APR/Synchronizer Controller
Both engine fuel computers limit maximum
takeoff power to the APR rating. Under nor-
mal takeoff conditions the APR/synchronizer
controller electrically trims down the power
settings to the normal (lower) rating.
When APR is triggered the controller allows
the computers to reset the APR (higher) rat-
ing; the engine response to throttle movement
being retained.
Failure modes
Failure of electrical power to the APR/syn-
chronizer controller will also result in both fuel
computers resetting to the APR ratings.
The synchronizer must be serviceable to sup-
ply N
2
comparisons for the APR auto mode.
Manual O/RIDE is independent of N
2
signals.
An engine fuel computer must be serviceable
and selected to AUTO in order to respond to
APR. Should an engine computer fail, or is se-
lected to manual, with APR armed, APR will
be triggered in the other engine if engine speed
differences exceed 5% N
2
.
7-23
FOR TRAINING PURPOSES ONLY
HAWKER 800 XP
PILOT TRAINING MANUAL
FlightSafety
international
Figure 7-20. APR—Armed 5% N
2
Sensed
5% DETECTOR
5% DETECTOR
SPEED TRIM
TEMP TRIM
SPEED TRIM
TEMP TRIM
LEFT ENG
COMPUTER
RIGHT ENG
COMPUTER
POWER SUPPLY
NO. 1
DIGITAL
COMPARATOR
POWER SUPPLY
NO. 2
SYNCHRONIZER
NETWORK
POWER SUPPLY
{
{
LEFT ENGINE
RIGHT ENGINE
APR O/RIDE
APR ARM
ENG SYNC
N
1
OFF
N
2
N
2
N
2
N
1
N
1
SYNCHRONIZER
APR CONTROL
NO. 2 SLAVE
SIGNALS FROM
COMPUTER MANUAL
MODE SOLENOIDS
TO RIGHT
ENG TRIM
28 VDC
APR
APR
ARMED
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