University of Southern California
Innovative Aviation Technology of the F-35B
William Blair
Phone: (510)499-6691
Email: wblair@usc.edu
05/04/2013
My name is William Blair, and I am an undergraduate Junior from Castro Valley,
California. I am studying Industrial & Systems Engineering, and hope to be a Naval
Aviator after graduation.
Abstract
Jet aircraft were first built in the late 1940s, and since then the technology has
continuously evolved. One such development is the F-35B’s turbofan engine. Unlike its
predecessors, it is designed to allow for aircraft to hover in mid-air, as well as take off
and land vertically. This article will outline how traditional turbofan engines work, as
well as give insight to the differences in the F-35B’s engine that give it these new
capabilities.
Introduction
Throughout history, military technology advancements have often been found to
also have civilian applications. For example, many civilian medical technologies have
arisen out of the need for emergency battlefield wound treatment. The aviation field has
been particularly impacted by military demand for advanced technology. For example,
ever since the military realized potential uses of aircraft in battle, military-funded
research and development has largely contributed to advancing aviation technology.
Specifically, ever since a member of the Royal Air Force created the first design for a jet
engine in 1930 [8], the military has been constantly seeking new and inventive designs
for jet engines. The latest innovation to aircraft engines is a feature of the F-35B Joint
Strike Fighter that allows the turbofan engine’s thrust to be redirected downward, giving
the plane the ability to take off and land vertically as well as hover in place. Though this
technology is very new, it could find civilian application in the future to change the
design of aircraft.
How Traditional Turbofan Engines Work
The term “jet engine” encompasses a variety of air breathing engines, including
turbojet, turbofan, turboprop, turboshaft, and propfan. The most commonly used of these
is the turbofan engine, named after the fan mechanism from which the main forward
thrust comes. This is the engine type used in most military and civilian jet-powered
aircraft, due to its high efficiency (energy produced per unit fuel) and power (force that
the engine is able to produce). The engine is particularly efficient because minimal
energy is lost through the engine’s processes, as the energy produced by the combustion
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of gasoline within the engine is mostly transferred into rotational energy that pushes the
engine forward.
Figure 1, Cross-section of a standard turbofan engine, with fan extending past
combustion chamber. (Picture taken from popsci.com)
The main components of turbofan engines are the fan, compressor, combustor,
turbine, and nozzle [9]. The front of the engine (where the fan is in the figure above) is
open to allow for the intake of air into the compressor, where a spinning shaft with blades
attached forces the air to the outer edge of itself, causing the air to become very dense.
This dense air then travels into the combustor, where it is mixed with jet fuel and ignited,
causing heat to be released and forced further rearward. The amount of fuel injected into
the combustion chamber is what determines the amount of thrust generated by the engine,
which can be controlled by the pilot within the cockpit of the airplane [7]. The dense air/
fuel mixture’s combustion creates a very large amount of force, and expands further into
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the turbine, which consists of angled blades resembling a windmill connected to a freely
rotating shaft, which is then connected to the fan at the front of the engine. Similar to a
windmill, the turbine converts this rearward moving air into rotational energy in the form
of spinning the high-pressure shaft attached to it. The air that passes through the turbine
then exits out of the engine’s nozzle, adding extra forward thrust.
Figure 2, showing the main components of a standard turbofan engine, and their
positions relative to one another. (Taken from dcradio.org.uk)
In the turbine, the high velocity air causes the turbine to rotate at an extremely fast
rate, and as a result the fan at the front of the engine is rotated as well since it is
connected to the turbine by a shaft. This fan extends out past the outer edge of the
compressor/ combustor, and forces air out through the rear of the engine. Then, this force
directed backward propels the engine (and attached airplane, of course) forward [7]. All
of the individual sections of the engine work to compress intake air, ignite it so it
becomes very hot and expands, and then transform this thermal energy into rotational
energy that causes a fan to act as a very fast propeller and force the plane forward.
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Using a fan rather than just allowing all of the engine’s thrust to be generated by
the exhausted air (i.e turbojet engines) is what gives the engine more power and
efficiency. Because of their improved efficiency, engines can be more compact while still
giving the same amount of thrust as a larger engine, reducing the weight of the aircraft.
Also, this makes the engine much quieter, which gives it an advantage to commercial
airlines that have to minimize noise pollution in crowded city areas.
How the F-35’s Engine Differs from Standard Turbofan Engines
The reason for the F-35’s development was to replace aging aviation technology
at a lower cost than previously used jet aircraft such as the F/A-18, which is becoming
too expensive to maintain and outdated [11]. It is intended to replace all military jet
aircraft, in all branches of the U.S. military, with specific models tailored to the needs of
each branch [10]. There are three variants of the plane’s design: F-35A (intended for the
Air Force), F-35B (Marine Corps), and F-35C (Navy) [3]. Each of these has the same
engine, avionics (electronic components), and structural components [5], but each has
specific features that optimize it for its specific branch’s use. One such feature is the F35B’s STOVL (Short Take-Off/ Vertical Landing) capability, which is made possible by
its engine’s thrust-vectoring nozzle. This is among the most innovative of the aircraft’s
features, and is not seen in any other aircraft engine in production. The need for an
aircraft that has this ability to take off and land using short distances arises from the
Marine Corps’ operating procedures. Marine Corps aircraft often land and take off on
Naval ships called amphibious assault ships (as seen below), which have much smaller
landing areas than what is needed for conventional aircraft operations. This creates a need
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for aircraft that do not require long runways to take off and land, and the F-35B is a
solution to this problem.
Figure 3, Amphibious Assault Ship (taken from Wikipedia.org)
The “thrust-vectoring nozzle” is unique to the F-35B’s Pratt & Whitney F135
Turbofan engine, and is the first of its kind. “The engine exhausts through a three-bearing
swivel nozzle that can deflect the thrust from horizontal to just forward of vertical” [6],
which means that the engine’s force can be diverted downward rather than rearward like
conventional turbofan engines. This gives the aircraft upward force rather than forward
force, allowing it to hover in midair.
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Figure 4, F-35B in hover (taken from http://juliantheaviator.files.wordpress.com)
The nozzle allows the pilots to be able to control the direction of thrust, allowing
the plane to also rotate its heading (direction) by 360°, as well as move side to side/ front
and back parallel to the ground (similar to how a helicopter would) as the nozzle is
redirected [4]. The engine’s main propulsion is also diverted into a lift fan near the front
of the plane (to counterbalance the downward force of the main engine at the rear of the
plane) so that the aircraft does not flip forward, as well as at the end of the wings to give
the pilot control over the roll (lateral stability) of the plane [1].
The F-35 program is still in the end stages of testing and production, and is
scheduled to be implemented into the military in 2016. Currently, this vertical lift
technology is unique to the F-35B, however has potential to have other applications.
Future Applications
As a result of this capability, aircraft can more easily take off and land on aircraft
carrier decks and smaller landing areas, reducing the area needed for safe operation of
jet-powered aviation. Because this technology is so new, it has not been applied to any
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civilian applications yet. However, it has potential to make its way into the civilian
aviation community similar to the way other military has transferred over to non-military
applications.
In the future, this technology could possibly be implemented in civilian aircraft,
enabling airplane landings in small areas such as rooftops or areas without otherwise
suitable airports. This would widen the capabilities of airplanes to now be able to land in
areas that could only previously be reached by helicopter (which have speed and distance
limitations that airplanes do not have). This technology could also be implemented in
spacecraft, enabling shuttles (which currently use engines more similar to traditional
airplanes) to land on the rough, uneven terrain of foreign planets that they cannot
currently land on. Though these are just hypothetical applications of the technology, it is
very likely that we will see this technology applied to non-military aircraft in the future.
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Terms and Definitions

Avionics: Electronic equipment fitted in an aircraft.

Compressor: A machine used to supply air or other gas at increased pressure, e.g.,
to power a gas turbine.

Turbofan Engine: fanjet: a jet engine in which a fan driven by a turbine provides
extra air to the burner and gives extra thrust.

Vectoring: Direct (an aircraft in flight) to a desired point.
Suggested Websites

Lockheed Martin F-35 website: https://www.f35.com

Site giving specifications and project history: http://www.fas.org/man/dod101/sys/ac/f-35.htm
Suggested Multimedia Applications
http://www.youtube.com/watch?v=ZD-J1KksHUQ, video by Lockheed Martin showing
how thrust-vectoring nozzle works to give the F-35B vertical lift.
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Bibliography
[1] Bevilaqua, Paul. "Joint Strike Fighter Dual-Cycle Propulsion System." Journal
of Propulsion and Power 21.5 (2005): 778-83. Print.1
[2] Craig, David. "The Thrust of the Matter: Inside a Jet Engine." USA Today 14
June 1994, Final ed., Bonus sec.: 12E. LexisNexis. Web. 23 Feb. 2013.
[3] "F-35 Lightning II Joint Strike Fighter (JSF), United States of America."
Airforce Technology.com. N.p., n.d. Web. 19 Feb. 2013.
[4] Kandebo, Stanley W. "New Nozzle Eyed For Stovl F-35." Aviation Week & Space
Technology 156.14 (2002): 41. LexisNexis. Web. 18 Feb. 2013.
[5] Lawson, Chris. "The Joint Strike Fighter." Leatherneck 81.5 (1998): 14-19.
Proquest. Web. 18 Feb. 2013.
[6] "’Lift Fan Spherical Thrust Vectoring Nozzle’ in Patent Application Approval
Process." Defense & Aerospace Week. N.p., 21 Nov. 2012. Web. 18 Feb. 2013.
[7] Patrício, Pedro, and José M. Tavares. "Simple Thermodynamics of Jet Engines."
American Journal of Physics 78.8 (2010): 809. Print.
[8] Scott, Phil. "Birth of the Jet Engine." Mechanical Engineering 117.1 (1995): 66.
ProQuest. Web. 20 Feb. 2013.
[9] Shaw, Robert J. "Engines." Engines. NASA, 13 Sept. 2010. Web. 23 Feb. 2013.
[10] Thompson, Mark. "The Most Expensive Weapon Ever Built." Time Magazine.
N.p., 18 Feb. 2013. Web. 18 Feb. 2013.
[11] Wilson, Jim. "America's F-35 Joint Strike Fighter Plane." Popular Mechanics.
N.p., 07 Dec. 2004. Web. 18 Feb. 2013.
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