Aero Chapter 01, General Aerodynamics Review
T-45 Aerodynamics Student Workbook
AERO CHAPTER 01, GENERAL AERODYNAMICS REVIEW
OVERVIEW
This lesson reviews the basic forces acting on an aircraft in flight, the aerodynamic principles involved in
producing lift, aircraft stability, and the “envelope.” It does not contain T-45 aircraft specific material, as do
the remaining aerodynamic lessons.
PRESENTATION
LIFT
Four basic forces act upon an aircraft in flight.
They are lift, drag, weight, and thrust (Figure 1).
Lift acts through the aerodynamic center (AC) of
Aerodynamic
Center
the aircraft. Thrust and drag are sometimes said
to act through the center of gravity (CG), but this is
THRUST
DRAG
JET
a vast simplification of the physics involved.
DANGER
E
INTAK
Weight always acts through the center of gravity.
Center
In steady flight, it is true that the sum of thrust and
of Gravity
drag through the CG is zero. Since Naval
Aviators do not require all the underlying physics
WEIGHT
to fly an aircraft, this course will consider that
Figure 1: AERODYNAMIC FORCES
weight, thrust, and drag act through the center of
gravity.
LIFT
Lift, the primary support force of an aircraft, is usually thought of as the force acting in an upward direction.
However, lift acts 90 degrees to the relative wind. The aircraft attitude may be such that the lift is acting in
varying directions to the other forces that act through the center of gravity.
Lift is the result of air flowing faster over the upper surface of the wing in comparison to the lower surface.
According to Bernoulli’s principle, this difference in
airflow velocity creates an area of low pressure on the
upper surface of the wing compared to the lower surface.
High Ratio
The pressure differential produces lift.
The basic lift equation is L = CL 1/2 r V2 S
Low Ratio
WHERE: L
=
LIFT
CL
=
COEFFICIENT OF LIFT
r
=
AIR DENSITY
THICKNESS-TO-CHORD RATIO
V
=
AIRCRAFT TRUE AIRSPEED
S
=
WING SURFACE AREA
COEFFICIENT OF LIFT
High
The coefficient of lift (CL) is determined by the shape of
the wing, the wing airfoil section/planform, and the angle
CL
C
L
of attack (AOA). Angle of attack is the angle measured
between the chord line of the wing and the relative wind.
Low
Shape of the wing includes wing thickness, chord,
camber, leading edge radius, and wing sweep. The
shape of a wing is dictated by the intended use of the
AOA
AOA
aircraft, whether glider or fighter (Figure 2).
Figure 2: CL CURVE OF HIGH VS LOW
THICKNESS-TO-CHORD RATIOS
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