(b)
Depress annunciator press test switch located in upper left instrument panel, and check that ARM-AUTOFEATHERand FAIL-AUTOFEATHER lamps light.
(c)
Release switch and observe if lights extinguish.
(d)
Using autofeather test switch located on lower left instrument panel, feather left engine propeller.
(e)
Move switch to center OFF position. Ensure prop unfeathers.
(f)
Move test switch to right. Ensure right engine propeller feathers.
(g)
Return switch to center OFF position. Ensure prop unfeathers.
(h)
Advance power lever to 80% N1 + 3/- 0%. Ensure ARM-AUTOFEATHER light illuminates.
(i)
Return engines to idle rpm.
10. Autofeather Electrical System Ground Checks
(a)
Remove avionics bay access cover.
(b)
Locate autofeather computer at FS 30.0 (approx). Remove connector E411 from computer.
(c)
Ensure autofeather circuit breaker, located on right side of non-essential circuit breaker panel, is pushedin.
(d)
Establish 28 Vdc electrical power on non-essential bus.
(e)
Place AUTOFEATHER OFF-ARM switch, located on lower left instrument panel, in ARM position.
(f)
Using a high quality MULTIMETER, perform the following test:
Test Between Connector E411 Multimeter Reading
ReceptacleNumbers Voltage/Resistance OhmmeterScale
21 and aircraft ground* 28 Vdc
28 and aircraft ground* (0 ohms) R x 1/lowest
scale
1 and aircraft ground* Open (high resistance) R x 100,000
2 and aircraft ground* Open (high resistance) or highest
5 and aircraft ground* Open (high resistance) scale
6 and aircraft ground* Open (high resistance)
7 and aircraft ground* Open (high resistance)
8 and aircraft ground Open (high resistance)
11 and 15 0 ohms R x 1/lowest
11 and 9 0 ohms scale
14 and 10 0 ohms
14 and 12 0 ohms
4 and 26 30 ohms R x 1 scale
22 and 27 30 ohms
*Make certain to have excellent ground connections to "BAREMETAL".
(g)
After completing above tests, set AUTOFEATHEROFF-ARMswitch to OFF position. Remove powerfrom aircraft circuits.
(h)
Reconnect connector E411 to autofeather computer.
(i)
Reinstall avionics bay access cover.
EFFECTIVITY: 040-999
Jan 10/9061-20-00
PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL
A. Controlling (continued)
11. Propeller Synchrophaser System
The propeller synchrophaser system is designed to maintain continuousengine synchronization by matchingrpm of engines automatically.
NOTE: Refer to Wiring Diagram Manual (P/N 761 853) 61-22-01 for electrical schematicdiagram of Propeller Synchrophaser Installation.
NormalFlight
(a)
Synchronizeenginesmanually.
(b)
Turnsynchrophaserswitch ON. If synchrophaser fails to synchronize properly,repeatsteps (a) and (b).
(c)
When automatic synchronizationis attained, subsequent rpm adjustments must be made by movingboth propeller governor control levers simultaneously.
Switch
PropellerSynchrophaserSystem Figure 1
EFFECTIVITY:
040-999
61-20-00 PAGE
61-20-00 Jan 10/905
PIPERAIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL
A. Controlling (continued)
CHART 1 FAULT ISOLATION (SYNCHROPHASER INSTALLATION)
Fault Cause
Synchrophaserinoperative. Defectivepower lead or circuit breaker.
Defectiveground lead.
MagneticpickupOPEN
or SHORTED to ground.
Pickupwiringor connectorOPENor SHORTEDto ground.
Magneticpickupvoltage
too low.
Faulty receptacle half
at system connector.
Control box defective.
RPMsurgeor hunt. Synchrophasergain too high.
Synchrophasercoil, leads, aircraft wiring or connectors OPEN.
Synchrophasercoil, leads, aircraft wiring or connectors SHORTED together.*
Left engine increases rpm Left coil, coil lead,
out of sync when the associatedwiring or
synchrophaseris turned on. connectorgrounded.
Left pickup output low.
*Results in permanent control box damage.
Jan 10/9061-20-00
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