Transport Airplane Directorate

1601 Lind Avenue, S.W.

Renton, Washington 98057-3356

Exemption No. 35063

Regulatory Docket No. FAA-2012-0972

December 21, 2012

Mr. Doug Lane, Director, 

Deputy Lead 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 

exemption, if granted, would provide relief from cabin decompression requirements 

following an uncontained 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. 

This request, which you submitted to the Department of Transportation’s Federal Docket 

Management System, 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 engine 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, 

CO2, NOx, etc., showing the decrease in environmental emissions from the new airplane and 

a specific estimate of fuel savings by flying above 40,000 feet. Note that on similar petitions 

for exemption Boeing and other applicants have supplied the estimated reduction in fuel, as 

well as reduction in selected engine emissions.

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 economics for the airlines 

provided by the 787-9 and explain how 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, we have 

requested that all petitioners utilize models similar to those from the Aviation Rulemaking 

Advisory Committee (ARAC) Mechanical Systems Harmonization Working Group 

(MSHWG) Report on § 25.841(a)(2) and (3), dated August 2003, 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 

analysis, which included a measure of the 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 proprietary 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 system, 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 types 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 Policy Memo ANM-03-112-16 states that the primary means to ensure occupant 

survivability rests in quickly bringing the occupants to a cabin pressure where they can 
3

survive. The policy guidance requests “The petitioner should provide information about any 

existing 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 minimize failures 

that could lead to loss of cabin pressurization. We request that Boeing provide a description 

of any improvements in the systems 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 system to minimize system failures that could 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, as 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 

does not provide any definitive information showing the effect of these differences. Please

provide the impact on emergency descent performance from these changes in design. 

Acceptance 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 predicted 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 

analysis, such as, airplane cabin pressure time history, or comparisons with other 

predictions, such as data from the D6-57019 Uncontained 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 other 

applicants have provided information on the airplane operating envelope, such as, 

boundaries set by maximum and minimum airplane weight, and have substantiated that their 
4

design can successfully meet the cabin pressure exposure limits in FAA Policy Memo

ANM-03-112-16. 

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 website. 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 request,

please contact Stephen Happenny, ANM-112, at 425-227-2147, or e-mail, 

Stephen.Happenny@faa.gov.

Sincerely, 

/s/

Victor Wicklund

Manager

ANM-112, Propulsion/Mechanical Systems

Transport Airplane Directorate

Aircraft Certification Service