The SCU computer controls the GTE brakes, valve
moisture separator/blow-in panels. A manually operated
alignment, cooling fan, and vent damper automatically
anti-icing valve is located downstream of each GTM
to fulfill any legal engine state change requested by the
bleed air regulating valve. The anti-icing valve position
operator.
is monitored by the computer in the SCU, which
generates a status message on the PDU. An ICING alarm
The GTE emergency controls consist of three
indicator for each GTE is provided on the PACC
separate, but interrelated, categories: (1) emergency
propulsion mimic panel.
stops, (2) automatic shutdowns, and (3) GTE fire
detection and control.
GTE Control System
An operator can initiate an emergency stop while a
GTE is in the ON or ON LINE state by depressing
EMER STOP, PRI OR RSV HALON RLSE, or
Control and monitoring of all four GTEs is available
MODULE VALVE CLOSE. Depressing a HALON
from the PACC. However, normal control functions are
RLSE or MODULE VALVE CLOSE push button
only available from either the PACC or the appropriate
indirectly causes the SCU to send an emergency stop
SCU at any one time. The following items of the GTE
command to the interim integrated electronic control
control system are discussed in this section:
(IIEC). The SCU sends an emergency stop command to
the IIEC in response to a module Halon actuation alarm
1. Engine fan control
or loss of GTE fuel manifold pressure.
2. Engine state logic
An IIEC automatic shutdown is indicated when the
3. Emergency controls
AUTO SHUT DOWN lamp on the PACC illuminates.
The engine fan control computer program function
Each automatic shutdown causes the SCU computer to
is always enabled. It automatically operates the module
carry out an emergency stop in addition to the IIEC
cooling fan and damper in response to three inputs: (1)
shutdown sequence. There are nine automatic
the GTE cooling air outlet temperature transducer, (2) a
shutdowns associated with the MCS system. GTE lube
GTE start command, or (3) the Halon release command.
oil supply pressure low, power turbine vibration high,
The SCU computer controls the GTE cooling fan and
and power turbine overspeed shutdown are examples of
vent damper.
automatic shutdowns. Five of the nine automatic
shutdowns are inhibited when BATTLE OVRD ON is
There are five possible engine states for a GTE.
depressed. The five automatic shutdowns inhibited by
Each engine state is associated with a computer program
battle override are as follows:
function in the SCU computer. An engine state computer
program function senses the actual state of the GTE and
1. GTM fail to light off or flameout shutdown
allows an operator to start an engine state change. The
2. GTM lube oil supply low-pressure shutdown
push buttons that enable an engine state change are on
3. GTM power TIT high shutdown
the gas turbine propulsion mimic of the PACC and SCU.
The five engine state logic computer program functions
4. GTM gas generator vibration high
are as follows:
5. GTM power turbine vibration high
1. Off - Fuel off; power turbine (PT) brake on and
The GTE tire detection system consists of three
disconnected from programmed control
ultraviolet flame detectors in the module and a signal
2. Motor - Engine off before alignment of an air
conditioner located under the module. When a fire is
system for motoring
detected, an alarm message appears on the PDU and a
MODULE FIRE lamp illuminates on the PACC and
3. On - Engine running at idle, disconnected from
SCU. At the PACC, the operator can activate Halon by
programmed control; PT brake on; and stop not
depressing the PRI OR RSV HALON RLSE push
commanded
button. AHALON SYSTEM ACTUATED alarm is then
4. On line - Engine running, connected to
displayed on the PDU.
programmed control; PT brake off; and clutch
engaged
Thrust Control System
5. Cooldown - Engine running at idle, dis-
The thrust control system consists of throttle/pitch
connected from programmed control; and PT
brake on
and brake mode control from an MCS control station.
3-15
