Starting Air System.-- The starting air system is
for the lube oil service pumps. Operator commands are
supplied by the high-pressure air system through banks
started by push-button indicators in the reduction gear
lube oil section of the propulsion mimic panel.
of high-pressure air flasks and the bleed air header. The
bleed air system is the normal source of starting air when
Motor-driven lube oil service pump control signals
gas turbines are operating. The high-pressure air system
from the PACC are sent via the DMS to the appropriate
flasks are the starting air source when no turbines are
SCU computer. Two modes of motor-driven lube oil
operating or a bleed air PRESS LOW alarm is set.
service pump control are available: MANUAL and
AUTO LEAD. MANUAL mode allows the operator to
The operator selects the starting air source at the
select pump speed with OFF, LOW SPEED, and HIGH
PACC by depressing the starting air BLEED or HIGH
SPEED push-button indicators. AUTO LEAD also
PRESS push-button indicator. These push buttons
allows the operator to select pump speeds manually and
interface with the starting air select computer program
tells the SCU computer which pump to start first in
function in the SCU computer. When the BLEED or
response to the MRG hydraulically most remote bearing
H I G H PRESS push button is depressed, a status
pressure. The control location switch on a lube oil
message appears on the PDU. The BLEED or HIGH
service pump motor controller must be in REMOTE for
P R E S S signal is sent with an ON or ON LINE
the computer to control pump operation. Manual control
command, to align the appropriate starting air valve.
of the lube oil pumps is individually accomplished with
Valve alignment for a BLEED or HIGH PRESS start is
three push-button indicators. Automatic and manual
initiated by the SCU engine state logic-on computer
p u m p operation are enabled when the operator
program function.
depresses an AUTO LEAD pushbutton. AUTO LEAD
A GTE maybe motored with bleed or high-pressure
prevents the operator from commanding pump speeds
air using the same air paths as a bleed or high-pressure
that contradict the lube oil service pump's automatic
start. The only difference is the motor air regulator valve
mode logic. When pump control is in AUTO LEAD, the
i s set to the motor position by the engine state
pumps cycle as a function of the MRG hydraulically
logic-motor computer program function. The motor air
most remote bearing pressure.
regulator valve regulates air pressure to 22 psig when in
the motor position. A motor sequence is started when the
Air System
MOTOR push button at the PACC is depressed for a
There are two compressed air systems associated
GTM in the OFF state.
with the GTEs and the GTGSs: (1) the bleed air system
Masker Air System. The masker air system is
and (2) the high-pressure air system. We will look at the
a l i g n e d by the HULL MASKER ON and OFF
bleed air system first.
push-button indicators at the PACC. These pushbuttons
BLEED AIR SYSTEM. The bleed air system
operate the masker air select computer program function
contains four distinct subsystems that include the
in the SCU computer. The HULL MASKER ON push
following:
button places the bleed air transfer valve in the masker
position if a GTE start or motor command is not active
1. Starter air
in the same MER. The HULL MASKER OFF push
2. Masker air
b u t t o n places the bleed air transfer valve in the
3. Prairie air
start/motor position. The bleed air transfer valve
position is displayed on the PDU.
4. Anti-icing air
Prairie Air System. The prairie air system is
The bleed air system is supplied with combustion
supplied with bleed air through a prairie air cooler and
air extracted from each operating GTE and SSGTG
supply valve in each MER. The PRAIRIE ON and OFF
compressor. Each GTE and SSGTG has a bleed air valve
push-button indicators provide manual inputs to the
that controls the flow of air from the engine to the bleed
SCU computer to issue commands to its connected
a i r header. The bleed air valve for each GTE is
prairie air supply valve. When the prairie air supply
motor-operated and may be controlled from the SCU or
valves are operated from the PACC, the appropriate
the PACC. The bleed air valve for the SSGTG is
indicator illuminates and a status message is displayed
solenoid-operated and may be controlled from the
on the PDU.
SSGTG LOCOP or the EPCC.
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