5) Pull the second float switch wire and its TFE-2X16Sw sleeve through the TFE-2X6TW sleeve with the string. a) Pull until the TFE-2X6TW sleeve toughes the base of the float switch.
NOTE: Keep the strings tied to the wires. You will use this string to help pull the wires back through the conduit.
6) Do not cut the TFE-2X6TW sleeve. a) Keep the full length of sleeve until the float switch is installed in the airplane.
(13) Install the float switch in the airplane with the procedure in AMM 28-21-71/401 and with these additional steps:
(a) Tie a short string around the TFE2X6TW sleeve.
NOTE: It is recommended to use the knot shown in Figure 603.
NOTE: If you are re-installing the old float switch, then start the knot at a location that will be there about 3 inches outside of the conduit on the airplane. Use the mark you made before you removed the wire from the airplane to find this location.
(b)
Tie the strings you installed previously to the strings you have through the conduit.
NOTE: Remember to put the nut and washers over the wires (AMM 28-21-71/401).
(c)
Pull the wires through the conduit.
1) Disconnect the conduit at one location (AMM 20-10-51/401).
NOTE: If you try to pull the wires through the full length of the conduit at one time. the string or wire can break.
(d)
Some airplanes have a rubber plug in the fitting at the front spar.
1) If your airplane had this rubber plug, do not re-install it.
NOTE: Removing the plug permits the Teflon sleeve to come out of the conduit.
Sep 01/02 28-21-71 Page 607
(e) After the wires are in the conduit, cut the TFE-2X6TW sleeve and the wires so that they are sufficiently long to tie the wire bundle on the front spat. 1) You must tie a minimum of 3 inches of the sleeve to the wire bundle with a
minimum of four ties.
NOTE: If the float switch wires are too short, then make a small cut in the TFE-2X6TW sleeve. Push the wires out of this cut and splice them. When you complete the splice, push the wires back in the sleeve. Use tape (or equivalent) to seal the cut in the sleeve.
2) When you splice the float switch wires, make a moistureproof splice in a fuel vapor area as shown in SWPM 20-30-12.
D. Put the Airplane Back to Its Usual Condition
(1) Do the steps in AMM 28-21-71/401 to put the airplane back to its usual condition.
4. 737-200 AIRPLANES WITHOUT VOLUMETRIC TOP-OFF UNITS; Center Tank Float Switch Electrical Conduit Inspection
A. Equipment
(1)
Source -Air pressure, regulated, able to supply 20 psi
(2)
Gage -Pressure, 0-20 to 0-50 psi (or equivalent)
(3)
Plug - BACP20AU8 or MS21913-8 (or equivalent), to plug the end of the conduit where the float switch was removed.
(4)
Valve - Shut-off, to shut off the air supply
(5)
Plumbing - To connect the pressure gage and the valve to the float switch conduit and to an air supply. The thread on the conduit is 3/4 16.
B. Inspection Procedure - To Be Used With the Float Switch Wiring Inspection When the Wiring is Removed
(1)
Use the necessary fittings to plug one end of the electrical conduit and to connect a pressure gage and air supply to the other end of the electrical conduit.
(2)
Pressurize the electrical conduit to approximately 20 psi and shut-off the supply of air.
(3)
After 5 (five) minutes, with no supply of air, make sure the pressure gage does not show a decrease in pressure.
NOTE: You must connect the pressure gage so that it shows the pressure in the electrical conduit, even when the air supply is shut-off.
(4)
If you find leakage, then you must replace the section of the electrical conduit where the leak is before the next flight.
(5)
If you do not find a leak, then it is not necessary to replace the electrical conduit immediately. However if you found indications of arcing (in the task: Fuel Float Switch Wiring Inspection), then refer to SB 28-1132 for more data about the necessary inspection intervals.
28-21-71 Sep 01/02 Page 608
C. Inspection Procedure - To Be Used When the Wiring is not Removed
(1) Do these steps to do an inspection for the fuel leaks from the electrical conduit:
(a)
Fill the center tank with fuel.
(b)
Fill the No. 2 tank to a minimum of half full.
NOTE: After you finish this inspection, but before you move the airplane, move fuel between the tanks until the airplane is correctly balanced. 中國航空網 www.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：737 AMM 飛機維護手冊 燃油 FUEL(99)
