Page 16 - Understanding Flight

CH01_Anderson PFS2 7/25/01 8:55 AM Page 3

Basic Concepts 3

surface. The purpose of the trim tabs is to reduce the necessary force
on the control wheel, called a yoke, for the pilot to maintain a desired
flight attitude.
Most modern airplanes have single wings mounted either above or
below the fuselage. Most but not all high-winged airplanes have wings
that are supported by struts. Struts allow for a lighter wing but at the
expense of more drag (resistance to motion through the air).
The movable surfaces on the outer trailing edge of the wings are the
ailerons, which are used for roll control (rotation around the axis of
the fuselage). They are operated by the rotation of the control wheel
or by the left-right movement of the stick. The ailerons are
A tail dragger is also known as
coupled so that when one swings up the other swings down.
conventional gear because before
Control surfaces are discussed in detail below.
WWII nose wheels were rare.
The hinged portions on the inboard part of the trailing edge
of the wings are the flaps. These are used to produce greater lift at low
speeds and to provide increased drag on landing. This increased drag
helps to reduce the speed of the airplane and to steepen the landing
approach angle. Flaps are discussed in detail in the chapter on wings.
Small airplanes have two configurations of landing gear. Tricycle
landing gear has the main landing gear just behind the center of
balance of the airplane and a steerable nose gear up forward. The tail
dragger has the main landing gear forward of the center of balance and
a small steerable wheel at the tail. The nose gear and the tail wheel are
steered with the rudder pedals.

Airfoils and Wings
An airfoil is a shape designed to produce lift. As shown in Figure 1.3,
an airfoil is the shape seen in a slice of a wing. Besides the wing, pro-
pellers and the tail surfaces are also airfoils. Even aeronautical engi-
neers (in discussions) sometimes mistakenly use the terms wing and
airfoil interchangeably. But an airfoil is just the shape seen in a slice
of the wing and not a wing itself. For some wings, slices taken at dif-
ferent places along its length will reveal different airfoils.
An airfoil, as shown in Figure 1.3, has a leading edge and a trailing
edge. As detailed in Figure 1.4, a chord and a camber also characterize
an airfoil. The chord is an imaginary straight line connecting the