Description Of Heater And Basic Components; Spark-Spray Ignition - Piper TWIN COMANCHE PA-30 Service Manual

PIPER TWIN COMANCHE SERVICE MANUAL
d. Connect the combustionair
blower inlet hose (13) to the tubeattached to the
bottom panel of the nose section and secure with screw, washer and nut.
e. Connect the fuel drain (6) to the bottom of the heater.
f.
Connect the air inlet tube (12) to the forward end of the heater and secure
with clamp.
g. Connect the fuel supply line (10) to the heater.
Slide the shroud sleeve (16)
and shroud (9) into place and secure with clamps.
h. Attach the air outlet control cable (4) to the air distribution box (3) of the
heater and secure.
Position the cable wire and shroud to allow the valve full
travel in the distribution box. Also, ascertain that the wire rotates freely on the
valve arm.
i.
Attach the heat control cable (5) to the heat control switch (15). Ascertain
that the cable is attached to allow full travel of the control arm. (Refer to Para-
graph 13-106, c, for additional adjustments.
j.
Connect the electrical
leads to the terminal block of the heater as shown in
Figures 13-15 and 13-19.
k. Connect the heat outlet hoses (1) and the defroster hose (2) to the air dis-
tribution box and secure with clamps.
1. Check operation of the heater.
m. Install the nose section access panel.
13-83.
DESCRIPTION OF HEATER AND BASIC COMPONENTS.
13-84.
SPARK-SPRAY IGNITION. (Refer to Figure 13-16.) The controlled at-
omized spray from a specially designed spray nozzle, coupled with high voltage
spark plug ignition, insures instant firing and continuous burning under all flight
conditions.
Heat is produced by burning a fuel-air mixture in the combustion chamber
of the heater.
Aviation gasoline is injected into the combustion chamber through
the spray nozzle. The resulting cone-shaped
fuel spray mixes with combustion
air and is ignited by a spark from the spark plug.
Electric current for ignition
is supplied by an ignition unit which converts 12 volts to high-voltage oscillating
current to provide a continuous spark across the spark plug gap. A shielded,
high-voltage lead connects the ignition assembly to the spark plug. Combustion
air enters the combustion chamber tangent to its surface and imparts a whirling
or spinning action to the air.
This produces a whirling flame that is stable and
sustains combustion under the most adverse conditions because it is whirled
around itself many times. Therefore,
ignition is continuous and the combustion
process is self-piloting.
The burning gases travel the length of the combustion
tube, flow around the inside of the inner tube, pass through cross-over
passages
HEATING AND VENTILATING
Issued: 12/29/72
4C8