Aircraft engines are the powerhouse behind propelling various types of airplanes across the skies. They come in several forms, each with their unique characteristics and applications. As technology advances, engineers continue to develop innovative and efficient propulsion systems to meet the demands of modern air travel. This article will explore some of the most common types of aircraft engines, including piston, turboprop, turbofan, and turbojet engines.

Piston engines, also known as reciprocating engines, have been widely used since the early days of aviation. They are internal combustion engines that typically use gasoline or avgas as fuel. These engines power propellers, converting the linear motion of pistons into rotational motion, allowing aircraft to take flight. Piston engines are known for their reliability, affordability, and ease of maintenance, making them popular choices for general aviation and smaller aircraft.

On the other hand, turbine engines, including turboprop, turbofan, and turbojet engines, dominate the world of commercial and military aviation. These engines function by using the exhaust gases generated by burning fuel to spin turbines, which, in turn, drive the propellers or fans. Each type showcases different features that cater to specific flight requirements – turboprops for efficient short-to-medium range flights, turbofans for quieter operation and reduced fuel consumption, and turbojets for supersonic speeds and high altitude capabilities. Dive into the world of aviation engines as we explore the specifics of each type and their unique contributions to aircraft propulsion.

Fundamentals of Aircraft Engines

Aircraft engines are critical components of an airplane’s propulsion system, providing the necessary power for flight. There are several types of aircraft engines, but this section will focus on two main types: Piston Engines and Gas Turbine Engines.

Piston Engine

Piston engines, also known as reciprocating engines, are often used in smaller, low to moderate-performance aircraft. These engines function by converting the linear motion of pistons into rotational motion, which is then used to drive a propeller and generate thrust. Piston engines are typically found in general aviation aircraft, such as the Piper Cherokee, which utilizes a 4-cylinder, 160 hp (119.3 kW) piston engine to drive a fixed-pitch propeller¹.

Some key features of piston engines include:

Internal combustion design
Often air-cooled
Utilize a propeller for thrust
Typically found in smaller aircraft

Gas Turbine Engine

Gas turbine engines are powerful, robust, and versatile, which makes them suitable for various types of aircraft. They operate on the principle of compressing air, introducing fuel, and then igniting the mixture to produce high-speed exhaust gases. These gases then provide the thrust required for flight. Some of the key types of gas turbine aircraft engines are Turbojets, Turboprops, and Turbofans.

Turbojets were the first type of gas turbine engines developed for aircraft. They produce thrust by expelling exhaust gases at high speeds out of the rear of the engine, through a suitably shaped propelling nozzle². Turbojets are mainly found on military and older commercial aircraft.

Turboprops combine the principles of the gas turbine and the propeller, by utilizing a turbine engine to drive a propeller for generating thrust. Turboprops are typically more fuel-efficient than piston engines and offer better performance in the 5,000 lb to 6,000 lb max takeoff weight range³. They are commonly found in regional and smaller commercial aircraft.

Turbofans are the most widely used type of engine in modern commercial aircraft. They are designed to produce additional thrust by utilizing a large fan at the front of the engine, which generates a bypass airflow around the core of the engine. This results in greater fuel efficiency and reduced noise levels.

Types of Aircraft Engines

In this section, we will discuss various types of aircraft engines, including Piston Engines, Turboprop Engines, Turboshaft Engines, Turbofan Engines, and Turbojet Engines. These engines power many different types of aircraft, from small private planes to large commercial jets.

Piston Engines

Piston engines are internal combustion engines that use reciprocating pistons to transmit power, and they are commonly used in smaller aircraft. The power generated by these engines is converted into thrust by an attached propeller. The arrangement of cylinders in these engines can vary, with one common configuration being the horizontally opposed engine, which typically has four to six cylinders lying flat and arrayed two or three on each side.

Turboprop Engines

Turboprop engines are turbine-based engines whose primary purpose is to drive a propeller. First developed in the 1930s, these engines became more popular in commercial aviation after World War II. Turboprop engines connect to a gearing system to turn a propeller, providing more efficient and powerful thrust for larger aircraft with propellers. Turboprop engines are often used in regional airliners and military aircraft.

Turboshaft Engines

Turboshaft engines are a type of gas turbine engine designed primarily to power helicopters and other rotary-wing aircraft. These engines work by transferring power from the gas producer section of the engine to the power turbine, which then drives the aircraft’s main rotor or other required mechanical loads. Turboshaft engines are fuel-efficient, lightweight, and provide significant power output for their size.

Turbofan Engines

Turbofan engines are the most common type of engine for commercial aircraft. They are a type of gas turbine engine that produces thrust by expelling a large volume of air at high speed, generated by a large fan at the front of the engine. Turbofan engines are quieter and more fuel-efficient than turbojet engines, making them ideal for modern air travel. Major Western manufacturers of turbofan engines include Pratt & Whitney, General Electric, Rolls-Royce, and CFM International.

Turbojet Engines

Turbojet engines are gas turbine engines that produce thrust by expelling exhaust gases at high speeds. These engines are less fuel-efficient than turbofan engines, but they can operate at higher speeds and altitudes. Turbojet engines were widely used in early jet aircraft, but they have been largely replaced by turbofan engines in commercial aviation due to their improved efficiency and noise reduction. However, turbojet engines are still used in some military aircraft and high-speed applications.

Components and Functioning

Aircraft engines come in various types, including piston, turboprop, turbofan, and others. This section focuses on the components and functioning of these engines, providing an overview of how they work to generate power and thrust in different ways.

Compressor

The compressor plays a crucial role in aircraft engines. It draws in air from the atmosphere and compresses it before sending it to the combustion chamber. Compressing the air increases its pressure and temperature, making it more suitable for combustion. In many engines, such as turbojets and turbofans, the compressor is typically composed of several stages with rotating and stationary blades.

Combustion Chamber

The combustion chamber is where fuel is mixed with the compressed air and ignited. The fuel-air mixture burns, producing a high-temperature, high-pressure gas. This energy-rich gas is then routed toward the turbine section of the engine.

Turbines

Turbines extract energy from the high-pressure gas generated in the combustion chamber. As the gas passes through the turbine blades, it causes them to spin, converting the gas’s kinetic energy into mechanical energy. This mechanical energy drives the compressor and, in some cases, a propeller or fan. The turbines also serve to reduce the pressure and temperature of the gas before it exits the engine through the exhaust nozzle.

Exhaust Nozzle

The exhaust nozzle is the final component of an aircraft engine, where the gas from the combustion process is expelled at high velocity. This high-speed exhaust generates thrust through Newton’s third law of motion (for every action, there’s an equal and opposite reaction), propelling the aircraft forward.

Fan and Bypass Air

In turbofan engines, the fan is a large, rotating component at the front of the engine. It functions as an additional compressor, drawing in more air than the core engine can process. This excess air, called bypass air, is accelerated around the core engine and expelled through a separate nozzle, generating additional thrust.

The fan and bypass air help improve engine efficiency by reducing the exhaust’s temperature and velocity, ultimately resulting in lower fuel consumption and emissions.

This section briefly described the main components and functioning of aircraft engines, including compressors, combustion chambers, turbines, exhaust nozzles, as well as fan and bypass air systems. Understanding these elements helps to appreciate the complexity of aircraft propulsion systems and their role in powering various types of engines, such as piston, turboprop, and turbofan engines.

Performance and Efficiency

When discussing aircraft engines, it’s crucial to analyze their performance and efficiency in various aspects such as thrust, fuel consumption, and operating speeds and altitudes. This section will provide insights into these factors for different engine types, including Piston, Turboprop, Turbofan, and Turbojet.

Thrust and Power

‌Thrust is the force an engine produces to move an aircraft forward, while power is the rate at which an engine does work. Different engine types provide varying thrust and power output:

Piston Engines: These engines are used in small, general aviation airplanes and produce lower thrust levels. They rely on the combustion of fuel and air mixture within cylinders to generate rotary power, transferred to a propeller.
Turboprops: Turboprop engines generate more thrust than piston engines, using a gas turbine to drive a propeller. They are found in regional and low-speed transport aircraft, delivering better power and efficiency at low altitudes. The TBM 930 is an example of a turboprop with impressive performance.
Turbojets: These engines produce high thrust levels by expelling exhaust gas at high velocity. They are mostly used in military and supersonic aircraft.
Turbofans: Turbofan engines are an improvement of the turbojet design. They offer high thrust with improved fuel efficiency, making them widely used in commercial aviation.

Fuel Efficiency and Consumption

Fuel efficiency is a major concern for aircraft, as it directly affects operational costs and environmental impact. Here’s how different engine types fare when it comes to fuel efficiency:

Piston Engines: Due to their lower power output and relatively simple design, piston engines are less fuel-efficient than jets or turboprop engines.
Turboprops: These engines provide better fuel efficiency than piston engines, especially at low altitudes. Their performance often exceeds that of turbofan engines in this regard.
Turbojets: Turbojets consume more fuel than both piston engines and turboprops. However, they deliver a high thrust-to-weight ratio, compensating for their fuel consumption in certain applications (e.g., high altitudes and velocities).
Turbofans: With their improved design, turbofans consume less fuel than turbojets. Their higher bypass ratio allows them to utilize more airflow, resulting in better fuel efficiency and lower noise levels.

Operating Speeds and Altitude

Each engine type has distinct characteristics in terms of operating speeds and altitude:

Piston Engines: Typically found in small, general aviation airplanes, piston engines operate at lower speeds and do not fly as high as jet or turboprop aircraft.
Turboprops: Turboprop-powered aircraft operate efficiently at low to medium altitudes and have a higher cruising speed than piston engines but slower than turbofan-powered aircraft. The TBM 930 is a turboprop offering slightly better speed and efficiency than its turbofan counterpart, the Cirrus Vision Jet.
Turbojets: These engines excel at high speeds and altitudes, making them suitable for supersonic and military applications. Higher airspeeds result in increased engine performance, particularly at high altitudes.
Turbofans: The versatile turbofan engine operates efficiently across a wide range of speeds and altitudes. That’s why they are commonly used in commercial aviation, regional jets, and business jets.

Applications and Use Cases

General Aviation Aircraft

General aviation aircraft mainly use piston engines and turboprop engines. Piston engines are common in small, propeller-driven airplanes due to their lower cost and fuel efficiency (source). Turboprop engines, on the other hand, are found in slightly larger aircraft, offering more power and performance while still maintaining fuel efficiency (source).

Piston engines: ideal for small, cost-effective, and fuel-efficient aircraft
Turboprop engines: suitable for medium-sized aircraft with increased power and performance demands

Commercial Airplanes

Commercial airplanes predominantly use turbofan engines for their aeronautics needs. Turbofan engines offer a balance of high performance, safety, and fuel efficiency, which is crucial for long-haul flights and large commercial airliners (source).

Turbofan engines: high performance, safety, and fuel efficiency ideal for commercial aviation

Helicopters

Helicopters typically employ turboshaft engines as their primary power source. Turboshaft engines are similar to turboprop engines but specifically designed for helicopter applications. They provide the necessary power and responsiveness for the unique flight characteristics of helicopters (source).

Turboshaft engines: optimized for power and responsiveness in helicopter flight

Military Aircraft

Military aircraft use a range of engine types, depending on the specific mission and performance requirements. Turbojet engines are utilized in high-performance fighter jets due to their high-speed capabilities and responsive acceleration. Turbofan engines can be found in larger military aircraft such as transport planes, providing increased efficiency and range (source). In some cases, military aircraft also use ramjet and scramjet engines for supersonic and hypersonic flight capabilities.

Turbojet engines: high-speed and responsive acceleration for fighter jets
Turbofan engines: efficiency and range for larger military transport aircraft
Ramjet and scramjet engines: supersonic and hypersonic flight capabilities for advanced military applications

Notable Manufacturers and Innovations

Rolls-Royce

Rolls-Royce is a British multinational engineering company known for manufacturing aircraft engines since the early 20th century. Over the years, Rolls-Royce has introduced several groundbreaking technologies in their engines. Their Trent family, a series of high-bypass turbofan engines, showcases the company’s commitment to innovation by incorporating advanced materials, efficient design, and emission reduction technologies.

General Electric

General Electric (GE) is an American multinational conglomerate with a long history of producing aircraft engines. As one of the leading manufacturers, GE has introduced several significant engines, such as the GE90, which powers the famous Boeing 777. Additionally, GE’s CF6 series has successfully powered long-range aircraft like the Airbus A330 and Boeing 767. GE’s innovation in aircraft engine technology includes the implementation of composite materials, 3D-printed parts, and the development of fuel-efficient, quieter engines.

CFM International

CFM International, a joint venture between General Electric and France’s Safran Aircraft Engines, has quickly become a leading aircraft engine manufacturer in the single-aisle commercial aircraft market. Their flagship product, the CFM56 series, has powered various aircraft, such as the Boeing 737 and Airbus A320 families. The successor to the CFM56, the LEAP (Leading Edge Aviation Propulsion) engine, features leading-edge technology for increased efficiency, reduced emissions, and lower operating costs.

Aviadvigatel

Aviadvigatel is a Russian aircraft engine manufacturer known for producing turbofan and turboprop engines. One of their notable engines is the PS-90, which powers Russia’s Ilyushin Il-96 and Tupolev Tu-214 aircraft. Aviadvigatel’s innovations include developing noise reduction technologies, environmentally friendly emissions reductions, and efficient fuel consumption.

Lycoming

Lycoming Engines is an American company with a rich history in producing piston engines for general aviation aircraft. As one of the world’s leading manufacturers of small general aviation engines, the company has constantly evolved and improved its engine technology. Some innovations from Lycoming include the implementation of fuel injection systems, turbocharging, and advanced manufacturing techniques for increased reliability and performance.

Types of Aircraft Engines: Exploring Piston, Turboprop, Turbofan, Turbojet, and More