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Airfoil
A structure or body which produces a useful reac on to air movement.
Chord Line
An imaginary straight line from the leading edge to the trailing edge of an airfoil.
Rela ve Wind
The wind felt by an airfoil (Parallel and in the opposite direc on to the flight path of the airfoil).
Angle of A#ack
The angle between the chord line of the airfoil and the rela ve wind.
Angle of Incidence
The angle at which a wing is a#ached to the aircra& fuselage.
Lateral Axis
An imaginary line from wing p to wing p.
Pitch
Rota on around the lateral axis, controlled by the elevators.
Longitudinal Control or Longitudinal Stability
Stability due to pitch.
Longitudinal Axis
An imaginary line from the nose to the tail.
Roll
Rota on around the longitudinal axis, controlled by the ailerons.
Lateral Control or Lateral Stability
Stability due to Roll.
Ver cal Axis
,An imaginary line extending ver cally through the intersec on of the lateral and longitudinal
axis.
Yaw
Rota on about the ver cal axis, controlled by the rudder.
Direc onal Control or Direc onal Stability
Stability due to yaw.
Center of Gravity
The imaginary point where all the weight is concentrated. The three axis meet at this point.
Weight
Downward acing force that must be overcome by li&. P
Li&
Upward ac ng force that must overcome weight.
Drag
Rearward ac ng force that must be overcome by thrust.
Thrust
Forward ac ng force that must overcome drag.
Bernoulli's Principle
As the velocity of a fluid increases, its pressure decreases.
How is li& created?
There is a pressure difference between the top and the bo#om of the wing. Air accelera ng
over the top of the wing creates an area of low pressure.
What 2 things can the pilot control in order to increase li&?
Increasing either the angle of a#ack or airspeed.
Parasite Drag
The resistance of the air produced by any part of an airplane that does not produce li&. This
kind of drag increases as airspeed increases.
Induced Drag
,A by-product of li&. High pressure air beneath the wing tries to flow to the area of low pressure,
causing a vortex behind the wing ps and along the trailing edge of the wing. As the angle of
a#ack is increased, li& will increase and so will the vor ces and downwash. This kind of drag
increases as airspeed decreases.
Stability
The inherent ability of an airplane to return, or not return, to its original flight condi on a&er
being disturbed by an outside force.
Posi ve Sta c Stability
The ini al tendency of an aircra& to return or not return to its original posi on.
Posi ve Dynamic Stability
The tendency of an oscilla ng airplane to return to its original posi on rela ve to me.
Horizontal Li& Component
Horizontal force that forces the airplane from straight and level flight and causes it to turn.
Ver cal Li& Component
This component is reduced in turns, resul ng in a loss of al tude unless total li& is increased by
increasing angle of a#ack, airspeed, or both.
Load
The force that must be supported by an airplane structure in flight.
Load factor
Loads imposed on the winds in flight
What load does an airplane in straight and level flight support?
The sum of the weight of the aircra& plus its contents, equal to 1 "G."
Centrifugal Force
Acts toward the outside of the curve any me an airplane is flying a curved path (turns, climbs
or decent).
What do turns do to the load factor?
Increase the load factor.
Increasing the angle of bank of a turn increases...?
, The load factor.
An increased load factor will cause the airplane to...?
Stall at a higher speed.
Condi ons that increase the load of an aircra& are...?
Overloading the airplane, too steep an angle of bank, turbulence and abrupt movement of the
controls.
Rectangular Course
The flight path should be posi oned outside the field boundaries just far enough that they may
be easily observed from either pilot seat. The closer the track of the airplane is to the field
boundaries, the steeper the bank necessary at turning points.
Turns around a point
the wings will be in alignment with the pylon only during the me the airplane is flying directly
upwind or directly downwind.
Wind Correc on Angle
keeps the wings from poin ng directly at the pylon any me the airplane is not flying directly
upwind or downwind.
S-Turn
First half (star ng downwind): begin shallow and increase in steepness as the airplane turns
crosswind. If the turn is started with too steep a bank angle, the bank will increase too rapidly
and the upwind half of the "S" will be smaller than the downwind half.
Stalls
At an angle of a#ack of approximately 18-20 degrees turbulence over the upper wing surface
decreases li& so dras cally that flight cannot be sustained and the wing stalls.
Cri cal Angle of A#ack
The angle at which a stall occurs.
Spin
When an aircra& has stalled and the outside wing con nues to provide more li& than the inside
wing and the aircra& remains stalled.
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