GS-18TO

GS-18TO starter-generator in aircraft DC power systems

The GS-18TO is an aircraft DC starter-generator used both as a starter motor and as a generator for the onboard electrical system. It is a six-pole DC electrical machine with shunt excitation and heat-resistant construction. In starter mode, the unit delivers torque to rotate the connected engine or auxiliary power unit. After the start sequence, it can work as a generator and supply the aircraft DC network. The unit is normally considered together with the engine accessory gearbox, voltage regulation equipment, protection relays, brush gear, and aircraft power distribution circuits.

Starter mode operation of the GS-18TO

In starter mode, the GS-18TO works as a DC electric motor. Starting current is supplied from aircraft batteries or a ground power source through the starting and control equipment. The unit drives the engine or APU rotor through its mechanical connection to the accessory gearbox. In this mode, the series winding is used to provide high starting torque. On Mi-8T and Mi-8AT helicopters, the starter-generator is associated with TV2-117 engines, with one unit installed for each engine. The same general principle applies on aircraft APU installations where the unit is used to start an auxiliary turbine unit.

Generator mode of the GS-18TO unit

After the engine or APU reaches the required operating condition, the GS-18TO changes function and operates as a DC generator for the aircraft electrical network. The generator output is regulated through the RN-180 voltage regulator, while connection to the onboard power bus is controlled through protection and switching equipment such as the DMR-600T differential-minimum relay. In this configuration, the unit supplies the 28.5 V DC network and works as part of the aircraft power generation chain. Faults in this area may involve the starter-generator, but also the regulator, relay, wiring, terminals, brush assembly, or load circuits.

Aircraft and engine application of GS-18TO

The GS-18TO, together with related GS-18T and GS-18MO modifications, is used on several Soviet aircraft and helicopter installations. On Mi-8 family helicopters, including Mi-8T and Mi-8AT, it is fitted to TV2-117 series engines, including TV2-117A and TV2-117AG versions. On An-24, An-26 and An-30 aircraft, the unit is associated with the RU19A-300 auxiliary turbojet engine installed in the right nacelle. On An-32 aircraft, it is used with the TG-16M turbogenerator unit, which supports autonomous starting of the AI-20 main engines and ground power supply.

Maintenance and identification of GS-18TO

The GS-18TO requires regular inspection as part of aircraft electrical and engine maintenance. Typical work includes checking the commutator and brush assembly, terminals, insulation condition, bearing condition, cooling air path, and the mechanical drive connection. Aviation carbon brushes of the correct type, including 8A5.593.088 where applicable, should be matched to the maintenance documentation. Before ordering, the marking on the unit should be checked against the aircraft parts catalog, engine documentation, or repair records. The product is also known under alternative designations GS-18TO and ГС-18ТО.

Product Type: DC starter-generator
Function: Engine or APU starting; DC power generation for onboard electrical network
Application / Where Used: Aircraft and helicopter DC power supply and starting systems
System / Installation Area: Engine accessory gearbox / APU drive / aircraft DC electrical system
Compatible Aircraft / Equipment: Mi-8T, Mi-8AT, An-24, An-26, An-30, An-32
Associated Engines / Units: TV2-117, TV2-117A, TV2-117AG, RU19A-300, TG-16M
Related Modifications: GS-18T, GS-18MO
Electrical Machine Type: Six-pole DC machine with shunt excitation
Generator Mode Rated Power: 18 kW
Starter Mode Power: Up to 26 kW on engine shaft
Onboard Network Voltage: 28.5 V DC
Cooling Type: Forced air cooling
Rotation Direction: Left-hand rotation, viewed from drive side
Length: 430 mm
Housing Diameter: 180–190 mm
Mounting Type: Flanged mounting with quick-release band clamp
Weight: 42 kg ±1 kg
Main Terminals: “Я” armature; “Ш” shunt/excitation winding; “С” series winding; корпус/ground
Associated Control Equipment: RN-180 voltage regulator; DMR-600T differential-minimum relay
Service Items: Commutator and brush assembly; aviation carbon brushes, including 8A5.593.088 where applicable
Technical Documentation: Aircraft and engine maintenance documentation; product passport and repair documentation

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