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Axes of Rotation
The aircraft is free to move around 3 different axes.
l The LONGITUDINAL AXIS is an imaginary line( line X - X ) from nose to tail. Rotation around
the LONGITUDINAL axis is called ROLL. Roll is controlled by the ailerons. When the pilot turns
the CONTROL WHEEL (or in some aircraft a control stick), to the RIGHT the right aileron
deflects upward, while the left aileron deflects downward. This causes the right wing to produce
less lift and the left wing to produce greater lift. This unequal lift causes the airplane to ROLL to
the right as long as the ailerons remain in this condition. In order to stop the roll, it is necessary to
neutralize the ailerons. The aircraft will remain in a "banked" condition until rolled back to level
by application of opposite aileron action.
l The LATERAL AXIS is an imaginary line ( line Y-Y ) from wingtip to wingtip. Rotation around
the LATERAL axis is called PITCH. The "nose up" or "nose down" pitch of the aircraft is
controlled by use of the elevator surfaces of the tail. When the pilot pulls the control wheel (or
control stick) rearward, the elevators deflect upward, forcing the tail downward. This is referred to
as a "nose up attitude". When the control wheel or stick is moved forward, the opposite reactions
occur, causing a "nose down attitude".
l The VERTICAL AXIS is an imaginary vertical line (line Z_Z )running through the center of
gravity of the aircraft. Rotation around the VERTICAL axis is called YAW. Yaw is predominately
controlled by use of the rudder. Left rudder pedal depression in the cockpit deflects the rudder
surface to the left. This causes the tail of the aircraft to move to the right, creating a yaw to the left
about the vertical axis. Application of right rudder similarly causes yaw to the right.
Back tBoa Hcokm teo TabTloe P orfi Cnocniepnltes of Lift
The Airplane
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http://www.uncletom2000.com/gs/lift.htm
LIFT
When Lift is mentioned, most people think primarily of the wings. However there are several other
surfaces which generate lift, although not necessarily in an upward direction. These are the Propeller,
Elevators, Rudder, Ailerons, and Flaps.
l Principles of Lift
The structure of the wing best demonstrates the principle of airfoil lift. In the 19th century a scientist
named Bernoulli discovered that the intenal pressure of a fluid (liquid or gas) reduces the faster the fluid
flows. If you take a tube, and make the tube smaller in diameter in the middle, this creates a "neckeddown"
section called a venturi. When air is forced through the pipe, as much air has to come out the exit
as goes in the tube entrance. The air in the venturi section must travel faster to get through. Bernoulli
found that the pressure at the venturi section was less than at the two ends of the pipe. This is because the
speed of the air through the venturi section is traveling faster than at the ends of the tube.
l The Airfoil
The shape of a wing is called an AIRFOIL. Usually the bottom of the wing is flat or nearly flat. The top
of the wing is curved, with the wing being thicker at the front edge of the wing, and tapering to a thin
surface at the trailing edge of the wing.
When a wing airfoil surface passes through the atmosphere, the atoms of the air on the top of the airfoil
(shown as minus) must travel faster than their cousins (shown as plus) passing along the lower and flater
surface. This occurs because the distance the air must pass over the curved top of the wing is longer than
the distance along the lower surface. According to the Bernoulli Principle, the pressure above the wing is
less than the pressure of air below it. Consequently, a pressure difference between the lower and upper
surfaces exist. This results in LIFT being produced. The amount of lift depends on the airfoil design and
the speed of the air over its surfaces.
l Camber
The curved surface of an airfoil is called Camber. It can be both Positive and Negative. The curved upper
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surface of a wing is called Positive Camber. If the lower surface of the airfoil is curved downward, this
would constitute a negative camber.
l Chord
The chord of a wing is an imaginary line from the leading edge to the trailing edge of the wing. The term
is used in the definition of "Angle of Incidence" and "Angle of Attack" (defined later).
l Angle Of Incidence
The angle which the chord of the wing makes with the longitudinal centerline of the aircraft is known as
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