RAIN REMOVAL SYSTEM

The modulating valves maintain a controlled flow of bleed air to the leading edge distribution system, and they are controlled by pneumatic thermostats. The complete system is monitored for hot spots by heat-sensing switches. Before flight, the deicing manifold system may be tested for leakage. This leak testis performed by pressurizing the system: OPEN the No. 4 engine bleed-air valve; the Nos. 1, 2, and 3 engine bleed-air valves remain CLOSED, and both fuselage shutoff valves are in the OPEN position. When the bleed-air pressure on the bleed-air manifold reads 70 psi, the No. 4 engine bleed-air valve is closed and the leak test switch is actuated. As the bleed-air pressure drops, the time-delay relay will illuminate the ACCEPT light after an 8-second delay if the system is tight. The light will go out when the test switch is released. Maintenance The involvement of the AME2 and AMEC in the maintenance of the deicing system normally consists of troubleshooting. To troubleshoot intelligently, you must be familiar with the system. In addition, you must know the function of each component in the system and have a mental picture of the location of each component in relation to other components in the system. This can be achieved by studying the schematic diagrams of the system. As an aid, the aircraft manufacturer furnishes troubleshooting charts, which give recommended procedures to follow during troubleshooting. Figure 3-5 shows a deicing system overheat warning troubleshooting chart. This chart lists the most probable cause first and then branches to the next most probable cause. By following the recommended charts and procedures, you can save many valuable maintenance hours. RAIN REMOVAL SYSTEM The rain removal system shown in figure 3-6 controls windshield icing and removes rain by directing a flow of heated air over the windshield. This heated air serves two purposes. First, the air breaks the rain drops into small particles, which are then blown away. Secondly, the air heats the windshield to prevent the moisture from freezing Figure 3-5.-Deicing troubleshooting chart. 3-6