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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
115V AC
TANK NO. 1 IND
CTR TANK 1 CELL IND
CTR TANK 2 CELL IND
CTR TANK 3 CELL IND
CTR INTEG TANK IND
TANK NO. 2 IND
AFT AUX 810 TANK IND
AFT AUX 1070 TANK IND
AFT AUX 400 TANK IND
TANK QTY
JUMPER
17 10V AC REF
18 TOTAL FUEL 19 SIGNAL GROUND
J1 24 REG & HLDC RECT

REG & LLDC RECT J1 REG 23
LLDC
DEMOD
1
LATCH
DEMOD
2
LATCH
DEMOD
3
LATCH
DEMOD
4
LATCH
DEMOD
5
HLDCLATCH
DEMOD
6
LATCH CPU D/A

DEMOD
7
LATCH
DEMOD
8
LATCH
DEMOD
9
LATCH
20
21
22
RESET CLEAR
WJ123 4

FAILURE
MONITOR

POWER
12

EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH EFIS ú

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SUPPLY LLDC MONITOR
Fuel Summation Unit Schematic Figure 10
AND A SINGLE FMC  ú  CONFIG  1
 ú  07  Page 35
 ú  Mar 15/96 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
C95262
A
737-300/400/500MAINTENANCE MANUAL
 C.  Any unused tank inputs are grounded to eliminate spurious signals.
 D.  The fuel summation unit scans and inputs one fuel quantity indicator line at a time. As each tank fuel quantity is input, it is added to a running total and saved. If any line has over 3 consecutive errors, its quantity is set to zero and an error flag is set. In-line memory tests are performed during the operation of the summation unit. A malfunction of the summation unit will cause the total fuel quantity output to be set to zero but will not affect the individual fuel indicators.
 E.  The summation unit provides an analog output proportional to total fuel quantity. The CPU controls the analog output amplitude with a 12 bit digital-to-analog converter (D/A). A 10v ac winding on the power transformer provides the reference voltage to the D/A. The output of the D/A is scaled between 0 and 10v ac depending on the binary combination latched into the converter by the CPU.
 F.  A failure monitor circuit checks the CPU for normal operation. Any abnormal operation causes a reset which zeros the output of the CPU and clears the D/A. The power supply monitor will also cause a reset through the failure monitor if the LLDC is too low.
 G.  Four jumpers (for internal calibration) are within the fuel summation unit. The jumpers permit the unit to be pre-calibrated for full scale analog signal output.
 8.  Performance Computations (Fig. 11)__________________________________
 A.  General
 (1)  The FMCS provides optimal thrust, speed, and flight path profile prediction. The optimization is based upon sensor measurements of actual flight path conditions; and the operations definition of the flight cost factors that the pilot wishes to optimize.
 B.  Economy Cost Factor
 (1)  Fuel burn is not the only consideration in evaluating trip economy. Time has a tangible value. Speed schedules for optimal operation of the airplane in the climb, cruise, and descent phases of a flight are determined largely as a function of a variable known as cost index. Cost index is a number which relates the direct hourly flying costs to the cost of fuel. It is generally the case that fuel-economical speed schedules are slower schedules. A consequence to this is that decreased fuel burn results in increased trip time. The FMCS cost index is an enterable variable that can be manipulated by the operator. This permits the economy speed schedules for climb, cruise, and descent to be biased for a particular set of operating conditions. Costs can change in the day-to-day operating environment. As costs change the operator can change the value of cost index accordingly, to optimize the performance of the airplane.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH EFIS ú

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