(2)
During a ground autostart, the SCU will send the EICAS CAUTION message "ENG 1 (2,3, or 4) AUTOSTART" to the flight deck if one of the conditions that follow occur: N2<16% after 20 seconds, a hung start, or a locked low (N1) rotor.
(3)
During a ground autostart, the SCU will also send the two EICAS messages, CAUTION and STATUS, "ENG 1 (2,3, or 4) AUTOSTART" to the flight deck if the second start attempt is a failure.
(4)
During an in-flight autostart, the SCU will send the EICAS CAUTION message "ENG 1 (2,3, or 4) AUTOSTART" to the flight deck when one of the conditions that follow occur:
-the input from the EEC data bus is not available
-EGT is more than the redline limit.
D. During a starter assisted in-flight start, the SCU will restart the engine only if starter cutout speed is not reached. If the autostart is successful, the SCU will disengage at idle. If the autostart is not successful, the SCU will stop the fuel supply and ignition. Then the SCU will try a starter-assisted autostart again until one of the conditions that follow occur:
-
the start is successful
-
the pilot selects the "OFF" mode on the ENGINE AUTOSTART switch(es)
-
the pilot sets the FUEL CONTROL switch(es) to the CUTOFF position.
E. During an in-flight start, the SCU will try a windmill start if the start valve does not open in less than 5 seconds, or if N2 is not 16% in less than 20 seconds. The SCU will also try a windmill restart if the first windmill start failed.
6. Engine Ignition Control Module (Fig. 1)
______________________________
A. The engine ignition control module, installed on the P5 overhead panel, includes four engine START switches, an automatic ignition control selector, a continuous ignition switch, and standby ignition selector. Four FUEL CONTROL switches are used in conjunction with the start and ignition switches. In addition, ENGINE AUTOSTART switches are installed on the EEC panel assembly on the P5 overhead panel.
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80-11-00
ALL ú ú N05 Page 7 ú Feb 10/93
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
B. The functions of the automatic ignition control selector, continuous ignition switch, standby ignition selector, FUEL CONTROL switches, and the engine START switches pertaining to ignition are described in 74-31-00, Engine Ignition Control - Description and Operation.
C. Engine START switch
(1)
There is one engine START switch for each engine.
(2)
When an engine START switch is pulled to the "ON" position, the corresponding engine start valve opens and the switch light comes on.
(3)
The engine START switch is released to the "OFF" position and the switch light goes off when N2 rpm gets to approximately 50% and the start valve closes.
D. ENGINE AUTOSTART switch
(1)
There is one ENGINE AUTOSTART switch for each engine.
(2)
The ENGINE AUTOSTART switch is guarded in the "ON" and "OFF" positions to prevent accidental operation during starts.
(3)
When set to the "ON" position, the autostart controller, a component in the SCU, automatically controlls engine start and monitors engine parameters.
7. Operation
_________
A. Functional Description (Fig. 4)
(1)
With 28 volts dc power supplied to the engine START switches, the engine start system is armed.
(2)
In addition, pneumatic power must be supplied to the start valve from the airplane pneumatic system to start the engine start procedure.
(3)
After the desired ignition system is set with the AUTO ignition selector, pulling the applicable START switch out initiates the engine start system by opening start valve.
(4)
When the start valve opens, compressed air flows into the starter air inlet. The air goes through the starter inlet nozzles and is flowed axially through the turbine rotor, imparting high speed rotation to the rotor. Low energy exhaust air from the starter is discharged in the engine cowling through an exhaust screen in the starter housing.
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