating, this washer offers superior corrosion protection and a controlled coefficient of friction. The cadmium finish is a "sacrificial" coating that prevents galvanic corrosion between the steel washer and aluminum airframe components, a vital requirement for long-term airworthiness in the varied thermal and moisture environments encountered during flight.
Key Features
S-TEC Systems Specified: Engineered as a direct replacement part for S-TEC autopilot servos, capstans, and bridle cable attachments, ensuring compliance with the original Supplemental Type Certificate (STC).
Cadmium Type II Plating: Provides excellent lubricity and corrosion resistance, specifically formulated to prevent "seizing" of fasteners and to inhibit oxidation in saline or high-humidity environments.
Precision Dimensional Tolerance: Featuring a .203" Inner Diameter (ID) and a .438" Outer Diameter (OD), it is perfectly sized for #10 (3/16") aircraft fasteners, ensuring a snug fit without excessive lateral movement.
Low-Profile Thickness: At .031" thick, this washer provides the necessary load distribution while maintaining a minimal stack-up height, critical for installations with tight clearance tolerances.
Load Distribution Logic: Prevents "pull-through" and surface deformation of thin-gauge sheet metal or mounting brackets when fasteners are torqued to final flight specifications.
Technical Specifications
Part Number: 1201C10-031A
Manufacturer: S-TEC / Genesys Aerosystems
Component Type: Plain Flat Washer
Inner Diameter (ID): 0.203 Inch (Nominal for #10 Fastener)
Outer Diameter (OD): 0.438 Inch
Thickness: 0.031 Inch
Material: Carbon Steel
Finish: Cadmium Plated (Yellow/Gold Chromate, Type II)
Certification: FAA-PMA / Part of S-TEC STC Hardware Kits
Aircraft Compatibility
S-TEC Autopilot Installations: Used across the System 20, 30, 40, 50, 55, 55X, and 60 series autopilots.
General Aviation (GA): Found in the autopilot installations of Cessna 172/182, Piper PA-28/PA-32, Beechcraft Bonanza/Baron, and Mooney M20 series.
Experimental Airframes: Frequently utilized by builders for precise shim and bearing surfaces in custom flight control linkages.
Note: Consult the S-TEC Installation Manual for your specific airframe to verify the correct washer placement within the servo stack-up or cable bridle assembly.
Applications
The 1201C10-031A is utilized for Fastener Load Management and Shimming. Its primary roles include:
Servo Mounting: Providing a bearing surface between the mounting bolt and the autopilot servo bracket.
Bridle Cable Attachments: Ensuring the bolts securing the cable clamps are properly seated without damaging the clamp surface.
Spacing & Shimming: Fine-tuning the alignment of autopilot drive pulleys and capstans.
Why Choose 1201C10-031A?
Choosing the genuine S-TEC 1201C10-031A ensures that the clamping tension of your autopilot hardware remains constant. Commercial "zinc-plated" washers lack the specific thickness and corrosion-inhibiting properties of cadmium-plated steel. In a high-vibration environment, a sub-standard washer can compress or corrode, leading to a loss of fastener preload. For an autopilot system, this can result in "bridle cable slip" or servo oscillation, directly impacting flight safety and system reliability.
The 1201C10-031A functions as a Mechanical Interface governed by the principles of Load Distribution and Friction Control. By increasing the area over which the bolt head’s compressive force is applied, it reduces the localized stress on the mounting surface, preventing material fatigue. The Cadmium plating serves two critical physical roles: it acts as a lubricant during the torquing process to ensure accurate "stretch" of the bolt, and it provides a sacrificial anode to protect the steel core. This is especially vital in Fly-By-Wire or high-fidelity autopilot systems where mechanical "play" caused by surface corrosion or fastener loosening could introduce unwanted signal noise or mechanical hysteresis into the flight controls.
Note: This is a specific hardware component for certified flight control systems. Do not substitute with non-aerospace hardware. Prior to installation, inspect for "burrs" or uneven plating that could affect the seating of the fastener. Installation must be performed by a certified A&P/IA mechanic in accordance with the S-TEC Autopilot Installation Manual and FAA AC 43.13-1B.