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the air (air starts), with or without the starter motor. The air used for starting
is ducted by means of the bleed air manifold from any of the three sources
listed above. The cranking operation is accomplished by a pneumatic
starter mounted on the right hand (HP) gearbox. The motion of the starter
(rotation) engages a series of gears and a drive shaft. The drive shaft is
connected to the HP spool of the engine, causing it to turn. The starter
rotates the engine up to approximately 15% HP RPM, at which point fuel is
introduced with ignition from the ignitors within the two liners. The starter
now assists engine spool-up to approximately 38 to 45% HP RPM.
Each engine ignition system incorporates two transistorized high energy
ignition units. They are operated automatically when the engine is being
started to deliver high voltage and amperage to the igniter plugs. Each
igniter plug is served by a high-energy ignition unit. The plugs, when fired,
ignite the fuel/air mixture and the resultant flame passes through
interconnectors located between each liner to complete the flame
propagation. Cranking the engine over without ignition can be
accomplished by selective switching by the crew. Ignition may also be used
independently of the engine starting system if a relight in flight is required.
NOTE:
For additional information pertaining to the engine
ignition system, see Section 2A-74-10, Engine Ignition
System.
Electrical power for ground starting and ignition power is obtained from the
Essential 28V DC bus. Ignition indication is displayed through the Engine
Instrument and Crew Advisory System (EICAS) located on the center
console.
B. Operation:
The engine starting system provides the flight crew with a means of using
supplied pneumatic power (starting air) for the following tasks:
(1) Normal Engine Starts (Ground): See Section 03-03-20, Starting
Engines.
(2) Alternate Engine Starts (Ground):
The five types of alternate engine starts available on the ground are
as follows:
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS 2A-80-00
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May 31/01
Revision 4
• Cold start: see 03-08-10, Cold Start
• External air start: see 03-08-20, External Air Start
• Crossbleed start: see 03-08-30, Crossbleed Start
• Engine cranking cycle: see 03-08-40, Engine Cranking Cycle
• Engine start (battery power only): see 03-08-50, Engine Start
- Battery Power Only
(3) Engine Airstarts:
The two types of engine airstarts are as follows:
• Immediate: see 05-10-20, Airstart - Immediate
• Normal: see 05-10-30, Airstart - Normal
(4) Starter-Assisted Air Starts:
Engine starting mode inflight within the starter-assist region of the
airstart envelope in which the flight crew controls the start sequence.
(5) Wet And Dry Cranks:
Engine operating mode in which the engine is motored but without
igniters ON. Wet cranking allows fuel to the engine whereas dry
cranking does not. See Section 03-08-40: Engine Cranking Cycle,
for engine cranking procedures.
C. Subsystems, Units and Components:
The engine starting system is composed of the following subsystems, units
and components:
• Pneumatic Starter
• Shuttoff Differential Pressure Regulator
NOTE:
The pneumatic starter and the shutoff differential
pressure indicator are combined together to form the
starter motor assembly.
2. Description of Subsystems, Units and Components:
A. Pneumatic Starter:
The pneumatic starter is electrically controlled and pneumatically operated.
It consists of a single-stage turbine rotor, a 16:1 reduction gear, output
shaft assembly exhaust housing and gear housing assembly.
Starter motor operation is controlled by the following four switches located
on the ENGINE START panel on the cockpit overhead panel (see Figure 1
and Figure 2):
• MASTER (two switches, CRANK and START, both with ON / OFF
positions)
• START (L ENG and R ENG)
B. Shuttoff Differential Pressure Regulator:
The shutoff differential pressure regulator consists of a pneumatic actuator,
a filter, a switcher solenoid valve assembly, a metering valve assembly,
servo assembly, overpressure limiter, butterfly valve, valve body assembly
and actuator assembly. The regulator functions both as an air pressure
OPERATING MANUAL
2A-80-00 PRODUCTION AIRCRAFT SYSTEMS
Page 2
May 31/01
Revision 4
regulator and as an air flow shutoff valve.
Control air enters the valve body assembly through the upstream pressure
sensing tube. The air passes through the filter to the metering valve
　
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