A triple-breech cartridge starter.
Cartridge
7. Cartridge starting is sometimes used on military
engines and provides a quick independent method of
starting. The starter motor is basically a small
impulse-type turbine that is driven by high velocity
gases from a burning cartridge. The power output of
the turbine is passed through a reduction gear and
an automatic disconnect mechanism to rotate the
engine. An electrically fired detonator initiates the
burning of the cartridge charge. As a cordite charge
provides the power supply for this type of starter, the
size of the charge required may well limit the use of
the cartridge starters. A triple-breech starter is
illustrated in fig. 11-4.
Iso-propyl-nitrate
8. This type of starter provides a high power output
and gives rapid starting characteristics. It has a
turbine that transmits power through a reduction gear
to the engine. In this instance, the turbine is rotated
by high pressure gases resulting from the
combustion of iso-propyl-nitrate. This fuel is sprayed
into a combustion chamber, which forms part of the
starter, where it is electrically ignited by a highenergy
ignition system. A pump supplies the fuel to
the combustion chamber from a storage tank and an
air pump scavenges the starter combustion chamber
of fumes before each start. Operation of the fuel and
air pumps, ignition systems, and cycle cancellation,
is electrically controlled by relays and time switches.
An iso-propyl-nitrate starting system is shown in fig.
11-5.
Air
9. Air starting is used on most commercial and
some military jet engines. It has many advantages
over other starting systems, and is comparatively
light, simple and economical to operate.
10. An air starter motor transmits power through a
reduction gear and clutch to the starter output shaft
which is connected to the engine. A typical air starter
motor is shown in fig. 11-6.
11. The starter turbine is rotated by air taken from
an external ground supply, an auxiliary power unit
(A.P.U.) or as a cross-feed from a running engine.
The air supply to the starter is controlled by an electrically
operated control and pressure reducing valve
that is opened when an engine start is selected and
is automatically closed at a predetermined starter
speed. The clutch also automatically disengages as
the engine accelerates up to idling r.p.m. and the
Starting and ignition
124
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