connected to the OD box. The scale platform holds the
feedback potentiometer and local pitch indicator, as
shown in views A and B of figure 3-10. This indicator
is defined as temperature compensated because the
indicator arm is connected to the prairie air tube. Look
at view B. The prairie air tube is normally pressurized
with air at a controlled temperature, and will have a fixed
amount of thermal growth. Hence, the indicator arm is
provided with a thermally stable (temperature-
compensated) surface, a primary means to sense and
indicate propeller pitch, and a means to relay that
information to the machinery control system (MCS).
Electronic Pitch Indicator System. In addition
to the temperature-compensated pitch indicator
installed on the OD box of DDG-51 class ships, an
electronic pitch position transducer is installed behind a
Figure 3-10.Pitch scale platform showing temperature-compensated pitch indicating system.
3-14