Turbojet and Turbofan Jet Engine Overview

Part of a series of Jet Engine Overviews

Turbojet/Turbofan engines are the most common type of jet engines in use today. From commercial airliners to jet fighters, the vast majority of production jet aircraft utilize at least one of these types of engines. These engines are relatively simple air breathing designs which follow the basic layout of a jet engine.

Turbojet Engines

The turbojet engine is considered to be the most basic jet engine design.  It consists of an intake, a compression chamber, a combustion chamber, a turbine and an exhaust nozzle.

Air enters the intake and immediately passes into the compression chamber. In the compression chamber air is compressed by spinning fans as it passes through a narrowing duct into the combustion chamber. Just before the air reaches the combustion chamber, it is mixed with fuel. Inside the combustion chamber, the fuel/air mixture is ignited. The hot, high-pressure air expands out of the combustion chamber where it passes through a set of turbines. The passing air spins these turbines which, in turn, spin the compressive fans at the fore of the engine, sustaining the flow of air. After passing the turbines, the air exits the back of the engine through the exhaust nozzle. In engines with an afterburner, air is reheated between the turbine and the exhaust nozzle. Afterburners are typically about 4 times less efficient than the primary combustion chamber due to the decreased air pressure aft of the turbine.

The following graphs allow an easier visualization of the air temperature, pressure and velocity during the operation of a turbojet engine.

Turbofan Engines
The turbofan engine is an augmentation of the turbojet engine. As the name would imply, the turbo fan adds a fan which functions similarly to a prop on a propeller driven plane. The turbofan engine contains a standard turbojet engine at its core but adds a duct around the outside of this engine for some air to pass through.

The flow that passes through the integral turbojet is called core airflow while the air that moves through the outer duct is called bypass flow.
In General, there are 2 different types of turbofan engines, they are…

  1. Low Bypass Turbofan Engines
    In low bypass engines, a relatively large portion of the air that passes through the engine is core airflow. To put it another way, there is a lower amount of bypass flow. The ratio of bypass airflow to core airflow is usually around 2:1 or less, with low bypass engines being optimized for efficient flight at higher Mach numbers. Most modern fighter jets utilize low bypass engines. Fighters like the F-16 and F/A-18 have bypass ratios of around .35:1.
  2. High Bypass Turbofan Engines
    Conversely, high bypass engines allow lots of air to bypass the integral turbojet. High bypass engines usually have ratios between 5:1 and 10:1. These engines are optimized for efficient subsonic flight, usually around Mach .8. Most modern commercial airliners and some military transports use this type of engine.

Turbojet/Turbofan History

  • In 1939, the He 178 was the first turbojet aircraft to fly. 
  • Shortly thereafter, in 1944, the Me 262 became the first operational jet fighter, followed closely by the Gloster Meteor in the same year.
  • By the 1950s, jet engines were nearly ubiquitous on military aircraft, and some had even been approved for civilian use, such as those mounted on the de Havilland Comet.
  • By the 1970s, jet engines had become all but ubiquitous in the commercial air industry due to the introduction of the high bypass turbofan.
  • In 2003, the Concord makes its last flight, marking the end of the turbojet engine in the commercial airline industry.
  • As of writing, all current production fighter planes use some form of turbofan engine, along with most bombers and most commercial airliners.

Turbojet/Turbofan pros and cons

Turbojet Pros

  • Smaller engine circumference means more compact engine
  • Capable of attaining high speeds
  • Good specific impulse at lower Mach numbers

Turbojet Cons

  • Misses many improvements in power and efficiency when compared with turbofan
  • Loud

Turbofan Pros

  • Excellent specific impulse at useful range of speeds
  • Quieter than turbojet and many other jet engines

Turbofan Cons

  • Larger diameter
  • More complexity
  • More vulnerable to ice damage

Thanks for reading. It’s always nice to hear feedback, questions and/or suggestions. Tell me what you liked, what you didn’t like, and don’t forget to smash that mf follow button. If you suggest a topic that I end up covering I will make sure to tag you in the post so you don’t miss it. Stand by for more jet engine overviews.

Rey’s Speeder: Info. Graph + Transparency 

Rey’s speeder is categorised as a repulsorlift vehicle. A repulsorlift vehicle creates thrust by pushing against the planets gravity (fancy name for a hovercraft). Rey built her speeder through parts acquired from the Niima Outpost junkpiles, Starship Graveyard and the Teedo traders. Her eclectic array of parts (from military hardware to civilian machinery) classifies her vehicle as a hybrid: speeder and swoop. Rey’s speeder is comprised of duel turbojet engines salvaged from a cargo-hauler. In addition, Rey recovered air amplification intake ducts from an Imperial gunship and an array of repulsors from X-wing fighters.

Some speculations: Due to her mechanical knowledge, it would be conceivable that Unkar Plutt recruited Rey to work on the Millennium Falcon. This might give explanation to her rather unrealistic and detailed knowledge of the Falcon portrayed in the movie. Rey was easily able to ‘bypass the compressor’ because of her expertise in mechanics - not from sheer luck.

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Two General Electric J47 turbojet engines mounted outboard of the three Pratt & Whitney R-4360 Wasp Major piston engines on each wing of the Convair B-36 Peacemaker.

Back before the British aviation industry killed itself by constant and systematic bickering among themselves (just like their car industry would end up doing some 20 years later), they had such an interesting plethora of prototypes and concepts, here are some of those: Ultra-heavy lift helicopters, the most notable being the W-85:

The W-85 was a projected 100-seat military helicopter powered by six Armstrong Siddeley Adder turbojet engines mounted in pairs on each blade-tip. The machine had nose-loading doors, with a small passenger-sized ventral exit at the rear. The crew compartment was located high in the fuselage, above the nose doors. With a rotor diameter of 104 ft., this machine had an all-up weight in the 60,000 lb. class.

Oh Britain, you could have led the way…

The original Caspian Sea Monster, officially «KM» (Korabl Maket, Russian - Корабль-макет Naval Prototype), also known as the “Kaspian Monster”, was an experimental ground effect vehicle (or ekranoplan)—a craft that flies, but stays close to the ground so it can rely on the ground effect. It was developed at the design bureau of Rostislav Alexeyev.

Powered by 10 turbojet engines and capable of reaching 500 km/h (311 mph), it was used for testing  since 1966 and for 15 years, until it sank after an accident caused by pilot error in 1980.

This craft led to the development of the Lun-class ekranoplan


Turboshaft Jet Engine Overview

Part of a series of jet engine overviews

Turboshaft engines are a specific, yet widely employed form of the turbojet engine. This type of engine is most commonly used on helicopters and low airspeed airplanes, but it also sees use on some armored vehicles, ships.


Turboshaft engines are not actually jet engines, as they do not a use a jet of fluid to produce thrust, however they are worth mentioning because of their similarity to turbojet engines and their widespread use. Turboshaft engines are extremely similar to turbojet and turbofan engines. In a turboshaft engine, air is drawn into an intake and compressed by a series of axial flow compressors.

After it is compressed it is injected with fuel and passes into a combustion chamber where it is ignited. After ignition, the hot high energy gas moves rearward past a series of turbines. In a turbojet engine, the turbines would extract a small amount of energy from the gaseous stream, just enough to power the compressors at the fore of the engine. The turboshaft engine instead, extracts most, if not all of the energy from the passing air via the turbines. Whatever energy is not used to power the axial compressors is then used to rotate a shaft which provides mechanical energy.



Turboshaft engines are used in a variety of aerial application. When used on airplanes to drive props, they are known as turboprop engines.

Turboprop engines are used to achieve high fuel efficiency at low airspeeds. They are used in many commercial aircraft, and large low-airspeed military transports such as the C-130. Other notable applications include the Tupolev Tu-95 Bear, the Super Tucano and the infamous Republic XF-84H, a turboprop plane whose supersonic propellers produced shock waves powerful enough to knock a man over and noise loud enough to cause nausea and fainting among ground crews.

Additionally, turboshaft engines are commonly used to power helicopters. Helicopters commonly use multiple turboshaft engine both for increased power and for redundancy. Most large military and civilian helicopters use turboshaft engines in lieu of piston engines, due to their increased efficiency and reliability. Some notable turboshaft helicopters include the Sikorsky Black Hawk, the Bell Boeing Osprey, and the Mil V-12, the worlds largest helicopter.


The turboshaft engine has seen use on a variety of land vehicles from cars to tanks. Examples of civilian ground application include the Fiat Turbina concept car, the Y2K Turbine Superbike motorcycle and the Howmet TX racecar, the only turbine powered racecar to ever win a race. Military ground application of turbine engines began in 1944 when the Nazis attempted to install a turbine engine in a Panther Tank. In 1954, the British installed a turbine in a Conqueror tank. The Swedish Stridsvagen 103, developed in the 1950s, employed a turboshaft engine as an Auxiliary Power Unit or APU. The American M1 and the Russian T-80 both mount turboshaft engines as their main source of propulsion. Turbine engines allow for more power and for greater fuel flexibility (the M1, for example, can burn gasoline, diesel, jet fuel or kerosene.) However, they are extremely inefficient and vulnerable to sand and dirt.


Maritime use of turboshaft engines is widespread. Turboshaft engines are commonly used on frigates, destroyers, corvettes and cutters. Among the countries that deploy turboshaft powered ships are the US, Denmark, Sweden, Britain and Finland. Naval turboshaft engines experience high levels of wear due to salt in the air and fuel, and lower grades of fuel.

As always, I appreciate hearing from yall. Let me know if you have any suggestions for future topics. Finals are coming up so I might be posting with slightly less frequency, but I will hopefully be able to put out pulse jets and rockets by the beginning of next year. I definitely want to do a post on torpedoes in the near future as well.

In a secret Cold War-era project, the U.S. military tried to design a flying saucer. 

Initially funded by the Canadian military, the project aimed to use turbojet engine exhaust to funnel an air cushion below the aircraft, which would allow it to hover. When the project became too expensive, the U.S. government took over. Military specialists sought to design a vehicle that could be used for reconnaissance and troop transport, as well as hover below enemy radar then zoom away at supersonic speeds. After a few initial tests, prototypes proved unstable, too slow, and too hard to control. 

Gif courtesy of the U.S. National Archives ( @todaysdocument ). 

Experimental German Go 229,in flight.

Performance characteristics of the Go 229A-0
"Gotha" Go 229A-0 (estimate)

Type: single-seat fighter-bomber.

two turbojet engine Junkers Jumo V each thrust 8,73 kN.

Aircraft performance characteristics:
max speed 977 km/h at an altitude of 12,000 m,
initial rate of climb 1320 m/min,
a service ceiling of 16,000 m,
the range of 1900 km, with fuel tanks 3170 km.

the aircraft operational empty 4600 kg,
maximum take-off 9000 kg.

the wingspan of 16,76 m,
the length of 7,47 m,
height 2.8 m,
wing area 52,50 m2.

four MK 103 or MK 108 caliber 30 mm and two 1000-pound bombs.