asgmnt pneu eng starting.ppt

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4 Aeroplane 3



PNEUMATIC STARTING SYSTEM

To rotate engine to the rpm range where starting can be

accomplished.

Controlled by two start switches (located on the

forward overhead panel)

two pneumatic starters two starter valves

associated pneumatic plumbing

Consists

of



CENTER INSTRUMENT

PANEL

FORWARD OVERHEAD

PANEL



COMPONENT LOCATION







GENERAL

Air pressure in the pneumatic manifold

Engine accelerate to starting speed & engine start

Starter rotate & transmitted to the N2 compressor

through the accessory drive gear system

Low pressure heat the pneumatic starterturbine blades

Start switch supply electrical power to open the

starter valve



Start switch Control the system

4-position rotary switches

Other than ground start position

switch remain in its original

position until another selection is

made.

Electrical power source 28 -volt dc battery bus

115-volt ac transfer bus

115-volt ac standby bus

GRD, OFF, CONT and FLT

3 separatecompressed

air sources:

-APU-Ground carts

-Cross-bleed air



Lightweight turbine-type air motor

Converts kinetic energy starting torque

Use low pressure air and electrical power for starter operation.

5 basic parts:

PNEUMATIC STARTER

Scroll assembly

Turbine wheel

Reduction gear assembly Engaging mechanism

Output shaft



Starter valve

open admit air to

the inlet

connection passes through the

starter vanes (starter

scroll ass.) air directed radially

inward ( throughturbine wheel )

give high

speedrotation

Exhaust air passes

air outlet screen or

turbine wheel

containment ass.

(reduction gear)transmit high

speed, low torque

low speed,

high torque

Transmitted

to output

shaft

Transmitted

to the N2

compressor



.

speed of output shaft >

speed of internal gear hub clutch mechanism

provide automatic

disengagement

cutout switch mechanism

(actuated by centrifugal

force) closed starter valve

automatically when outputshaft reaches

predetermined cutout speed



Controls airflow to the pneumatic starter during engine

starting.

Operated pneumatically and solenoid- controlled.

Consists of two assemblies:

STARTER VALVE

Valve body assemblyPiston type pneumaticactuator assembly



PNEUMATIC STARTING SYSTEM CIRCUIT



ENGINE STARTING USING

AUXILIARY POWER UNIT

Pack valves and wing thermal anti-ice valves closed.

Applicable engine bleed valve open.

Bleed air isolation valve switch in AUTO.

Both air conditioning packs off.

The APU bleed valve ON.

Compressed air is supplied to the starter to rotate the N2

compressor of the engine.




EXTERNAL AIR SOURCE

Depends on the external low pressure air source

connected to the ground pneumatic connection.

Procedure for starting is same as using the APU

except that bleed air valve for the applicable engine

must be opened manually if ac power is notavailable.




ENGINE CROSS BLEED AIR

Can be done by using 8th-stage bleed air from the

operating engine.

The operating engine must operate at approximately80% N2 rpm.

The procedure for starting is the same as using theAPU.



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asgmnt pneu eng starting.ppt

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