Division Boeing 737 Series Aeroplanes - AD/B737/125 Amdt 3 - Centre Wing Fuel Tank Float Switch Wiring - Boeing 737 Series Aeroplanes

Boeing 737 Series Aeroplanes

AD/B737/125 Amdt 3	Centre Wing Fuel Tank Float Switch Wiring	4/2005

Applicability:	Model 737-200, -200C, -300, -400 and -500 series aeroplanes, on which centre wing fuel tanks are activated.Note 1: This Airworthiness Directive is not applicable to aeroplanes equipped with centre wing tank volumetric top-off systems or alternating current (AC) powered centre tank float switches.
Requirement:	1. Accomplish either of the following on Model 737-200, -300, -400 and -500 series aeroplanes having line numbers 1 to 3108 inclusive:a. Remove the fuelling float switch and wiring from the centre fuel tank and perform a detailed visual inspection of the float switch wiring, in accordance with Boeing Alert Service Bulletin (ASB) 737-28A1132 dated 2 December 1998 or Revision 1 dated 15 January 1999 or Revision 2 dated 17 June 1999, to detect discrepancies (i.e. evidence of electrical arcing; exposure of the copper conductor; presence or scent of fuel on the electrical wiring; or worn insulation). After the effective date of this Directive only Revision 2 may be used.Note 2: For the purposes of this Directive, a detailed inspection is defined as:“An intensive visual examination of the specific structural area, system, installation or assembly to detect damage, failure or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses etc may be used. Surface cleaning and elaborate access procedures may be required.”orb. Deactivate the centre tank float switch by either:i. Cutting the two wires for the float switch at the splices on the front spar, capping and stowing the four wire ends. Then paint a ‘Caution’ that shows a conservative maximum fuel capacity for the centre tank on the underside of the right-hand wing near the fuelling station door; and install an ‘INOP’ placard on the fuelling panel.
	orii. Cutting, stowing and splicing the two wires for the float switch at the splices on the front spar. Then paint a ‘Caution’ that shows a conservative maximum fuel capacity for the centre tank on the underside of the right-hand wing near the fuelling station door.orc. Accomplish the inspection and modification of the pressure fuelling system in accordance with Boeing ASB 737-28A1141 Revision 3 dated 9 December 2005.Note 3: Accomplish the requirements specified in either 1.b.i. or 1.b.ii., in accordance with Part 2 of the Accomplishment Instructions of Boeing ASB 737-28A1132 or Revision 1 or Revision 2.2. If no discrepancy is detected during the Requirement 1.a. inspection, carry out either of the following:a. Measure the resistance between the wires and the float switch housing, in accordance with the ASB 737-28A1132 or Revision 1 or Revision 2.orb. Replace the float switch and wiring with a new float switch and wiring, and install double Teflon sleeving over the wiring of the float switch, in accordance with the ASB; or replace the float switch and wiring with a new, improved float switch and wiring in accordance with the Accomplishment Instructions of Boeing ASB 737-28A1141 Revision 3, except, if the replacement float switch and wiring are not available, accomplish Requirements 1.b. and 10.Note 4: After the effective date of this Directive only a new, improved float switch and wiring may be installed.3. If the resistance measured at Requirement at 2.a. is less than 200 megohms , replace the float switch with a new float switch, and install double Teflon sleeving over the wiring of the float switch and wiring, in accordance with the ASB 737-28A1132 or Revision 1 or Revision 2; or replace the float switch and wiring with a new, improved float switch and wiring in accordance with the Accomplishment Instructions of Boeing ASB 737-28A1141 Revision 3; except, if the replacement float switch and wiring are not available, accomplish Requirements 1.b. and 10.

Applicability:

Model 737-200, -200C, -300, -400 and -500 series aeroplanes, on which centre wing fuel tanks are activated.Note 1: This Airworthiness Directive is not applicable to aeroplanes equipped with centre wing tank volumetric top-off systems or alternating current (AC) powered centre tank float switches.

Requirement:

1. Accomplish either of the following on Model 737-200, -300, -400 and -500 series aeroplanes having line numbers 1 to 3108 inclusive:a. Remove the fuelling float switch and wiring from the centre fuel tank and perform a detailed visual inspection of the float switch wiring, in accordance with Boeing Alert Service Bulletin (ASB) 737-28A1132 dated 2 December 1998 or Revision 1 dated 15 January 1999 or Revision 2 dated 17 June 1999, to detect discrepancies (i.e. evidence of electrical arcing; exposure of the copper conductor; presence or scent of fuel on the electrical wiring; or worn insulation). After the effective date of this Directive only Revision 2 may be used.Note 2: For the purposes of this Directive, a detailed inspection is defined as:“An intensive visual examination of the specific structural area, system, installation or assembly to detect damage, failure or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses etc may be used. Surface cleaning and elaborate access procedures may be required.”orb. Deactivate the centre tank float switch by either:i. Cutting the two wires for the float switch at the splices on the front spar, capping and stowing the four wire ends. Then paint a ‘Caution’ that shows a conservative maximum fuel capacity for the centre tank on the underside of the right-hand wing near the fuelling station door; and install an ‘INOP’ placard on the fuelling panel.

orii. Cutting, stowing and splicing the two wires for the float switch at the splices on the front spar. Then paint a ‘Caution’ that shows a conservative maximum fuel capacity for the centre tank on the underside of the right-hand wing near the fuelling station door.orc. Accomplish the inspection and modification of the pressure fuelling system in accordance with Boeing ASB 737-28A1141 Revision 3 dated 9 December 2005.Note 3: Accomplish the requirements specified in either 1.b.i. or 1.b.ii., in accordance with Part 2 of the Accomplishment Instructions of Boeing ASB 737-28A1132 or Revision 1 or Revision 2.2. If no discrepancy is detected during the Requirement 1.a. inspection, carry out either of the following:a. Measure the resistance between the wires and the float switch housing, in accordance with the ASB 737-28A1132 or Revision 1 or Revision 2.orb. Replace the float switch and wiring with a new float switch and wiring, and install double Teflon sleeving over the wiring of the float switch, in accordance with the ASB; or replace the float switch and wiring with a new, improved float switch and wiring in accordance with the Accomplishment Instructions of Boeing ASB 737-28A1141 Revision 3, except, if the replacement float switch and wiring are not available, accomplish Requirements 1.b. and 10.Note 4: After the effective date of this Directive only a new, improved float switch and wiring may be installed.3. If the resistance measured at Requirement at 2.a. is less than 200 megohms , replace the float switch with a new float switch, and install double Teflon sleeving over the wiring of the float switch and wiring, in accordance with the ASB 737-28A1132 or Revision 1 or Revision 2; or replace the float switch and wiring with a new, improved float switch and wiring in accordance with the Accomplishment Instructions of Boeing ASB 737-28A1141 Revision 3; except, if the replacement float switch and wiring are not available, accomplish Requirements 1.b. and 10.

Boeing 737 Series AeroplanesBoeing 737 Series Aeroplanes

Get a plain-English read of Boeing 737 Series Aeroplanes

Boeing 737 Series Aeroplanes