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and airspeeds. Since Lift and Weight must be equal in order to maintain level flight, it is obvious that
there is a relationship between Lift (L), Airspeed (V), and Angle of Attack (AT). This relationship can be
"generalized" with the following expression. (Note: the expression is not an exact equation).
Lift = Angle of Attack x Velocity
Since angle of attack and speed also have a relationship to Induced Drag and Parasite Drag, the
relationship of Lift/Drag is shown by the graph below.
Aerodynamics
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Parasite drag increases with
speed. Induced drag decreases
with speed. The SUM of the
two drags (Total Drag curve)
shows that there is only one
airspeed for a given airplane
and load that provides
MINIMUM total drag. This is
the point M which is the
maximum lift over drag ratio
(L/D). It is the airspeed at which
the aircraft can glide the farthest
without power (maximum glide
range). This is the airspeed
which should immediately be
set up in the event of a power
failure. This maximum glide
airspeed is different for each
aircraft design. The Pilot
Operating Handbook should be
consulted for this airspeed and the pilot should memorize it to eliminate need to search manuals during
an emergency.
Ground Effect
An aircraft can be flown near the ground or water at a slightly slower airspeed than at altitude. This is
known as Ground Effect.
The airflow
around the left
aircraft at
altitude can
flow around the
surface of the
aircraft in a
normal manner. The airflow around thr right aircraft is disturbed by the proximity to the ground. The
normal downwash of air produced by the wing and tail surfaces cannot occur, and the air becomes
compressed under these surfaces. A "cushioning" effect occurs which allows the airplane to fly at slightly
slower airspeed than at altitude.
The maximum ground effect occurs at approximately 1/2 the wingspan above the ground. It is this effect
which causes the plane to seem to float when near the ground on landing. It also allows the aircraft to be
Aerodynamics
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"pulled" off the ground before adequate climb speed is achieved.
Load Factor
The load factor is the total load supported by the wings divided by the total weight of the airplane. In
straight and level flight, the load factor is 1; i.e. the weight supported by the wings is equal to the weight
of the loaded aircraft. The load factor is described as 1G Force. With a load factor of 1, the G force is 1.
In other terms, the load supported by the wings equals the total weight of the loaded aircraft.
In a turn, the weight of the aircraft increases due to the addition of centrifugal force. The rate of turn
determines the total weight increase. A faster turn (steeper bank) generates greater centrifugal force. The
centrifrugal force is straight out from the center of the turn. When the downward weight of the aircraft is
mathematically resolved with the horizontal centrifrugal force, the load on the wings is the Resultant
Load.
In a
45
degree banked turn, the resultant load factor is approximately 1.4 G. In other words, the load on the
wings is 1.4 times the loaded weight of the aircraft. In a 60 degree banked turn, the load factor is 2G. The
load on the wings is TWICE the loaded weight of the aircraft. The G force is greater than 1 in a loop
maneuver for the same reason; i.e. a centrifugal force adds to the airplane’s weight. An abrupt change
from level to nose down creates an upward centrifugal force, decreasing the G load to less than 1G.
Aerodynamics
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Aerodynamics
The effects of the bank angle is shown in the graph on the right. The G
Force is shown on the Left Side, and the Bank Angle is shown on the
bottom of the graph.
The maneuver of most importance to the private pilot is the forces in a
turn. The most critical time is in tu rns in the traffic patern, when
airspeeds are low, and the attention to bank angle and airspeed may be
distracted by other duties.
Back tBoa Hcokm teo TabTloe P oift Cootn e&n Sttsatic System
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Pitot and Static System
Pitot and Static System
The Pressure System
The pitot-static pressure system provides the source of air pressure for the
l ALTIMETER (ALT)
l VERTICAL SPEED INDICATOR (VSI)
l AIRSPEED INDICATOR (ASI)
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