closed, solenoid-operated regulating valve. It
AIR START SYSTEM
regulates airflow to the starter to 450 50
The engine air start system (fig. 3-22) has an
psig. A bypass line with an orifice and a pilot valve
air turbine starter, a starter exhaust system, and
provides for smooth engagement of the starter
two independent air supply systems. Each system
teeth. An HP start signal will cause the pilot valve
has its own control valve. Air from the LP starter
to open. This allows air to flow through the orifice
air control valve enters the starter inlet through
to the starter at less than 50 psig to engage the
a 3-inch line. Air from the HP starter air control
starter teeth. After about one-quarter second, the
valve enters the inlet through a 1 1/2-inch line.
pilot valve will cause the air control valve to open.
Exhaust air from the starter is discharged through
Full pressure is then applied to the starter for
a 6-inch line into the engine module cooling air
rotation. A manual needle bypass valve is
duct downstream of the fire damper.
provided for manual HP starting.
Low-Pressure Air Start System
Air from the ship's bleed air system enters the
Air Starter Motor
starter LP air control valve. The control valve is
a normally closed, solenoid-operated regulating
The Bendix air turbine starter is mounted
valve. It regulates airflow to the starter at 45 psig.
on the generator side of the reduction gear
high-speed input shaft. It is directly coupled
High-Pressure Air Start System
to the engine through the reduction gear high-
speed pinion and PTO shaft during the start
Air from the HP air flasks enters the starter
cycle.
HP control valve. The control valve is a normally
Figure 3-22.--GTGS air start system.
3-29
