This page shows the parts of an airplane and their functions. Airplanes are transportation devices which are designed to
move people and cargo from one place to another. Airplanes come in many
different shapes and sizes depending on the mission of the aircraft. The airplane shown on this slide is a turbine-powered airliner which has been chosen as a representative aircraft.
For any airplane to fly, one must lift the
weight of the airplane itself, the fuel, the passengers, and the cargo. The
wings generate most of the
lift to hold the plane in the air. To generate lift, the airplane must be pushed through the air. The air resists the motion in the form of aerodynamic
drag. Modern airliners use
winglets on the tips of the wings to reduce drag. The
turbine engines, which are located beneath the wings, provide the
thrust to overcome drag and push the airplane forward through the air. Smaller, low-speed airplanes use
propellers for the
propulsion systeminstead of turbine engines.
To
control and maneuver the aircraft, smaller wings are located at the tail of the plane. The tail usually has a fixed horizontal piece, called the horizontal stabilizer, and a fixed vertical piece, called the vertical stabilizer. The stabilizers' job is to provide stability for the aircraft, to keep it flying straight. The
vertical stabilizer keeps the nose of the plane from swinging from side to side, which is called
yaw. The
horizontal stabilizerprevents an up-and-down motion of the nose, which is called
pitch. (On the Wright brother's first aircraft, the horizontal
stabilizer was placed in front of the wings. Such a configuration is called a
canard after the French word for "duck").
At the rear of the wings and stabilizers are small moving sections that are attached to the fixed sections by hinges. In the figure, these moving sections are colored brown.
Changing the rear portion of a wing will change the amount of force that the wing produces. The ability to change forces gives us a means of controlling and maneuvering the airplane. The hinged part of the vertical stabilizer is called the
rudder; it is used to deflect the tail to the left and right as viewed from the front of the fuselage. The hinged part of the horizontal stabilizer is called the
elevator;it is used to deflect the tail up and down. The outboard hinged part of the wing is called the
aileron; it is used to
roll the wings from side to side. Most airliners can also be rolled from side to side by using the
spoilers.Spoilers are small plates that are used to disrupt the flow over the wing and to change the amount of force by decreasing the lift when the spoiler is deployed.
The wings have additional hinged, rear sections near the body that are called
flaps. Flaps are deployed downward on takeoff and landing to increase the amount of force produced by the wing. On some aircraft, the front part of the wing will also deflect.
Slats are used at takeoff and landing to produce additional force. The
spoilers are also used during landing to slow the plane down and to counteract the flaps when the aircraft is on the ground. The next time you fly on an airplane, notice how the wing shape changes during takeoff and landing.
The
fuselage or body of the airplane, holds all the pieces together. The pilots sit in the
cockpit at the front of the fuselage. Passengers and cargo are carried in the rear of the fuselage. Some aircraft carry fuel in the fuselage; others carry the fuel in the wings.
As mentioned above, the aircraft configuration in the figure was chosen only as an example. Individual aircraft may be configured quite differently from this airliner. The Wright Brothers
1903 Flyer had pusher propellers and the elevators at the front of the aircraft. Fighter aircraft often have the jet engines buried inside the fuselage instead of in pods hung beneath the wings. Many fighter aircraft also combine the horizontal stabilizer and elevator into a single
stabilator surface. There are many possible aircraft configurations, but any configuration must provide for the
four forces needed for flight.
Airplanes are transportation devices which are designed to
move people and cargo from one place to another. Airplanes come in many
differentshapes and sizes depending on the mission of the aircraft. The airplane shown on this slide is a turbine-powered airliner which has been chosen as a representative aircraft.
The
fuselage, or body of the airplane, is a long hollow tube which holds all the pieces of an airplane together. The fuselage is hollow to reduce
weight. As with most other parts of the airplane, the shape of the fuselage is normally determined by the mission of the aircraft. A
supersonic fighter plane has a very slender,
streamlined fuselage to reduce the
drag associated with high speed flight. An airliner has a wider fuselage to carry the maximum number of passengers. On an airliner, the pilots sit in a
cockpit at the front of the fuselage. Passengers and cargo are carried in the rear of the fuselage and the fuel is usually stored in the wings. For a fighter plane, the cockpit is normally on top of the fuselage, weapons are carried on the wings, and the engines and fuel are placed at the rear of the fuselage.
The
weight of an aircraft is distributed all along the aircraft. The fuselage, along with the passengers and cargo, contribute a significant portion of the weight of an aircraft. The
center of gravity of the aircraft is the average location of the weight and it is usually located inside the fuselage. In flight, the aircraft
rotates around the center of gravity because of
torques generated by the
elevator,
rudder, and
ailerons. The fuselage must be designed with enough strength to withstand these torques.
Thrust is the
force which moves any aircraft through the air. Thrust is generated by the
propulsion system of the aircraft. Different propulsion systems develop thrust in different ways, but all thrust is generated through some application of Newton's
third law of motion. For every action there is an equal and opposite reaction. In any propulsion system, a
working fluid is accelerated by the system and the reaction to this acceleration produces a force on the system. A general derivation of the
thrust equation shows that the amount of thrust generated depends on the
mass flow through the engine and the
exit velocity of the gas.
During World War II, a new type of airplane engine was developed independently in Germany and in England. This engine was called a
gas turbine engine. We sometimes call this engine a
jet engine. Early gas turbine engines worked much like a
rocket engine creating a hot exhaust gas which was passed through a
nozzle to produce thrust. But unlike the rocket engine which must carry its oxygen for
combustion, the turbine engine gets its oxygen from the surrounding air. A turbine engine does not work in outer space because there is no surrounding air. For a gas turbine engine, the accelerated gas, or
working fluid, is the jet exhaust. Most of the mass of the jet exhaust comes from the surrounding atmosphere. Most modern, high speed
passenger and
military aircraft are powered by gas turbine engines. Because gas turbine engines are so important for modern life, we will be providing a lot of information about turbine engines and their operation.
Turbine engines come in a wide
variety of shapes and sizes because of the many different aircraft missions. All gas turbine engines have some
parts in common, however. On the slide we see pictures of four different aircraft equipped with gas turbine engines. Each aircraft has a unique mission and therefore a unique propulsion requirement. At the upper left is a DC-8 airliner. Its mission is to carry large loads of passengers or cargo for a long distance at high speed. It spends most of its life in high speed
cruise. At the lower left is an F-14 fighter plane. Its mission is to shoot down other aircraft in air-to-air combat. It spends most of its life in cruise, but needs
high acceleration when in combat. At the lower right is a C-130 cargo aircraft. Like the DC-8, it carries cargo a long distance, but it does not have the high speed requirement of the DC-8. At the upper right is a T-38 trainer. It is used to teach pilots how to fly jet aircraft and does not have the acceleration requirements of the F-14. The DC-8 is powered by four high-bypass
turbofan engines, the F-14 by two
afterburning low-bypass turbofans, the C-130 by four
turboprop engines, and the T-38 by two
turbojet engines.
EngineSim is an interactive Java applet which allows you to study different types of jet engines. You can learn the fundamentals of turbine engine propulsion with the EngineSim simulator.
RangeGames is an interactive Java applet which allows you to study how different types of aircraft use different types of engines to meet their mission.
Ailerons can be used to generate a
rolling motion for an aircraft.
Ailerons are small hinged sections on the outboard portion of a wing. Ailerons usually work in opposition: as the right aileron is deflected upward, the left is deflected downward, and vice versa. This slide shows what happens when the pilot deflects the right aileron upwards and the left aileron downwards.
The ailerons are used to bank the aircraft; to cause one wing tip to move up and the other wing tip to move down. The banking creates an unbalanced side force component of the large wing lift force which causes the aircraft's flight path to
curve. (Airplanes turn because of banking created by the ailerons, not because of a
rudder input.
The ailerons work by changing the effective shape of the airfoil of the outer portion of the wing. As described on the
shape effects slide, changing the angle of deflection at the rear of an airfoil will change the amount of lift generated by the foil. With greater downward deflection, the lift will increase in the upward direction. Notice on this slide that the aileron on the left wing, as viewed from the rear of the aircraft, is deflected down. The aileron on the right wing is deflected up. Therefore, the lift on the left wing is increased, while the lift on the right wing is decreased. For both wings, the lift force (Fr or Fl) of the wing section through the aileron is applied at the
aerodynamic center of the section which is some distance (L) from the aircraft
center of gravity. This creates a
torque
T = F * L
about the center of gravity. If the forces (and distances) are equal there is no net torque on the aircraft. But if the forces are unequal, there is a net torque and the aircraft
rotates about its center of gravity. For the conditions shown in the figure, the resulting motion will roll the aircraft to the right (clockwise) as viewed from the rear. If the pilot reverses the aileron deflections (right aileron down, left aileron up) the aircraft will roll in the opposite direction. We have chosen to name the left wing and right wing based on a view from the back of the aircraft towards the nose, because that is the direction in which the pilot is looking.
You can test the roll effect yourself using a paper airplane. Just cut some control tabs into the rear of both wings. Bend one tab up and the other down, and you will see the airplane roll when it is flown. The roll will be in the direction of the tab that is pulled up. The same thing will work on a simple wooden glider. The tabs can be yellow stick-ums or tape attached to the wings.]
When you travel on an
airliner, watch the wings during turns. The pilot rolls the aircraft in the direction of the turn. You will probably be surprised at how little deflection is necessary to bank (roll) a large airliner. But be warned that there is a possible source of confusion on some airliners. We have been talking here about rolling the aircraft by using a pair of ailerons at the very trailing edge of both wings to increase or decrease the lift of each wing. On some airliners, the aircraft is rolled by killing the lift on only one wing at a time. A plate, called a
spoiler, is raised between the leading and trailing edges of the wing. This effectively changes the shape of the airfoil, disrupts the flow over the wing, and causes a section of the wing to decrease its lift. This produces an unbalanced force with the other wing, which causes the roll. Airliners use spoilers because spoilers can react more quickly than ailerons and require less force to activate, but they always decrease the total amount of lift for the aircraft. It's an interesting trade! You can tell whether an airliner is using spoilers or ailerons by noticing where the moving part is located. At the trailing edge, it's an aileron; between the leading and trailing edges, it's a spoiler. (Now you can dazzle the person sitting next to you on the plane!)
You can view a short movie of "Orville and Wilbur Wright" explaining how wing warping was used to roll their aircraft. The movie file can be saved to your computer and viewed as a Podcast on your podcast player.
Spoilers are small, hinged plates on the top portion of wings. Spoilers can be used to slow an aircraft, or to make an aircraft descend, if they are deployed on both wings. Spoilers can also be used to generate a
rolling motion for an aircraft, if they are deployed on only one wing. This slide shows what happens when the pilot only deflects the spoiler on the right wing.
Spoilers Deployed on Both Wings
When the pilot activates the spoilers, the plates flip up into the air stream. The flow over the wing is disturbed by the spoiler, the drag of the wing is increased, and the lift is decreased. Spoilers can be used to "dump" lift and make the airplane descend; or they can be used to slow the airplane down as it prepares to land. When the airplane lands on the runway, the pilot usually brings up the spoilers to kill the lift, keep the plane on the ground, and make the brakes work more efficiently. The friction force between the tires and the runway depends on the
"normal" force, which is the weight minus the lift. The lower the lift, the better the brakes work. The additional drag of the spoilers also slows the plane down.
Spoiler Deployed on Only One Wing
A single spoiler is used to bank the aircraft; to cause one wing tip to move up and the other wing tip to move down. The banking creates an unbalanced side force component of the large wing lift force which causes the aircraft's flight path to
curve. (Airplanes turn because of banking, not because of the force generated by the
rudder.
On the figure, the airplane's right wing spoiler is deployed, while the left wing spoiler is stored flat against the wing surface (as viewed from the rear of the airplane). The flow over the right wing will be disturbed by the spoiler, the drag of this wing will be increased, and the lift will decrease relative to the left wing. The lift force (F) is applied at the
center of pressure of the segment of the wing containing the spoiler. This location is some distance (L) from the aircraft
center of gravity which creates a
torque
T = F * L
about the center of gravity. The net torque causes the aircraft to
rotateabout its center of gravity. The resulting motion will roll the aircraft to the right (clockwise) as viewed from the rear. If the pilot reverses the spoiler deflections (right spoiler flat and left spoiler up) the aircraft will roll in the opposite direction. We have chosen to name the left wing and right wing based on a view from the back of the aircraft towards the nose, because that is the direction in which the pilot is looking.
You can test the roll effect yourself using a wooden glider. Just put some control tabs on the top of both wings. Bend one tab up and leave the other flat, and you will see the airplane roll when it is flown. The roll will be in the direction of the tab that is pulled up. The tabs can be yellow stick-ums or tape attached to the wings near the center of the
chord (a straight line connecting the leading and trailing edges of an airfoil).]
When you travel on an
airliner, watch the wings during turns. The pilot rolls the aircraft in the direction of the turn. You will probably be surprised at how little deflection is necessary to
bank (roll) a large airliner. But be warned that there is a possible source of confusion on some airliners. We have been talking about rolling the aircraft by using a spoiler near the center of the wing chord to decrease the lift of one wing. On most airliners, the aircraft is rolled by using
ailerons to increase the lift on one wing and decrease the lift on the other wing. This produces an unbalanced force, which causes the roll. You can tell whether an airliner is using spoilers or ailerons by noticing where the moving part is located. At the trailing edge, it's an aileron; between the leading and trailing edges, it's a spoiler. (Now you can dazzle the person sitting next to you on the plane!)
The amount of lift generated by a wing depends on the
shape of the airfoil, the
wing area, and the aircraft
velocity.
During takeoff and landing the airplane's velocity is relatively low. To keep the lift high (to avoid objects on the ground!), airplane designers try to increase the wing area and change the airfoil shape by putting some moving parts on the wings' leading and trailing edges. The part on the leading edge is called a
slat, while the part on the trailing edge is called a
flap. The flaps and slats move along metal tracks built into the wings. Moving the flaps
aft (toward the tail) and the slats forward increases the wing area. Pivoting the leading edge of the slat and the trailing edge of the flap downward increases the effective
camber of the airfoil, which increases the lift. In addition, the large aft-projected area of the flap increases the
drag of the aircraft. This helps the airplane slow down for landing.
The next time you fly in an airliner, watch the wings during takeoff and landing. On takeoff, we want high lift and low drag, so the flaps will be set downward at a moderate setting. During landing we want high lift and high drag, so the flaps and slats will be fully deployed. When the wheels touch down, we want to decrease the lift (to keep the plane on the ground!), so you will often see
spoilers deployed on the top of the wing to kill the lift. Spoilers create additional drag to slow down the plane.
At the rear of the
fuselage of most aircraft one finds a
horizontal stabilizer and an
elevator. The stabilizer is a fixed wing section whose job is to provide stability for the aircraft, to keep it flying straight. The horizontal stabilizer prevents up-and-down, or
pitching, motion of the aircraft nose. The elevator is the small moving section at the rear of the stabilizer that is attached to the fixed sections by hinges. Because the elevator moves, it varies the amount of force generated by the tail surface and is used to generate and control the pitching motion of the aircraft. There is an elevator attached to each side of the fuselage. The elevators work in pairs; when the right elevator goes up, the left elevator also goes up. This slide shows what happens when the pilot deflects the elevator.
The elevator is used to control the position of the nose of the aircraft and the angle of attack of the wing. Changing the
inclinationof the wing to the local flight path changes the amount of lift which the wing generates. This, in turn, causes the aircraft to
climb or dive. During take off the elevators are used to bring the nose of the aircraft up to begin the climb out. During a banked turn, elevator inputs can increase the lift and cause a tighter turn. That is why elevator performance is so important for fighter aircraft.
The elevators work by changing the effective shape of the airfoil of the horizontal stabilizer. As described on the
shape effects slide, changing the angle of deflection at the rear of an airfoil changes the amount of lift generated by the foil. With greater downward deflection of the trailing edge, lift increases. With greater upward deflection of the trailing edge, lift decreases and can even become negative as shown on this slide. The lift force (F) is applied at
center of pressure of the horizontal stabilzer which is some distance (L) from the aircraft
center of gravity. This creates a
torque
T = F * L
on the aircraft and the aircraft
rotates about its center of gravity. The pilot can use this ability to make the airplane loop. Or, since many aircraft loop naturally, the deflection can be used to
trim or balance the aircraft, thus preventing a loop. If the pilot reverses the elevator deflection to down, the aircraft pitches in the opposite direction.
You can test the pitch effect yourself using a paper airplane. Just cut some control tabs in the rear of both wings. Bend both tabs up to make the tail go down and the nose go up, and the airplane loops when it is flown. Make small adjustments to trim the airplane and suppress the loops. The same thing will work on a simple wooden glider--the tabs can be yellow stick-ums or tape attached to the horizontal stabilizer.]
On many fighter planes, in order to meet their high maneuvering requirements, the stabilizer and elevator are combined into one large moving surface called a
stabilator. The change in force is then created by changing the
inclination of the entire surface, not by changing its effective shape as is done with an elevator. On some aircraft, the pitch stability and control is provided by a horizontal surface placed forward of the center of gravity (a tail in the front). This surface is called a
canard. The name is the French word for duck and it is used because the shape when viewed from above resembles a duck with bulges near the neck. The Wright brother's first
aircraft used a forward
elevator.
You can view a short movie of "Orville and Wilbur Wright" explaining how the elevator was used to control the pitch of their aircraft. The movie file can be saved to your computer and viewed as a Podcast on your podcast player.
At the rear of the
fuselage of most aircraft one finds a
horizontal stabilizer and an
elevator to provide stability and control of the up-and-down, or
pitching, motion of the aircraft nose. On many fighter planes, in order to meet their high maneuvering requirements, the stabilizer and elevator are combined into one large moving surface called a
stabilator. Because the stabilator moves, it varies the amount of force generated by the tail surface and is used to generate and control the pitching motion of the aircraft. There is usually a stabilator on each side of the fuselage and they work in pairs; when the right stabilator goes up, the left stabilator also goes up. This slide shows what happens when the pilot deflects the stabilators.
The stabilator is used to control the position of the nose of the aircraft and the angle of attack of the wing. Changing the
inclination of the wing to the local flight path changes the amount of lift which the wing generates. This, in turn, causes the aircraft to
climb or dive. During take off the stabilators are used to bring the nose of the aircraft up to begin the climb out. During a banked turn, stabilator inputs can increase the lift and cause a tighter turn. That is why stabilator performance is so important for fighter aircraft.
The stabilators work by changing the angle of attack of the horizontal stabilizer. As described on the
inclination effects slide, changing the angle of attack of an airfoil changes the amount of lift generated by the foil. With greater downward deflection of the leading edge, lift increases in the downward direction. With greater upward deflection, lift increases in the upward direction. The lift force (F) is applied at the
center of pressure of the the stabilator which is some distance (L) from the aircraft
center of gravity. This creates a
torque
T = F * L
on the aircraft and the aircraft
rotates about its center of gravity. The pilot can use this ability to make the airplane loop or dive.
On most
aircraft, the horizontal stabilizer and elevator are separate pieces with the elevator being connected to the stabilizer by a hinge. These aircraft rely on changing the
shape of the tail airfoil to produce a change in the down force for control. On some aircraft, the pitch stability and control is provided by a
canard which is a horizontal surface placed forward of the center of gravity (a tail in the front). The Wright brother's 1903
flyer used a forward
elevator for pitch control.
At the rear of the
fuselage of most aircraft one finds a
vertical stabilizerand a
rudder. The stabilizer is a fixed wing section whose job is to provide stability for the aircraft, to keep it flying straight. The vertical stabilizer prevents side-to-side, or
yawing, motion of the aircraft nose. The rudder is the small moving section at the rear of the stabilizer that is attached to the fixed sections by hinges. Because the rudder moves, it varies the amount of force generated by the tail surface and is used to generate and control the yawing motion of the aircraft. This slide shows what happens when the pilot deflects the
rudder, a hinged section at the rear of the vertical stabilizer.
The rudder is used to control the position of the nose of the aircraft. Interestingly, it is NOT used to turn the aircraft in flight. Aircraft
turns are caused by banking the aircraft to one side using either
ailerons or
spoilers. The banking creates an unbalanced side force component of the large wing lift force which causes the aircraft's flight path to curve. The rudder input insures that the aircraft is properly aligned to the curved flight path during the maneuver. Otherwise, the aircraft would encounter additional drag or even a possible
adverse yaw condition in which, due to increased drag from the control surfaces, the nose would move farther off the flight path.
The rudder works by changing the effective shape of the airfoil of the vertical stabilizer. As described on the
shape effects slide, changing the angle of deflection at the rear of an airfoil will change the amount of lift generated by the foil. With increased deflection, the lift will increase in the opposite direction. The rudder and vertical stabilizer are mounted so that they will produce forces from side to side, not up and down. The side force (F) is applied through the
center of pressure of the vertical stabilizer which is some distance (L) from the aircraft
center of gravity. This creates a
torque
T = F * L
on the aircraft and the aircraft
rotates about its center of gravity. With greater rudder deflection to the left as viewed from the back of the aircraft, the force increases to the right. If the pilot reverses the rudder deflection to the right, the aircraft will yaw in the opposite direction. We have chosen to base the deflections on a view from the back of the aircraft towards the nose, because that is the direction in which the pilot is looking
You can test the yaw effect yourself using a paper airplane. Just cut a control tab in the rear of the body. Bend the tab right to make the tail go right and the nose go left, and the airplane will turn to the left when it is flown. The same thing will work on a simple wooden glider. The tab can be a yellow stick-um or tape attached to the vertical stabilizer.]
On all
aircraft, the vertical stabilizer and rudder create a
symmetric airfoil. This combination produces no side force when the rudder is aligned with the stabilizer and allows either left or right forces, depending on the deflection of the rudder. Some fighter planes have two vertical stabilizers and rudders because of the need to control the plane with multiple, very powerful engines.
@seven0seven @Starlord
