NR-3VM-T

Fuel metering function of the NR-3VM-T

The NR-3VM-T supplies aviation kerosene to the engine fuel manifold and working nozzles with the flow required for each operating mode. During start-up, it begins fuel delivery at the specified compressor rotor speed and helps the engine reach self-sustained operation. At idle, cruise and high-power modes, it changes fuel supply according to the position of the engine control lever and the engine’s actual parameters. Poor adjustment or internal wear of the unit can show itself as weak start, slow acceleration, unstable speed, incorrect power limitation or abnormal fuel flow.

NR-3VM-T as part of the automatic control system

The NR-3VM-T works inside the hydromechanical and electronic control architecture of the TV3-117 engine. The fuel pump-regulator is connected with electronic control units, temperature limiting devices and actuators that correct the amount of fuel supplied to the combustion chamber. In this system, the pump-regulator is not an isolated component. It receives fuel from the aircraft fuel system, follows mechanical input from the engine control lever, reacts to external correction signals and at the same time provides hydraulic control pressure for other engine functions.

Interaction of the NR-3VM-T with ERD-3VM and actuators

In many TV3-117VM / TV3-117VMA installations, the NR-3VM-T works with the ERD-3VM or ERD-3VMA electronic engine regulator. Correction commands may act through an electromechanical actuator, while the gas temperature regulator and other limiting devices protect the engine from exceeding permitted parameters. This combination allows the engine to keep the required power while limiting compressor speed, free turbine speed and gas temperature. If an engine does not hold the correct mode, the fault may be in the pump-regulator itself, but it may also be in the actuator, wiring, electronic regulator or related control lines.

Fuel path and compressor control through NR-3VM-T

Fuel enters the NR-3VM-T from the low-pressure side of the helicopter fuel system, normally after the booster pump. Inside the unit, fuel is pressurized, metered and sent further to the engine fuel manifold and nozzles. The same fuel pressure is also used as a working hydraulic medium for compressor control functions. The unit participates in control of the inlet guide vanes and compressor guide vanes, and also works with the compressor bleed system. This is why cleanliness of fuel, filtration quality and preservation of the aggregate are critical for reliable operation after storage or repair.

Installation and operating environment of the NR-3VM-T

The NR-3VM-T is mounted on the engine accessory gearbox, with its drive shaft connected to the engine gearing. According to passport data, the unit is designed for harsh engine-compartment conditions, including wide temperature ranges and vibration loads. The fuel entering the unit must be filtered to the specified cleanliness level. During maintenance, the condition of mounting points, shaft coupling, fittings, control levers, sealing plugs, safety wire, preservation and external damage must be checked carefully. For a unit of this class, visual condition alone is not enough; bench test data and documentation are essential.

Passport data and acceptance checks for NR-3VM-T

The passport for the NR-3VM-T includes both basic technical data and control results after testing. These values include fuel inlet pressure, direction of rotation, maximum permitted drive speed, operating temperature ranges, current parameters for the actuator and solenoid valve, dry weight and checked adjustment points. The control table also records actual values such as fuel delivery start, starter cut-off speed, speed limitation settings, fuel flow values and jet diameters. These figures are important when assessing a unit from storage or after repair, because they show whether the aggregate was adjusted and accepted within the required limits.

Supply and identification of the NR-3VM-T unit

For purchase, replacement or overhaul, the unit should be requested by its full designation NR-3VM-T. It should not be confused with visually similar pump-regulators from other TV3-117 versions, because settings, execution and associated control units may differ. A proper supply should include passport or repair documents, information on production or overhaul year, preservation status, storage conditions and remaining life where available. Before installation, the aggregate should be matched with the exact engine version, aircraft configuration and maintenance documentation.