The Wing
To understand aerodynamic forces, a pilot needs to
Understand basic terminology associated with airfoils.
Figure 2-1 illustrates a typical airfoil.

The chord line is the straight line intersecting the leading
and trailing edges of the airfoil, and the term chord refers
to the chord line longitudinal length (length as viewed from
the side).

The mean camber is a line located halfway between the
upper and lower surfaces. Viewing the wing edgewise, the
mean camber connects with the chord line at each end, The
mean camber is important because it assists in determining
aerodynamic qualities of an airfoil. The measurement of
the maximum camber; inclusive of both the displacement
of the mean camber line and its linear measurement from
the end of the chord line, provide properties useful in
evaluating airfoils,

Review of Basic Aerodynamics
The instrument pilot must understand the relationship
and differences between several factors that affect the
performance of an aircraft in flight. Also, it is crucial to
understand how the aircraft reacts to various control and
power changes, because the environment in which instrument
pilots fly has inherent hazards not found in visual flying. The
basis for this understanding is found in the four forces acting
on an aircraft and Newton's Three Laws of Motion.

Relative Wind is the direction of the airflow with respect to
an airfoil.

Angle of Attack is the acute angle measured between the
relative wind, or flight path and the chord of the airfoil.
[Figure 2-2]

Flight path is the course or track along which the aircraft is
flying or is intended to be flown.

The Four Forces
The four basic forces [Figure 2-3] acting upon an aircraft in
flight are lift, weight, thrust, and drag.

Lift
Lift is a component of the total aerodynamic force on an
airfoil and acts perpendicular to the relative wind. Relative
wind is the direction of the airflow with respect to an airfoil.
This force acts straight up from the average (called mean)
center of pressure (CP), which is called the center of lift. It
should be noted that it is a point along the chord line of an
airfoil through which all aerodynamic forces are considered
to act. The magnitude of lift varies proportionately with
speed, air density, shape and size of the airfoil, and angle
of attack. During straight-and-level flight, lift and weight
are equal.

Figure 2-2. Angle of Attack and Relative Wind.