and Electronics Training Series (NEETS), module
of the rudder shaker system. When the aircraft
reaches stall angle of attack, the AOA indicator
cam-actuated switch completes the rudder shaker
motor circuit to ground. When the angle of attack
returns below stall conditions, the cam deactuates
A gyroscope is a spinning wheel or rotor with
universal mounting. This mounting allows the
the switch. The switch action removes the ground
gyroscope to assume any position in space. Any
to the rudder shaker motor.
spinning object exhibits gyroscopic properties.
The wheel, with specific design and mounts to
Early aircraft were flown by visually aligning
use these properties, is a gyroscope. The two
the aircraft with the horizon. With poor visibility,
important design characteristics for instrument
it was not possible to fly the aircraft safely. The
need for flight instruments to correct this
1. high density weight for small size, and
condition lead to the development of fyroscopic
instruments. The gyroscopic properties of a
2. high speeds rotation with low-friction.
spinning wheel made precision instrument flying,
precise navigation, and pinpoint bombing
The mountings of the gyro wheels are gimbals.
They can be circular rings or rectangular frames.
practical and reliable. Some of the instruments
However, some flight instruments use part of the
that use this principle are the turn-and-bank
indicator, directional gyro, gyro horizon, and the
instrument case itself as a gimbal. A simple
drift meter. Systems that use the gyroscopic
The two general types of mountings for gyros
principle include the AFCS, gyrostabilized
are the free or universal mounting and the
flux-gate compass, and the inertial navigation
restricted or semirigid mounting. The type of
system. The following paragraphs contain a brief
review of gyroscopic principles.
mounting the gyro uses depends on the gyro's
A gyro can have different degrees of freedom.
The degree of freedom depends on the number
of gimbals supporting the gyro and the arrange-
ment of the gimbals. Do not confuse the term
degrees of freedom, as used here, with an angular
value as in degrees of a circle. The term degrees
Figure 6-34.-Simple gyroscope.
Figure 6-33.-Rudder shaker schematic (simplified).