747飞机维护手册AMM CHAPTER 34 - NAVIGATION 第34章导航1(94)

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 4.  TAT/N1 Limit Indicator (Fig. 1)
______________________
 A.  The TAT/N1 limit indicator is a dc motor-driven, electromechanical indicator which is not hermetically sealed. The indicator displays total air temperature from -60 to +60.C, engine fan speed (N1) limit from 75 to 125 percent RPM and mode of operation.
 B.  The TAT and N1 limit displays consist of rotating counters which are driven by permanent magnet type dc motors. The mode of operation is displayed on an eight position drum, actuated by a rotary solenoid-potentiometer combination. Meter movements are used to provide failure indications and to indicate whether the TAT readout is positive or negative. Warning flags drop over the TAT and/or N1 limit displays when a failure is detected by the computer or indicator.
 C.  A self-contained power supply in the indicator allows the TAT portion of the indicator to operate independently of the computer. Without a computer installed, the indicator can still be used as a valid TAT indicator.
 5.  Operation (Fig. 2)
_________
 A.  Functional Description, TAT/N1 Limit System
 (1)  General
 (a)  The A/T-TAT/N1 limit mode selector panel controls the TAT/N1 limit system and the A/T system in terms of basic A/T selection and precise N1 control in the N1 mode for the varying conditions under which the engines are required to operate; e.g., takeoff, climb, cruise, go-around. Different engine N1 limits and auto throttle operating mode, alternate engine ratings and derating limits plus a test mode are provided on the panel.
 EFFECTIVITY
 LH 011-030,051-070,082-099;

 AF 121-199; AZ 221-299; AND GN 601-699 AIRPLANES  CONFIG 1 WITHOUT PMS  16 Page 5
   Sep 25/94

34-15-00

V94 VALVE-PACK 2 FLOW CONT & SD (STA 1231, WL 109, LBL 70)
TAT/N1 Limit Indicating System Schematic
Figure 2 (Sheet 1)

EFFECTIVITYLH 011-030,051-070,082-099;
CONFIG 1 AF 121-199; AZ 221-299; AND799 Page 6GN 601-699 AIRPLANES WITHOUT PMS Apr 25/95
34-15-00

V93 VALVE-PACK 1 FLOW CONT & SD
(STA 1113, WL 96, LBL 56)

TAT/N1 Limit Indicating System Schematic
Figure 2 (Sheet 2)

EFFECTIVITYLH 011-030,051-070,082-099;
CONFIG 1AF 152-199; AZ 221-299; AND 799 Page 7GN 601-699 AIRPLANES WITHOUT PMS Apr 25/95
34-15-00

TAT/N1 Limit Indicating System Schematic
Figure 2 (Sheet 3)

EFFECTIVITYLH 011-030,051-070,082-099;
CONFIG 1 AF 121-199; AZ 221-299; AND799 Page 8GN 601-699 AIRPLANES WITHOUT PMS Apr 25/95
34-15-00

JUMPER TO TEST FOR HIGH "SERVO NULL" LOGIC 1 = POSITIVE VOLTAGE _____PININSERT
ALPHA ___ ______
WITHIN INDICATOR NORMALLY USED IN B XX (A)
COMPONENT BENCH TEST ONLY F XX (B)
TAT/N1 Limit Indicating System Schematic
Figure 2 (Sheet 4)

EFFECTIVITYLH 011-030,051-070,082-099;
CONFIG 1AF 121-199; AZ 221-299; AND799 Page 9 GN 601-699 AIRPLANES WITHOUT PMS Apr 25/95
34-15-00
 (b)  
A detent held solenoid reset rotary switch is provided on the mode selector panel for selection of the TAT/N1 limit modes. The output of the switch is a voltage ratio derived from the TAT/N1 limit computer voltage references. The TAT/N1 limit modes that can be selected are takeoff dry (TOD), continuous (CON), climb (CLB), cruise (CRZ), and go-around (GA).

 (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/N1 limit computer, which transmits the rating information to TAT/N1 limit indicator and the A/T computer.

 (d)  
The N1 derate switch permits selection of incremental reduction of N1 limit whether the auto throttle is engaged or not. The switch is used to select the desired derate which is displayed on digital panel readouts.

 (e)  
The test switch on the mode selector panel enables the TAT/N1 limit computer functions to be tested. Pushing the switch connects a ground signal to the TAT/N1 limit computer via the auto throttle to initiate the testing. When the auto throttle computer is engaged, testing of the TAT/N1 limit computer is inhibited to stop the auto throttle computer receiving spurious information.

 (f)  
The N1 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.
　
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