you should realize that a pilot can move a helicopter
forward or rearward, or to the right or left, simply by
tilting the main rotor in the desired direction.
Look at figure 3-10. This points out another major
difference
between
fixed-wing
and
rotary-wing
aircraft. The fixed-wing aircraft can't move up or down
or right or left without forward movement. Remember,
a fixed-wing aircraft's primary direction is forward.
However, a helicopter can move in any direction, with
or without forward movement.
Hovering
Hovering is defined as maintaining a position
above a fixed spot on the ground. A helicopter has the
ability to remain in one spot in the air with little or no
movement in any direction. This is done by equalizing
all the forces acting on the helicopters (lift, drag,
weight, and thrust). This action also allows a helicopter
to take off or land without a runway. This is another
advantage the rotary-wing aircraft has over the
fixed-wing aircraft.
Torque Reaction
As the helicopter's main rotor turns in one
direction, the body (fuselage) of the helicopter tends to
rotate in the opposite direction (Newton's third law).
This is known as torque reaction. In a single main rotor
helicopter, the usual way of getting rid of torque
reaction is by using a tail rotor (anti-torque rotor). This
rotor is mounted vertically on the outer portion of the
helicopter's tail section. See figure 3-11. The tail rotor
produces thrust in the opposite direction of the torque
reaction developed by the main rotor. Figure 3-11
shows the manner in which torque reaction is
eliminated in a single main rotor helicopter.
Q3-9.
How does the pilot change the angle of attack
on (a) an airplane and (b) a helicopter?
Q3-10.
What is the main difference between a
helicopter and an airplane?
Q3-11.
What maneuver can a helicopter perform that
an airplane cannot?
SUMMARY
In this chapter, you have been introduced to the
principles of flight. You have learned about the
principles of flight for fixed-wing and rotary-wing
aircraft.
3-7
Figure 3-10.—Directional flight attitudes.
Figure 3-11.—Torque reaction.
