An aircraft may appear similar from the outside, but what powers it can be completely different. The engine determines how fast an aircraft flies, how much fuel it consumes, how much weight it can carry and even the airports it can operate from.
Over the past century, aircraft engines have evolved from simple piston-powered systems to highly efficient turbofan engines capable of flying more than 16 hours without stopping. At the same time, specialised engines continue to power regional aircraft, helicopters and military fighters.
Here's a closer look at the major types of aircraft engines and why each serves a unique purpose.
An aircraft engine does far more than generate thrust. It influences:
Aircraft manufacturers select engine types based on an aircraft's intended role rather than using a one-size-fits-all solution.
As airlines seek to lower fuel consumption and carbon emissions, engine manufacturers continue investing in more efficient designs and alternative aviation fuels.
The piston engine is the oldest aircraft engine still in widespread use.
Its operating principle is similar to a conventional automobile engine. Fuel burns inside cylinders, pushing pistons connected to a crankshaft. The crankshaft rotates a propeller, generating thrust.
A piston engine contains components including:
These engines are commonly found in:
Two common piston engine designs are based on the Otto cycle and diesel cycle.
Although piston engines are reliable and relatively inexpensive to operate, they are best suited to lower speeds and shorter flights.
Commercial aviation entered a new era when turbine engines became practical during the twentieth century.
Unlike piston engines, turbine engines compress incoming air before mixing it with fuel inside a combustion chamber.
The combustion process produces high-energy gases, which spin turbine blades. These turbines power the compressor while creating thrust to propel the aircraft forward.
Compared with piston engines, turbine engines offer:
Today, almost every modern airliner relies on a turbine-based engine.
The turbofan is the most widely used aircraft engine in commercial aviation.
Its most recognisable feature is the large fan at the front of the engine. Rather than relying solely on hot exhaust gases, the fan moves enormous volumes of air around the engine core.
Most of this airflow bypasses the combustion chamber, producing thrust more efficiently than older jet engines.
Modern turbofan engines power aircraft including:
Manufacturers continue increasing fan diameters because larger fans generally improve fuel efficiency and reduce operating costs.
One of the most striking examples is the Boeing 777X, whose GE9X engines have one of the largest fan diameters ever fitted to a commercial aircraft.
At first glance, a turboprop resembles a piston-powered aircraft because both use visible propellers.
The similarity ends there.
A turboprop is a turbine engine that directs most of its power to spinning a propeller rather than generating jet thrust.
This makes turboprops particularly efficient on shorter routes where high cruising speeds are less important.
They are widely used by:
Popular turboprop aircraft include the ATR 72 and De Havilland Dash 8 families.
These aircraft can operate from shorter runways while consuming less fuel than comparable regional jets on many sectors.
The turboshaft shares many design features with the turboprop.
Instead of driving a propeller, however, it transfers power through a shaft to rotate helicopter rotor blades.
Its compact size and high power output make it ideal for helicopters performing a wide range of missions, including:
Nearly all modern medium and large helicopters rely on turboshaft engines.
The turbojet was the first practical jet engine used in commercial aviation.
Unlike a turbofan, it generates almost all of its thrust from high-speed exhaust gases leaving the engine.
Turbojets deliver exceptional speed but consume considerably more fuel and produce significantly more noise than modern turbofans.
For these reasons, they have largely disappeared from commercial passenger aviation.
They remain suitable for applications where speed is the highest priority, particularly certain military aircraft.
Modern airlines overwhelmingly favour turbofan engines because they provide the best balance between performance and efficiency.
Compared with earlier jet engines, turbofans offer:
As global passenger traffic continues to grow, improvements in engine technology are becoming increasingly important for airlines seeking to reduce both costs and emissions.
Manufacturers are also developing engines capable of operating with higher blends of sustainable aviation fuel while exploring future propulsion technologies.
No single aircraft engine is suitable for every aircraft.
A small training aircraft requires a lightweight piston engine. A regional airline benefits from fuel-efficient turboprops. Long-haul passenger aircraft depend on high-bypass turbofans, while helicopters require turboshaft engines to power their rotor systems.
Each design has evolved to meet a specific operational need.
As aviation moves towards cleaner propulsion and greater efficiency, aircraft engines will continue to evolve. Yet the basic objective remains unchanged: delivering safe, reliable and efficient flight for every mission, whether it is a 30-minute regional journey or a non-stop flight across continents.
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