The powerplant is the part of an aircraft's propulsion system that produces the thrust and mechanical energy required for flight and for running the systems that support the aircraft. Whether the airplane is driven by a reciprocating engine turning a propeller or by a turbojet or turbofan accelerating a stream of air, the engine by definition makes the airplane.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is a powerplant in an aircraft?
A powerplant in an aircraft is the complete propulsion system that develops the mechanical force to power the aircraft. The powerplant is the combination of engine and propeller, or the engine alone in jet installations, together with every part necessary for propulsion and every unit that affects the control or safety of the major propulsive units. Thus, while the engine itself is the part that develops shaft horsepower or thrust, the broader powerplant installation includes accessories, controls, fire zones, and all related systems that support the operation of the aircraft.
An aircraft engine is a propulsion system for an aircraft, and the engine powers the aircraft. The powerplant produces thrust, and aircraft engines are almost always either lightweight piston engines or gas turbines. A reciprocating engine is the most common powerplant among general aviation, while some aircraft utilize gas-turbine engines. Engines can be placed on the front of an aircraft, which is typical, or on the back, which is atypical.
What is the function of an airplane powerplant?
The function of an aircraft powerplant is to provide mechanical force to power the aircraft and the accessories necessary for flight. It produces thrust to propel the aircraft and drives the various systems that support its operation. While the engine is running it drives an alternator which produces electricity to recharge the batteries and supplies the aircraft's systems. Reciprocating engines work in combination with a propeller to produce thrust: the engine power rotates the propeller, which converts the rotational motion into thrust.
Turboprop engines work in combination with a propeller, using a gas turbine to drive the propeller through a reduction gear assembly. Turbojet and turbofan engines produce thrust by increasing the velocity of the air flowing through the engine: the compressor increases the pressure of the incoming air, the combustion section adds heat energy by igniting the fuel-air mixture, and the turbine extracts power from the expanding exhaust gases to drive the compressor while the exhaust nozzle accelerates the exhaust to create thrust. Thus, whether by turning a propeller or expelling high-velocity exhaust, the powerplant supplies the force that moves the airplane through the air.
What are the parts of an airplane powerplant?
The parts of an airplane powerplant are listed below.
- Carburetors
- Engine mounts
- Cylinders
- Pistons
- Power assembly
- Gas generator (core)
- Crankcase
- Valves
- Reduction gear assembly
- Combustor
- Air inlet
- Exhaust
- Fuel system
- Turbines/exhaust
- Connecting rods
- Propeller
- Valve-operating mechanism
- Magnetos
- Nacelle
- Hydraulic pumps
- Ignition system
- Starter
- Torque-meter assembly
- Crankshaft
- Compressor
- Accessory drive
- Vacuum pumps
- Generator
- Pneumatic pumps
- Tachometer drive
An airplane powerplant is the complete engine installation and its immediate supporting systems. The Federal Aviation Administration groups this hardware under PA.I.G.K1c. In a reciprocating engine the core assembly comprises the crankcase, cylinders, pistons, connecting rods, valves, valve-operating mechanism and crankshaft. The accessory section bolted to the crankcase carries magnetos, carburetors, starter, generator, tachometer drive, fuel pump, oil pump and vacuum pump. Electrical wiring, bus-bar fuses and circuit breakers complete the engine's accessories. Engine mounts - either integral lugs on the crankcase or detachable struts - attach the entire engine assembly to the fuselage or wing nacelle, while the cowling streamlines the installation and ducts cooling air across cylinder heads and exhaust valves.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
Turbine powerplants divide the same functions between a cold section and a hot section. The cold section contains the air inlet, fan, compressor and diffuser while the hot section houses the combustion chambers, turbine, exhaust and optional afterburner. Together these stages form the gas generator, the most fundamental part of any turbine engine. A turboprop adds a power turbine and reduction gear assembly that converts the gas generator's high-rpm, low-torque output into low-rpm, high-torque shaft power that turns the propeller. Because the propeller itself produces thrust, the FAA treats it as part of the powerplant. Its governor maintains constant rpm and its pitch change mechanism absorbs the engine's brake horsepower and converts it into thrust horsepower.
Regardless of engine type, the powerplant installation always includes the fuel system that delivers metered fuel, the oil lubrication system that supplies oil to bearings, gears, pistons and valve trains, and the induction system that brings filtered air to the cylinders or compressor. Instrumentation required by the FAA - tachometer, manifold-pressure gauge, exhaust-gas and cylinder-head temperature gauges, oil pressure and temperature gauges, fuel-flow and turbine-inlet temperature displays - are likewise deemed powerplant components.
What is the difference between a powerplant and an engine in aviation?
The difference between a powerplant and an engine in aviation is that an engine is the mechanical assembly that converts fuel into rotating power whereas a powerplant is that engine plus every item the airframe needs to make the power useful - mounts, cowling, ducts, exhaust, and, on piston airplanes, the propeller.
When the airplane is driven by a turbojet, the distinction collapses because the engine itself produces thrust directly, so engine and powerplant are used interchangeably.A reciprocating engine develops only shaft horsepower; it must be paired with an additional means - propeller, fan, or helicopter rotor - to turn that rotation into thrust. Therefore, the piston engine is only one part of the reciprocating powerplant that dominates general aviation.
Approved mechanics hold a powerplant license, authorizing work not just on the engine block but on the complete propulsion unit, including propeller controls, reduction gears, and accessories.
What are the types of aircraft powerplants?
The types of aircraft powerplants are listed below.
- Piston Engine is a type of aircraft powerplant
- Turboprop Engine is a type of aircraft powerplant
- Turbojet Engine is a type of aircraft powerplant
- Turbofan Engine is a type of aircraft powerplant
- Turboshaft Engine is a type of aircraft powerplant
The main types of aircraft engines are piston, turboprop, turbojet, turbofan and turboshaft. Atmospheric air is used for propulsion in every type of aircraft powerplant except rockets. Most aircraft engines are either piston engines or gas turbines. Gas turbine engines include turbofan, turboprop, turboshaft and turbojet. A reciprocating engine uses one or more reciprocating pistons to convert high temperature and high pressure into rotating motion. Piston engines are known for reliability and efficiency. Turbojet engines are known for high-speed capability but have low fuel efficiency. Turbojet engines were used in early commercial jets. Turboprop engines turn a propeller through a speed reduction gear box. Turboprop engines power Beechcraft King Air 350. Turboshaft engines have higher power-to-weight ratio than piston engines. Turbofan engines provide better fuel efficiency and reduced noise levels and power Boeing 777 and Airbus A320.
Which powerplants are selected for various aircraft speeds?
Below 250 mph (402.3 km/h) the reciprocating powerplant is chosen because its efficiency is excellent and its cost is low. In the speed range 180 to 350 mph (290 to 563 km/h) the turboprop engine performs very well, so it is the usual choice for low-speed transport aircraft.
From 350 mph (563.27 km/h) up to Mach 0.8-0.9 turbofan engines are generally used for airline operations. They provide a higher maximum speed than reciprocating or turboprop powerplants. High-bypass turbofans are reserved for efficiency on commercial aircraft, while low-bypass turbofans are typically used for high-speed aircraft like military fighters. Aircraft intended to operate at Mach 1 or higher are powered by pure turbojets, afterburning turbojets, or low-bypass turbofans. For higher supersonic speeds the turbojet remains a viable option. It outperforms the reciprocating powerplant to the right of line D, the turboprop to the right of line E, and the turbofan to the right of line F.
