Synchrophaser System Operational Checks - Piper Navajo Chieftain PA-31-350 Service Manual

NAVAJO CHIEFTAIN SERVICE MANUAL
The propeller RPM should be manually adjusted as close to synchronization as possible for cruise, and
the quadrant friction control set. Turn the switch to the phase position, if the unit does not synchronize
the props, return the selector switch to manual. After 45 seconds adjust engine RPM manually to within 25
to 30 RPM of each other and return the selector switch to the phase position.
Keep the function switch in manual position except when desiring automatic control. The engine
synchrophaser will bring into phase, engines with an RPM difference of over 30 RPM. However, the closer
the RPM is set manually the sooner automatic phasing will be established.
Note the lack of an audio beat when the propellers are in phase; this should be checked in flight. When
an audible beat is heard with the system operating, it is undoubtedly not holding the slave engine in phase
with the master engine. Return the selector switch to its manual position for 45 seconds and readjust engine
RPM manually to operating RPM. Set selector switch to phase position for automatic operation. If the
phasing is not established after the above procedure, it is possible that some unit of the system is not
operating properly, and further ground checks should be made.
14-137. OPERATIONAL CHECKS(PA-31-350, S/N31-5001thru31-7852037). Thetollowingchecksmay
be made to evaluate system operating condition. A test unit should be fabricated to perform the required
checks. Refer to Figure 14-51 for parts and wiring schematic to fabricate the test unit.
a. Connect an ammeter with a two ampere scale to the meter jack on the front panel of computer
amplifier. (Refer to Figure 14-51.) Use a suitable cable and 1 4 inch phone plug to connect to the computer.
NOTE
When fabricating this test box, it is advisable to make the
connecting cable long enough to extend from the computer into
the cockpit.
b. Connect a zero center reading 12 volt voltmeter to test wires A and B in the six pin plug which
connects to the computer. When the tests are completed the wires can be taped and tied back. ( Refer to Figure
14-51.)
c. With meters connected as shown in Figure 14-51. proceed with the ground checks to determine if
various units are working properly.
d.
Connect the phone plug from the test box to the computer and observe the ammeter, it should
show a reading with the master switch ON. This will confirm that there is voltage to the computer.
NOTE
The following steps should be performed from within the cockpit
with the use of the aircraft starter switches.
e. Ascertain that the magneto switches are OFF. Turn the master switch ON, and set the
synchrophaser switch on MANUAL. Read the solenoid current on the ammeter. A stabilized reading should
be 1 ampere ± .2 ampere.
NOTE
When first selecting the manual operation, the meter current may
be near zero or near maximum of meter scale. The solenoid
current is slowly corrected and takes five to thirty-five seconds to
stabilize.
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ACCESSORIES AND UTILITIES