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B496 CMPTR-TAT/EPR LIM (E2-1)(STA 1113, WL 96, LBL 56)
TAT/EPRL Indicating System Schematic
Figure 2 (Sheet 2)
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TAT/EPRL Indicating System Schematic
Figure 2 (Sheet 3)
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COMPONENT BENCH TEST ONLY B XX (A) F XX (B)
TAT/EPRL Indicating System Schematic
Figure 2 (Sheet 4)
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(c)
Two switches are provided on the mode selector panel for selection of either of two engine ratings. The master dim and test module provides 12 volts dc to continuously illuminate the type of engine and 28 volts dc to illuminate the selection of a rating (either I or II) when that switch is pressed. This action also closes the contacts of the appropriate relay in the TAT/EPRL computer, which transmits the rating information to TAT/EPRL indicator and the A/T computer.
(d)
The EPR DECR switch permits selection of incremental reduction of EPR limit whether the auto throttle is engaged or not. The switch is used to select the desired decrease which is displayed on digital panel readouts.
(e)
The test switch on the mode selector panel enables the TAT/EPRL computer functions to be tested. Pushing the switch connects a ground signal to the TAT/EPRL computer via the auto throttle to initiate the testing. When the auto throttle computer is engaged, testing of the TAT/EPRL computer is inhibited to stop the auto throttle computer receiving spurious information.
(f)
The EPRL mode switch and the indicator receive plus and minus 5-volt dc reference voltages from the computer. The action of the switches varies the voltage on the mode lines to the computer, which eventually drives the annunciators on the indicator. When computer reference power to the indicator is not available, the indicator displays TAT with no loss of accuracy.
(g)
The TAT/EPRL system provides the following functions within
the auto throttle system: EPR limit mode selection Computation of the required EPR limit Visual readout of the selected EPR limit mode, computed EPR limit, and total air temperature Transmittal of the EPR limit mode, EPR limit, and TAT signals to the auto throttle computer
(2) Computation of TAT/EPRL
(a)
The TAT/EPRL computer receives analog input signals representative of airplane altitude and mach, total air temperature (TAT), and flight mode. These inputs are utilized by the computer in EPRL computations. In addition to outputting EPRL and mode data to the TAT/EPRL indicator and the auto throttle system, the computer supplies auxiliary outputs to the AIDS recorder and EPR command counter on EPR indicators.
(b)
The computer utilizes additional discrete inputs such as nacelle and wing anti-ice, CADC valid, test, and discrete inputs from the airplane air conditioning bleed air system (a/c pack 1=0, 2=0, and 3=0) as shown in Fig. 2. The computer also receives an added discrete (aspirated probe) to designate whether a standard TAT probe or aspirated probe is in use.
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(c)
The CADC valid signal informs the computer that its mach and altitude input signals are valid. A go, no-go TAT/EPRL system check may be accomplished by sending a test signal to the computer from the system mode selector panel. The computer computes and outputs a preprogrammed EPRL to the system TAT/EPRL indicator for comparison by the operator.
(d)
The computer contains eleven plug-in boards and a power supply and may be divided into two general sections. Boards A1 thru A5 and A7 make up the central processor section. Boards A8 thru A12 comprise the MADDAM section (multiplexed analog-to-digital digital-to-analog multiplexed).
(3) Central Processor
(a)
The central processor controls and coordinates all of the subunits of the computer. It provides for the orderly transfer of information between all parts of the system.
(b) 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航1(100)
