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### proposing this supplemental NPRM toprevent electrical current from flowing through
fuel tank. This condition, incombination with flarrunable fuel vapors, could result in a MOY actuator into afuel tank, which could create apotential ignition source inside the electrical bond resistance between the motor operated valve (ivIOV) actuators and airplane structure forthemain, ~enter, auxiliary, andhorizontal stabilizer fuel tanks, as applicable, and corrective action!ifnecessary. The original NPRM also required a revision tothemaintenance pro~'am to incorporate airworthiness limitation (AWL)
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# , No. 28-AWL-21 orAWL No. 28-AWL-27, as applicable. The original NPRM resulted from fuel system reviews condJtcd by themanufacturer. This supplemental NPRl\1 I 

### would revise the original NPRM by 

### adding airplanes to the applicability, andwould require replacing Production-ins~alled laminate phenolic spacers with metallic spacers between the fueljettison MOV andthe airplane structure, as applicable. We are SUMMARY: We are revising anearlier proposed airworthiness directive (AD) for certain Model 747 airplanes. The original NPRM would have required measuring the ACTION: Supplemental notice ofproposed rulemaking (NPRM); reopening ofcomrne period. AGENCY: Federal Aviation Administration (FAA), DOT. Ainvorthiness Directives; 'I:heBoeing Company Model 747 Airplanes

fuel tank explosion and consequent loss ofthe airplane. IDocket No. FAA-2008-0090; Directorate Ideotifier 2007-NM-312-ADI RlN 2120-AA64

DATES: Wemust receive cO.Qllllcnts 

### on this supplemental NPRM by 

### [INSERT DATE 2S DAYS AFTER DATE OFPUBLICATION INTIIE FEDERAL REGISTER].(4910·13·PI DEPARTMENT OF TRANSPORT AnON Federal Aviation Adminis:tnltion



## I 1.4CFR Part 39 [Doc,ketNo. fAA-201O-++++j Directorate Identifier 2007-Ni\'1-31!-AD] RlN 2120·AA64 Ainvorthiness Directives; The Boeing Company Model 747 Airplanes AGENCY: Feder.nl Aviation Administration (FAA)) DOT. ACTION: Supplemental notice ofproposed rulemaking (NPRM); rcopeni.ng ofcomme period. SUMMARY: We are revising anearlier proposed aif\"'onhiness directive (AD) for cenain Model 747 airplanes. The original NPRM would have required measuring the electrical bond resistance bcr""cill the motor operated valve (MOV) aClual'Or5 and airplane structure for the main, center, auxiliary, and horizontal stabilizer fuel tanks. as appJjcablc. and corrective action ifnecessary. The original NPRM also required a revision to the maintenance prog~al11to incorporate airworthiness limitation (AWL) No. 28-AWL-21 or AWL No. 28-AWL-27, as applicable. The original NPRM resulted "n<L~ _"1'N(;S'MflO1. 

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from fuel syslem reviews, conduyed by the manufacturer. This supplemental NPRlvt would revise the original NPRM byadding airplanes to the applicability, and would require replacing production-installed laminate phenolic spacers with metallic spacers between the fueljenison 

### MOV and the airplane structure. as applicable. We are proposing this supplemental NPR.~I to prevent electrical current from fJawing through a 

### MOV actuator into a fuel tank, which could create apOlential ignition source inside the



# I fuel tank. This condition. incombination with flammable fuel vapors, could result illa fuel tank explosion and consequent loss ofthe ai.rplane.
. DATES: We must receive commbnts on this supplemental NPRM by [INSERT DATE 25 DAYS AFTER DATE OF PUBUCATION 

### TN THE FEDERAL REGISTER). 

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""E14910-13-1'1 DEPARTMENT OFTRANSPORTATION Federal Aviation Administration 14eFR Pari 39 IDocke! No. FAA~2010-++++: Directorate Identifier 2007-N!\1-312-ADJ RIN 2) 20-AA64 Airworthiness Directives; The Boeing Company Model 747 Airplanes AGENCY: Federal Aviation Adminislration (FAA), DOT. _....a;""'''rr~ r"",~·_.<)o,

ACTION: Supplemental notice ofproposed mlernak.ing (NPRM); reopening ofcomme { '" 'lC/=>.c> period. SUMMAR Y: \Vcarc revising :mearlier proposed airworthiness directive (AD) for certain Model 747 airplanes_ The original NPRM would have required measllring the electrical bond resistance between themotor operated valve (MOV) aclUators.md <lirplancstnlcture for the main, center. auxiliary, and horizoll1al stabilizer fllel tanks, tiS -\ ~ applic:lble, and con"cctive action ifnecessary. The original NPRM also requir>.-"'d a revision to the maintenance program to Incorporate airworthiness llmitation (AWL) No. 28·AWL-2J or AWL No_28-AWL-27, as applicable. Theorigmal NPRIv1 resulted frolll fuel ~ystcm rcvic",,·sconducted by the manufacturer. This supplemental NPRIvl would revise the onginal NPRM by adding airplanes to the applicability. and would require replacing productioll-lIlstal1ed lamill3te phenolic spacers with metallic spilcers bCl\vecn the fueljettison MOV and the airplane structure, as applicable. ,",Ve are proposing this supplemcnl<ll 

### NPR1vl to prevent electrical curren! from flowing through a MOV actuaLorinio a fuel tank, which could create apotential ignition source inside the fuel tank. This condition, in combination with flammable fuel vapors, could result ina (tIe! t<lnkexplosion and 'consequent loss ofthe lIlrplane. DATES: We must receive comments on Ihis supplemental NPRM by [INSERT DATE 25 DAYS ArTER DATE OF PUBLICATION IN THE FEDERAL HEGlSTER]. 

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