2-48 Change 4
DE.ICE CONTROL PANEL
AB0700
SA
CONTROL/ FUNCTION
INDICATOR
TEST IN PROGRESS Green light goes on during
test cycle. At end of test
cycle, light should go off.
MODE selector
AUTO System off-time is controlled
by ice rate signal.
MANUAL Gives pilot manual control of
system off-time.
T Sets a .xed element-off-time
for trace icing.
L Sets a .xed element-off-time
for light icing.
M Sets a .xed element-off-time
for moderate icing.
2.50.3 Blade Deice Test. The BLADE DE-ICE TEST panel (Figure 2-15) allows the pilot to check the blade deice system for failures that are otherwise dormant during the normal TEST mode, but that can allow abnormal operation during use. The panel accomplishes this by introducing selected failure signals into the system and requiring the deice controller built-in-test circuitry to function in a spe-ci.c manner. The blade deice test should be done during the ground checkout before each .ight when blade deice use is anticipated. In the NORM position, the test panel allows system test to be done without the introduction of false failure signals. Thus, the system should complete its self checkout cycle without failure indications on the cau-tion display. In the SYNC 1 and SYNC 2 positions, the test panel interrupts the distributor sync line and provides the controller with a false sync input. The controller must inter-pret these false signals as indications of distributor failure, and produce MR DE-ICE FAIL caution legend for both cases. In the OAT position, the test panel short circuits the OAT sensor input to the controller. BITE circuitry within the controller must sense the simulated failure and turn on both the MR DE-ICE FAIL and TR DE-ICE FAIL cau-tion legends. In the EOT position, the test panel biases BITE circuitry in the controller and the OAT sensor to simulate malfunctioning primary EOT timing circuits. The biased BITE circuit is thus deceived into believing that the primary circuits are in error. The controller must turn on both the MR DE-ICE FAIL and TR DE-ICE FAIL leg-ends when this occurs. The test panel also functions auto-matically during blade deice system use to sense contradic-tory signals from the deice power circuits. If electrical power remains applied to either the main or tail rotor heat-ing elements after the controller signals a FAIL condition or when the system is OFF, then the corresponding PWR monitor light on the BLADE DE-ICE TEST panel turns on. The light informs the crew that further action is required to isolate the deice loads indicated. The test panel provides a reliability check of critical deice system functions. The pilot, after doing the indicated tests properly, can be con.-dent that the deice system primary and BITE electronics are functioning within speci.ed tolerances.
2.50.4 Blade Deice Test Panel. The control for select-ing test functions of the blade deice system is on the BLADE DE-ICE TEST panel (Figure 2-15). Two PWR lights on the panel warn of power malfunctions of the main and tail rotor deice. Control and indicators are as follows:
CONTROL/ INDICATOR FUNCTION
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