737 Flight Crew Operations Manual
Engines, APU -
Engine System Description
Boeing Proprietary. Copyright © Boeing. May be subject to export restrictions under EAR. See title page for details.
D6-27370-866-EGP 7.20.11
Engine Ignition System
Each engine has two igniter plugs. The EEC arms the igniter plug(s) selected by
the ignition select switch. The left igniter plug receives power from the associated
AC transfer bus. The right igniter plug receives power from the AC standby bus.
Auto-Relight
An auto-relight capability is provided for flameout protection. Whenever the EEC
detects an engine flameout, both igniters are activated. A flameout is detected
when an uncommanded rapid decrease in N2 occurs, or N2 is below idle RPM.
Inflight Starting
Two methods of starting an engine inflight are available, windmill and crossbleed.
None of the ground start protection features are functional during inflight start.
Note: At low N2 values, the oil scavenge pump may not provide enough pressure
to return oil to the tank, causing a low oil quantity indication. Normal oil
quantity should be indicated after start.
If crossbleed starting is required, the X–BLD indication (XB for the compact
engine display) is displayed above the N2 dial. This indication is based on airplane
altitude, airspeed and N2.
September 26, 2013
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