Piper SEMINOLE PA-44-180, Maintenance Manual

Page: 745 / 881

GENERAL.
DESCRIPTION OF OPERATION.
The gear reduction starting motor consists of six major components: The Commutator End Head Assembly,
the Armature, the Frame and Field Assembly, the Gear Housing, the Pinion Housing, and the Bendix Drive
Assembly.
When the starting circuit is energized, battery current is applied to the starting motor terminal. Current flows
through the field coils, creating a strong magnetic field. At the same time, current flows through the brushes to
the commutator, through the armature windings to ground. The magnetic force created in the armature combined
with that created in the field windings begins to turn the armature.
The gear cut on the drive end of the armature shaft extends through the gear housing, where it is supported by
a roller bearing. The gear mates with the teeth of the reduction gear that drives the bendix shaft. The shaft is
keyed to the reduction gear. The Bendix drive is held in position on the shaft by a “spiral” pin. The shaft is
supported in the gear housing by a closed end roller bearing and in the pinion housing by a graphitized bronze
bearing.
When the armature turns the reduction gear, the Bendix drive pinion meshes with the flywheel ring gear by
inertia and action of the screw threads within the Bendix sleeve. A detent pin engages in a notch in the screw
threads which prevents demeshing if the engine fails to start when the starting circuit is de-energized.
When the engine reaches a predetermined speed, centrifugal action forces the detent pin out of the notch in the
screw shaft and allows the pinion to demesh from the flywheel.
TROUBLESHOOTING.
CHART 8001. TROUBLESHOOTING (STARTER)
Trouble Cause Remedy
STARTER
Starter fails to operate. Low battery charge. Check and recharge if
necessary.
Defective or improper wiring Refer to electrical wiring
or loose connections. diagram and check all wiring.
Defective starter solenoid or Replace faulty unit.
control switch.
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
8 0 - 0 0 - 0 2
Page 80-01
Revised: May 15, 1989
3I13
PIPER AIRCRAFT