(2)
Wet tank method (alternate) is accomplished with fuel in tanks. Some accuracy is sacrificed by necessity of disconnecting immersed tank and compensator units from system in order to "zero" indicators plus inability to account for stray capacitance. Inability to measure and compensate for stray capacitance may cause an adjustment error equivalent of up to 15 gallons, or 101 pounds, of fuel per tank.
NOTE: Alternate method should only be used as an interim procedure. For optimum accuracy, empty tank method should be performed as soon as possible.
C. Whenever a fuel/fueling quantity indicator is replaced, subsequent to system adjustment, replacement indicator may be bench adjusted to proper settings by use of data affixed to indicator being replaced.
D. Use care, when inserting test equipment into fuel quantity indicating system, to turn off electrical power or to make circuit interruption as brief as possible.
CAUTION: DO NOT LEAVE CONNECTORS DISCONNECTED WITH ELECTRICAL POWER ON. OPEN CIRCUITED FUEL QUANTITY UNITS DRIVE QUANTITY INDICATOR POINTER AGAINST STOP, AND CONTINUED RUNNING WILL DAMAGE INDICATOR CLUTCH.
E. If erratic fuel quantity indicator readings are observed, check for presence of water in fuel tanks before performing system adjustment. Drain off water at sump drains and, if necessary, clean and unplug drain holes in wing tank spanwise stringers to permit water accumulation to drain to sumps.
F. Several components of fuel quantity indicating system's equipment are interrelated with various components in their respective calibration adjustments. Following table shows which adjustments must be accomplished when one of interrelated components have to be changed.
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
UNIT CHANGED REQUIRED ADJUSTMENT ADDITIONAL ADJUSTMENT REQUIRED
RELATED UNIT ADJUSTMENT
Fuel Quantity Indicator *[1] Empty, Full Fueling Quantity Indicator FULL
Fuel Summation Unit (PDCS Instl) FULL (on channel for changed unit)
Fueling Quantity Indicator *[1]* FULL None None
Fuel Summation Unit (PDCS Instl) EMPTY FULL (F1, F2, FC) None None
Tank Unit or None Fuel Quantity Indicator FULL, EMPTY
Compensator Unit None Fueling Quantity Indicator FULL
*[1] When a fuel quantity indicator is moved from a center instrument panel (P2) to the fueling panel (p15) or vice-versa, it must be readjusted for the position in which it is installed.
G. Calibrate fuel summation unit for correct total fuel signal transmission to performance data computer system (PDCS) (AMM 28-41-81/501) only after completion of calibration adjustments covered in this section
2. Adjustment of Fuel Quantity Indicating System - Empty Tank Method (Preferred)
A. General
(1)
In this adjustment method, the fuel tanks must be defueled and sump fuel drained. Indicators are first adjusted to read zero, the zero adjustment is checked, and then full adjustment is made by capacitance substitution. For proper adjustment of the fuel quantity indicating system, no part of the adjustment should be omitted.
(2)
During adjustment, additional (stray) capacitance is present in the system because of test equipment. To minimize error, ensure that stray capacitance values are recorded and accounted for per adjustment procedure.
(3)
If system adjustment values are not met, perform tank unit and compensator unit adjustment/test (AMM 28-41-21/501) or troubleshoot (AMM 28-41-0/101).
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28-41-0 Page 502 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Jun 20/85
B. Equipment and Materials
(1)
System Tester
(a)
Model GTF-2, P/N 361-012-001, Gull Airborne Instruments, Inc., 55 Engineers Road, Smithtown, N.Y. 11787
(b)
P/N 472090-007, 472090-009, or PSD40-1, Simmonds Precision Products Inc., Panton Road, Vergennes, VT 05491
(c)
Model 8000, Barfield Instrument Corp., Miami, Florida 33142
(2)
System Test Harnesses
NOTE: Quantity of test cabling must be controlled, especially in regard to stray capacitance. Stray capacitance for test cables shall be less than 0.1 pf.
(a)
F72731-82 or Gull Airborne 467-177-007, -008
(b)
464534, Simmonds Precision Products Inc.
(c)
P/N 101-00542, Barfield Instrument Corp.
(3)
Fuel Truck with Flowmeter Calibrated to an Accuracy of + 0.5% at a Specified Fuel Flow Rate
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