### ( ^ Th e Boein g Company P.O . Bo x370 7 Seattle , W

A98124-220 7 

## : ARTMENTO

F ::-i^PORWIO N ^ , ^ ,^^„, , ^^'OPERATIGNS Septembe r19,201 1 RA-11-0506 1 

## ^! ! ';: P 2 ! P !2:0 1 U.S . Departmen t o fTransportatio n Docke t Operation s Docke t FAA-2008-124 9 Wes t Buildin g Groun d Floor , Roo m W12-14 0 120 0 Ne wJerse yAvenue , S E Washingto n D.C . 2059 0 Subject : Clarificatio n o fExemptio n 9791 C fro m 1 4 CF R §25.853(a) Reference : (a ) FAAExemptio n Numbe r9791C , RegulatoryDocke tNo .

FAA-2008-124 9 Dea rSi ro rMadam : Th e Boein g Compan yrespectfull yrequest s a clarificatio n o fth e Referenc e (a ) tim e limite d exemptio n fro m th e requirement s o f1 4 CF R §25.853(a) . Th e clarificatio n addresse s modificatio n kit s an d spar e part s certifie d prio rt o th e expiratio n o fth e reference d tim e limite d exemptio n o n Novembe r28 , 2011 bu t whic h ar e subsequentl yshippe d t o o rinstalle d b yairline s afte rNovembe r 28,2011 . Th e Referenc e (a ) tim e limite d exemptio n state s th e following : "Th e Boein g Compan yi s therebygrante d a n exemptio n fro m tii e flammabilit ytestin g requirement s o f1 4 CF R 25.853(a) , t o th e exten trequire d t o permi ttyp e ceiiificatio n o f th e Boein g airplan e type s not e i n th e reference d petitio n unti l Novembe r28 , 2010 . Th e followin g limitation s appl yt o thi s exemption : Thi s exemptio n i s limite d t o th e Boein g an d forme rMcDonnel l Dougla s airplan e model s note d i n th e petitio n an d applie s t o th e followin g adhesives : •BM S 5-9 2 Typ e I (3 M Scotchwel d EC2216B/A ) •BM S 5-9 2 Typ e V(3 M Scotchwel d EC2615B/A ) •J D Lincol n L-30 1 •J D Lincol n L-30 1 R •BM S 5-10 7 (Araldit e 42 0 A/B ) •Lor d 27 0 A/ B •3 M Scotchwel d 9323- 2 A/ B •Aerobon d 150 7 /^ B •Aerobon d 150 8 A/ B (fir e retardant ) I n addition , thi s gran t i s extende d t o thos e ST C holder s an d applican ttha tmodif yo rhav e modifie d th e airplane s liste d abov e durin g th e perio d o fexemption. " Th e dat e wa s late rextende d t o Novembe r28 , 2011 . Th e curren t positio n i n Referenc e (a ) primaril yaddresse d ne waircraf tdelivere d fro m th e Boein g Compan yan d Supplementa l Typ e Certificate s t o th e airplan e liste d i n th e referenc e tim e limite d exemption . Pe rtha t agreement , Th e Boein g Compan yha s ensure d tha tth e subjec tditc h an d po t joint s tha t ar e part o fth e Typ e Desig n o fan yaircraf tdelivered afte rNovembe r28 , 201 1 ar e show n complian t t o 14CF R 25.853(a) . Th e Boein g Compan yha s als o ensure d tha tan yditc h an d

### ( ^ Lette rRA-11-0506 1 Pag e 2 po t joint s involve d i n post-deliverychange s t o Typ e Desig n tha tar e certifie d afte rNovembe r28 , 201 1 ar e als o show n complian t t o 14CF R 25.853(a) . However , i n discussion s wit h th e FAA , w e hav e discovere d tha treferenc e Adi d no tclearl ydefin e expectation s fo rarticle s i n th e Typ e Desig n whic h ar e no tparto fne wdeliverie s o rne w modifications . Th e Boein g Compan yha d assume d tha tthes e article s woul d no trequir e re approva l t o th e ne wmean s o fcompliance , becaus e ther e i s n o certificatio n activit yassociate d wit h them (e.g . n o certificatio n projects , finding s o fcomplianc e o rstatement s o fcomplianc e ar e currentl yassociate d wit h them) . FAAspecialist s hav e aske d whethe rthi s interpretatio n i s correct , o rwhethe rth e re fAexemptio n woul d requir e a n assessmen to fal l previousl yapprove d Typ e Design , regardles s o fth e dat e o fapprova l (i.e . potentiall yal l design s tha tinclud e ditc h an d po t joints , whethe rcurrentl ymanufacture d o rmodified , o rnot) . Th e Boein g Compan yi s requestin g tha t Referenc e (a ) b e clarifie d t o includ e allowance s fo rmodificatio n kit s an d spar e part s tha t hav e bee n certifie d prio rt o expiratio n o fthi s tim e limite d exemption . Boein g i s requestin g tha t followin g thre e proposal s b e conside ri n th e amendmen tt o Referenc e (a) . 1 . Modificatio n kit s an d spar e part s wit h ditc h an d po tjoin tconstructio n o n project s tha t hav e bee n certifie d prio rt o th e en d o fth e Referenc e (a ) Tim e Limite d Exemptio n perio d d o no t nee d t o re-substantiate d fo rcomplianc e afte rth e exemptio n perio d ha s concluded . I n addition , th e follow-o n incorporatio n o fmodificatio n kit s an d spar e part s wil l no trequir e a ne wshowin g o fcomplianc e unles s the yhav e changed . Example : Amodificatio n projec tma yinvolv e severa l airplane s bein g modifie d ove ra perio d o ftim e usin g th e sam e design . I fth e engineerin g fo rsuc h a projec ti s complete d an d th e projec t i s close d befor e th e en d o fth e Tim e Limite d Exemptio n perio d an d on e o r mor e airplane s complet e modificatio n befor e th e en d o fth e TL E period , bu ton e o rmor e ar e modifie d afte rth e TL E expires , thos e modifie d afte rth e TL E expire s woul d no t requir e an yadditiona l certificatio n activity . 2 . Part s wit h ditc h an d po t join tconstruction s delivered o n a n aircraf tcertifie d prio rt o th e en d o fth e tim e limite d exemptio n perio d d o no tnee d t o b e substantiate d b ywa yo fa ne w findin g o fcomplianc e onc e th e exemptio n perio d ha s expired . Example : Spar e part s requir e n o additiona l certificatio n activitie s providin g the yremai n unchange d afte rth e expiratio n o fth e tim e limite d exemption . 3 . Previousl ycertifie d part s tha thav e bee n changed , bu td o no taffectditc h an d poin tjoints , d o no t requir e a ne wfindin g o fcomplianc e fo rth e ditc h an d poin tjoint s no timpacte d by th e change . Example : Amodificatio n projec tma yaffec ta n assembl ytha tcontain s ditc h an d po t joints , bu t th e change s mad e d o no taffec tth e ditc h an d po tjoints . I n suc h a cas e n o showin g o fcomplianc e specifi ct o th e ditc h an d po tjoint s i s required . Fo rexample , a placar d ma yb e adde d t o th e exterio rwal l o fa close ttha tinclude d a ditc h an d po tjoint . A s lon g a s th e chang e doe s no taffec tth e joint , ou rchange-base d certificatio n proces s woul d no t requir e a ne wassessmen to fth e joint . Th e rational e fo rrequestin g thi s amendmen ti s t o ensur e tha tth e modificatio n kit s an d spar e part s ca n stil l b e provide d t o th e airlin e industryi n a timel yan d efficien tmanner . Re substantiatio n an d re-certificatio n o fpreviousl yapprove d modificatio n kit s an d spar e part s drive s additiona l wor k

statemen t an d cos tt o Boeing , th e FAA , th e airlin e customer , an d th e aircraf t industrya whole . I n addition , thes e ditc h an d po tconstruction , whil e no tshow n complian tt o 1 4 CF R 25.853(a) , d o no t presen t an yadditiona l safet yconcern . Finall ya s ne wdesign s ar e developed , thes e futur e ditc h an d po tjoin tdesign s will , ove ra relativel yshortperio d time , begi n t o replac e th e designs tha t ar e bein g addresse d b ythi s exemption .^ . Lette rRA-11-0506 1 Pag e 3 Applicatio n afte rth e Exemptio n Perio d Boein g plan s t o appl yth e complianc e criteri a tha twil l b e outline d i n th e FAA' s fina l policyo n ne w findings o fcomplianc e fo rditc h an d po tjoint s whe n th e exemptio n expires . Ane wfindin g o f complianc e woul d b e require d fo ra ditc h an d po tjoin twhe n th e join ti s change d o ri fth e pane l desig n i s substantiall ynew . Previousl ycertifie d panel s wit h change s tha td o no tinvolv e thes e join t construction s wil l b e considere d follow-o n construction s fo rthi s feature , withou tth e nee d fo r a ne wfindin g o fcompliance . Statemen t o fN o Advers e Effec t t o Safet y Fo rth e sam e reason s provide d i n ou rorigina l petition , whic h wer e accepte d b yth e FAAi n grantin g o fExemptio n 9791B , amendin g Exemptio n 9791 C t o includ e allowance s fo rmodificatio n kit s an d spar e part s wil l no t adversel yaffec taviatio n safety , Statemen t o fPubli cinteres t Fo rth e sam e reason s provide d i n ou rorigina l petition , whic h wer e accepte d byth e FA Ai n grantin g o fExemptio n 9791B , amendin g Exemptio n 9791 C t o includ e allowance s fo rmodificatio n kit s an d spar e part s i s i n th e publi cinterest . A s w e ha d previousl yrequeste d i n ou rorigina l petition , i n accordanc e wit h §11.8 1 (h) . Th e Boein g Compan yals o request s th e privilege s o fth e requeste d applicatio n o fth e guidanc e fo r modificatio n kit s an d spar e part s b e extende d outsid e o fth e Unite d States . Thes e privilege s ar e necessaryfo roperation s base d withi n foreig n countrie s havin g bilatera l agreement s wit h th e Unite d State s acceptin g th e FAA' s 1 4 CF R part2 5 a s thei rairworthines s standard s fo rtransport categoryaircraft . Arespons e t o thi s petitio n fo rextensio n i s requeste d b ySeptembe r8 , 2011 , t o supportth e developmen t o fyear-en d deliveries . You rtimel ycooperatio n i n thes e matter s i s greatl yappreciated . Sincerely , 

### (AA-K ^ Dougla s Lan e Director , RegulatoryAdministratio n Cc : Mr . A

N Bahram i Mr . Angelo s Xidia s Mr . Mik e Kaszyck i Mr . Bo b Brenema n Federa l Aviatio n Administratio n Transport Airplan e Directorat e 160 1 Lin d Avenu e S.W . Ronton , W A98055-405 6