turboshaft

A turboshaft is a type of gas turbine engine designed primarily to produce shaft power rather than jet thrust. It consists of a gas generator, which includes a compressor, a combustor, and a turbine, and a power turbine that drives an output shaft. The exhaust remains hot and contributes only a small amount of thrust compared with other gas-turbine configurations.

How it works is similar to other gas turbines: air is compressed, mixed with fuel and burned in the combustor, and the resulting high-energy gases expand through turbines. The gas-generator turbines power the engine’s core, while energy is extracted by the separate power turbine to turn a shaft connected to a load, such as a helicopter rotor or a ship propeller. The output shaft often requires reduction gearing to match the speed and torque needs of the driven device.

Configurations vary. Many turboshafts use a free-turbine arrangement where the power turbine is on its own shaft and is not mechanically connected to the gas-generator turbine, allowing independent speeds and easier starting and control. Some designs employ gearing or direct-drive to deliver higher torque at lower rotor speeds. Multi-spool layouts can improve efficiency and response. In helicopters, the turboshaft provides a high power-to-weight ratio; in ships and industrial settings, it can drive generators or other heavy loads.

Applications and history: Turboshafts were developed in the mid-20th century to meet the demand for compact, high-power propulsion without large, heavy engines. They are widely used in rotorcraft and also serve in naval propulsion, electrical power generation, and other stationary power applications where reliable, quickly responsive shaft power is required.