Engine ignition is provided by two engine-driven magnetos, and two spark plugs in each cylinder. The right magneto fires the lower right and upper left spark plugs, and the left magneto fires the lower left and upper right spark plugs. Normal operation is conducted with both magnetos due to the more complete burning of the fuel-air mixture with dual ignition.
Ignition and starter operation
is controlled by a rotary type switch located on the left switch and control
panel. The switch is labeled clock wise, OFF, B, L, BOTH, and START. The engine
should be operated on both magnetos (BOTH position) except for magneto checks.
The B and L positions are for checking purposes and emergency use only. When the
switch is rotated to the spring-loaded START position (with the master switch in
the ON position), the starter contactor is energized and the starter will crank
the engine. When the switch is released, it will automati cally return to the
AIR INDUCTION SYSTEM
Ram air for the engine induction
system is received through the left opening in the nosecap. An induction system
airscoop is located in the aft vertical baffle just behind the engine on the
left side. This scoop is covered by an air filter which removes dust and other
foreign matter from the induction air. After passing through the filter, the
induction air enters an airbox which is mounted on the carburetor inlet. From
the airbox, the air enters the carburetor and is ducted to the engine cylinders
through intake manifold tubes. In the event carburetor ice is encountered or the
intake filter becomes blocked, alternate heated air can be obtained from a
shroud around number four cylinder exhaust riser. This heated air is ducted to
the airbox and passes through a valve controlled by the carburetor heat control
on the instrument panel. Heated air from the shroud is obtained from unfiltered
air inside the cowling. Use of full carburetor heat at full throttle will result
in a loss of approximately one inch of manifold pressure.
Exhaust gas from each cylinder
passes through riser assemblies to a muffler and tailpipe. The muffler is
constructed with a shroud around the outside which forms a heating chamber for
cabin heater air.
CARBURETOR AND PRIMING SYSTEM
The engine is equipped with a horizontally-mounted, side-draft, float- type, fixed jet carburetor mounted below the engine adjacent to the firewall. The carburetor is equipped with an enclosed accelerator pump, an idle cut-off mechanism, and a manual mixture control. Fuel is delivered from the fuel system to the carburetor by gravity flow, the engine-driven fuel pump, and! or auxiliary fuel pump. In the carburetor, fuel is atomized, proportionally mixed with intake air, and delivered to the cylinders through intake manifold tubes. The proportion of atomized fuel to air may be controlled, within limits, by the mixture control located on the center area of the switch and control panel.
For easy starting in cold
weather, the engine is equipped with a 3- cylinder manual primer. The primer is
actually a small pump which draws fuel from the fuel strainer when the plunger
knob is pulled out, and injects it into the engine intake ports when the knob is
pushed back in. The plunger knob is equipped with a lock and, after being pushed
full in, must be rotated either left or right until the knob cannot be pulled
Ram air for engine cooling enters through two intake openings in the front of the engine cowling. The cooling air is directed around the cylinders and other areas of the engine by baffling, and is then exhausted through cowl flaps on the lower aft edge of the cowling. The cowl flaps are mechanically operated from the cabin by means of a cowl flap lever on the right side of the control pedestal. The pedestal is labeled OPEN, COWL FLAPS, CLOSED. Before starting the engine, and throughout takeoff and high power climb operation, the cowl flap lever should be placed in the OPEN position for maximum cooling. This is accomplished by moving the lever to the right to clear a detent, then moving the lever up to the OPEN position. Anytime the lever is repositioned, it must first be moved to the right. While in cruise flight, cowl flaps should be adjusted to keep the cylinder head temperature at approximately two-thirds of the normal operating range (green arc). During extended let-downs, the cowl flaps should be completely closed by pushing the cow] flap lever down to the CLOSED position.
A winterization kit is available
for the airplane. Details of this kit are presented in Section 9,
The airplane has an all-metal, two-bladed, constant-speed, governor- regulated propeller. A setting introduced into the governor with the propeller control establishes the propeller speed, and thus the engine speed to be maintained. The governor then controls flow of engine oil, boosted to high pressure by the governing pump, to or from a piston in the propeller hub. Oil pressure acting on the piston twists the blades toward high pitch (low RPM). When oil pressure to the piston in the propeller hub is relieved, centrifugal force, assisted by an internal spring, twists the blades toward low pitch (high RPM).
A control knob on the center area of the switch and control panel is used to set the propeller and control engine RPM as desired for various flight conditions. The knob is labeled PROP RPM, PUSH INC. When the control knob is pushed in, blade pitch will decrease, giving a higher RPM. When the control knob is pulled out, the blade pitch increases, thereby decreasing RPM. The propeller control knob is equipped with a vernier feature which allows slow or fine RPM adjustments by rotating the knob clockwise to increase RPM, and counterclockwise to decrease it. To make rapid or large adjustments, depress the button on the end of the control knob and reposition the control as desired.