Airworthiness Directive · Amendment 39-16447 · Fuel
The Boeing Company Model 747-400, 747-400D, and 747-400F Series Airplanes
This AD applies to The Boeing Company Model 747-400, 747-400D, and 747-400F series airplanes, certificated in any category; as identified in the service bulletins listed in paragraphs (c)(1) and (c)(2) of this AD.
(1) Boeing Service Bulletin 747-28A2266, Revision 1, dated December 10, 2009.
(2) Boeing Alert Service Bulletin 747-28A2267, dated December 18, 2008.
We are adopting a new airworthiness directive (AD) for Model 747-400, 747-400D, and 747-400F series airplanes. This AD requires installing a hot short protector (HSP) for the fuel quantity indicating system (FQIS) of the center fuel tank and, for certain airplanes, the horizontal stabilizer fuel tank. This AD results from fuel system reviews conducted by the manufacturer. We are issuing this AD to prevent an electrical hot short from a source outside the FQIS to the densitometer wiring from causing failure of the FQIS densitometer resistors, which could result in an ignition source inside the center or horizontal stabilizer fuel tanks. An ignition source, in combination with flammable fuel vapors, could result in a fuel tank explosion and consequent loss of the airplane. This AD is effective November 5, 2010. The Director of the Federal Register approved the incorporation by reference of certain publications listed in the AD as of November 5, 2010.
You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.
Within 60 months after the effective date of this AD: Do the applicable installations of the HSP specified in paragraphs (g)(1) and (g)(2) of this AD.
Note 1: Boeing Service Bulletin 747-28A2266, Revision 1, dated December 10, 2009; and Boeing Alert Service Bulletin 747-28A2267, dated December 18, 2008; refer to Cinch Service Bulletin CN1036-28-01, Revision C, dated January 18, 2007, as an additional source of guidance for installing the HSP in the fuel tanks which must be done before or concurrently with the actions specified in Boeing Service Bulletin 747-28A2266, Revision 1, dated December 10, 2009; and Boeing Alert Service Bulletin 747-28A2267, dated December 18, 2008.
(1) For all airplanes: Install the HSP in the center wing tank, in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-28A2266, Revision 1, dated December 10, 2009.
(2) For airplanes identified in Boeing Alert Service Bulletin 747-28A2267, dated December 18, 2008: Install the HSP in the horizontal stabilizer tank, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-28A2267, dated December 18, 2008.
Actions accomplished before the effective date of this AD according to Boeing Alert Service Bulletin 747-28A2266, dated December 18, 2008, are considered acceptable for compliance with the corresponding action specified in this AD, provided that Cinch Service Bulletin CN1036-28-01, Revision C, dated January 18, 2007, is used as an additional source of guidance.
