Airworthiness Directive · Amendment 39-15479 · Boeing Model 747-400F and -400 Series Airplanes
Boeing Model 747-400F and -400 Series Airplanes
Superseded. A later AD replaced this one: AD 2014-05-31. Comply with the one in force.
This AD applies to Boeing Model 747-400F airplanes as identified in Boeing Alert Service Bulletin 747-25A3370, Revision 1, dated April 27, 2006; and Model 747-400 series airplanes as identified in Boeing Alert Service Bulletin 747-25A3526, dated November 13, 2007; certificated in any category.
We are adopting a new airworthiness directive (AD) for certain Boeing Model 747-400F and -400 series airplanes. This AD requires installing drains and drain tubes to eliminate water accumulation in the dripshield above the M826 Card File in the main equipment center. This AD results from a report that water from the dripshield entered the card file and damaged a circuit card, causing the AFT CARGO FIRE MSG message to be illuminated and resulting in an air turn back. We are issuing this AD to prevent water from entering the card file and damaging a circuit card. Failure of one or more of the 15 fuel system circuit cards in the card file could cause loss of fuel management, which could cause unavailability of fuel. Failure of one or more of the 35 fire detection circuit cards could cause a false message of a fire, or no message of a fire when there is a fire.
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 24 months after the effective date of this AD, install two drains and drain tubes in the dripshield above the M826 Card File over the nose wheel left side in the main equipment center at station 400, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-25A3370, Revision 1, dated April 27, 2006 (for Model 747-400F series airplanes); or Boeing Alert Service Bulletin 747-25A3526, dated November 13, 2007 (for Model 747-400 series airplanes).
Installing the drains and drain tubes is also acceptable for compliance with the requirements of paragraph (f) of this AD if done before the effective date of this AD in accordance with Boeing Alert Service Bulletin 747-25A3370, dated September 8, 2005.
