766300A-1-T

766300A-1-T fuel filling control valve in helicopter systems

The 766300A-1-T is an aircraft float-type fuel filling control valve used in helicopter fuel systems. The valve is designed to control fuel flow during ground refueling and to help prevent overfilling of the fuel tank. It operates as part of the onboard fuel filling line, where fuel is supplied under pressure from ground refueling equipment. The unit is not a manual drain or shut-off fitting; it is a fuel level-responsive valve that automatically changes the flow condition when the fuel level reaches the required limit inside the tank.

Automatic fuel shut-off function of 766300A-1-T

The main function of the 766300A-1-T is automatic interruption of fuel flow during refueling. The valve uses a float mechanism that reacts to the fuel level in the tank. When the fuel rises to the set level, the float acts on the valve mechanism and closes the passage, stopping or limiting further fuel delivery. This prevents excessive filling and reduces the risk of fuel overflow through tank vents or service openings. In operation, this function is important for safe refueling, correct fuel system servicing, and protection of aircraft structure from fuel spillage.

766300A-1-T in Mi-8, Mi-17, Mi-171 and Mi-172 fuel systems

The 766300A-1-T is used in the fuel systems of Mi-8 family helicopters, including Mi-8, Mi-17, Mi-171, and Mi-172 series aircraft depending on configuration. It is typically installed in the fuel tank filling line, where it works during pressure refueling operations. The exact installation point should be verified by the aircraft parts catalog and maintenance documentation, because fuel system layout may differ depending on helicopter version, tank configuration, modernization status, and refueling system arrangement. Correct identification of the valve is important when replacing fuel system components.

Float mechanism operation in the 766300A-1-T valve

The 766300A-1-T operates by mechanical response to fuel level rather than by an electrical command. The float senses the rising level of fuel and transfers movement to the internal valve element. This makes the unit a direct fuel level control component within the refueling line. Since the valve works in contact with aviation fuel, the condition of its moving parts, sealing surfaces, float element, and passage area is important. Contamination, sticking, deformation, or damage to the float mechanism can affect shut-off accuracy and may cause incorrect refueling behavior.

Operating conditions for the 766300A-1-T valve

The valve is designed for operation with fuel as the working medium and air as the surrounding medium. According to the technical data shown in the documentation, the valve is intended for operation within a defined fuel pressure range and a wide aircraft temperature range. These limits are important because the unit must operate reliably during refueling in different climates and under typical aviation service conditions. The nominal passage diameter is also relevant for system compatibility, as it defines the flow path size and helps match the valve to the correct refueling line.

Identification, inspection and supply of 766300A-1-T

The product is identified by the designation 766300A-1-T. Before installation or supply, the valve should be checked against the aircraft documentation, fuel system diagram, and required installation position. During inspection, attention should be given to the housing, fittings, passage area, float mechanism, sealing condition, corrosion, contamination, and signs of fuel leakage. The documentation indicates that completeness is not provided as a separate set, so supply should be clarified in advance if additional fittings, adapters, seals, or mounting hardware are required. For aviation use, manufacturer technical documentation or passport records should accompany the item where available.

Product Type: Float-type aircraft fuel filling control valve
Designation: 766300A-1-T
Function: Automatic shut-off of fuel flow during refueling
Application / Where Used: Helicopter fuel systems
System / Installation Area: Fuel tank refueling line
Compatible Aircraft / Equipment: Mi-8, Mi-17, Mi-171, Mi-172 series helicopters depending on configuration
Working Medium: Fuel
Ambient Medium: Air
Operating Pressure: 0.5 to 3 kgf/cm²
Operating Temperature Range: −60 to +60 °C
Nominal Passage Diameter: 45 mm
Dimensions: Approx. 118 × 124 × 96 mm
Weight: Not more than 1.1 kg
Completeness of Supply: Not provided as a set
Technical Documentation: Manufacturer technical documentation / product passport where available

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