GOL 737-8, Руководство по эксплуатации, Страница: 1043 / 1826

737 MAX Flight Crew Operations Manual
Engines, APU -
Engine System Description
MN-FLT-OH-201 7.20.9
Engine Start System
Starter operation requires pressurized air and electrical power. Air from the bleed
air system powers the starter motor. The APU, an external ground cart, or the other
operating engine provides the bleed air.
In the GRD position, the engine start switch uses battery power to close the engine
bleed air valve and open the start valve to allow pressure to rotate the starter. When
the start valve opens, an amber START VALVE OPEN alert is provided on the
MDS Engine Display. The starter rotates the N2 compressor through the accessory
drive gear system. The EEC performs Bowed Rotor Motoring (BRM) after the
Engine Start Switch has been moved to the GND position and before the Engine
Start Lever is moved to IDLE. BRM straightens the N1 and N2 rotor shafts which
will bow due to thermal buildup after the engine is shutdown. BRM is active for
6-90 seconds on the ground only. During BRM, MOTORING is displayed on the
N2 gauge between 18% and 24% N2. When the engine accelerates to the
recommended value (25% N2 or max motoring), moving the engine start lever to
the IDLE position, the EEC performs a test of the TCMA and EOS functions.
During this test, fuel flow will indicate zero and the engine fuel shutoff valve will
open and close repeatedly. The ENG VALVE CLOSED light will illuminate and
remain bright blue during this logic test, and will extinguish when the test is
complete. Once the test is complete, the engine start sequence continues, the fuel
valves on the wing spar and engine opens, and causes the EEC to supply fuel and
ignition to the combustor where the fuel ignites.
At starter cutout speed (approximately 63% N2), power is removed from the start
switch holding solenoid. The engine start switch returns to OFF, the engine bleed
air valve returns to the selected position, and the start valve closes.
Abnormal Start Protection (Ground Starts Only)
During ground starts, the EEC monitors engine parameters to detect impending
hot starts, engine stalls, EGT start limit exceedances, and wet starts. These
protection features do not function during inflight starts.
If an impending hot start is detected by a rapid rise in EGT or EGT approaching
the start limit, or a compressor stall occurs, the white box surrounding the EGT
digital readout flashes white. The EEC turns off the ignition and shuts off fuel to
the engine for an impending hot start or stall. The flashing white box resets when
the start lever is moved to CUTOFF or the engine reaches idle N2.
If the EGT exceeds the starting limit, the EGT display, both box and dial, turn red.
The EEC automatically turns off the ignition and shuts off fuel to the engine. The
alert terminates and the display returns to white when EGT drops below the start
limit. Following shutdown of both engines, the EGT box turns red to remind the
crew of the exceedance.
March 1, 2021