8-1930-720A

Hydraulic damper cylinder 8-1930-720A for the main rotor hub

8-1930-720A is a double-acting hydraulic damper cylinder used in the main rotor hub assembly of Mi-8 and Mi-17 helicopters. The unit works as part of the blade damping system and is installed in the main rotor hub, where blade motion must remain controlled during ground and flight operation. Its purpose is to damp oscillations of the main rotor blades in the plane of rotation and support stable dynamic behavior of the rotor system. In an articulated rotor system, this function is important because blade movement is affected by aerodynamic forces, centrifugal loads, control inputs and vibration.

Damping function of the 8-1930-720A cylinder

The 8-1930-720A cylinder absorbs cyclic loads transmitted through the blade root and hub mechanism. During rotor operation, each blade can move relative to the hub structure, and these movements must be controlled to avoid excessive oscillation. The hydraulic damper resists rapid unwanted motion and helps reduce dynamic instability in the rotor system. One of its practical roles is suppression of vibration and ground resonance tendencies that may occur in articulated rotor systems when blade movement and airframe oscillations interact. A serviceable damper helps keep rotor response predictable during starting, ground running, takeoff, flight and shutdown.

8-1930-720A in the 8-1930-000 hub assembly

The 8-1930-720A is installed as part of the hydraulic damping system of the 8-1930-000 main rotor hub, including Series 2 and later configurations where applicable. The cylinder is not a standalone flight-control unit; it operates together with the hub body, blade pitch control lever, hinge assemblies, hydraulic damping circuit, seals and approved working fluid. Its condition affects the behavior of the complete hub assembly. Leakage, internal wear, damaged attachment points, poor damping action or incorrect installation can increase vibration and reduce stability of the rotor system.

Installation of 8-1930-720A between hub and blade control lever

The 8-1930-720A damper cylinder is installed between the hub body and the blade pitch control lever. In this position, it works directly with the mechanical path where blade loads and pitch-related movements are transmitted through the hub. Correct installation is important because the damper must move through its working stroke without binding, misalignment or leakage. During maintenance, technicians normally check mounting eyes, attachment hardware, seal condition, hydraulic fluid traces, free movement and general external condition. Any replacement should be performed according to the aircraft maintenance and hub overhaul documentation.

Aircraft application of the 8-1930-720A damper

The 8-1930-720A hydraulic damper cylinder is used on Mi-8, Mi-8T, Mi-8MT and Mi-17 helicopters equipped with compatible 8-1930-000 main rotor hub assemblies. Applicability should still be checked by aircraft modification, hub series and repair documentation. Helicopters that have passed through overhaul or modernization may have configuration differences in the main rotor hub and damping elements. For this reason, the damper should be selected by part number, hub assembly reference and maintenance documentation rather than by visual similarity alone.

Identification and ordering of 8-1930-720A

Before ordering 8-1930-720A, it is useful to confirm the helicopter type, main rotor hub designation, hub series, installed damper configuration, required condition and documentation set. The product may be supplied as a separate spare part for main rotor hub repair or as part of a larger hub maintenance requirement. If the item is intended for overhaul work, the supplier should clarify whether the customer requires manufacturer documentation, inspection records, preservation status or repair documentation. The Russian designation may be written as 8-1930-720А, while the Latin export-style designation is usually written as 8-1930-720A.

Product Type: Double-acting hydraulic damper cylinder
Designation: 8-1930-720A
Alternative Designations: 8-1930-720А
Function: Damping of main rotor blade oscillations in the plane of rotation
Application / Where Used: Main rotor hub hydraulic damping system
System / Installation Area: Main rotor hub assembly
Part of System / Included in Set: Main rotor hub 8-1930-000, Series 2 and above where applicable
Compatible Aircraft / Equipment: Mi-8, Mi-8T, Mi-8MT, Mi-17 helicopters
Installation Location: Between hub body and blade pitch control lever
Working Medium: Aviation hydraulic oil AMG-10 or approved equivalent according to maintenance documentation
Operating Role: Absorption of cyclic blade loads and reduction of rotor dynamic instability
Design Type: Double-acting hydraulic damping cylinder
Material: High-strength aviation alloy component
Condition: As applicable
Technical Documentation: Manufacturer technical documentation, aircraft maintenance documentation, main rotor hub overhaul documentation

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