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Instrument Flying Handbook
Flight Instruments
Gyroscopic Instruments

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Instrument Flying


Table of Contents

Chapter 1. Human Factors
Chapter 2. Aerodynamic Factors
Chapter 3. Flight Instruments
Chapter 4. Section I
Airplane Attitude Instrument
Using Analog Instrumentation
Chapter 4. Section II
Airplane Attitude Instrument
Using an Electronic Flight

Chapter 5. Section I
Airplane Basic
Flight Maneuvers
Using Analog Instrumentation
Chapter 5. Section II
Airplane Basic
Flight Maneuvers
Using an Electronic Flight

Chapter 6. Helicopter
Attitude Instrument Flying

Chapter 7. Navigation Systems
Chapter 8. The National
Airspace System

Chapter 9. The Air Traffic
Control System

Chapter 10. IFR Flight
Chapter 11. Emergency

Heading indicators like the one in Figure 3.31 work on the
same principle as the older horizontal card indicators, except
that the gyro drives a vertical dial that looks much like the
dial of a vertical card magnetic compass. The heading of the
aircraft is shown against the nose of the symbolic aircraft on
the instrument glass, which serves as the lubber line. A knob
in the front of the instrument may he pushed in and turned
to rotate the gyro and dial. The knob is spring loaded so it
disengages from the gimbals as soon as it is released. This
instrument should be checked about every 15 minutes to see
if it agrees with the magnetic compass.

heading indicator
Figure 3-31. The heading indicator is not north seeking, but must
be set periodically (about emery 15 minutes) to agree with the
magnetic compass.

Turn Indicators
Attitude and heading indicators function on the principle
of rigidity, but rate instruments such as the turn-and-
slip indicator operate on precession. Precession is the
characteristic of a gyroscope that causes an applied force to
produce a movement, not at the point of application, but at
a point 90° from the point of application in the direction of
rotation. [Figure 3-32]

Turn-and-Slip Indicator
The first gyroscopic aircraft instrument was the turn indicator
in the needle and ball, or turn and bank indicator, which
has more recently been called a turn-and-slip indicator.
[Figure 3-33]

Figure 3-32. Precession. causes a force applied to a spinning
wheel to be felt 90° from the point of application in the direction
of rotation.

The inclinometer in the instrument is a black glass ball sealed
inside a curved glass tube that is partially tilled with a liquid
for damping. This ball measures the relative strength of the
force of gravity and the force of inertia caused by a turn.
When the aircraft is flying straight-and-level, there is no
inertia acting on the ball, and it remains in the center of the
tube between two wires. In a turn made with a bank angle
that is too steep, the force of gravity is greater than the inertia
and the ball rolls down to the inside of the turn. If the turn is
made with too shallow a bank angle, the inertia is greater than
gravity and the ball rolls upward to the outside of the turn.

The inclinometer does not indicate the amount of bank, nor
does it indicate slip; it only indicates the relationship between
the angle of bank and the rate of yaw.

Turn-and-Slip Indicator.
Figure 3-33. Turn-and-Slip Indicator.