Page 19 - Understanding Flight

CH01_Anderson PFS2 7/25/01 8:55 AM Page 6

6 CHAPTER ONE

the lift of the wings. Finally, yaw, which is controlled by the rudder, is
rotation about the vertical axis, which is a line that goes vertically
through the center of the wing. It is important to note that all three
axes go through the center of gravity (often abbreviated c.g.) of the air-
plane. The center of gravity is the balance point of the airplane. Or,
equivalently, all of the weight of the airplane can be considered to be
at that one point.

The Turn

The first flight attendants One common misconception by those who are not pilots is
(stewardesses) were required that, as with a boat, the rudder is the control used for making
to be registered nurses. a turn. Although very small direction changes can be made
with the rudder, the ailerons are use in making turns. The air-
plane is rolled to an angle in the direction of the desired turn. The lift
developed is perpendicular to the top of the wing. In straight-and-level
flight, this is straight up. As shown in Figure 1.6, when the airplane
rolls to some angle, the direction of lift is now at an angle with part of
the lift force used for turning and part used to support the weight of
the airplane. In a turn the rudder is only used to make small correc-
tions and coordinate the turn.
As shown in the figure, the pilot feels a force equal to the lift but
in the opposite direction. Occasionally in the following chapters we
refer to the 2g turn. A 2g turn is a turn where the force felt by the pilot
is twice the force of gravity (2g) and the force, or load, on the wing
has been doubled. In aeronautical terms the load factor, which is the

60°
Lift
Weight
Weight
Turning force
Force felt by the pilot Forces in a
30° turn.

Fig. 1.6. Forces on an airplane in a turn.