Smiths Aerospace
Electronic Systems – Malvern
DOC NO.0134ED
MAINTENANCE MANUAL SUPPLEMENT
BOEING B737-100/200/300/400/500
28-41-04
7. V-Reference Totalizer Indicator (Where Applicable)(Fig. 1)
A. Some aircraft are equipped with a V-Reference totalizer indicator which is located on the center
instrument panel. This indicator provides an instantaneous summation of the fuel quantities from the
fuel quantity indicators. The weight is displayed to the nearest 100 units. This indicator also displays a
Landing Reference Speed in knots. The aircrew must set the aircraft Zero Fuel Weight and Flap
setting into this indicator.
8. Digital Calibration Trim Unit (DCTU) (Fig. 1)
A. Digital calibration trim units (DCTU) installed behind each fuel quantity indicator is used to program
the indicators with six fuel tank parameters. This programming permits the replacement of any fuel
quantity indicator by any other fuel quantity indicator.
9. Capacitance Trimmers (Where Applicable) (Fig. 1)
A. Capacitance trimmers, found on the forward left side of the control stand above the hand mike jack,
are adjusted to a minimum setting, and are not used for calibration.
10. Fuel Measuring Sticks (Fig. 3)
A. The fuel measuring sticks are used to measure the fuel quantity in the No. 1 and No. 2 tanks by
mechanical means. Each main tank has five fuel measuring sticks, calibrated in inches, found in the
tank access doors No. 1, 4, 6, 8, and 10. The fuel measuring stick unit of calibration is marked on
each stick approximately 1 inch from the end.
B. The value on the fuel measuring stick and the applicable measuring stick conversion document (Ref
12-11-00/301) help the ground crew in the refuel operations when electrical power for the fuel quantity
indicators is not available. The fuel measuring sticks are also used to compare the fuel weight shown
by the fuel quantity indicators to the value shown by the fuel measuring sticks to make sure the fuel
quantity indicator operates correctly.
C. To operate the fuel measuring stick (see Figure 4), the fuel measuring stick is unlocked from the base
by applying a slight pressure and a 90-degree counterclockwise turn to the end of the stick sub
assembly. When the stick sub assembly is unlocked, it is lowered to the fully extended position.
Depending on fuel level, a bearing located on top of the stick sub assembly will magnetically Latch
onto a magnet in the float before full extension. In this event, a slight pressure should be applied to
assure a full extension. At the fully extended position, the stick sub assembly stops against a cushion
giving a soft firm feel.
(1) To find the fuel level, the stick sub assembly is gently raised until the magnetic latch is felt to
engage. There is a positive feel in this position since the magnetic latch is strong and will jerk the
stick sub assembly into its position. The stick sub assembly is now read to find the fuel level in
the fuel tank.
(2) If the fuel measuring stick is being monitored during a refuel or defueling operation, the float and
stick sub assembly will move with the fuel level. However, since the magnetic attachment
between the magnets of the stick sub assembly and float causes a small friction against the
housing, the stick sub assembly and float will not move up smoothly with the fuel level, but in
distinct jumps as the fuel level rises on the float to overcome the static friction. On declining fuel
levels when defueling, friction will occur in the opposite direction. Calibration marks on the stick
sub assembly are set to read on rising fuel levels and the most accurate reading will be
immediately after a jump of the stick sub assembly.
Page 15
Dec 18/02
Airplanes with Smiths 2307 Model Fuel Quantity
Indicators with TSU
EFFECTIVITY
