15-19 Figure 15-29.  Air filter for vacuum system.  Figure 15-27.  A vacuum regulator. Figure 15-28.  A manifold assembly used in multiengine aircraft  deice systems. Construction and Installation of Deice Boots Manifold Assembly Inlet Filter Deice boot system air pressure is controlled by a pressure  regulator valve located somewhere in the system downstream  of the pump or oil separator, if installed. The regulator may  be a stand-alone unit, or it may be combined into another  deice system component. Regardless, the spring-loaded  valve relieves pressure overboard when it exceeds the limit  for which the system is designed. A vacuum regulator is installed in the vacuum manifold on  the suction side of the air pump to maintain the vacuum at  the designed level. Also known as a suction regulating valve  or similar, the spring-loaded valve contains a filter for the  ambient air drawn through the valve during operation. This  filter must be changed or kept clean per manufacturer’s  instructions.  [Figure 15-27] In all pneumatic deice boot systems, it is necessary for check  valves to be installed to prevent backflow of air in the system.  The location(s) depend on system design. Sometimes, the  check valve is built into another system component. On  twin-engine aircraft, it is common to unite the air supplied  from each engine-driven pump to provide redundancy.  Check valves are required to guard against backflow should  one pump fail. A manifold assemble is commonly used to  join both sides of the system.  [Figure 15-28]  It contains the  required check valves in a single assembly. instructions.  Figure 15-29  shows a typical inlet air filter.  Figure 15-30  shows the relationship of the vacuum regulator  and inlet air filter to other system components. Deicer boots are made of soft, pliable rubber, or rubberized  fabric, and contain tubular air cells. The outer ply of the  deicer boot is of conductive neoprene to provide resistance  to deterioration by the elements and many chemicals. The  neoprene also provides a conductive surface to dissipate static  electricity charges. These charges, if allowed to accumulate,  would eventually discharge through the boot to the metal  skin beneath, causing static interference with the radio  equipment.  [Figure 15-31] On modern aircraft, the deicer boots are bonded with an  adhesive to the leading edge of wing and tail surfaces. The  trailing edges of this type boot are tapered to provide a smooth  The air used in a deice boot system is ambient air drawn  in upstream of the gyroscopic instruments on the suction  side of the engine-driven air pump. This air must be free  of contaminants for use spinning the gyros, as well as for  inflation of the deice boots. To ensure clean air, an inlet  filter is installed as the air intake point for the system. This  filter must be regularly maintained as per manufacturer’s 