Chapter 3: Use and Effect of Controls

CHAPTER THREE

USE AND EFFECT OF CONTROLS

300.

INTRODUCTION

This chapter briefly discusses the devices with which the pilot operates the airplane in the air and

on the ground and how those devices are to be used effectively. These controls may be grouped

into four categories:

Primary flight controls.

Secondary flight controls.

Power controls.

Auxiliary controls.

301.

PRIMARY FLIGHT CONTROLS

To maneuver an airplane, the pilot must control its movement about its lateral, longitudinal, and

vertical axes. This is accomplished by the use of the flight controls (elevators, ailerons, and

rudder) which can be deflected from their neutral position into the flow of air as the airplane

moves forward through the air. During flight, the flight controls have a natural "live pressure"

due to the force of the airflow around them.

With this in mind, the pilot should think not of moving the flight controls, but of exerting force

on them against this live pressure or resistance.

Elevators. The elevators control the movements of the airplane about its lateral axis. They

form the rear part of the horizontal stabilizer, are free to be moved up and down by the pilot, and

are connected to a control stick in the cockpit by means of cables and pulleys. Applying forward

pressure on the stick causes the elevator surfaces to move downward. The flow of air striking

the deflected elevator surfaces exerts an upward force, pushing the airplane's tail upward and the

nose downward. Conversely, exerting backpressure on the control causes the elevator surfaces

to move up, exerting a downward force to push the tail downward and the nose upward.

In effect, the elevators are the angle of attack control. When backpressure is applied on the

control, the tail lowers and the nose rises, thus increasing the wing's angle of attack and lift.

Ailerons. The ailerons control the airplane's movement about its longitudinal axis. There

are two ailerons, one at the trailing edge of each wing, near the wingtips. They are movable

surfaces hinged to the wing's rear spar and are linked together by cables so that when one aileron

is deflected down, the opposite aileron moves up. Contrary to popular belief, the lift on the

wings is the force that turns the airplane in flight-not the rudder (Figure 3-1).

To obtain the horizontal component of lift required to pull the airplane in the desired direction of

turn, the wings must be banked in that direction. When the pilot applies pressure to the left on

USE AND EFFECT OF CONTROLS

3-1