RMO-16

Maximum speed relay RMO-16 in aircraft start systems

RMO-16 is an aircraft maximum speed relay used in engine and auxiliary power unit start circuits. Its main job is to monitor the start process and switch the control circuit when the rotating unit reaches the required speed range. In practice, this relay is part of the automatic start logic. It does not start the engine by itself and does not generate power. It works with the starter-generator control circuit, contactors, cockpit start controls and protection elements that manage the transition from start to normal operation.

Start control function of the RMO-16 relay

During start, the starter-generator operates as an electric starter and accelerates the engine or APU rotor. The RMO-16 relay is used to interrupt the start circuit at the correct stage, so the starter is not kept engaged after the unit has reached self-sustaining speed. This prevents unnecessary load on the starter-generator and protects the start contactor circuit. In a typical start system, the relay breaks the self-holding circuit of the start contactors and allows the electrical machine to move from starter operation toward generator operation, depending on the system layout.

RMO-16 with AI-9V and Mi-8 equipment

RMO-16 is most often associated with the start system of the AI-9V auxiliary power unit used on Mi-8 family helicopters, including Mi-8MT and Mi-17 configurations. In this system group it may work with the StG-3 starter-generator, start panel circuits, relays, contactors and cockpit indication. The exact wiring depends on the aircraft modification and the version of the installed APU equipment. A relay removed from one aircraft should not be treated as a universal replacement until the marking and documentation are checked.

Construction and installation notes for RMO-16

The RMO-16 is made as an aviation relay unit in a protected metal housing with an aircraft electrical connector for connection to the control harness. The label shown in the supplied documentation identifies the unit as relay RMO-16, with product documentation references 167.078.004.1 ET and 167.078.004.1 TU. For maintenance work, the relay should be checked together with the start circuit rather than separately by appearance. A start fault can come from the relay, contactors, wiring, starter-generator, cockpit switch or APU control circuit.

Identification and ordering of RMO-16

Before ordering RMO-16, the marking on the unit and the aircraft technical documentation should be compared. This is especially important when the request mentions RMO-16TV, because similar names can refer to different versions or installation requirements. For correct selection, provide the aircraft type, APU or engine type, part number from the logbook, and a photo of the relay label. The product is also known under alternative designations RMO-16, RMO-16TV, РМО-16 and РМО-16ТВ.

Product Type: Aircraft maximum speed relay
Function: Automatic switching of the start circuit when the required rotational speed is reached
Application / Where Used: Engine and auxiliary power unit start systems
System / Installation Area: Electrical start control circuit
Compatible Aircraft / Equipment: AI-9V APU, Mi-8 family helicopters, Mi-8MT, Mi-17 configurations
Associated Equipment: StG-3 starter-generator, start contactors, cockpit start controls, APU start system relays
Operating Voltage: 27 V DC aircraft electrical system
Construction: Protected aviation relay housing with electrical connector
Weight: Not more than 0.75 kg, according to the label data shown
Technical Documentation: 167.078.004.1 ET; 167.078.004.1 TU; aircraft and APU start system documentation

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