5.
Turn off heater switch, and remove wedge at squat switch.
6.
To insure that the heater fuel line is free of airlock, cautiously loosen the fuel connection at the heater. This will bleed the line between the heater and fuel source. Then tighten the fuel line connection.
7.
Reconnect the wire (H10A) to the heater terminal No. 2.
8.
Place the air intake lever in the “OPEN” position and the temperature control lever in the center of its travel.
9.
Install a 0 to 10 psi pressure gauge in the outlet line of the fuel regulator by installing a “T” fitting in the OUTLET opening of the regulator.
10.
Turn on the master switch, then press the press-to-test overheat indicator light. The lamp should illuminate indicating the lamp filament is intact.
11.
Turn on heater switch. The heater should ignite and continue to operate until the thermostat turns it off. Cycling in this manner should continue until the heater switch is turned off.
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12.
With the heater in operation, check the pressure gauge. The gauge should read from 6.5 to 7.5 psi, if the heater is running and the pressure indicated is more or less than required, adjust the regulator accordingly. If the required pressure cannot be reached after a couple turns of the regulator's adjustment screw, troubleshoot the fuel pump.
13.
Place the heater switch in the “FAN” position. The heater should turn off and the ventilation blower should continue to operate. Allow this blower to operate for a full two minutes, then place the air intake lever in the closed position. The blower should turn off.
— Note —
This procedure should be followed after every shutdown to cool off the burn chamber.
14.
With the air intake closed, turn on the heater switch, the heater should not ignite and neither fan should operate. Turn off the heater switch and master switch.
15.
Remove the pressure gauge and “T” fitting from the regulator.
DESCRIPTION OF HEATER AND BASIC COMPONENTS.
SPARK-SPRAY IGNITION. (Refer to Figure 21-3.)
The controlled atomized 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 14 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 circulated about 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 crossover passages into an outer radiating area, then travel the length of this surface and out the exhaust.
Ventilating air passes through the heater between the jacket and combustion tube assembly outer surface and through an inner passage in the assembly. Consequently, ventilating air comes into contact with two or more heated cylindrical surfaces.
21-40-00 Page 21-14 Revised: February 28, 2002
1H12
THE NEW PIPER AIRCRAFT, INC.
PA-44-180
AIRPLANE MAINTENANCE MANUAL
2311-A
1.
COMBUSTION HEATER
2.
AIR DISTRIBUTION MANIFOLD
3.
AIR DISTRIBUTION VALVE
21-40-00 Page 21-15 Revised: February 28, 2002
1H13
21-40-00 Page 21-16 Revised: February 28, 2002
1H14
FUEL REGULATOR AND SHUTOFF VALVE. (Refer to Figure 21-4)
This unit provides preset, regulated fuel pressure as well as remove shutoff to the heater, regardless of fuel inlet pressure variations. It is set for 7.5 ± 0.5 psi. The shutoff valve is operated by a solenoid.
DUCT SWITCH. (Refer to Figure 21-5)
This switch is installed in the ventilating manifold upstream from the heater to sense the ventilating air outlet temperature. To select the desired cabin temperature, the switch may be adjusted manually from a high of 250°F ± 10° downward through a range of 146°F ± 6°. The switch has a differential of 15°F ± 5° at any given setting.
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