IM-47

IM-47 actuator in the TV3-117 control system

The IM-47 is an aircraft electrohydraulic actuator used in the automatic control system of TV3-117 turboshaft engines. It forms the link between the electronic control section and the hydromechanical fuel control unit. The actuator is structurally integrated into the NR-3VM fuel control unit and is not normally operated as a separate standalone device. Its function is connected with fuel metering control on takeoff and emergency operating modes of the engine.

Fuel metering control through IM-47

During engine operation, the actuator receives electrical commands from electronic regulators and converts them into hydraulic action inside the fuel control unit. This action changes the position of the main metering needle by controlling pressure in the relevant hydraulic chamber. As a result, fuel flow to the combustion chamber is adjusted according to the required engine operating condition. The actuator works with fuel already present under pressure inside the pump-regulator circuit.

IM-47 with ERD-3VM and RT-12-6 regulators

The actuator can receive control influence from the ERD-3VM or ERD-3UVM electronic engine regulator and from the RT-12-6 gas temperature regulator. These signals may act separately or be combined, depending on the engine operating condition. This arrangement allows the system to respond to compressor rotor speed control requirements and gas temperature limitation. If the engine does not respond correctly to control commands, the check should include the electronic regulators, wiring, fuel control unit and hydraulic section.

Protective function of the IM-47 actuator

The unit includes a hydraulic blocking spool used for protection and safe disconnection of the actuator circuit under defined conditions. The mechanism can shut off the drain line and remove the actuator from active control if the compressor rotor speed falls below the specified threshold. This prevents an unsafe reduction of engine power in case of false electronic command or abnormal control behaviour. The protective function is part of the fuel control logic, not a separate cockpit-operated function.

Identification and ordering of IM-47

Before ordering, the actuator should be checked against the NR-3VM fuel control unit documentation, engine manual and aircraft maintenance records. Since the unit is built into the pump-regulator, supply or repair requirements may depend on the condition and configuration of the complete fuel control unit. For correct selection, provide the engine type, fuel control unit marking, electronic regulator type, aircraft application and any available passport or overhaul records. The product is also known under alternative designations IM-47 and ИМ-47.

Product Type: Aircraft electrohydraulic actuator
Function: Conversion of electronic control commands into hydraulic action for fuel metering control
Application / Where Used: Automatic control systems of TV3-117 turboshaft engines
System / Installation Area: NR-3VM fuel control unit / engine automatic control system
Compatible Engine Family: TV3-117, including VM and VMA modifications
Associated Fuel Control Unit: NR-3VM pump-regulator
Associated Electronic Regulators: ERD-3VM, ERD-3UVM, RT-12-6
Control Object: Main fuel metering needle of the pump-regulator
Construction Type: Two-stage electrohydraulic amplifier of jet-throttle type
Electrical Input Stage: Polarized relay with movable armature-flapper
Control Signal Type: Pulse signal with variable duty cycle / PWM
Working Fluid: Aviation fuel T-1, TS-1, RT
Nominal Working Pressure: 6 MPa / 60 kgf/cm²
Operating Temperature Range: −60 to +100 °C
Protective Element: Hydraulic blocking spool
Automatic Disconnection Threshold: Compressor rotor speed below 84%
Technical Documentation: Engine control system documentation, NR-3VM documentation, product passport where applicable

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