Turboshaft in the context of Shaft horsepower

A gas turbine engine, or, informally, a gas turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the direction of flow:

• a rotating gas compressor
• a combustor
• a compressor-driving turbine.

Additional components have to be added to the gas generator to suit its application. Common to all is an air inlet but with different configurations to suit the requirements of marine use, land use or flight at speeds varying from stationary to supersonic. A propelling nozzle is added to produce thrust for flight. An extra turbine is added to drive a propeller (turboprop) or ducted fan (turbofan) to reduce fuel consumption (by increasing propulsive efficiency) at subsonic flight speeds. An extra turbine is also required to drive a helicopter rotor or land-vehicle transmission (turboshaft), marine propeller or electrical generator (power turbine). Greater thrust-to-weight ratio for flight is achieved with the addition of an afterburner.

A turbine–electric transmission, or turbine–electric powertrain, system includes a turboshaft gas turbine connected to an electrical generator, creating electricity that powers electric traction motors. No clutch is required.

Turbine–electric transmissions are used to drive both gas turbine locomotives (rarely) and warships.

The turbojet is an airbreathing jet engine which is typically used in aircraft. It consists of a gas turbine with a propelling nozzle. The gas turbine has an air inlet which includes inlet guide vanes, a compressor, a combustion chamber, and a turbine (that drives the compressor). The compressed air from the compressor is heated by burning fuel in the combustion chamber and then allowed to expand through the turbine. The turbine exhaust is then expanded in the propelling nozzle where it is accelerated to high speed to provide thrust. Two engineers, Frank Whittle in the United Kingdom and Hans von Ohain in Germany, developed the concept independently into practical engines during the late 1930s.

Turbojets have poor efficiency at low vehicle speeds, which limits their usefulness in vehicles other than aircraft. Turbojet engines have been used in isolated cases to power vehicles other than aircraft, typically for attempts on land speed records. Where vehicles are "turbine-powered", this is more commonly by use of a turboshaft engine, a development of the gas turbine engine where an additional turbine is used to drive a rotating output shaft. These are common in helicopters and hovercraft.

The Hughes/McDonnell Douglas/Boeing AH-64 Apache (/əˈpætʃi/ ə-PATCH-ee) is an American twin-turboshaft attack helicopter with a tailwheel-type landing gear and a tandem cockpit for a crew of two. Nose-mounted sensors help acquire targets and provide night vision. It carries a 30 mm (1.18 in) M230 chain gun under its forward fuselage and four hardpoints on stub-wing pylons for armament and stores, typically AGM-114 Hellfire missiles and Hydra 70 rocket pods. Redundant systems help it survive combat damage.

The Apache began as the Model 77 developed by Hughes Helicopters for the United States Army's Advanced Attack Helicopter program to replace the AH-1 Cobra. The prototype YAH-64 first flew on 30 September 1975. The U.S. Army selected the YAH-64 over the Bell YAH-63 in 1976, and later approved full production in 1982. After acquiring Hughes Helicopters in 1984, McDonnell Douglas continued AH-64 production and development. The helicopter was introduced to U.S. Army service in April 1986. The advanced AH-64D Apache Longbow was delivered to the Army in March 1997. Production has been continued by Boeing Defense, Space & Security. As of March 2024, over 2,700 Apaches have been delivered to the U.S. Army and 18 international partners and allies.

The Light Observation Helicopter (LOH) program was a United States Army program to evaluate, develop and field a light scout helicopter to replace the Army's aging Bell OH-13 Sioux. It gained impetus with the advent of the Vietnam War, and was aided by advances in helicopter technology, specifically the development of the turboshaft engine.

The Rolls-Royce Spey (company designations RB.163 and RB.168 and RB.183) is a low-bypass turbofan engine originally designed and manufactured by Rolls-Royce that has been in widespread service for over 40 years. A co-development version of the Spey between Rolls-Royce and Allison in the 1960s is the Allison TF41.

Intended for the smaller civilian jet airliner market when it was being designed in the late 1950s, the Spey concept was also used in various military engines, and later as a turboshaft engine for ships known as the Marine Spey, and even as the basis for a new civilian line, the Rolls-Royce RB.183 Tay.