Aircraft engine types have gotten bigger and better, aircraft engine is the power component of an aircraft propulsion system. Most aircraft engines are either piston engines or gas turbines, although a few have been rocket powered and in recent years many small UAVs have used electric motors.
In commercial aviation the major Western manufacturers of turbofan engines are Pratt & Whitney (a subsidiary of Raytheon Technologies), General Electric, Rolls-Royce, and CFM International (a joint venture of Safran Aircraft Engines and General Electric). Russian manufacturers include the United Engine Corporation, Aviadvigatel and Klimov. Aeroengine Corporation of China was formed in 2016 with the merger of several smaller companies.
The largest manufacturer of turboprop engines for general aviation is Pratt & Whitney. General Electric announced in 2015 entrance into the market.
1- Shaft engines
Reciprocating (piston) engines
Inline engine refers only to engines with a single row of cylinders, as used in automotive language, but in aviation terms, the phrase “inline engine” also covers V-type and opposed engines, and is not limited to engines with a single row of cylinders. This is typically to differentiate them from radial engines.
Cylinders in this engine are arranged in two in-line banks, typically tilted 60–90 degrees apart from each other and driving a common crankshaft. The vast majority of V engines are water-cooled. The V design provides a higher power-to-weight ratio than an inline engine, while still providing a small frontal area.
2- Horizontally opposed engine
A horizontally opposed engine, also called a flat or boxer engine, has two banks of cylinders on opposite sides of a centrally located crankcase. The engine is either air-cooled or liquid-cooled, but air-cooled versions predominate.
H configuration engine
An H configuration engine is essentially a pair of horizontally opposed engines placed together, with the two crankshafts geared together.
This type of engine has one or more rows of cylinders arranged around a centrally located crankcase. Each row generally has an odd number of cylinders to produce smooth operation.
A radial engine has only one crank throw per row and a relatively small crankcase, resulting in a favorable power-to-weight ratio. Because the cylinder arrangement exposes a large amount of the engine’s heat-radiating surfaces to the air and tends to cancel reciprocating forces, radials tend to cool evenly and run smoothly.
The lower cylinders, which are under the crankcase, may collect oil when the engine has been stopped for an extended period.
Rotary engines have the cylinders in a circle around the crankcase, as in a radial engine, but the crankshaft is fixed to the airframe and the propeller is fixed to the engine case, so that the crankcase and cylinders rotate.
The advantage of this arrangement is that a satisfactory flow of cooling air is maintained even at low airspeeds, retaining the weight advantage and simplicity of a conventional air-cooled engine without one of their major drawbacks.
The Wankel is a type of rotary engine. The Wankel engine is about one half the weight and size of a traditional four-stroke cycle piston engine of equal power output, and much lower in complexity.
In an aircraft application, the power-to-weight ratio is very important, making the Wankel engine a good choice. The Wankel engine does not seize when overheated, unlike a piston engine. This is an important safety factor for aeronautical use.
The most common combustion cycle for aero engines is the four-stroke with spark ignition. Two-stroke spark ignition has also been used for small engines, while the compression-ignition diesel engine is rarely used.
In general, Diesel engines are more reliable and much better suited to running for long periods of time at medium power settings. The lightweight alloys of the 1930s were not up to the task of handling the much higher compression ratios of diesel engines, so they generally had poor power-to-weight ratios and were uncommon for that reason.
Improvements in Diesel technology in automobiles (leading to much better power-weight ratios), the Diesel’s much better fuel efficiency and the high relative taxation of AVGAS compared to Jet A1 in Europe have all seen a revival of interest in the use of diesels for aircraft.
3- Power turbines
While military fighters require very high speeds, many civil airplanes do not. Yet, civil aircraft designers wanted to benefit from the high power and low maintenance that a gas turbine engine offered.
Thus was born the idea to mate a turbine engine to a traditional propeller. Because gas turbines optimally spin at high speed, a turboprop features a gearbox to lower the speed of the shaft so that the propeller tips don’t reach supersonic speeds.
Often the turbines that drive the propeller are separate from the rest of the rotating components so that they can rotate at their own best speed (referred to as a free-turbine engine).
A turboprop is very efficient when operated within the realm of cruise speeds it was designed for, which is typically 200 to 400 mph (320 to 640 km/h).
Turboshaft engines are used primarily for helicopters and auxiliary power units. A turboshaft engine is similar to a turboprop in principle, but in a turboprop the propeller is supported by the engine and the engine is bolted to the airframe: in a turboshaft, the engine does not provide any direct physical support to the helicopter’s rotors.
The rotor is connected to a transmission which is bolted to the airframe, and the turboshaft engine drives the transmission. The distinction is seen by some as slim, as in some cases aircraft companies make both turboprop and turboshaft engines based on the same design.
A number of electrically powered aircraft, such as the QinetiQ Zephyr, have been designed since the 1960s. Some are used as military drones. In France in late 2007, a conventional light aircraft powered by an 18 kW electric motor using lithium polymer batteries was flown, covering more than 50 kilometers (31 mi), the first electric airplane to receive a certificate of airworthiness.
On 18 May 2020, the Pipistrel E-811 was the first electric aircraft engine to be awarded a type certificate by EASA for use in general aviation. The E-811 powers the Pipistrel Velis Electro.
Reaction engines generate the thrust to propel an aircraft by ejecting the exhaust gases at high velocity from the engine, the resultant reaction of forces driving the aircraft forwards.
The most common reaction propulsion engines flown are turbojets, turbofans and rockets. Other aircraft engine types such as pulsejets, ramjets, scramjets and pulse detonation engines have also flown.
In jet engines the oxygen necessary for fuel combustion comes from the air, while rockets carry oxygen in some form as part of the fuel load, permitting their use in space.
4- Jet turbines
A turbojet is a type of gas turbine engine that was originally developed for military fighters during World War II. A turbojet is the simplest of all aircraft gas turbines.
It consists of a compressor to draw air in and compress it, a combustion section where fuel is added and ignited, one or more turbines that extract power from the expanding exhaust gases to drive the compressor, and an exhaust nozzle that accelerates the exhaust gases out the back of the engine to create thrust.
A turbofan engine is much the same as a turbojet, but with an enlarged fan at the front that provides thrust in much the same way as a ducted propeller, resulting in improved fuel efficiency.
Though the fan creates thrust like a propeller, the surrounding duct frees it from many of the restrictions that limit propeller performance. This operation is a more efficient way to provide thrust than simply using the jet nozzle alone, and turbofans are more efficient than propellers in the transsonic range of aircraft speeds and can operate in the supersonic realm.
A turbofan typically has extra turbine stages to turn the fan.
Rocket engines are not used for most aircraft as the energy and propellant efficiency is very poor, but have been employed for short bursts of speed and takeoff. Where fuel/propellant efficiency is of lesser concern, rocket engines can be useful because they produce very large amounts of thrust and weigh very little.
Precooled jet engines
It is thought that this design of engine could permit sufficient performance for antipodal flight at Mach 5, or even permit a single stage to orbit vehicle to be practical. The hybrid air-breathing SABRE rocket engine is a pre-cooled engine under development.
The 2.87 m diameter, 16-blade fan gives a 33.7 ultra-high bypass ratio, driven by a geared low-pressure turbine but the high-pressure compressor drive comes from a piston-engine with two 10 piston banks without a high-pressure turbine, increasing efficiency with non-stationary isochoric-isobaric combustion for higher peak pressures and temperatures. The 11,200 lb (49.7 kN) engine could power a 50-seat regional jet.
The World’s Most Powerful Aircraft Engines
When it comes to making a new aircraft, engine design is at the top of the list for any manufacturer. Powerful and efficient engines can allow aircraft to travel longer distances with a lower fuel burn, a key factor for airlines.
As expected, the most powerful commercial plane engines are found on widebody aircraft. The most powerful engines are also found on twin-engine jets rather than four-engine ones due to the need for more thrust on twin-engine planes.
General Electric GE9X
The current leader in the engine market is the upcoming GE Aviation GE9X. While not in commercial service yet, the engine will feature on the upcoming Boeing 777X and has already flown a number of test flights. The engine is based on the design of the GE90, which is found on the older 777.
General Electric GE90 series
Coming in at second place is another GE engine, the GE90, which can be found on the popular 777 aircraft lineup.
The engine first came into service in 1995 with British Airways’ 777-200s. As the 777 family grew, so did the GE90 variants, with the third-generation engines being the most powerful to date. These are the GE90-115B and -110B, which are found on the 777-300ER and 777-200LR and 777F, respectively.
Pratt & Whitney PW4000-112
Pratt & Whitney makes it to the list of most powerful engines in the world with its popular PW4000 series, which is found on the Airbus A330, Boeing 767, and 747, was also re-engineered for the 777.
Rolls-Royce Trent XWB
Next on the list is the Rolls-Royce Trent XWB, exclusively powering the popular Airbus A350 model. There are two variants of this engine in service, the XWB-84 and XWB-97, which power the A350-900 and A350-1000, respectively. The engine came into service in 2015 with Qatar Airways on the first A350.
Rolls-Royce Trent 800
The Trent 800 was Rolls-Royce’s engine offering for the Boeing 777. The engine first came into service with Thai Airways in 1996, the last of the three engine providers for the first-generation 777.