
ENGINE SYNCHRONIZATION
The function of the synchronization system is
to reduce cabin noise level and increase pas-
senger comfort. This process eliminates the au-
dible and often objectionable beat frequency
produced by engines operating in close prox-
imity.
The synchronizer system is incorporated into
the DEEC software and includes data crosslink
communication between the two engines and
a three position (OFF, N1, N2) switch labeled
“ENG SYNC.” The switch is located on the en-
gine/fuel control panel (Figure 7-19). The left
engine is generally identified as the master
engine.
The system functions from flight idle to the
maximum power rating as long as the engines
are operating in the computer-on mode and
within the system limits.
If the sync switch is placed in the N
1
or N
2
po-
sition the system is turned on and a “SYNC”
annunciator will illuminate on the EICAS. If
N1 is selected, “SYNC” annunciates between
the N1 indicators. If the switch is placed to the
N2 position, “SYNC” appears between the
N2 digital displays on the EICAS (Figure 7-
20). In both cases, N1 or N2 selected, the an-
nunciator will be green if the landing gear is
up and amber if the gear is not locked up. Sync
must be off for takeoff and landing; thus, the
amber color is to alert the pilot to turn the
synchronization system off if the landing gear
is selected down.
During operation, the speed (N1 or N2) of the
slave engine is slowly biased up or down as re-
quired to match the speed of the master engine.
Synchronization of the engines occurs more
rapidly if the engines are closely matched be-
fore sync is initiated.
The sync switch circuits are powered through
a SYNC SW circuit breaker in the engine
group on the pilot’s circuit breaker panel.
L E A R J E T 4 5
P I L O T T R A I N I N G M A N U A L
7-27
FOR TRAINING PURPOSES ONLY
FlightSafety
international
Figure 7-19. ENG SYNC Switch
N1
ITT
LBS
FUEL
4450
50.0
76
60
984
50.0
80
60
1002
N2
OIL PSI
OIL
°
C
FF PPH
550
550
75.0
75.0
SYNC
SYNC
Figure 7-20. EICAS SYNC Annunciation