Q16. What indicator shows the lateral attitude
of an aircraft?
ENGINE INSTRUMENT SYSTEMS
Learning Objective: Recognize the operat-
ing principles and characteristics of various
engine instrument systems, including
tachometer, temperature indicating, fuel
flow, oil pressure, fuel pressure, oil
temperature, exhaust-nozzle indicating,
and torquemeter systems.
Engine instruments provide indications of tail
pipe temperature, oil and fuel pressure, engine
RPM, oil temperature, and fuel flow rate. The
pilot must be aware of engine operation at all
times. If oil pressure falls below the normal
operating limit or tail pipe temperature becomes
excessively high, the engine instruments provide
these indications to the pilot.
TACHOMETER SYSTEMS
Figure 6-43.-Tachometer indicators: (A) jet engine (radial);
(B) jet engine (vertical scale).
The tachometer indicator is an instrument that
shows the speed of a gas turbine engine (jet) main
rotor assembly. Figure 6-43 shows tachometer
element. The problem of changes in generator
indicators for various types of engines. The dials
output voltage is cut out by the generator and
of tachometer indicators used with jet engines are
synchronous-motor combination. These units
shown in percentage of revolutions per minute
make a frequency-sensitive system for sending an
(RPM), based on takeoff RPM.
indication of engine speed to the indicator with
absolute accuracy.
Several types and sizes of generators and
indicators are used in the tachometer systems of
For many installations, it is desirable to send
naval aircraft. As a rule, they all operate on the
a single engine-speed indication to two different
same basic principle. This section introduces you
stations in the aircraft. The frequency-sensitive
to information on tachometer systems. A typical
system is ideal for this application because there
is no change in indication when a second indicator
generator and a typical indicator are described
because it is not practical to describe all the
connects in parallel with the first. Synchronous-
motor operation in each indicator depends only
generators and indicators. For detailed informa-
tion on a particular system, you should refer to
on the availability of enough power in the
the manufacturer's manuals.
generator to operate both indicator motors.
Essentially, the tachometer system consists of
Tachometer Generator
an ac generator coupled to the aircraft engine and
an indicator consisting of a magnetic-drag element
Tachometer generator units are small and
on the instrument panel. The generator transmits
electric power to a synchronous motor, a part of
compact (about 4 inches by 6 inches). The
the indicator. The frequency of this power is
generator is constructed with an end shield
proportional to the engine speed. An accurate
designed so the generator can attach to a flat plate
indication of engine speed is obtained by applying
on the engine frame or reduction gearbox, with
the magnetic-drag principle to the indicating
four bolts.
