(j)
The N1 limit flag is held out of view by the N1 valid signal and the failure monitor circuit. Loss of the N1 valid input signal, removes the operating voltage from the N1 limit flag, indicating a failure. A loss of power from the failure monitor removes the ground and causes the N1 limit flag to indicate a failure. The failure monitor also monitors the N1 limit counter and mode annunciator motors supply voltages. Any excessive supply voltages applied removes the ground and causes the flag to indicate a failure.
(k)
The 26 volts ac from autotransformer No. 3 to the TAT power supply provides the ac and dc power for the total air temperature indication. Total air temperature is sensed by a resistance wire probe excited from the ac and dc current in the TAT sense module. The module converts the probe resistance to a dc voltage which is proportional to the reference voltage. This uncompensated voltage is buffered and routed to the computer through the TAT sense circuit for N1 computations in all modes except takeoff.
(l)
An identical output voltage is also applied to the function generator which provides a reference voltage and a varying input signal to the servo-amplifier. As the varying input to the servo-amplifier becomes less negative or more negative than the reference voltage, the servo-amplifier produces a negative or positive output signal. This output signal causes the TAT motor to drive the wiper arm of the follow-up potentiometer toward a negative or positive supply voltage and the increasing negative or positive potential is applied to the function generator. This process continues until the varying output signal is equal to the reference voltage and the servo-amplifier stops driving the TAT motor.
EFFECTIVITY
LH 011-030,051-070,082-099;
AF 121-199; AZ 221-299; AND GN 601-699 AIRPLANES CONFIG 1 WITHOUT PMS 02 Page 14
Sep 25/94
34-15-00
(m)
The servo failure monitor controls the TAT failure flag and the plus-minus display. The failure monitor circuit provides a ground to one end of the control solenoid for either a plus or minus display. The TAT failure monitor circuits also monitors for a power failure by removing ground from both leads of the control solenoid, causing the plus-minus indicator to display a failure flag.
(n)
With a TAT probe short or open, an abnormally high positive or negative output signal from the TAT sense module is applied to the function generator. The excessively high input, if negative, is applied to the level detector; if positive, it is inverted and applied to the level detector. The level detector changes from a normal negative output stage and produces a positive output to the failure monitor. This causes the failure monitor to remove the ground from the control solenoid and a failure flag is displayed.
(o)
During test conditions, when the TEST switch is pressed and the auto throttle is not engaged, a ground and 28 volts dc is provided on the test lines from the computer. The dc voltage energizes the test relay in the indicator and establishes fixed operating voltages for the TAT servo loop. This fixed operating voltage causes the TAT motor to drive and display approximately +10.C. The N1 limit computation circuits are also adjusted so the combination of mode and test signals produce specific test displays on the N1 limit readout.
B. Modes of Operation
(1)
Takeoff Dry (TOD)
(a) This is the maximum thrust available without the use of water injection. The rating is selected by setting the airplane throttle to obtain the computer TOD thrust in terms of engine N1 limit for the existing ambient temperature and barometric pressure. The rating is time limited and is used only for takeoff and as required for reverse thrust operations during landing.
(2)
Go-Around (GA)
(a) The GA or inflight takeoff is similar to TOD. This rating is the power setting for a missed approach.
(3)
Maximum Continuous (CON)
(a) This rating is the maximum thrust that may be used continuously and is intended only for emergency use. The rating is selected by adjusting the throttle to obtain a predetermined engine N1 limit.
(4)
Maximum Climb (CLB)
(a) This rating is the maximum thrust approved for normal climb. The rating is selected by adjusting the throttle to obtain a predetermined engine N1 limit.
(5)
Maximum Cruise (CRZ)
EFFECTIVITY
LH 011-030,051-070,082-099;
AF 121-199; AZ 221-299; AND GN 601-699 AIRPLANES CONFIG 1 WITHOUT PMS 02 Page 15
Sep 25/94
34-15-00
(a) This rating is the maximum thrust approved for cruising. It is obtained in the same manner as maximum climb and maximum continuous thrust.
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本文链接地址：747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航1(97)
