115-389009-3 - Textron Aviation OEM Belt for King Air Aircraft

115-389009-3 – Textron Aviation OEM V-Belt for King Air Aircraft ⚙️

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Overview

The Textron Aviation 115-389009-3 is an Original Equipment Manufacturer (OEM) V-Belt specifically designed for the accessory drive system on various Beechcraft King Air turboprop aircraft. This component is not a commodity belt but a highly engineered, certified part crucial for the reliable operation of engine-driven accessories. Its primary function is the synchronous transmission of torque from an engine accessory gearbox pulley to one or more essential, high-load components, typically including the secondary hydraulic pump, air conditioning compressor, or a high-capacity generator/alternator.

Operating in the demanding environment of the engine nacelle—characterized by extreme temperature fluctuations, high rotational speeds, and continuous shock loads from the engine—the 115-389009-3 belt must maintain dimensional stability and flexibility without exhibiting excessive stretch or catastrophic failure. As a certified OEM part, it guarantees the precise cord material, tensile strength, and flank friction coefficient required to meet the operational demands and regulatory standards for safety and reliability in King Air operations.

Key Features

• High-Tensile Strength Cords: Constructed with internal reinforcing tension cords (often aramid or specialized polyester fiber) embedded within the rubber matrix to provide minimal stretch and maximum power transfer efficiency.

• Oil and Heat Resistant Elastomer: The outer elastomeric compound is formulated to resist chemical degradation from oil, hydraulic fluid, and the high temperatures present in the turboprop nacelle environment.

• Precision Profile: Designed with an exact V-profile angle to ensure optimal seating and grip within the pulley grooves, maximizing friction and preventing slippage under maximum accessory load.

• Static Conductive: Often engineered to be electrically static conductive (per specific Mil-Spec or SAE standards) to prevent static charge buildup that could interfere with sensitive avionics.

• OEM Vibration Dampening: The belt structure is tuned to absorb and damp torsional vibrations originating from the engine, protecting the accessory bearings from excessive wear.

Technical Specifications

• Part Number: 115-389009-3

• Component Type: V-Belt / Drive Belt (Accessory Drive)

• OEM Manufacturer: Textron Aviation (Beechcraft)

• Governing Specification: Manufactured to Beechcraft/Textron Aviation engineering drawings; often cross-references to SAE J636 or equivalent aerospace standards.

• Material: Specialty Rubber/Synthetic Elastomer Compound with high-modulus tension cords (Specific composition proprietary).

• Length/Size: Must be confirmed by OEM drawing. The dash number (-3) typically denotes a specific length code in the Beechcraft system.

• Application Load: Engineered for high, continuous power transmission (Specific torque and horsepower limits proprietary).

• Certification: Original Production Certificate (PC) Approved by the FAA.

• Maintenance Requirement: Considered a life-limited or on-condition item subject to frequent inspection for cracking, cord separation, and tension monitoring.

Aircraft Compatibility

• Primary Models: Found on various twin-turboprop models of the Beechcraft King Air Series, including:

  • King Air C90, E90, F90 (Specific P&W PT6A variants)

  • King Air 200 Series (B200, B200GT)

  • King Air 300 Series (350, 350i)

• System Integration: Used in accessory drive systems (e.g., hydraulic pump drive or secondary generator drive) powered off the engine's accessory gearbox or reduction gearbox.

• Verification Note: The Illustrated Parts Catalog (IPC) for the specific aircraft model and serial number is the definitive and final authority for part applicability.

Applications Section

The 115-389009-3 V-Belt provides reliable mechanical power for:

• Hydraulic System: Driving a hydraulic pump that provides fluid power for landing gear, flaps, or brakes (on models with belt-driven pumps).

• Electrical System: Powering a generator or high-output alternator to supplement the main electrical system, especially during ground operations or low-power flight.

• Environmental System: Driving the compressor for the vapor-cycle air conditioning system.

Why Choose the 115-389009-3 OEM V-Belt?

The failure of an engine accessory drive belt is a non-redundant system failure that can lead to the loss of a critical flight system (e.g., loss of hydraulic pressure or electrical generation). Therefore, the Textron Aviation 115-389009-3 OEM V-Belt is critical because its load carrying capacity and stretch limits are precisely certified for the King Air's operational envelope. Non-certified commercial belts cannot guarantee the chemical stability in the presence of synthetic turboprop oils or the tensile cord material needed to handle the high transient loads without stretching permanently (taking a "set"), which leads to immediate loss of tension and premature slip, burning, and failure. This OEM belt ensures maximum safety and adherence to the aircraft's Minimum Equipment List (MEL).

The power transmission mechanism relies on the coefficient of friction ($\mu$) between the belt flanks and the pulley groove. The relationship between the input tension T_1, output tension T_2, and the angle of wrap \phi is governed by the Euler-Eytelwein formula, simplified for V-belts. The 115-389009-3 elastomeric compound is specifically tuned to maximize $\mu$ and minimize heat generation under slip conditions. Furthermore, the embedded tension cords are designed to have an extremely low modulus of elasticity to maintain a constant overall installed length under load, which directly preserves the critical belt tension required for effective friction, preventing dynamic slip and premature belt failure.

Note: The 115-389009-3 V-Belt is a maintenance-critical component. It must be inspected frequently for any signs of cracking, fraying, oil saturation, or glazing (which indicates excessive slip). The belt tension is non-negotiable and must be set precisely using the specified tension gauge and procedure outlined in the King Air Maintenance Manual; incorrect tension drastically reduces belt life and can damage accessory bearings. Never use a commercial belt due to inadequate strength and material stability. Installation and tension setting must be performed and certified by a licensed A&P mechanic in strict accordance with the Beechcraft Maintenance Manual.

Documentation

No public-facing OEM or regulatory documentation was located for this specific part number. Consult the Beechcraft King Air Maintenance Manual and Illustrated Parts Catalog (IPC) for the specific model to verify fitment, correct tension specifications, and mandatory inspection intervals.