Rockwell Commander 112 - IGNITION SYSTEM

ROCKWELL
COMMANDER
112/B/TC/TCA
MAINTENANCE MANUAL
SECTION IV
POWER PLANT
AND PROPELLER
turer, provides complete information concerning en-
gine maintenance, and component disassembly, repair,
and reassembly. The material contained in this man-
ual provides information concerning this particular
application of the TO-360 series engine, and the in-
formation necessary for routine field maintenance
and
servicing (see Figure 4-1).
IGNITION SYSTEM
IGNITION SWITCH
The ignition switch is installed in the left instrument
sub-panel. This spring-loaded switch returns to the
BOTH position automatically when released from the
ST ART position. The ignition switch has five positions:
1-
2.
3.
4.
5.
OFF - Both magnetos are grounded.
R - Right magneto
operating - left magneto OFF.
L - Left magneto operating - right magneto OFF.
BOTH - Both magnetos operating.
START - Starter solenoid actuated.
I WARNING I
Magneto switches must be in OFF posi-
tion before rotating a propeller by hand.
The magneto(s) will be hot any time the ignition switch
wires are disconnected; therefore, an unintentional
engine
start is possible if the propeller is rotated. To
avoid this possibility, remove the high tension outlet
plate from the appropriate magneto before breaking
the ignition circuit.
IGNITION SYSTEM OPERATION
When the ignition switch is held in the ST ART pOSition,
the starter relay closes allowing battery current to
drive the starter. The left impulse magneto generates
electrical impulses to fire the left upper and right
lower spark plugs and automatically retards spark
when starting the engine. As soon as the engine starts,
the ignition switch is released from the START posi-
tion and returns to the BOTH pOSition, deactivating the
starter relay. The engine is now operating on both
magnetos and ignition
occurs in the normal advance
position.
MAGNETO
MODELS 112/B. Bendix S4LN-1227 (left) impulse
coupled magneto and S4LN-1209 (right) high altitude
magneto are installed on the IO-360-CID6 engine (see
Figure 4-2). The shielded ignition wiring is arranged
so that the left magneto fires the bottom plugs in cyl-
inders one and three and the top plugs in cylinders two
and
four. The right magneto provides spark for the
opposite
spark plugs. The magnetos are driven at 1-
1/2 times engine crankshaft speed. Each magneto con-
tains a two-pole rotating magnet, a transformer coil
and a
distributor. A two-lobe cam is secured to the
breaker end of the rotating magnet shaft. The distri-
butor gear is driven at one-third magneto shaft speed.
High tension current, generated in the magneto trans-
former secondary coil winding, is conducted to the
distributor by means of a spring-loaded carbon brush
and through the finger on the distributor gear to the
distributor block where it is transmitted through high
tension cables to the spark plugs. The left magneto,
through
the START position of the ignition switch,
provides retarded ignition for engine starting. Inter-
rupted battery current is permitted to flow through
the
primary and secondary transformer windings of
the
left magneto and across the spark plug electrodes,
to provide high tension voltage for engine starting.
Release ignition switch if starter does
not engage immediately. Starter cir-
cuit is not protected by circuit breakers.
MODELS 112TC/TCA. Bendix D4LN-2021 impulse
coupled high altitude dual magneto is installed on the
TO-360-ClA6D engine (see Figure 4-2). The shielded
ignition
wiring is arranged so that the left portion of
the magneto fires the bottom plugs in cylinders one
and
three and the top plugs in cylinders two and four.
The
right portion of the magneto provides spark for
the opposite spark plugs. The magneto is driven at
engine crankshaft speed. Each magneto contains a
two-pole
rotating magnet, and a transformer and dis-
tributor for both the right and left portions of the mag-
neto. A two-lobe cam is secured to the breaker end
of the
rotating magneto shaft. The distributor gears
are driven at one-half magneto shaft speed. High
tension current, generated in each of the two magneto
transformers, is conducted to each of the distributors
by means of spring-loaded carbon brushes and through
the fingers on the distributor gears to the right and
left distributor blocks where it is transmitted through
high
tension cables to the spark plugs. The magneto
provides retarded ignition for engine starting. Inter-
rupted battery current is permitted to flow through the
primary and secondary transformer windings and
across the spark plug electrodes to provide high ten-
sion voltage for engine starting.
Release ignition switch if starter does
not engage
immediately. Starter cir-
cuit is not protected by circuit breakers.
MAGNETO REMOVAL
a. Remove upper half of cowling.
b. Remove high
tenSion outlet cable plate from
magneto.
4-3
Copyright Commander Owners Group 2013 All Rights Reserved
**unofficial copy**