Airworthiness Directive · Amendment 39-16818 · Fuel
The Boeing Company Model 737-600, -700, -700C, -800, and -900 Series Airplanes
This AD applies to The Boeing Company Model 737-600, -700, -700C, -800, and -900 series airplanes, certificated in any category; as identified in Boeing Alert Service Bulletin 737-28A1201, Revision 1, dated May 28, 2009.
We are superseding an existing airworthiness directive (AD) for the products listed above. That AD currently requires replacement of the power control relays in the P91 and P92 power distribution panels for the fuel boost and override pumps with new, improved relays having a ground fault interrupter (GFI) feature, or installation and maintenance of universal fault interrupters (UFIs) using a certain supplemental type certificate. This new AD continues to require the actions of the existing AD and also specifies which relays may be replaced by GFIs or UFIs. This AD was prompted by a need to clarify which relays may be replaced by installation of UFIs. We are issuing this AD to prevent pump housing burn-through due to electrical arcing, which could create a potential ignition source inside a fuel tank. This condition, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane.
Comply with this AD within the compliance times specified, unless already done.
Within 60 months after the effective date of this AD, do the actions required in paragraphs (g)(1) and (g)(2) of this AD.
(1) Replace the power control relays that are located in the R18, R19, R20, and R21 positions in the P91 and P92 power distribution panels for the fuel boost pumps with new, improved relays, part number KDAG-X4F-001, having a ground fault interrupter (GFI) feature, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-28A1201, Revision 1, dated May 28, 2009, except as provided in paragraphs (h) and (i) of this AD.
(2) Replace the power control relays that are located in the R54 and R55 positions in the P91 and P92 power distribution panels for the fuel override pumps, in accordance with the actions required in paragraph (g)(2)(i) or (g)(2)(ii) of this AD.
(i) Replace with new, improved relays, part number KDAG-X4F-001, having a GFI feature, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 737-28A1201, Revision 1, dated May 28, 2009, except as provided in paragraphs (h) and (i) of this AD.
(ii) Install and maintain TDG Aerospace universal fault interrupters (UFIs) in accordance with a method approved by the Manager, Seattle Aircraft Certification Office, FAA.
Note 1: Boeing Alert Service Bulletin 737-28A1201, Revision 1, dated May 28, 2009, refers to Honeywell Service Bulletin 1151932-24-61 and Honeywell Service Bulletin 1151934-24-62, both Revision 5, both dated May 25, 2009, as additional sources of guidance for replacement of the power control relays in the P91 and P92 power distribution panels.
Note 2: Guidance on installing TDG Aerospace universal fault interrupters (UFIs) can be found in Supplemental Type Certificate ST02076LA.
(h) Where Boeing Alert Service Bulletin 737-28A1201, Revision 1, dated May 28, 2009, specifies accomplishing actions in the P91 and P92 power distribution panels while those panels are installed on the airplane, this AD does not require that the panels are on the airplane while the actions are accomplished. This AD allows the actions on the P91 and P92 panels to be accomplished while those panels are removed from the airplane.
Note 3: Section 24-21-21, “Power Distribution Panel,” of the Practices and Procedures section of the Boeing 737-600-700-800-900 Aircraft Maintenance Manual may be used as an additional source of guidance on removing and reinstalling the P91 and P92 power distribution panels.
(i) Where Note (a) in Figures 1 and 2 of the Accomplishment Instructions of Boeing Alert Service Bulletin 737-28A1201, Revision 1, dated May 28, 2009, specifies procedures for marking the part numbers of the panels, this AD does not require a specific method for marking. Operators are allowed to use any industry-accepted method.
Actions done before the effective date of this AD in accordance with Boeing Alert Service Bulletin 737-28A1201, dated February 19, 2007, are acceptable for compliance with the requirements of paragraphs (g)(1) and (g)(2)(i) of this AD, provided that Revision 5 of Honeywell Service Bulletins 1151932-24-61 and 1151934-24-62, both dated May 25, 2009, were used as an additional source of guidance.
