U.S. Department of Transportation Federal Aviation Administration January 30,2015

Mr. Douglas M. Lane Director, Regulatory Administration The Boeing Company P.O. Box 3707, MC 03-56 Seattle, WA 98124-2207

Dear Mr. Lane: Transport Airplane Directorate 1601 Lind Avenue, S

.W. Renton ,Washington 98057-3356

ExemptionNo. 11081A Regulatory DocketNo. FAA-2014-0330

This letter is to inform you that we have granted yourpetition for an amendment to exemption no. 11081. Itexplains the basis for our decision and describes its effect. The Basis for Our Decision By letterno. RA-15-00350, dated January 27, 2015, you petitioned the Federal Aviation Administration (FAA), on behalfofThe Boeing Company, for an amendmentto exemption no

. 11081. That exemption provides temporary relieffrom the requirements of § 25.1305(c)(5), Amendment 25-120, ofTitle 14, Code ofFederal Regulations (14 CFR) to allow The Boeing Company to incorporate engine ice protection system changes withoutthe powerplant ice protection system indication on Model 787-8 and 787-9 series airplanes powered by General Electric (GE) GEnx-1B engines. Boeinghas thus far complied withthe provisions ofthe original exemption. Yourrequest to add a time-limited exemption from § 25.939(a), at Amendment 25-40, would allow changes to limitations in the airplane flight manual (AFM) ofModel 787-8/-9 airplanes imposed by Airworthiness Directive (AD) 2013-24-01. The changes will allowpartial relieffrom AD-mandated AFM limitations preventing flight into certain ice crystal icing (ICI) environments. The GEnx-1B engines installed on Model 787-8/-9 airplanes have been shown to be susceptible to flameout and engine damage during operation in ICI conditions in service. Ingestion ofice crystals results in ice accretion in the engine. This ice accretion canrelease, resulting in engine damage and power interruption. GE and Boeing determined that periodically opening the variable bleed valve (VBV) doors in the engine compressorreduces the formation ofice. The latest GEnx-1B electronic engine control (EEC) software includes ICI logic designed to detect the presence ofICI conditions and cycles the VBV doors to2

reduce the risk offlameout and/orrollback. Boeing is proposingto revise the AFM limitations associated withthis interim solution to raise the current airplane operating restriction in ICI conditions from 30,000 feet to 37,500 feet with use ofa flightcrew procedure to maintain adequate engine power levels. Boeing is showing that this ICI logic in the EEC software, in conjunctionwith the AFM limitations that this amendment would revise, will be effective in identifying ICI conditions and addressing the ICI threat. Boeing is requesting an amendmentto the original time-limited exemption in order to introduce this interim design modification while Boeing implements an updated engine configurationthat is compliant with § 25.939(a). Section 25.939(a) at Amendment 25-40 requires that, for turbine-engine powered airplanes, "engine operating characteristics must be investigated in flight to determine that no adverse characteristics (such as stall, surge, or flameout) are present, to a hazardous degree, during normal and emergency operation within the range ofoperating limitations ofthe airplane and ofthe engine." The operational procedure proposed to be included in the AFM limitation, would require maintaining minimum Mach numbers or airplane speeds at certain altitudes and airplane gross weights, to ensure that a minimum engine power setting is maintained to prevent ice accretion on internal engine components that could be mechanically damaging to compressor stages. The FAAhas issued ADs to require in-flight crewprocedures to restrict power settings to address identified unsafe conditions. However,the FAA does not accept in-flight crewprocedures to restrict power settings as a method ofcomplying with § 25.939(a). The purpose ofthis regulatory requirement is to assure engines will provide acceptable operating characteristics within the airplane operating envelope without undue burden on the flightcrew to manually control engine power settings. The Boeingproposed AFM limitations and operating procedure for operating near or in ICI conditions require the flightcrew to maintain a minimum airplane speed, which maintains an adequate level ofsafety for the time period ofthis exemption. Although not compliant with §25.939(a), Boeing states that this AFM limitation is consistent, from a flightcrew workload perspective, with other AFM limitations such as engine anti ice system, weight limitations, center ofgravity limits, and ground operations in icing conditions. As part ofthe certificationprocess, Boeing must demonstrate that this AFM limitation is acceptable from a flightcrew workload and complexity standpoint, and is operationally feasible

. Boeing's petition states that they will extensively communicate the revised AFM limitation and associated operating procedure to the operators and their flightcrews via Flight Crew Operations Manual, Fleet Team Digest, Multi-Operator Message and other operator forums. Although§ 25.939(a) prescriptively requires that "operating characteristics must be investigated in flight," Boeing did notpropose conducting flight tests in ICI conditions for certification ofthis AFM limitation change. Boeing proposed to use the results ofthe GE ground icing tests in combination with analysis to demonstrate the effectiveness ofthe EEC software change to sufficiently reduce ice accretion and mitigate the unacceptable operating characteristics below 37,500 feet. The FAA accepts Boeing's proposal as sufficient because this exemption is time limited in nature and part ofan interim design change to address the ICI issue.For the reasons cited in the original petition and repeated in the request for amendment, the FAA agrees with Boeing's statement ofpublic interest. 3

Boeingrequested the expiration date ofDecember 31,2015, for this amendmentto the timelimited exemption and also requested expedited processing. Boeing explains thatthe additional time is needed based onthe complexity ofthe design change and the showing of compliance. The FAA determined that Boeing has not substantiated the need for the additional time requested. Extendingthe deadline for the final design modifications would require more data and a thorough FAA review and would not supportthe timeline of Boeing's request for grantingthe amended exemption. Therefore we have maintained the June 30, 2015, compliance date for this time-limited exemption. As noted above, Boeingrequested expedited processing ofthis exemptionto meet customer needs. By granting relieffrom an additional regulation, this amendment supports an interim design change originally planned as part ofa series ofmodifications to address ICI that was communicated to and accepted bythe FAA. Furthermore, the FAA has previously approved similar AFM limitations on multiple occasions, including allowing relieffrom full compliance with 14 CFR 25.939(a), in orderto mitigate unsafe conditions addressed through ADs. Full compliance mustbe demonstrated priorto removal ofall associated limitations. Therefore, the FAAhas determined that good cause exists for not publishing a summary of the petition, for public comment, inthe Federal Register because the requested amendment to the exemption would not set a precedent, and any delay in acting onthis petitionwould be detrimental to The Boeing Company and operators and flightcrews of787-8/-9 airplanes. Our Decision The FAAhas determined that thejustification for the issuance ofexemption no. 11081 remains valid with respect to this amendment and is in the public interest. The Effect ofOur Decision Our decision adds a time-limited exemptionfrom§ 25.939(a), at Amendment 25-40, to exemption no. 11081 for Model 787-8 and 787-9 airplanes that have incorporated engine ice protection system modifications and associated AFM limitations. This grantofamended exemptionprovides a specific expiration date. The Grant ofAmended Exemption In consideration ofthe foregoing, I find that a time-limited grant ofexemption is in the public interest regarding 14 CFR25.939(a) at Amendment 25-40. Therefore, pursuantto the authority contained in 49 U.S.C. 40113 and 44701 , delegated to me by the Administrator, I grant The Boeing Company an exemptionuntil June 30, 2015, from the requirements of § 25.939(a), as amended by Amendment 25-40. Specifically, this amendment approves substituting laboratory and ground tests for the requirement to investigate engine operating characteristics in flight and permittinguse ofairplane speed as a means to setminimum engine power needed to maintain engine operability in ice crystal icing environments. This amendmentto the exemption is applicable to new production and in-service BoeingModel 787-8 and 787-9 airplanes incorporating modified EEC software with engine ice protection system changes and associated AFM limitations.4

Boeing must show full compliance to 14 CFR 25.939(a), at Amendment 25-40, for newly produced Model 787-8 and 787-9 airplanes in orderto receive a certificate ofairworthiness after June 30, 2015. Design changes and modifications to in-service Model 787-8 and 787-9 airplanes involving engine ice protection systems and associated AFM limitations made after June 30, 2015, must also fully comply with 14 CFR25.939(a) at Amendment 25-40. All conditions and limitations ofExemption No. 11081 remain the same. This letter mustbe attached to, and is a part of , exemption no. 11081

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Jeffrey E. Duven Manager, Transport Airplane Directorate Aircraft Certification Service