Page 20 - Understanding Flight

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

Basic Concepts 7

6

5

4

Load Factor 3

2

1

0
0 20 40 60 80
Bank Angle (degrees)
Fig. 1.7. Load factor as a function of bank angle.

load divided by the weight, on the airplane in a 2g turn is 2. Figure
1.7 shows the load factor as a function of bank angle for any airplane
in flight. One thing to understand is that the forces on the pilot (or the
load) are only related to the bank angle, which is the angle made by
the wing and the horizon. In Figure 1.6 the bank angle is 60 degrees.
The vertical part of the lift must always be equal to the weight of the
airplane if the altitude of the airplane does not change during the
turn. This is called a level turn. So the steeper the bank angle the
greater the lift and thus the greater the force felt by the pilot. The
insert in the figure shows the forces of a 30 degree turn for
comparison. The weight part of the lift is the same, but the other two
forces are less. A 2g turn is achieved by banking the airplane at an
angle of 60 degrees, independent of the speed of the airplane. Turns
will be discussed in more detail in the chapter on “Airplane
Performance.”