Types of Aircraft Engines: A Complete Guide to Principles and Performance

Ever since the Wright brothers created the small piston engines that powered their aircraft, engines have continually evolved, giving rise to powerful turbines and components for electric engines.

Aircraft have always been accompanied by engines, and ever since the very first engines. Each of them has its own fuel usage, performance, and speed. The wrong selection of engines can lead to increased cost, weak performance, or reduced range. So, let’s explore different Types of Aircraft Engines, explaining the workings, their major benefits, and applications. So, keep reading!

Understanding the Classification of Aircraft Engines

The types of aircraft engines are categorised into two groups of air-breathing and non-air-breathing engines. 

The air-breathing engines, such as piston engines, turboprop engines, turbojet engines, turbofan engines, turboshaft engines and ramjet engines, intake atmospheric air and run the processes of compressing it, fuel mixing, and the last step igniting to produce thrust. They require their environment and are non-operational in space.

Non-air-breathing engines, such as rocket engines, are aircraft engines that have an oxidiser and fuel on them, which allows them to operate in high altitudes and in space. Spacecraft are their major application, and their limited durations of operations are proportional to high fuel usage.

Moreover, engines can also be grouped according to the means of propulsion. Piston, electric, and turboprop engines are all propeller-driven, as are electric and turboprop engines, which function well at lower and medium speeds. 

Well, for higher speeds and longer distances, jet engines (turbofan, turbojet, ramjet) accelerate air and exhaust gases. Quiet and emission-free electric fuel motors are currently found in smaller drones and aircraft.

The type of aircraft engine to use is often dictated by the task at hand. Aimed at shorter distances, electric and piston engines are more effective. For regional routes, turboprops are the preferred choice, while long-haul airliners rely on turbofans. Supersonic flights or space travel mandate the use of specialised jets or rockets. 

All classes are made to achieve the maximum effectiveness in set conditions. Let’s discuss one by one.

Piston Engines

Piston or reciprocating engines are engines which are widely known as power sources in the aircraft industry. They are well accepted in the small aircraft markets due to their affordable price, ease of servicing, and dependable functionality.

Working Principle

A piston engine operates similarly to a car engine. Fuel and air are taken into the cylinder and mixed. A piston compresses the mixture, which is then ignited by a spark. The expanding gases burn the fuel and create an explosion, which forces the piston down. 

The piston’s up-and-down motion turns the crankshaft, which rotates the propeller to generate thrust. While the engine is running, this process is performed several times a second.

Common Designs

Inline engines: Cylinders arranged in a single straight line. This configuration is narrow in shape, but less efficient in cooling.

Radial engines: Cylinders arranged in a circle around the crankshaft. Known for excellent cooling and durability, especially in older aircraft.

Horizontally opposed engines:  Cylinders arranged facing each other. They are compact and well-balanced. And, these are most common in small modern aircraft.

Benefits

• Reduced acquisition and operational expenses

• Simpler repair and maintenance processes

• Effective fuel economy at low speeds and low altitudes

Drawbacks

• Comparatively lower power-to-weight ratio relative to turbine engines

• Reduced efficiency at higher speeds and altitudes

Examples in Use

The Cessna 172 and Piper Cherokee are well-known piston-engine aircraft. Cessnas are used widely for both training and touring flights. Cherokees are popular among private pilots. Their simple design and reliable performance ensure a lasting presence in general aviation.

Turboprop Engines

Turboprop engines are a mix of turbine and propeller-driven aircraft. Unlike purely propeller-driven aircraft, they use a gas turbine to drive a propeller, which is fed by a jet. This design makes putting in use for intermediate-range to regional travel aircraft more efficient as they focus on takeoff performance rather than speed.

Working Principle

A turboprop works by drawing air into the engine’s compressor, where it is compressed and mixed with fuel. This mixture is ignited in the combustion chamber, creating hot, high-pressure gases. These gases spin a turbine, which is connected to a reduction gearbox. 

The gearbox slows the turbine’s high rotation speed to a level suitable for driving the propeller efficiently. While a small amount of thrust comes from the exhaust, most of the propulsion is generated by the spinning propeller.

Advantages

• Excellent short-runway performance, allowing operation from smaller airports

• Very efficient at medium flight speeds (around 250–400 knots)

• Lower fuel consumption compared to jets on short and medium routes

• Lower top speed compared to pure jet engines

• Propeller and gearbox operation can increase noise in the cabin compared to jets

Applications

Turboprop engines are commonly found in the commuter and regional aircraft sector. The ATR 72 is well-known for short-haul routes in remote regions, while the Bombardier Q400 is appreciated for its performance and reliability for regional carriers.

Turbojet Engines

One of the pioneering jet engines and almost efficient jet engines is the Turbo Engine, having the capability to power an aircraft while creating thrust. Furthermore, these engines are very advantageous for excess speed and sharp thrust, which makes them instrumental for very rapid and fast flights.

How it Works

In the case of turbojets, air is drawn into the engine and processed with the aid of a multi-jet compressor. The resultant high-pressure air is also enriched and combined with hot combustion gases. The resultant high-temperature and pressure air expands rapidly. 

Well, the gases not only aid in turbine movement for the compressor, but also aid in filtering. The resultant gas jet, which is at this time moving at a very high speed, assists the aircraft in thrust. Thus, turbojets utilise the fast jet method of thrust production.

For enthusiasts and learners, building or studying a jet engine model can help visualize how air intake, compression, combustion, and exhaust work in a turbojet.

Benefits

• Obtaining and retaining the excess speed of the jet, and supersonic speed, is not a problem for the turbo engines.

• The turbine engine's mechanical structure is very simple, thus compact in size.

• High-excel aircraft are suited specifically for turbo engines, thus exploiting the compact size feature.

Disadvantages

• Fast-moving exhausts result in a turbo engine jet creating excess noise.

• The gas engines are extremely inefficient at lower speeds.

• In comparison to turboprop engines, speed is not a forte, thus resulting in stalling.

Turbofan Engines

Turbofan engines are now widely in use on commercial and military aircraft. They jet off turbo engines and are more fuel efficient and quieter, which makes them suitable for both short and long-distance flights.

How They Work

The front part of turbofan engines possesses a huge fan that pulls in a considerable amount of air. This air, which is in turn separated into 'bypass' air, partially circulates around the engine core, and the rest goes into the core, where it is compressed, combusted with fuel, and burnt. 

After combusting hot gas, it goes through the turbine, which also drives the fan and the compressor. The bypass air also provides cooling and significant quieting of the exhaust while providing thrust.

High-Bypass vs. Low-Bypass

High bypass turbofans: In commercial airliners like the Boeing 787 and Airbus A350, these provide the greatest use of thrust from bypass air. These are more fuel-efficient.

Low bypass turbofans: These are more compact and provide strong speed performance, making them common in military aircraft. These also provide more thrust from the engine core.

Benefits

• Outstanding fuel economy, particularly at subsonic speeds

• Less noisy than turbojets, thus more compatible with airports

• Best for heavy payloads and long-haul flights

At EngineDIY, we provide modern aviation with our detailed piston, turbofan, turboprop, and turboshaft aircraft engine model kits. They are ideal for aviation hobbyists, students, and collectors, as our models are based on the engineering processes of contemporary jetliners. 

EngineDIY aircraft engine models come with specially designed kits like the TECHING 1/10 Dual-Spool Turbofan Engine and SKYMECH Trent 900 to showcase the accuracy of modern engineering and operational realism. 

Turbofan engines consist of high-thrust generators like gas turbine cores and powerful front fans. Each turbofan engine model kit offers powerful aids to aid modellers understand modern aerospace technology and make a beautiful model. With EngineDIY, every kit is a hands-on exploration of engineering principles, and every model built is a work of art waiting to be finished.

Turboshaft Engines

Turboshaft engines are specialised gas turbine engines which provide power to a shaft rather than producing jet thrust. They are primarily found in helicopters, but have also been adapted in some ships and in certain auxiliary power units.

How They Work

Turboshafts share elements with turboprops in that a gas turbine power drives a shaft. Instead of a propeller, the shaft connects to the rotor of a helicopter or other equipment. Most of the engine power is allocated to turning the output shaft, with a small portion going to exhaust thrust.

Advantages

• For a given power output, the engine is lightweight, thus more ideal for airborne use.

• The engine has a high power-to-weight ratio, enabling helicopters to lift heavier payloads.

• Reliable and efficient across a wide range of conditions.

Applications

Modern helicopters are Turboshaft powered, for example, the Bell 407, which uses a Rolls-Royce 250-C47B engine and the Sikorsky UH-60 Black Hawk, powered by twin General Electric T700 engines. 

Black Hawk helicopters are noted for their exceptional lift and endurance, while the Bell 407 is praised for the smooth and efficient performance of the Rolls-Royce 250-C47B engine.

Ramjet Engines

Ramjet engines are designed for high-speed flight and offer simple and lightweight propulsion. In contrast to other jet engines, they do not feature a compressor or turbine. Rather, these engines use the forward motion of the aircraft to compress the incoming air.

How They Work

The high-speed movement of the aircraft compresses air, which enters the engine inlet through the shape of the intake. In the combustion chamber, the compressed air is mixed with fuel and undergoes combustion, producing high-pressure exhaust gases that exit through the nozzle. Thrust is created, and the ramjet becomes more efficient as the aircraft accelerates.

Advantages

• Outstanding performance at supersonic speeds.

• Lightweight with no rotating components

• Simple construction compared to other jet engines

Drawbacks

• The initial speed required for operation must come from a booster or another engine

• Subsonic speeds become inefficient

• Only designed for high-speed use

Use Cases

The ramjet is utilised within the MBDA Meteor missile and is designed into high-speed and hypersonic research aircraft as well as test vehicles.

Rocket Engines

Rocket engines are one of the most powerful propulsion systems. They can operate within the Earth’s atmosphere and in the vacuum of space. In addition, they have a fuel tank and a separate oxidiser tank. Well, rocket engines do not depend on the atmosphere for oxygen during combustion, as air-breathing engines do.

How They Work

A solid or liquid propellant, which consists of fuel and an oxidiser, is stored in a combustion chamber. A rocket engine burns the propellant, which releases extremely hot and fast gas. The exhaust gas grows exhaustively and is expelled from a nozzle. This reaction produces powerful torque and propels the rocket, fulfilling Newton’s third law.

Advantages

• An operator unable to perform in space or at extremely high altitudes where air is present.

• Expectant extremely high torque output relative to other types of propulsion.

• Flexible fuel types, solid, liquid, or hybrid propellant.

Drawbacks

• Efficiency is outperformed by heavy fuel consumption.

• Limited propellant reserve leading to short operational duration.

• In high cost of operation and manufacturing.

Electric Motors for Aircraft

Electric motors for aircraft are an innovative type of propulsion technology which substitutes combustion engines with electric engines. They transform energy from batteries and hybrid-electric setups into electric motors, which drive propellers and ducted fans.

How They Work

Electric aircraft engines operate by storing energy in batteries or via hybrid-electric systems. The electric power strengthens an electric motor, which in turn rotates a fan or propeller for thrust production. Compared to fuel-based engines, this approach is far more efficient in the way of the mechanical systems involved. For learners, building an electric engine model can help visualize how battery power is converted into thrust.

Advantages

• No emissions during flight, resulting in lower environmental damage.

• Less noise, appropriate for short and urban flights.

• Less maintenance due to reduced moving mechanical systems, no combustion, and no fuel involved.

Drawbacks

• Less efficient range because of current battery energy density limits.

• Compared to refuelling, charging takes longer.

• Decreased fuel limit capacity while carrying heavier battery packs.

Examples

Electric propulsion systems are already in use, for example, the Pipistrel Velis Electro, which is the world’s first certified electric plane and the Eviation Alice prototype, which is meant for regional and training flights.

The Future of Aircraft Engines

To be honest, the performance, efficiency, and sustainability goals of aircraft engines have regions of improvement. One prospective option is hybrid-electric propulsion, which merges turbines with simpler electric engines, alleviating the fuel and emission footprints on a regional scale.

Short to medium-haul flights can be fueled without the emission of carbon using pollution-free hydrogen fuel cells. Though a carbon-less alternative, a complete overhaul of refuelling stations would be required. Moreover, SAF is an alternative which can be implemented without altering the existing infrastructure, since it can be used with current engines.

The patented open-rotor and ultra-high-bypass engines can move greater amounts of air at lower speeds than is currently possible and would require to burn lesser fuel. So, integrating all the technologies would provide the air travel industry with the ability to drastically enhance efficiency.

Conclusion

Alright! There are turbojets and turbofans, turboprops, turboshafts, ramjets, scramjets, piston engines and electric motor engines; each has its own advantages. Depending on the mission, which could be efficiency, power, or speed, you can decide the best option. 

Well, the future of aviation is shaped by new technologies such as hybrid-electric systems, hydrogen fuel cells, and new designs. These innovations will transform the next generations of flight and the manner of travelling in the skies. Once again, if you want any type of Aircraft engine model, then Enginediy is a go-to choice. Good luck!