- To speed up. For example, when an airplane
takes off it accelerates down the runway until enough lift
is created by the air flowing over the wings so that it can fly.
- A field of fluid dynamics that studies
how gases, including air, flow and how forces act
upon objects moving through air.
- The study of flight and the science of building and operating an
- Control surfaces on the trailing
edge of each wing that are used to make the aircraft
roll. When flying straight and level, moving the
control stick to the right will raise the aileron on the right wing
and lower the aileron on the left wing. This will
cause the aircraft to roll
to the right.
- A machine used for flying. Airplanes, helicopters,
blimps and jets are all aircraft.
- The motion of air molecules as they flow
around an object, such as a wing.
- An object with a special shape that is designed to produce lift efficiently when the object is moved through the air. For
example, the cross-section of a wing is an airfoil.
- An aircraft that uses the force of air on its wings (called lift)
- The force created by air pushing
on a surface.
- The height of an object, like an airplane,
above sea level or above the earth's surface.
- To take something apart so it can be examined and studied.
angle of attack
- The angle of a wing to the oncoming airflow.
A pilot pulls back on the control
stick to raise the elevator. This causes the
aircraft to pitch which
increases the angle of attack.
- The operation of aircraft. There are three
types of aviation: general, commercial
- A straight line, through the center of
gravity, around which an aircraft rotates.
For example, an aircraft rolls
around its longitudinal axis which is a
straight line that runs through the center of the aircraft
from the nose to the tail.
- Opposing forces that are pushing
or pulling against each other an equal amount. For
example, if you and a friend pull on a rope, in
the opposite direction with the same force, neither
of you will move. This is because the forces are
- Daniel Bernoulli was a Swiss mathematician. He was born on February
8, 1700 in Groningen, Netherlands. As a university student he studied
philosophy and logic. His favorite subjects were mathematics and mechanics.
From 1725 to 1733 he worked as a mathematician with his brother, Nikolaus,
at the St. Petersburg Academy of Sciences in Russia. He then worked
as a professor at the University of Basel in Switzerland until his death
on March 17, 1782.
He is famous for his work in the field of fluid
dynamics. In 1738 he wrote a book called Hydrodynamica.
In this book he explained his theories about how gases and fluids
move, and how the speed at which they move affects the pressure they exert on objects they flow around. This is
the basis for the explanation of lift. His work helped to lay the foundation for aeronautics
which would be developed many years later.
- Daniel Bernoulli explained that the faster
molecules within a fluid move, the less pressure
they exert on objects around them. This applies to all fluids, including
water, air and gases. For example, the water in a pond will exert more
pressure on the pond's bottom than a flowing stream with
the same amount of water will exert on the streambed.
- An airplane with two sets of wings. The first airplane ever built
had two sets of wings, one on top of the other.
- The curve of an airfoil.
- a tail configuration (two small horizontal surfaces on either side
of the aircraft) mounted toward the front of the
aircraft, rather than at the rear.
center of gravity
- The force of gravity
acts on every individual part of an object, like an airplane.
However, engineers often treat the force of gravity on all the parts of
an object as a single force acting on a point in
the object called the center of gravity.
- A line from the front of an airfoil (the leading edge) to the trailing edge.
- A compartment in the front of the airplane
where the flight crew performs their job of flying the aircraft.
- The business of operating aircraft that carry
passengers by commercial companies. Airline companies such as American
Airlines, United Airlines and many others are examples of commercial
aviation. A Boeing 747 is an example of an airplane
that is owned by a company and operated in commercial aviation.
Computational Fluid Dynamics (CFD)
- The science of using supercomputers
to solve complex mathematical equations that predict how an object like
an aircraft responds to the air flowing around
it. CFD is a tool of aeronautics that enables engineers
to "fly an aircraft in a computer."
- An electronic machine that receives, processes and presents data. A computer can be programmed to perform complicated tasks,
like solving complex mathematical equations or controlling a flight
- Parts of an aircraft that are activated by
the controls to change the airflow
around the surfaces of the aircraft. The changes
in airflow cause the aircraft to roll, pitch, or yaw. Examples of control surfaces
are: ailerons, elevators and rudders.
- Devices which allow the pilot to direct the
movements of an aircraft. Examples of controls
are: rudder pedals that control the rudders and cause the airplane to yaw;
throttles that control the engines which generate
thrust for the airplane; and the control
stick that controls the ailerons and elevators
which cause the airplane to roll
- Information that is collected from an experiment. For example, an engineer
in a wind tunnel may collect data about how much lift
is created by a certain wing shape.
- To slow down. When an airplane comes in to
land, it decelerates and rolls to a stop.
- A sweepback wing that looks like a triangle
from above. The trailing edge of the wing
is the base of the triangle. The XB-70A is an example of an airplane
that has a delta wing. The XB-70A can fly faster than twice the speed
of sound at an altitude of 70,000 feet.
- The upward angle of the wings that is formed
where the wings connect to the fuselage.
- The force that resists the motion of the aircraft through the air. One type of drag is caused by air
molecules. As the aircraft
flies through the molecules, they resist the
motion of the aircraft. This resistance is due
to friction between the air molecules and the surface of the aircraft.
Airplanes are streamlined to decrease
the drag force.
- Control surfaces on the horizontal
part of the tail that are used to make the airplane
pitch. Pulling back on the
control stick will raise the elevators. This causes the aircraft
to pitch and increase the angle
- The parts of the airplane located at the
tail end. The empennage includes the horizontal
stabilizer, the vertical stabilizer,
- A machine that uses combustion to create energy. An airplane
will normally either have jet engines or engines that drive one or more propellers.
In either case, the engines provide the thrust
force that pushes the airplane
through the air.
- Someone who designs and builds mechanical or electrical devices.
For example, an aeronautical engineer designs and builds aircraft. To do this, an aeronautical engineer must study
aeronautics and understand fluid
dynamics and aerodynamics.
- A set of controlled procedures designed to test an idea or hypothesis. For example, a flight
simulation engineer will design an experiment to test whether or not
a pilot can control an airplane with a new wing design.
Federal Aviation Administration (FAA)
- The FAA is a government agency, under the Department of Transportation,
that oversees all aviation within the United
States. The FAA controls, for example, airport safety, air traffic control,
licensing of pilots, inspection of aircraft,
and investigates aviation mishaps.
- Another word for the vertical portion of the tail.
- Moveable parts of the trailing edge of
a wing that are used to increase lift
at slower air speeds. Flaps increase lift by changing
the shape of the airfoil. A pilot
will extend the flaps when the airplane is landing. By extending the flaps, the pilot
is increasing the camber of the wing,
the size of the wing and the wing's angle
of attack. All of these actions will cause lift
to decrease so the airplane can land more slowly.
- A tool of aeronautics
in which a flight simulator on the ground is used to create an environment
where a pilot sees, hears and feels like he or she is in a real aircraft.
Flight simulation is used to investigate how an aircraft responds to a pilot's movement
of the controls.
- A tool of aeronautics
in which a real aircraft is flown to gather
data which will accurately describe the capabilities of that
aircraft. Flight tests are used to investigate
how fast, how far and how high an aircraft can
go, and how it handles and performs.
- The study of how fluids move. Fluids include water and gases (such
- A push or a pull in a certain
direction that can be measured. Examples of forces are your hand pushing
on a doorknob, and a propeller pulling an airplane through the air.
forward sweep wing
- A wing that is swept toward the front of the
airplane, unlike most fast airplanes which have
wings that are swept toward the back of the airplane. The X-29 aircraft is an
example of a supersonic jet that has forward sweep wings. The X-29 is
capable of going over one and one-half (1 1/2) times the speed
- The part of the airplane to which the empennage and wings are attached. The
fuselage is where the passengers and cargo are located. It is streamlined
so that it produces the least possible drag.
- The operation of aircraft that belong to
- The natural force that pulls
an object toward the earth. We experience gravity as weight. An airplane
must generate enough lift to counteract the weight
of the aircraft.
- The horizontal part of the tail. The horizontal stabilizer helps
to increase the stability of the aircraft. It is
also known as a tailplane.
- Velocity greater than five times the speed
of sound. The Hyper-X is a reusable launch vehicle that will
fly into space and return. It will fly at hypersonic speeds as it re-enters
- A prediction which needs to be tested to tell if it is correct. An
engineer can offer the hypothesis that a particular
wing shape will not create enough lift
to enable an airplane to fly. His or her hypothesis must then be tested
using one or more of the tools of aeronautics to determine if it is correct.
- Tools used to observe, measure and control .
For example, pilots use instruments to measure and observe the altitude,
speed and direction of an aircraft.
- An engine that works by creating a high-velocity
jet of air to propel the engine forward.
- Another word for undercarriage. The
landing gear is often retractable - it can be pulled into the fuselage
of the aircraft to reduce drag.
- The axis extending through the center of gravity of an aircraft, and parallel to a line connecting the tips of the
wings. The lateral axis is sometimes called the
"y" axis. Pitch is a motion around the lateral
- The front edge of an airfoil. The leading
edge is normally rounded and thicker than the trailing edge.
- A force that is perpendicular to the airflow around an aircraft. In normal,
forward flight, the lift force "lifts" the aircraft
into the air. Engineers design airplanes
so that the lift created by the wings opposes the weight force.
- The axis extending through the center of the
fuselage from the nose to the tail. The longitudinal
axis is sometimes called the "x" axis. Roll is a motion around the longitudinal
- The operation of aircraft that belong to
the Armed Forces. The Air Force YF-23 is an example of an aircraft
that is flown only by the military.
- A copy of an object that is often times smaller than the original.
Wind tunnel engineers
create a model of an aircraft to put in a wind tunnel. The model is a precise replica of the outside
of an aircraft.
- The absolute tiniest part of something that can still be called by
that name. For example, two hydrogen atoms and one oxygen atom make
up one molecule of water.
- An airplane with one set of wings. Most aircraft built today have
only one set of wings and are classified as monoplanes.
National Advisory Committee for Aeronautics (NACA)
- NACA was a government agency that was started in 1917. NACA guided
research in aeronautics
until 1958 when its name was changed to the National Aeronautics
and Space Administration (NASA).
National Aeronautics and Space Administration (NASA)
- In 1958, NASA was created as a government agency to replace NACA. NASA's charter is to expand frontiers in air and space,
to inspire and serve America, and to benefit the quality of life on
- Forces that are pushing
or pulling in the opposite direction. For example, lift
is perpendicular to the airflow around an aircraft. If the
aircraft is flying straight and level, the lift
force (which is pulling up) will be opposing
the weight force (which is
pulling the aircraft toward
- The load carried by an aircraft that includes
passengers and cargo.
- A person who flies an aircraft.
- A rotational motion in which an airplane turns around its lateral axis.
Pushing forward on the control stick will lower
the elevators, which forces the tail upward.
The pilot will then see the nose of the aircraft
fall or pitch.
- A force being exerted on part of a surface.
When you stand, your feet put pressure on the ground. Air pressure refers to air molecules
pressing against a surface like the bottom of a wing.
- A device that consists of blades (shaped like airfoils) that spin around a central hub, like a fan. An engine
causes the blades to turn. When the blades turn, they create thrust
by biting into the air and forcing it to move back. The amount of thrust can be controlled by changing the speed of the propellers.
- To use force to bring something closer. The
force of gravity pulls objects
closer to the Earth.
- To use force to move something ahead or to the
side. During takeoff the thrust force, created by the engines, pushes
an airplane down the runway.
- In aviation, to fly over and look closely
at an area below to gather information about it.
- A carefully planned and performed investigation, searching for previously
regimes of flight
- A way of placing aircraft into different
categories based on their speeds. The regimes of flight are subsonic,
transonic, supersonic and hypersonic.
- A rotational motion in which the
aircraft turns around its longitudinal axis.
Pushing the control stick to the left will raise
the aileron on the left wing
and lower the aileron on the right wing.
This will cause the airplane to roll to the
left. The pilot will see the left wing
tip fall and the right wing tip rise.
- The turning of an object, like an airplane,
around an axis, or a propeller
around a hub. Pitch, roll and
yaw are the rotational motions of an airplane around the lateral, longitudinal
and vertical axes.
- A control surface on the trailing edge of the vertical part of the tail that is
used to make the aircraft yaw.
The rudder is controlled by rudder pedals. Pushing
the left rudder pedal will tilt the rudder to the left. This will cause
the nose of the aircraft to turn to the left.
- A systematic way of solving a problem or answering a question using
observation and measurement. The six steps of the scientific method
are: state the problem, create a hypothesis,
design an experiment, perform the experiment, organize and analyze the data, draw conclusions.
- A device that creates an environment that is as close as possible
to reality. In flight simulators, engineers
create a cockpit environment identical to the
one in a real airplane. In a flight simulator
a pilot will see, hear and feel like he or she is in a real aircraft.
- a sled-like runner used as part of the landing
gear for an aircraft.
speed of sound
- The speed at which sound waves travel. If you stand a distance away
from a friend and say something to him, the sound waves of your voice
will travel very quickly to the ear of your friend. The speed of sound
is the speed at which those waves traveled.
- A device, normally located on the top of the wing,
for changing the airflow around a wing
to reduce lift. Pilots deploy
spoilers when they land so that the airplane
is no longer "lifted" into the air.
- The condition of being steady. A motion of an aircraft
is said to have stability, or be stable, if the aircraft
will return to that motion after a disturbance, without the pilot
having to move the controls.
- A surface that helps to provide stability
for an aircraft. An airplane
has two stabilizers: a vertical stabilizer and a horizontal stabilizer. Stabilizers are like the
feathers on an arrow, which keep the arrow pointed in the right direction.
- A breakdown of the airflow over a wing, which suddenly reduces lift. When an
airplane stalls it will usually drop suddenly.
Pilots know how to recover from a stall and smooth
out the airflow over the wings
to produce more lift again.
- A wing that sticks straight out from the fuselage - it does not slant to the front or the rear.
The ER-2 is an example of an aircraft that has
- To shape an object so that it creates less drag
and moves smoothly and easily through the air. Airfoils
are streamlined, as is the fuselage.
- Velocity less than the speed of sound. The MD-11 is a subsonic aircraft
because it never flies above the speed of sound.
- A computer that is especially designed to
receive, process and present very large amounts of data
very quickly. The Cray Y-MP is an example of a supercomputer that
is resident at NASA Ames Research Center and is
used for CFD.
- Velocity greater than the speed of sound. The SR-71 is characterized as a supersonic
aircraft because it travels from three to four times the
speed of sound. A supersonic aircraft
can fly from New York to London in less than two hours.
- A wing that is slanted toward the rear of the
airplane. The F-18 aircraft is an example of a supersonic
jet that has sweepback wings.
- Another word for a horizontal stabilizer.
- The process of using the thrust of the engines to accelerate an airplane
down a runway until enough lift is generated so
that the aircraft begins to fly.
- A pilot that is specially trained to test aircraft. Test pilots must be exceptional pilots,
have a complete understanding of aeronautics
and aerodynamics, and be able to accurately
write and speak about what they see, feel and hear during the testing
of an aircraft.
- A force created by the engines
that pushes an aircraft
through the air.
- A device or process that is used to do some kind of work. A hand-held
calculator is a tool for doing mathematics accurately and quickly. The
tools of aeronautics (CFD,
Wind Tunnel Testing, Flight Simulation and Flight
Test) are processes that use special devices to perform research in aeronautics.
- The rear edge of an airfoil. The trailing
edge is normally thin and sharp. The ailerons are normally located on the trailing edge of the
- Motion along a straight line, such as an axis.
The translational motions of an aircraft are
forward and back along the longitudinal axis,
side to side along the lateral axis, and up and
down along the vertical axis.
- Velocity between nine tenths (.9) and one
and four tenths (1.4) times the speed of sound.
The X-1 was the first aircraft to fly faster
than the speed of sound. Several versions
of the X-1 were built. One succeeded at flying twice the speed of sound at an altitude
of 90,000 feet.
- Air flow which is not smooth and steady. When an airplane
flies through turbulent air, it can unexpectedly rise, drop, roll,
pitch or yaw very abruptly.
- The part of an aircraft that provides support
while the aircraft is on the ground. It includes
wheels, shock absorbers and support struts. There is an undercarriage
unit under the nose of the aircraft as well as approximately midway back, under the
fuselage. Undercarriage normally includes rubber
tires, but may have skis for landing on snow or floats for landing on
variable sweep wing
- Wings that are hinged so they can be slanted
forward or backward during flight. The F-14 aircraft
is an example of a supersonic jet with variable sweep wings.
- The speed of an object, in a certain direction.
- The axis extending straight up and down through
the center of gravity of an aircraft.
The vertical axis is perpendicular to the longitudinal and lateral axes.
The vertical axis is sometimes called the "z" axis. Yaw is a motion around the vertical
- The vertical part of the tail. The vertical stabilizer helps to increase
the stability of the aircraft. It is
also known as a fin.
- The force of gravity
acting on an object. The weight force pulls an aircraft toward the Earth and
must be overcome by a combination of lift and thrust.
wind tunnel testing
- A tool of aeronautics
that involves placing a model of an aircraft or part of an aircraft into
a wind tunnel and using instruments to gather data while air
is blown past the model. Wind tunnel testing is
used to investigate and accurately describe the effects of airflow
on an aircraft or part of an aircraft.
- A wind tunnel is a tube or cylinder in which a model
of an airplane or part of an airplane
is placed. Air is blown past the model so that
it experiences the same forces as it would if it
were actually flying. The struts that hold the model
in place measure these forces.
- A part of an airplane that is attached to
the fuselage. Wings are shaped like airfoils
and are used to provide lift for the airplane.
There are four basic types of wings: straight, sweep, delta
and variable sweep.
- a mechanism to provide lateral control of the
aircraft through flexible wing tips; wires enabled the wing tips
to arch so that the ends of the wings were four inches lower than the
center (the concept was devised by the Wrights after observing the wing
tips of a hawk in flight).
- A rotational motion in which the
aircraft turns around its vertical axis. This causes the aircraft's
nose to move to the pilot's right or left. Pushing the right
rudder pedal will tilt the rudder to the right.
The pilot will see the nose of the aircraft
turn to the right.