Technical data

13773-001
74-00
Page 1
IGNITION
1. GENERAL
This chapter describes those units and components which furnish, distribute, and control an electrical cur-
rent to ignite the fuel-air mixture in the engine cylinders. The ignition components include magnetos, igni-
tion harness, spark plugs, and ignition switch.
The magnetos are completely self-contained ignition generating devices. Mounted center aft on the acces-
sory case, each magneto utilizes a rotating magnet to induce a voltage into a magnetic coil. The magnetic
coil steps up the voltage at the distributor which distributes the high-energy voltage through the ignition
harness to the spark plugs.
Ignition system operation is controlled by the ignition switch mounted on the left side of the bolster panel.
With the switch OFF, the magnetos are grounded and will not produce spark. The right magneto fires the
upper right and the lower left spark plugs. The left magneto fires the upper left and the lower right spark
plugs. The magneto cases, spark plugs, cables, and connections are shielded to prevent radio interfer-
ence.
Each magneto has an impulse coupling installed for engine starting. The impulse coupling delays magneto
rotation, retarding spark until each piston reaches T.D.C. At T.D.C., the coupling spins ahead, generating
enough voltage for ignition at starting RPM. Impulse coupling disengages after engine start.(See Figure
74-001)
30 Nov 2000