ST3576-01 - Pratt and Whitney Canada OEM Lock Washer

ST3576-01 – Pratt & Whitney Canada OEM Lock Washer

Available now on the Airparts.aero Marketplace.

The Pratt & Whitney Canada ST3576-01 is a flight-critical, OEM lock washer engineered specifically for high-vibration, high-thermal-gradient aerospace applications within gas turbine and turbofan powerplants. In modern turbine propulsion systems, engine casings, accessory gearboxes, and structural flange connections are continuously subjected to severe, multi-axial harmonic oscillations alongside extreme cyclical thermal expansion. The ST3576-01 serves as a high-precision mechanical retention element, directly preventing counter-rotational backing-off and mitigating the critical risk of fastener torque decay.

This premium locking component has been thoroughly qualified to satisfy the strict dimensional and metallurgical tolerances set forth by Pratt & Whitney Canada standard specifications. For airframe and fleet maintenance logistics, the ST3576-01 serves as the mandatory OEM substitute for part number ST3181-01 across all Beechcraft spares applications. By providing a continuous, reliable mechanical bite or clamping load under severe environmental stress, it maintains the localized joint integrity of narrow-flange installations, accessory pad mounts, and internal case dividers where standard commercial-grade fasteners would rapidly fail due to material relaxation.

For propulsion engineers, quality assurance managers, and aviation maintenance technicians, the ST3576-01 is an indispensable component for scheduled line maintenance and complete power plant overhauls. Ensuring the integration of authentic OEM locking hardware eliminates the catastrophic possibility of hardware migration, preventing extensive downstream Foreign Object Damage (FOD) within the engine's compression or turbine gas paths and preserving complete regulatory type certificate compliance.

Key Features

• Advanced Precipitation-Hardened Metallurgy: Formulated from specialized corrosion-resistant steel (CRES) or high-nickel superalloys to retain its original spring temper, yield strength, and mechanical properties at elevated operational temperatures.

• Vibration-Resistant Mechanical Retention: Designed with precise dimensional configurations to absorb high-frequency harmonic oscillations and resist transverse micro-slip between mating fastener faces.

• High Creep and Stress Relaxation Resistance: Engineered to withstand sustained axial preloads under severe thermal cycling without undergoing sub-critical annealing or plastic deformation.

• Compact, Low-Profile Geometry: Features an optimized physical footprint (approximately 0.29-inch outer diameter) tailored for close-tolerance spacing, counterbored pockets, and narrow engine casing flanges.

• Aerospace Chemical Fluid Immunity: Fully passivated surface treatment provides absolute resistance against chemical breakdown from aggressive synthetic turbine lubricants (MIL-PRF-23699 or AS5780) and aviation fuels.

Technical Specifications

• Part Number: ST3576-01

• Component Type: Washer, Lock, Standard (ST) Specification

• OEM Manufacturer: Pratt & Whitney Canada (P&WC)

• Material: High-temperature corrosion-resistant steel (CRES) / Precipitation-strengthened aerospace alloy (Specific heat-treatment matrix verified via original OEM blueprint / Engine Maintenance Manual)

• Finish: Passivated per AMS2700 or proprietary OEM high-temperature chemical conversion coating

• Dimensions: Nominal Outer Diameter: 0.29 in. | Nominal Thickness: 0.04 in.

• Weight: 0.01 lbs

• Governing Specifications: Pratt & Whitney Canada Standard Hardware (ST) Specification

• Supersedure / Cross-Reference: Mandatory replacement/substitute for P/N ST3181-01 in all Beechcraft spares applications; integrated under Next Higher Assembly (NHA) 9912448-1 for specific turbofan installations

• Certification Status: FAA Form 8130-3 / EASA Form 1 Dual Release or OEM Certificate of Conformance (CoC) required for flight installation

Aircraft Compatibility

• Pratt & Whitney Canada PT6A Series Turboprop Engines (Including PT6A-11, -21, -27, -28, -34, -41, -42, -60, -65, -67, and -114 series variants)

• Pratt & Whitney Canada PT6T Series Turboshaft Engines (Including PT6T-6B Twin-Pac helicopter powerplants)

• Pratt & Whitney Canada PW530A Series Turbofan Engines

• Beechcraft King Air Series (King Air 200, 300, and 350 series airframe powerplant installations)

• Cessna Citation Series (Aircraft utilizing compatible PW500-series powerplants)

• Cessna 208/208B Caravan Utility Aircraft Powerplants

• Note: The aircraft or engine Illustrated Parts Catalog (IPC) for the specific engine serial number remains the final, absolute authority for part verification, quantities, and structural effectivity.

Applications

• Accessory Gearbox (AGB) Pad Mounting: Secures external engine accessories including fuel pumps, oil pump assemblies, starter-generators, and hydraulic drives against vibrational loosening.

• Turbine and Compressor Case Flanges: Provides high-reliability fastening across engine structural case separations and internal stator housing assemblies.

• External Plumbing and Bracketry Retention: Locks structural mounting hardware for high-pressure bleed air lines, fuel manifolds, and external plumbing brackets subject to persistent harmonic excitation.

Why Choose ST3576-01?

Sourcing the genuine OEM Pratt & Whitney Canada ST3576-01 ensures absolute compliance with Type Certification Data Sheet (TCDS) mandates and structural airworthiness standards. Standard commercial-grade washers or non-authorized components lack the precise metallurgical structure needed to handle the anisotropic thermal expansion of gas turbine cases. Under continuous thermal cycling, inferior hardware undergoes rapid stress relaxation, resulting in immediate loss of joint preload. This preload loss initiates joint fretting, thread shearing, or complete fastener migration, which can lead to catastrophic structural casing separation or catastrophic downstream Foreign Object Damage (FOD). Sourcing certified OEM hardware through Airparts.aero guarantees total part traceability, preserves operational safety margins, and satisfies FAA/EASA regulatory compliance during major overhauls or routine line maintenance.

The operational physics of the ST3576-01 lock washer rely on advanced mechanical interference principles designed to override torque-loss mechanisms within high-performance aerospace propulsion environments. In a gas turbine or turbofan assembly, joints are exposed to intense thermal gradients that induce anisotropic thermal expansion across dissimilar metals, such as an aluminum accessory gearbox housing bolted to a steel stud or titanium case flange. This thermal mismatch creates severe fluctuations in localized clamp load. Simultaneously, high-frequency transverse vibrations induce a phenomenon known as micro-slip at the thread interfaces, which converts static bolt tension into an unwinding rotational force. The ST3576-01 counteracts this dynamic breakdown through its precipitation-strengthened, spring-tempered alloy matrix. By acting as a constant-force mechanical spring interface, the washer maintains continuous axial tension across the elastic-plastic boundary of the joint. Its engineered material properties prevent the metallurgical creep and sub-critical stress relaxation common in standard steels, locking the fastener securely in place and shielding the joint from cyclic fatigue propagation.

Note: The ST3576-01 lock washer is a flight-critical, single-use mechanical retention element. Upon torque application, the component undergoes intentional elastic-plastic deformation and localized strain-hardening to secure the engineered clamp load. Reusing this hardware or altering its original physical state introduces severe micro-fissures and stress-concentration zones, drastically increasing the risk of fatigue failure, hydrogen embrittlement, or immediate hardware fracturing during engine operation. Installation must be executed exclusively by an FAA-certified A&P mechanic with an Inspection Authorization (IA) or an authorized MRO facility in strict accordance with the current Pratt & Whitney Canada Engine Maintenance Manual (EMM) or specific aircraft Illustrated Parts Catalog (IPC).

Documentation

No public-facing OEM or regulatory documentation was located for this part. Please cross-reference part numbers and modification status using the official Pratt & Whitney Canada technical publications portal or reference the engine-specific Illustrated Parts Catalog (IPC).