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3119854-01 – Pratt & Whitney Canada OEM Washer Key
Available now through the AirParts Aero marketplace.
Overview Section
The Pratt & Whitney Canada 3119854-01 is a high-precision Washer Key (also commonly referred to as a Tab Washer or Locking Washer) engineered for the internal rotating assemblies and accessory drives of the PT6A, PT6B, and PT6T turboprop engine series.
As a critical "safety-locking" device, the 3119854-01 is designed to physically prevent the loosening of high-torque nuts and bolts within the engine's gearbox or power section. It features a specialized internal or external "tab" that locks into a keyway on the shaft, while the outer tabs are bent against the flats of a nut after torque has been applied. This mechanical interference ensures that engine vibration and thermal expansion cannot cause a fastener to back off, which could result in catastrophic internal engine damage.
Key Features Section
High-Ductility Alloy: Manufactured from a specialized steel alloy that is strong enough to resist shear forces yet ductile enough to be bent multiple times during the locking process without cracking.
Precision Keyway Interface: Features a center-bore geometry designed to lock perfectly into the splines or keyways of P&WC shafts, ensuring zero rotational movement of the washer.
Corrosion & Heat Resistance: Specially treated to withstand the high-temperature environment and the chemical properties of synthetic turbine oils (MIL-PRF-23699).
Vibration Immunity: Provides a more reliable locking mechanism than chemical thread lockers or spring washers in high-frequency turbine environments.
OEM Tolerance: Machined to exact P&WC blueprint tolerances to ensure proper "stack-up" height in the assembly, maintaining the correct preload on bearings and gears.
Fail-Safe Design: The multi-tab configuration allows for at least one tab to be perfectly aligned with a nut flat, ensuring a secure lock regardless of final torque position.
Technical Specifications Section
| Specification | Detail |
| Part Number | 3119854-01 |
| Manufacturer | Pratt & Whitney Canada (P&WC) |
| Engine Series | PT6A, PT6B, PT6T (Twin-Pac) |
| Component Type | Washer Key / Tab Locking Washer |
| Material | High-Strength Aerospace Steel |
| Application | Accessory Gearbox (AGB), RGB, and Internal Shafts |
| Service Standard | Single-use/Replace upon removal |
Aircraft Compatibility Section
The 3119854-01 is a foundational hardware component for nearly all PT6-powered aircraft in the AirParts Aero network:
Beechcraft King Air: Used in the engine assemblies of the 90, 200, and 300 series.
Cessna Caravan: Essential for the PT6A-114A and -140 engines on the 208/208B.
Pilatus PC-6 & PC-12: Critical for the power sections of the PT6A-27 and -67 variants.
Air Tractor / Thrush: Found in the high-torque accessory drives for agricultural turboprops.
Bell 212/412: Utilized in the PT6T Twin-Pac power sections for helicopter operations.
Technical Applications & Safety
The Washer Key is often the only thing preventing a high-speed gear from detaching from its shaft. In the Accessory Gearbox (AGB), the 3119854-01 is frequently used to secure the nuts on starter-generator drives and fuel pump drives.
Safety Warning: NEVER REUSE A 3119854-01 WASHER. P&WC Maintenance Manuals strictly mandate the replacement of tab washers upon every removal. The process of bending the tabs "work-hardens" the metal. If a tab is straightened and re-bent, it becomes brittle and is highly likely to snap off due to engine vibration. A broken tab circulating in the gearbox can destroy gear teeth or clog oil jets, leading to engine failure.
Technical Engineering Insight
The engineering value of the 3119854-01 lies in its Shear-to-Thickness Ratio. The washer must be thin enough to not interfere with the overall gear spacing (which would affect "backlash") but thick enough that the tabs cannot be sheared off by the rotational torque of a nut attempting to loosen.
By choosing the genuine P&WC part through AirParts Aero, you ensure that the internal key is precisely chamfered. This prevents the washer from "riding up" on the radius of the shaft keyway, which would create an uneven load on the nut and lead to premature bearing wear.
Installation & Maintenance Addendum
Proper Bending: Use a specialized brass drift or a smooth-jawed tool to bend the tabs. Avoid using sharp-edged screwdrivers that can "score" or "notch" the bend line, as this creates a stress riser where the tab can break.
Alignment: Ensure the washer's internal key is fully seated in the shaft keyway before applying torque to the nut.
Visual Confirmation: After installation, verify that at least one tab is bent flat against the side of the nut and that no other tabs are interfering with surrounding gear clearances.
