Transport Airplane Directorate 1601 Lind Avenue, S.W. Renton, W ashington 98057 - 3356 **Exemption No. 35063 Regulatory Docket No. FAA** **- 2012**  **- 0972**  December 21 , 2012 Mr. Doug Lane, Director, Deputy L ead Administrator Regulatory

Administration The Boeing Company PO Box 3707 Seattle, Washington, 98124 Dear Mr. Lane; We received your petition for exemption from requirements of Title 14, Code of Federal Regulations (14 CFR) 25.841(a)(2) and (a)(3) at Amendment 25 - 87 for the Boeing Model 787 - 9 airplanes . We posted your petition for comment on September 10 , 2012 . The exemptio n, if granted, would provide relief from cabin decompression requirements following an unco ntained engine failure so the 787 - 9 airplanes would be able to operate where they

are most efficient, thereby reducing fuel burn and producing lower emissions. Thi s request, which you submitted to the Department of Transportation’s Federal Docket Management S ys tem, has been given Docket No.FAA - 2012 - 0972. Title 14, Code of Federal Regulations 11.81(d) states that in submitting your petition, you must provide information to show “ the reasons why granting your request would be in the public interest; that is, how it would benefit the public as a whole.” The FAA issued Policy Memorandum ANM - 03 - 112 - 16 , Interim Policy on High Altitude Cabin Decompression (Reference Amendment 25 - 87) , that provides design approval holders with the FAA’s methodology

for evaluating the basis, under 14 CFR part 11, to exempt an applicant from the requirements of § 25.841(a)(2)(i) and (ii). After reviewing your petition, we need the following supplemental information from you . You stated, “

Improvements in engine technology, application of lessons learned, and 2nd and 3rd generation engine design practices have resulted in a reduction in uncontained engine failure events and the risk of a rapid depressurization. ” Please summarize any 787 engine - related issues that have been encountered during the later stages of flight testing and in service, and explain how you have resolved them or explain why they would not contribute to an uncontained engin e failure.2

You stated, “ The reduction in fuel consumed will also result in reduced emissions. ” Please provide estimated level of reduction in representative engine emissions , for example , CO 2 , NOx, etc ., showing the decrease in environmental emissions f rom the new airplane and a specific estimate of fuel savings by fl yi ng above 40,000 feet . N ote that on similar petitions for exemption Boeing and other applicants have supplied the estimated reduction in fuel, as well as reduction in selected engine emissi ons . You stated, “

In addition, the 787- 9 will provide industry- leading operating economics, and environmental improvements. “ Please provide an estimated level of the lower operating costs and economi c s for the airlines provided b y the 787 - 9 and explain h ow it will improve the environment . Additionally , the FAA has requested that all petitions for exemption to § 25.841 follow the general guidance in FAA Policy Memo ANM - 03 - 112 - 16 , Interim Policy on High Altitude Cabin Decompression (Reference Amendment 25 - 87). Through the policy , w e have requested that all petitioners utilize models similar to those from the Aviation Rulemaking Advisory Committee ( ARAC ) Mechanical Sy stems Harmonization Working Group (MSHWG) Report on § 25.841(a)(2) and (3), dated August 20 03 , to provide an estimate of the effects on the airplane occupants from the rapid decompression . We note that on similar petitions for exemption , Boeing and other applicants provided the results of a decompression anal ys is, which included a measure of th e severity of exposure for occupants, based on a Depressurization Exposure Integral (DEI) from the ARAC MSHWG report. We request that Boeing submit this information to supplement its petition for an exemption. Please note that we will not disclose any prop rietary information to outside sources. Furthermore, Boeing requested an exemption from compliance with § 25.841(a)(2) and (a)(3) for cabin depressurization that can occur from uncontained engine rotor failures. The FAA notes that on similar petitions for exemption , Boeing and other applicants supplied data on the critical hole effective area , that is , the hole size at which a rapid decompression at max cruise flight altitude results in a cabin pressure altitude that just meets the current regulations that restrict cabin pressure to no more than 40,000 ft and higher than 25,000 ft for no more than 2 minutes. We request that Boeing provide similar data on the critical hole effective area for the 787 - 9 airplanes. Please also provide the probability of experiencing an uncontained engine rotor failure that results in a hole of this size . We also note that on similar petitions for exemption , Boeing and other applicants supplied data on the likelihood of various sy stem, structural, and engine failure events that result in the most severe cabin depressurization . For more established programs the applicant has provided failure hazard assessment documentation. We request information regarding the probabilities of the 787 - 9 airplanes experiencing rapid loss of cabin pressurization from some ty pes of severe failures such as loss of inflow, loss of a single bleed source, uncontained engine rotor failure, uncommanded opening of outflow valve, and other failures that can lead to the loss of cabin pressurization. FAA Pol icy

Memo ANM - 03 - 112 - 16 states that the primary means to ensure occupant survivability

rests in quickly

bringing the occupants to a cabin pre ssure where they can3

survive . The policy

guidance requests “ The petitioner should provide information about any exis ting or new design features that provide enhanced airplane emergency descent rates and occupant survivability. ” We note that on similar petitions for exemption , Boeing and other applicants provided descriptions of improvements in the design that would mini mize failures that could lead to loss of cabin pressurization. We request that Boeing provide a description of any improvements in the sy stems or structure to minimize failures that could lead to loss of cabin pressurization. Please identify any improvements you may have made to the design of the cabin pressurization control sy stem to minimize system failures that c ould lead to loss of cabin pressurization events . Boeing states in the petition that the 787 - 9 is a stretch derivative of the 787 - 8. The 787 - 9 aircraft differences that affect compliance to § 25.841(a)(2) and (a)(3) are:

 The lengthened fuselage sections use similar design and construction techniques as the 787 - 8.

 The lengthened fuselage increases the pressurized volume for the 787 - 9.

 The 787 - 9 design weight will be increased approximately 10% relative to the 787 - 8. This increased design weight will have an effect on the aircraft's emergency descent performance.

 The 787 - 9 engine thrust is increased relative to the 787 - 8 via revised ratings, a s these engines were designed to accommodate 787 - 9 thrust requirements. The increased thrust will have an effect on the aircraft's emergency descent performance. Boeing acknowledges that “ .... these differences between the 787- 8 and the 787- 9 have an effect on showing compliance to §§25 .841 (a)(2) and 25.841 (a)(3 ), ....” However, Boeing do es not provide any definitive information showing the e ffect of these differenc es . Please provide the impact on emergency descent performance f

ro m these changes in design . A cceptance of the level of risk from a rapid decompression is predicated on the probability of the failure event. We note that on similar petitions for exemption , Boeing and other applicants provided descriptions of engine debris models and the predi cted fuselage hole sizes that lead to loss of cabin pressurization. The Boeing petition for the 787 - 9 airplanes did not include any information on the resulting holes from uncontained engine failures versus probability

of occurrence , such as , hole sizes versus probability of rapid decompression event per flight hour or departure . Boeing provided no results of their decompression anal ys is , such as , airplane cabin pressure time history , or comparisons with other predictions, such as data from the D6 - 57019 Un contained Engine Debris Trajectory Study . Please provide this information. Finally , Boeing did not provide any estimated airplane descent rates and airplane descent time history

following a rapid depressurization at cruise altitude. Boeing and o ther app licants have provided information on the airplane operating envelope , such as , boundaries set b y maximum and minimum airplane weight , and have substantiated that their4

design can s uccessfull y meet the cabin pressure exposure limits in FAA Policy Memo ANM - 0 3 - 112 - 16 . In summary , please provide similar information to the supplemental material that Boeing provided on previous petitions for exemption to § 25.841(a)(2) and (a) (3). Please do not post proprietary information on the Regulations.gov public websi te. Either mail it to us by

certified mail or fax it to us at 425 - 227 - 1320 If we do not hear from you within 30 days, we will close the project without notifying you further. In the meantime, should you have any questions or concerns regarding this requ est, please contact Stephen Happenny, ANM - 112 , at 425 - 227 - 2147 , or e - mail, Stephen.Happenny @faa.gov. Sincerel y, /s/ Victor Wicklund Manager ANM - 112, Propulsion/Mechanical Sy stems Transport Airplane Directorate Aircraft Certification Service