King Air C90GTi, Pilot Training Manual

Page: 187 / 557

PROPELLER
SYNCHROPHASER SYSTEM
A Type II synchrophaser system is installed
in the King Air C90GTi and C90GTx. The
p r o p e l l e r s y n c h r o p h a s e r a u t o m a t i c a l l y
matches the r pm of the two propellers and
maintains the blades of one propeller at a
p r e d e t e r m i n e d r e l a t ive p o s i t i o n w i t h t h e
blades of the other propeller. The pur pose
of the system is to reduce propeller beat and
cabin noise from unsynchronized propellers.
Synchrophaser Operation
The Type II synchrophaser system (Figure 7-
40) is an electronic system, certif icated for
takeoff and landing. It is not a master-slave
system, and it functions to match the r pm of
both propellers and establish a blade phase
relationship between the left and right pro-
pellers to reduce cabin noise to a minimum.
The system cannot reduce r pm of either pro-
peller below the datum selected by the pro-
peller control lever. Therefore, there is no
indicating annunciator light associated with
the Type II system.
To prevent either propeller from losing ex-
cessive r pm if the other propeller is feath-
e r e d w h i l e t h e s y n c h r o p h a s e r i s o n , t h e
sy n ch ro p h aser h as a limited ran g e o f au -
thority from the manual gover nor setting.
In no case will the r pm fall below that se-
lected by the propeller control lever. Normal
gover nor operation is unchanged, b ut the
synchrophaser will continuously monitor
KING AIR C90GTi/C90GTx PILOT TRAINING MANUAL
7-42
FOR TRAINING PURPOSES ONLY
7
POWERPLANT
CLOSED AT
HIGH N1
OVER
400
FT LBS
OVER
200
FT LBS
LESS THAN
200
FT LBS
TORQUE SWITCHES
LESS THAN
400
FT LBS
DUMP
VALVE
AUTOFEATHER
LIGHTS
N.C.
DUMP
VALVE
N.C.
ARMING
RELAY
TEST
AUTO–
FEATHER
ARM
OFF
LEFT
POWER LEVER
SWITCHES
C/B
RIGHT
ARMING
RELAY
LEGEND
NO. 1 GENERATOR
NO. 2 GENERATOR
BATTERY
Figure 7-39. Autofeather Test Diagram