( ^ . Ronal d J . Hinderberge r Lea d Administrato r Regulator yAdministratio n Commercia l Airplane s Th e Boein g Compan y P.O . Bo x370 7 M C 03-5 6 Seattle . W A98124-220 7 

### JA N2 6 

### 201 2 RA-12-0036 7

U.S . Departmen t

o f Transportatio n Docke t Operation s Wes t Buildin g Groun dFloor , Roo mW12-14 0 120 0 Ne w Jerse y Avenue , S E Washington , D.C . 2059 0 '^ > zr: ) C D • " • ' ' ^ ' - '

L ' , Subject : Model : R A Projec t

No. : EAS A Projec t

No . EAS A Level : Respons e Due : Reference(s) : Petitio n for Exemptio n from1 4 CFR25.981(a)(3 ) for th e 747- 8 Horizonta l Stabilizer

Tan k (HST ) Fue l Tan k

Structura l Lightnin g Protectio n 747- 8 PS11-086 3 N/ A N/ A February 23 , 201 2 (a ) Teleconferenc e betwee n Boein g (Jame s Wilkinso n an dothers ) an dFAA (Su e Lucie r

an dothers) , Decembe r

21 , 2011 . (b ) FA A Exemptio n No . 1017 4 "h i th e matte r o f th e petitio n o f

Th e Boein g Compan y Regulatory Docke t No . FAA-2009-105 8 for a n exemptio n from § 25.981(a)(3 ) at Amendmen t

25-10 2 o f Title 14 , Cod e o f

Federal Regulations " date dDecembe r 14 , 2010 . (c ) FA A Polic y Mem o ANM-112-08-00 2 (Polic y o n Issuanc e o f Specia l Conditio n an dExemption s Relate dt o Lightnin g Protectio n o f

Fue l Tan k

Structure) , date dMay 26 , 2009 . Specia l Instructions : Thi s projec t i s for RC00 3

Thi s lette r

submits : Th e first

productio n incorporatio n o f th e chang e wil l occu r

o n 747- 8 (BBJ ) RC00 3 whic hi s schedule dt o AC-Eo n Apri l 1 , 2012 . Retaine dcomplianc e t o FAA , tha t i s dependen t

o n thi s petitio n request , i s schedule dfor

Februar y 23 , 2012 . (X ) Petitio n for

an Exemptio n Enclosed , pleas e findth e Boein g Petitio n for Exemptio n from1 4 CFR25.981(a)(3 ) for th e 747- 8 Horizonta l Stabilize r

Tan k (HST ) Fue l Tan k

Structura l Lightnin g Protection . Durin g th e referenc e (a ) meeting , th e applicability o f referenc e (b ) t o th e HS T wa s discussed . Boein g state dtha t

th e intent

wa s t o includ e th e HS T tan k an dit s structura l fastener s i n th e petitio n wordin g for

th e exemption , a s th e petitio n wa s base do n referenc e (c ) whic haddresse d

# 0- ^ Pag e 2 Mr . A . Xidia s RA-12-0036 7 th e lightnin g protectio n requirement s o f friel tan k structur e (Th e 747- 8 ha s fuel tank s bot hi n th e win g an dth e horizonta l stabilizer) . Th e FAA , after

consultin g wit

hlegal counsel , state dtha t th e wordin g o f

referenc e (b ) di dno t cove r th e 747- 8 HS T an dtha t

Boein g neede dt o petitio n for aseparat e exemptio n t o cove r th e HST . Waiver fromPubli c Comment Durin g th e referenc e (a ) meeting , th e FA A felt tha t suc ha n exemption , base do n referenc e (a) , can forg o th e publi c commen t process , a s allowe db

y 1 4 CFR11.87 , an db e issue dt o suppor t th e schedul e o f

RC00 3 certificatio n activities . Thi s lette r

i s sen t for : (X ) Postin g t o th e Federa l Docke t Pleas e contac t

thi s offic e o r

th e followin g individual s i f yo u hav e an y questions : (X ) Projec t

Administrato r

(PA) ; Jame s Wilkinso n at (425 ) 717-373 6 Th e informatio n bein g forwarde dt o th e FAA b y o r withthi s correspondenc e i s for th e exclusiv e purpos e o f

suppor t o f application s for

o r amendment s t o Typ e Certificates , i s considere d proprietar y t o Th e Boein g Compan y and/o r it s suppliers , an di s provide do n aconfidentia l basis . Th e dat aprovide dshoul db e returne dt o Boein g immediatel y followin g us e by th e FAA , includin g an y copie s thereo f tha t th e FA A may b e require dt o mak e i n th e cours e o f it s review . Boein g doe s no t

authoriz e th e FA A t o retai n any portio n o f th e material s bein g supplied . Very trul y yours , bal dJ . Hinderberge r ^ea dProgra mAdministrato r (425 ) 237-1355 , M C 03-5 6 FAX : (425 ) 294-934 0 Enclosure s cc : Nam e Sharepoin t Comment s G . Oltma n (747-8/8F ) Ye s (FAA ) 6Y-0 1 D . Tsuj i (747-8/8F ) Ye s (FAA ) 6Y-0 1Enclosur e t o RA-12-0036 7 Exemptio n Petitio n fro m1 4 CF R25.981(a)(3 ) fo r th e Horizonta l Stabilize r Fue l Tan k

Structura l Lightnin g Protectio n Introductio n Th e Boein g Compan y i s petitionin g for a n exemptio n for

1 4 CF R25.981(a)(3 ) at amendmen t

25-10 2 for

fuel tan k structura l lightnin g protectio n for th e horizonta l stabilize r fuel tank (HST) . Onl y th e 747- 8 passenge r airplan e i s equippe dwit hth e HST . A similar petitio n for

exemptio n fo r

th e 747-8F/- 8 win g fiiel tank s wa s submitte dt o th e FA A i n 200 9 an dgrante di n Exemptio n No . 1017 4 i n 2010 . Th e FA A ha s issue dPolic y Memorandu mANM-112-08-00 2 t o addres s th e impracticality o f complianc e t o 1 4 CF R25,981(a)(3 ) at amendmen t

25-10 2 withregard s t o structura l lightnin g protection . 1 4 CF R25.981(a)(3 ) at amendmen t

25-10 2 requires : (a ) N o ignitio n sourc e ma y b e presen t

a t eac hpoin t

i n th e fue l tan k

o r fue l tan k syste mwher e catastrophi c failur e coul doccu r du e t o ignitio n o f

fue l o r vapors . Thi s mus t b e show n by :

(3 ) Demonstratin g tha t

a n ignitio n sourc e coul dno t resul t fro meac h singl e failure , fro meac hsingl e failur e i n combinatio n witheac hlaten t failur e conditio n no t show n t o b e extremel y remote , an dfro mal l combination s o f failure s no t

show n t o b e extremel y improbable . The effect s o f manufacturin g variability , aging , wear , corrosion , an dlikel y damag e mus t

b e considered . Boein g i s petitionin g for

a n exemptio n t o 1 4 CFR25.981(a)(3 ) for fiiel tan k structura l lightnin g protection . Th e ANM-112-08-00 2 FA A polic y memorandu mprovide s th e followin g alternat e requirements : 1 , Instea dofcomplianc e wit hth e requirement s o f § 25.981(a)(3) , th e applican t mus t sho w tha t th e desig n include s at

leas t tw o independent , effective , an dreliabl e lightnin g protectio n feature s (o r set s o f features ) suc htha t

faul t toleranc e t o preven t lightning-relate dignitio n source s i s provide dfor eac hare ao f

th e structura l desig n are apropose dt o b e exemp t fromth e requirement s o f tha t regulation . Faul t

toleranc e i s no t

require dfor

an y specifi c desig n feature if : a . providin g faul t

toleranc e i s show n t o b e impractica l for tha t feature , an d b . fuel tan k

vapo r ignitio n becaus e o f

that featur e an dal l othe r

non-fault

toleran t features , whe n thei r

fuel tank vapo r ignitio n even t

probabilitie s ar e summed , i s show n t o b e extremel y improbable . 2 . Th e applican t

mus t perfor man analysi s t o sho w tha t th e design , manufacturin g processes , an dairworthines s limitation s sectio n o f th e instruction s for

continue d airworthines s includ e al l practica l measure s t o prevent , an ddetec t an dcorrect , failure s o f

structura l lightnin g protectio n feature s becaus e o f manufacturin g variability , aging , wear , corrosion , an dlikel y damage . Pag e 1 of 4Enclosur e to RA-12-0036 7

Discussio n Boein g ha s conclude dtha t complianc e t o 1 4 CF R25.981(a)(3 ) for fuel tan k structura l fastene r lightnin g protectio n woul drequir e thre e independen t layer s o f protection . Fo r fuel tan k fasteners , ther e ar e n o practica l mean s i n curren t technolog y t o obtai n tripl e redundan t mean s o f protectio n i n al l locations . Anothe r optio n woul db e t o appl y a n inspectio n interva l whic hmonitor s th e healt ho f eac hfastene r

tha t penetrate s th e fuel tanks . Wit

hthousand s o f

fastener s o n th e win g an dth e horizonta l stabilize r o f th e 747-8 , thi s optio n i s impractical . Increasin g th e numbe r o f in-tan k inspectio n interval s coul d als o hav e apotentia l unintende dconsequenc e o f damagin g th e lightnin g protectiv e feature s o r

othe r component s insid e th e fuel tank . Propose dRis k

Mitigatio n A s discusse dmth e FA A Policy Memo , Boein g wil l submi t detaile dProprietary informatio n t o th e FA A abou t th e measure s take n i n th e 747- 8 desig n t o provid e practica l structura l lightnin g protection . I n general , th e 747- 8 lightnin g protectio n feature s ar e basedo n state o f

th e ar t industr y desig n practice s for aluminim i win g structur e includin g inherentl y conductiv e low-resistanc e curren t path s tha t

hav e bee n use di n existin g in

servic e designs . Further , Boein g propose s t o enhanc e th e lightnin g protectio n by incorporatin g additiona l faul t toleran t protectio n for

fastener s i n area s o f

potentia l swep t lightnin g attachmen t

(referre dt o a s Zon e 2 ) b y cap sealin g th e fastener s t o contai n a possibl e spar

k i n th e even t

tha t th e primar y protectiv e feature s fail , thereb y increasin g th e leve l o f fue l tan k safety . Boein g wil l sho w that

th e structura l fastene r

desig n for

th e majority o f

th e mode l 747- 8 horizonta l stabilize r

wil l hav e tw o reliabl e an deffectiv e feature s for lightnin g protection . Testin g ha s show n tha t

th e fastene r

installatio n wil l b e saf

e fo r applicabl e Ughtnmg zon e requirement s an dwil l no t produc e an y sparks insid e th e fuel tanks . Additionally , Boein g ha s show n b y tes t

that aca p seal , a s asecon dlaye r o f protection , wil l contai n aspark shoul don e occu r

from afaile dfastener . Fo r th e limite darea s i n whic hasingl e failur e o f afastener coul dresul t

i n los s o f

bot hprotectio n features , o r an y othe r

are awher e asingl e laye r o f protection i s al l that

ca n practicall y b e provided , asafety assessmen t wil l b e don e t o sho w tha t

th e probability o f

alightning-relate dfuel tan k ignitio n even t

i s extremel y improbable . Th e system s supportin g structur e wil l als o b e analyze da s part o f th e faul t tree assessmen t

t o ensur e tha t

the y mee t

th e requirement s i n th e polic y memo . Additionally , Boein g wil l utiliz e productio n procedure s i n orde r t o minimiz e th e ris k

o f mis-installe dprotectiv e measure s an dt o identif y an drepai r

error s i n suc haway tha t th e lightnin g protection feature s wil l b e maintained . Th e instruction s for continue d airworthines s an drepai r

procedure s wil l als o b e provide dt o ensur e th e protectio n feature s ar e maintaine dthroughou t th e lif e o f th e airplane .

Pag e 2 of 4Enclosur e t o RA-12-0036 7

Issu e o f Publi c Interes t Boein g i s workin g t o improv e th e efficienc y o f th e 74 7 mode l b y aredesign . Th e 747- 8 ha s additiona l capabilit y an dcapacit y ove r th e 747-40 0 model . Fo r lightnin g protection , th e 747- 8 ha s additiona l feature s t o enhanc e safet y an dprotec t

th e fuel tank s from sparkin g du e t o alightnin g event . Al l practica l measure s hav e bee n utilized . Additiona l feature s t o directl y mee t

th e rul e ar e impractica l (a s th e FA A Policy Mem o notes ) an d woul dpotentiall y ad dsignifican t cost , weight , an dmaintenanc e t o th e airplan e withou t a measurabl e safety benefit. Further , additiona l lightnin g protectio n feature s coul dinhibi t th e ability t o inspec t

th e structur e (reducin g safety) . Requirin g th e 747- 8 t o attemp t t o directl y compl y withthi s rul e woul dsignificantl y inhibi t Boeing' s ability t o certif y th e HS T s o tha t

th e 747- 8 coul db e fuele dfor extende d rang e benefi t

o f th e operator . Thi s additiona l rang e capabilit y o f th e 747- 8 i s critica l t o it s operationa l mission . I f th e 747- 8 withth e HS T wer e no t abl e t o b e fueled , i t

woul d rende r th e 747- 8 t o b e o f

lesse r valu e t o th e publi c interes t wit hn o commensurat e increas e i n safety . Man y Boein g customer s ar e dependin g o n th e rang e o f th e 747- 8 t o mee t thei r busines s needs . Ne w 747- 8 aircraf t wil l typicall y replac e olde r les s fuel efficien t models , thu s reducin g th e publi c expens e for fuel consume di n ai r

travel . Therefore , i t

i s th e positio n o f

Th e Boein g Compan y tha t th e publi c interes t

woul db e bes t serve di f th e FA A wer e t o gran t

thi s exemption . Effec t o f Exemptio n o n Safet y Withcurren t

desig n practice s for

lightnin g protection , Boein g aircraf t design s hav e accumulate di n exces s o f 60 0 millio n revenu e servic e flight hour s wit hn o lightning

relate devents . Prio r

t o thes e design s an dservic e hours , ther e wer e tw o commercia l je t transpor t hul l los s event s whic har e believe dt o hav e bee n cause db y lightnin g strike s (referenc e ARA C Report : 199 8 ARA C Fue l tan k Harmonizatio n Workin g Grou p report . Tas k Grou p 1 Servic e History / Fue l Tan k

Safet y Leve l Assessment) . Th e first wa s i n 1963 , whic hle dt o th e developmen t o f lightnin g protectio n standard s for fuel tanks . Th e secon dan dlas t

even t wa s i n 197 6 whic hals o resulte di n improvement s i n fuel tan k lightnin g protection . I n addition , bot hevent s utilize dJP-4 , whic hi s awid e cut , highe r volatility fuel rarel y use dtoday . Th e 747- 8 airplane s wil l no t b e certifie dfor

us e withJP

4 o r othe r wid e cu t fuels . Th e hour s accumulate dsinc e th e las t even t represen t ove r si x time s th e hour s accumulate dwithearlie r design s throug h1976 . Th e accident-fre e fleet history sinc e 197 6 show s curren t Boein g win g design s hav e sufficien t protectio n agains t lightnin g induce dfuel tan k ignitio n events . Thi s safet y recor dfor

th e fuel syste mdesign s upo n whic hth e enhance dBoein g 747- 8 desig n i s base dindicate s tha t th e propose dfuel tan k

lightnin g protectio n desig n o f th e mode l 747- 8 wil l b e safe .

Pag e 3 of 4Enclosur e t o RA-12-0036 7

Conclusio n Boein g i s petitionin g for

an exemptio n for

1 4 CF R25.981(a)(3 ) a

t amendmen t

25-10 2 for fijel tan k structura l lightnin g protectio n for th e horizonte dstabilize r

fiiel tank . Th e Boein g mode l 747- 8 receive da n Amende dTyp e Certificat e i n Decembe r 201 1 withou t certificatio n fo

r th e horizonta l stabilize r

fuel tank . Grantin g thi s exemptio n wil l allo w Boein g t o certif

y th e HS T for

structura l lightnin g protection . Th e desig n for th e 747- 8 provide s an appropriat e leve l o f safet y agains t lightnin g induce dfuel tan k ignitio n an d wil l b e show n t o compl y withth e alternativ e requirement s provide di n th e FA A polic y mem o ANM-112-08-002 .

Pag e 4 o f 4