Ice And Rain Protection System Description And Operation - Piper PA-44-180 SEMINOLE Maintenance Manual

GENERAL.
The material contained herein provides information for general maintenance of the ice protection system. If
further information is necessary contact the product manufacturer or Piper Service Representative.
DESCRIPTION AND OPERATION.
The ice protection system may contain any of five separate systems: a pneumatic deice system; an electrical
prop deice system; an electrically heated windshield panel; heated pitot stall warning system; and a wing
inspection light installation. These systems can be installed individually or in several different combinations.
Except for the heated pitot/stall warning system, the systems are controlled from a control panel on the center
instrument panel.
The pneumatic system which utilizes boots to displace ice from the leading edges of the flight surfaces,
necessitates replacing the standard air pumps with pumps of greater capacity. Along with the boots and related
plumbing, the system also utilizes two control valves, two check valves, a deflate valve, and a timing module. A
control and check valve are used on each side of the system and, being mounted behind their respective firewall,
are accessible upon removal of the appropriate nacelle hatch cover. The deflate valve and time module are
mounted under the floor on the left side of the fuselage as shown in Figure 30-1.
Boots are attached to the leading edge of the wings, vertical stabilizer, and stabilator. The boots are of a fabric
reinforced rubber containing built-in span wise inflation tubes. A ply of conductive neoprene is cured to each
boot surface to dissipate static electric charges and prevent damage to the boots from those charges, as well as
preventing a fire hazard after each flight. Attached to the flight surfaces with cement, the boots are connected to
the plumbing, through the skin by flexible and/or aluminum air connections.
Operation of the pneumatic deice system is controlled by a momentary, single pole, single throw switch on the
control panel. During normal operation, vacuum, provided continuously from the pump inlets to the vacuum
system, is also directed to the boots system through the deflate valve to hold the boots down in flight. The
control valves, closed during normal operation, allow pressure air from the pumps to be dumped overboard.
Activation of the momentary switch however, initiates power to the deflate valve units causing: the deflate valve
to close the system to vacuum and outside pressure; and, to activate the timer in the timing module.
Having activated the switch, pressure begins to build in the system and upon reaching "10" psi, a pressure
switch on the deflate valve activates an indicator light on the control panel. With the system still operating,
pressure continues to build until a pressure activated switch (also on the deflate valve) senses 17 psi, or the timer
reaches "6" seconds, whichever comes first. At this point power is removed from the control valves and deflate
valve causing the control valves to close routing pump pressure overboard and the deflate valve to dump system
pressure overboard. As pressure decreases, the 10 psi switch is deactivated extinguishing the light. With the
pressure dumped from the system the deflate valve again directs vacuum to the boots. The system, now operating
in its normal condition, can be reactivated if necessary, through the momentary switch on the control panel. The
vacuum gauge may fluctuate momentarily upon deice cycling.
The propeller deice system, which can be installed by itself or included in a package with others of the ice
protection system, is designed for both the two and three bladed propeller installations. Each propeller deice
system consists of: an electrically heated boot bonded to each blade; a slip ring assembly connected to the hub of
each propeller; modular brush assemblies; a timer; a circuit breaker/ control switch located on the control panel;
an ammeter, and, a shunt installation.
The three bladed propeller deice system may not be installed in conjunction with the
pneumatic deice system.
PIPER AIRCRAFT
PA - 4 4 - 1 8 0 / 1 8 0 T
AIRPLANE MAINTENANCE MANUAL
— Note —
2D5
3 0 - 0 1 - 0 0
Page 30-01
Revised: May 15, 1989