350A31-1854-21 - Airbus Helicopter OEM Spherical Thrust Bolt 350A31185421

350A31-1854-21 – Airbus Helicopters OEM Spherical Thrust Bolt

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The Airbus Helicopters 350A31-1854-21 is a high-precision, flight-critical structural component specifically engineered for the main rotor head assembly of the H125/AS350 (Écureuil) and H130/EC130 families. This specialized spherical thrust bolt is a key element of the Starflex rotor system, a hallmark of Airbus Helicopters' design that replaces traditional mechanical hinges with composite flex-beams. The thrust bolt facilitates the transfer of centrifugal loads and aerodynamic forces from the rotor blades to the Starflex hub while allowing for the necessary lead-lag, flapping, and pitch-change movements.

Fabricated from high-strength, fatigue-resistant alloy steel, the 350A31-1854-21 features a precision-ground spherical head designed to interface with a corresponding spherical bearing or seat. This geometry is essential for maintaining a constant center of rotation during the complex dynamic oscillations of the rotor system. As an OEM component, this bolt is manufactured to withstand extreme cyclic loading and is subject to rigorous non-destructive testing (NDT) to ensure structural integrity across its service life.

Key Features

• Starflex Integration: Specifically designed to secure and align the thrust bearing assembly within the composite Starflex arm, ensuring precise rotor dynamics.

• Spherical Load Distribution: The hemispherical head design allows for multi-axis articulation, reducing localized stress and preventing binding during blade pitch transitions.

• High-Fatigue Alloy: Manufactured from premium aerospace-grade steel, heat-treated to achieve a specific balance of tensile strength and ductility required for high-vibration environments.

• Precision Threading: Features rolled threads (MJ profile) to ensure maximum fatigue resistance and consistent torque-tension relationships during installation.

• Advanced Surface Treatment: Coated with a specialized protective finish to prevent galvanic corrosion and fretting at the interface between the bolt and the bearing housing.

Technical Specifications

• Part Number: 350A31-1854-21

• Manufacturer: Airbus Helicopters (OEM)

• Component Type: Spherical Thrust Bolt / Main Rotor Attachment Bolt

• Material: High-Strength Aerospace Alloy Steel

• Standard: Airbus 350A Series Engineering Drawings

• Thread Type: Metric MJ Profile (High fatigue)

• Geometry: Spherical/Hemispherical Thrust Head

• Governing Specifications: EASA CS-27 / FAA Part 27 (Small Rotorcraft)

• Certification: EASA Form 1 / FAA-PMA / Airbus OEM Standard

Aircraft Compatibility

• Airbus H125 (formerly AS350 B3e)

• Airbus AS350 Series: B, BA, B1, B2, B3

• Airbus H130 (formerly EC130 T2)

• Airbus EC130 B4

• Note: This bolt is used in the main rotor mast/hub interface. Always verify the specific serial number effectivity in the Aircraft Maintenance Manual (AMM) and Illustrated Parts Catalog (IPC).

Applications

• Rotor Hub Assembly: Securing the frequency adapters and spherical thrust bearings to the Starflex arms.

• Dynamic Load Transfer: Transmitting the centrifugal force of the rotating blades to the rotor mast.

• Rigging and Maintenance: Replaced or inspected during major dynamic component overhauls (e.g., 144-month or 600-hour inspections).

Why Choose 350A31-1854-21?

In the H125/AS350 rotor system, the thrust bolt is subject to immense Centrifugal Forces (CF) and Coriolis Effects during every flight hour. Choosing the genuine Airbus OEM 350A31-1854-21 ensures that the bolt's Fracture Toughness and Surface Hardness are exactly as the designers intended. Using non-certified hardware in this application can lead to premature fatigue cracking, which in a "single-load-path" rotor head assembly, presents a catastrophic risk. The OEM bolt provides the documented life-limit tracking and metallurgical reliability required for Part 135 utility and passenger operations.

Note: The 350A31-1854-21 is a life-limited, flight-critical part. It must be installed using the specific lubricant and torque values mandated in the Airbus Helicopters AMM Chapter 62. Over-torqueing can induce stress-corrosion cracking, while under-torqueing can lead to fretting of the Starflex arm. Installation and NDT inspections must be performed by a certified helicopter mechanic (A&P or EASA Part 66 B1.3).

Documentation

• FAA AC 27-1B - Certification of Normal Category Rotorcraft

• Airbus Helicopters T.I.V.I. (Technical Information Visionary Interactive)