Exemption No. 14821 

UNITED STATES OF AMERICA 

DEPARTMENT OF TRANSPORTATION 

FEDERAL A VlATION ADMINISTRATION 

RENTON, WASHINGTON 98057-3356 

In the matter of the petition of 

The Boeing Company 

for an exemption from§ 25.841(a)(2) and (a)(3) 

of Title 14, Code of Federal Regulations 

Regulatory Docket No. F AA-2015-3366 

PARTIAL GRANT OF EXEMPTION 

By letter no. RA-1 5- 02563, received June 25, 2015, Mr. Gary E. Nagai, Project Administrator, 

The Boeing Company, P.O. Box 3707, Seattle, WA 98124-2207, petitioned to exempt the Model 

787-10 airplane from the requirements ofTitle 14, Code of Federal Regulations (14 CFR) 

25.841 (a)(2) and (a)(3), as amended by Amendment 25-87. If granted, the exemption would 

relieve these airplanes from the requirement that, during a decompression caused by an 

uncontained failure of one of the engines, airplane cabin pressure altitude does not exceed 25,000 

feet for more than two minutes, or exceed 40,000 feet for any duration. In addition to the 

materials Boeing submitted, which were posted in the docket, Boeing also provided the FAA 

additional proprietary information. This information is used in the FAA's analysis ofthis 

exemption. 

The petitioner requests relief from the following regulations: 

Section 25.841 (a)(2) at Amendment 25-87, requires that "The airplane must be designed 

so that occupants will not be exposed to a cabin pressure altitude that exceeds the 

following after decompression from any failure condition not shown to be extremely 

improbable: 

(i) Twenty-five thousand (25,000) feet for more than 2 minutes; or 

(ii) Forty thousand (40,000) feet for any duration." 

Section 25.841(a)(3) at Amendment 25-87, requires that "Fuselage structure, engine and 

system failures are to be considered in evaluating the cabin decompression." 
The petitioner supports its request with the following information: 

This section summarizes the petitioner's request. The complete petition is available at the 

Department of Transportation's Federal Docket Management System, on the Internet at 

http://regulations.gov, in docket no. F AA-20 15-3366. 

The Boeing Model 787-10 airplane is designed to operate at a maximum cruise altitude of 

41,100 feet pressure altitude. Should an uncontained engine-rotor burst event occur, it is 

possible that the cabin pressure could exceed the limits contained in current regulations. 

Boeing offers the following justification in support of its petition for exemption. Some of 

this justification is based on cabin-decompression evaluations performed and reported by 

the Mechanical Systems Harmonization Working Group (MSHWG) under the auspices 

of the Aviation Rulemaking Advisory Committee (ARAC). 1 

The Boeing Company requests an exemption from compliance with§§ 25.84l(a)(2), and 

25.841 (a)(3) for cabin depressurization that can occur from uncontained engine-rotor 

failures that result in large holes in the fuselage. Boeing states that, based on fleet service 

experience, these events are rare. The Model 787-10 airplane complies with the latest 

FAA requirements and, therefore, offers a significantly higher basic level of safety than 

previously certified transport-category airplanes. Modern transport-category airplanes 

have a 53-year safety record with millions of hours at altitudes similar to the maximum 

cruise altitude proposed for the Model 787-10 airplane. In addition, Boeing claims that 

neither the Joint Airworthiness Authorities nor the European Aviation Safety 

Administration have implemented similar restrictions. 

Boeing notes that very few, if any, decompression incidents have exposed an airplane 

cabin to pressure-altitude profiles that pose a risk of injury to passengers. Transportcategory-airplane industry history reveals that few cases of catastrophic decompressions 

at high altitude have occurred, and those that have occurred have typically involved small 

business jets, according to Boeing. The FAA has cited a few cases of rotor burst in cruise, 

according to Boeing. In one such instance, the crew of a DC-I 0 crossing New Mexico 

reported several cases of initial decompression sickness, apparently with no permanent 

mJunes. 

In addition, Boeing acknowledges 121 additional fatalities related to hypoxia from the 

Helios Airways Flight HCY522 accident. However, Boeing correctly states that this 

accident was not due to a system, structural, or engine-failure event, but a failure of the 

flightcrew to properl y configure the pressurization system, and a subsequent failure to 

recognize that the airplane was not pressurized after takeoff. 

Boeing supplied the results of analysis for the Model 787-10 airplane, powered by RollsRoyce Trent and General Electric GEnx engines, and provided information on the 

likelihood of various engine-failure events. In its decompression analysis, Boeing 

included a measure of the severity of exposure for occupants, based on a 

Depressurization Exposure Integral (DEI) from the Mechanical Systems Harmonization 

Working Group report on 25.841(a)(2) and (3). Boeing used the relationship between 

1 The Final Report of the MSHWG, dated August 2003, was approved by a majority of the members of ARAC's 

Transport Airplane Engine Issues Group (TAEIG). Seven members ofTAEIG voted to submit the report as a 

recommendation to the FAA, two members voted against submitting the report, and one member abstained. 

2 
cabin pressure and the Depressurization Severity Indicator (DSI), which is a measure of 

the partial pressure of oxygen, as was proposed by the Mechanical Systems 

Harmonization Working Group. The petitioner showed that, for the failure modes 

reviewed for this exemption, the resultant DSI levels were much less than the critical 

value specified by the MSHWG. The analysis considers certain design and operational 

features of the Model 787-10 airplane that would mitigate the effects of an increase in 

cabin pressure altitude. These design features include redundancy of key systems, such as 

electrical power, passenger oxygen, cabin pressure control, and spoiler actuation. 

The Model 787-1 0 airplane is designed to fly at cruise altitudes that will maximize fuel 

efficiency. The reduction in maximum cruise altitude resulting from compliance with 

§§ 25.84l(a)(2) and 25.841(a)(3) for uncontained engine failure is a concern shared by 

other manufacturers of airplanes with wing-mounted engines seeking new or amended 

type certification. No transport-category airplane with wing-mounted engines certificated 

today for operation above 39,000 feet can meet the new cabin altitude limits within the 

current§§ 25.841 (a)(2) and 25.841(a)(3) without an exemption. 

The Boeing Company mitigates risk to high cabin-altitude exposure by reasonable design 

requirements, proven design methodologies, and operational considerations regardless of 

the cause of the decompression event. It is intended that the proposed exemption 

addresses the intended concern for safety without imposing the operational economic 

penalties driven by §§25.841(a)(2) and 25.84l(a)(3) as currently written. 

Safety enhancement initiatives with respect to critical rotating parts (inspecting for cracks 

in disks and using continually updated maintenance data to refine disk-inspection 

criteria), as well as improvement in engine technology, lessons learned, and second- or 

third-generation engine-design practices, have resulted in a reduction in uncontained 

engine-failure events. The uncontained engine-failure rates of second- or third-generation 

engines compared to first-generation engines, have improved by approximately 95 

percent based on historical Boeing data on uncontained engine fai lures. 

Restricting airplane operations to lower altitudes will increase traffic congestion. 

Limiting operation of new generation airplanes to lower altitudes will result in higher 

traffic density, which, in turn, will result in higher cost of safety to maintain established 

air-traffic vertical and horizontal separation requirements. 

The Model 787-10 airplane will meet the latest amendments in effect at the time of 

application, except as noted within the Model 787-10 airplane certification basis. The net 

result is that the Model 787-10 airplane incorporates all the safety advancements as 

intended within these later amendments. Boeing states that any significant impact to the 

marketability of the Model 787-10 airplane will, at a minimum, result in a reduced 

number of airplanes with this higher level of safety as compared with the previous 

generation of airplanes, or at a maximum, prevent the manufacture of this new generation 

of airplanes. In either case, Amendment 25-87, according to Boeing, results in a reduced 

potential for overall aviation safety improvements. 

Boeing's petition reiterates that this request for exemption from §§ 25.841 (a)(2) and 

25.841(a)(3) is limited to only uncontained engine failures. For other sources of rapid 

depressurization, including system failures and specific structural failures, 

§§ 25.841 (a)(2) and 25.841 (a)(3) will be complied with as amended by Amendment 25-

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87. All mechanical or functional interfaces that could potentially violate the physiological 

limits imposed by § 25.841(a) are considered. Robust structural and systems design, and 

the ability for the airplane to rapidly descend, are key to assuring the safety of airplane 

occupants and are an inherent part ofthe Model787-IO airplane design. The Boeing 

Company states that its design practices refine the requirements into sub-requirements for 

systems, structures, aerodynamics, and performance to assure airplane-level compliance. 

Other threat minimization philosophies employed in the Model 787-1 0 airplane design 

include an automatic pressure demand mask (FAA-approved for 45,000 feet) for the 

pilots, which will be certified to§ 25.144l(d); and separation and redundancy ofkey 

systems such as electrical power, passenger oxygen, cabin-pressure control, and spoiler 

actuation. 

The petitioner's statement of public interest: 

With respect to uncontained engine-failure events, the impact of§ 25.841 (a), Amendment 

25-87, to the aviation industry and the flying public is significant. The "impact" of 

compliance takes three forms: (1) increase in air traffic congestion, (2) reduced potential 

for overall safety improvements, and (3) environmental. 

I. Restricting airplane operations to lower altitudes will increase traffic congestion. 

Boeing cited three studies showing that the numbers of transport-category 

airplane operations above 37,000 feet are significant today and the trend is for 

newer airplanes to cruise at these altitudes for even longer portions of their 

mission. Limiting operation of new-generation airplanes to lower altitudes will 

result in higher traffic density, which, in turn, will result in higher cost of safety to 

maintain established air-traffic vertical and horizontal separation requirements. 

2. Since the release of Amendment 25-87, a number of amendments to 14 CFR part 

25 have been released. Each of these amendments has the intent of an increase in 

aviation safety. The Model 787-10 airplane wi II meet the latest amendments in 

effect at the time of application, except as noted in the 787-10 certification basis. 

The net result is that the Model 787-10 airplane incorporates the safety 

advancements as intended within these later amendments. Any significant impact 

to the marketability of the Model 787-10 airplane will, at a minimum, result in a 

reduced number of airplane with this higher level of safety as compared with the 

previous generation of airplane, or at a maximum, preclude the manufacture of 

this new generation of airplane. In either case, Amendment 25-87 results in a 

reduced potential for overall aviation safety improvements. 

3. The restriction to maximum cruise altitude imposed upon the Model 787-10 

airplane due to compliance with§§ 25.84l(a)(2) and 25.841(a)(3), Amendment 

25-87, as relates to uncontained engine failure, has a significant adverse impact on 

Model 787-10 airplane fuel bum. This additional fuel burn will increase engine 

emissions, such as C02. 

Federal Register publication 

The FAA has determined that good cause exists for waiving the requirement for Federal Register 

publication for public comment because the request is identical in all material respects to 

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previously granted exemptions; the exemption, if granted, would not set a precedent; and any 

delay in acting on this petition would be detrimental to Boeing. 

The FAA's analysis 

The Boeing Company provided the following information to support its application for 

exemption from §§ 25.841 (a)(2)(i) and (ii) and 25.841 (a)(3): 

• a background of the current rule and recent activities to harmonize it; 

• a review of the safety history of high-altitude commercial flight; 

• a discussion of hypoxia physiology data upon which recent rulemaking activities are 

based; 

• a discussion of the impact of compliance with uncontained engine-rotor-burst aspects of 

the existing rule; 

• environmental and air traffic considerations; and, 

• statements addressing public interest and no adverse impact to safety. 

Boeing provided company proprietary data on the estimated cabin pressure altitude and airplane 

flight-altitude-time history plots that followed decompressions per emergency descent 

procedures, and a description of the Boeing methodology of evaluating the threat from an 

uncontained engine-rotor burst. 

1. Need for exemption 

Boeing requests relief from § 25.841 (a)(2)(i), which specifies that cabin pressure altitude may 

not exceed 25,000 feet for more than two minutes after decompression from any failure 

condition not shown to be extremely improbable. A grant of exemption from this regulation 

would allow the Model 787-1 0 airplane, to take longer than two minutes to descend from 41, I 00 

feet to 25,000 feet after such decompression. 

Boeing also requests relief from § 25.841 (a)(2)(ii), which specifies that cabin pressure altitude 

may not exceed 40,000 feet for any duration after decompression from any failure condition not 

shown to be extremely improbable. A grant of exemption from this regulation would allow the 

Model 787-10 cabin pressure altitude to exceed 40,000 feet after such decompression. 

Boeing has stated that the 787- 10 design will meet the requirements of§ 25.841 (a)(2)(i) and (ii) 

for all system and structural failures, but not for all types of engine failures. For some 

uncontained engine-rotor failures that result in pressure-vessel penetration by fragments, the 

design of the Model 787-10 airplane does not meet the requirements of§ 25.841 (a)(2)(i) and (ii). 

A grant of exemption from this regulation would allow the Model 787-10 airplane to operate up 

to 41 ,100 feet, which could briefly expose cabin occupants to this altitude in the event of a 

worst-case decompression: a rotor burst creating a large hole in the fuselage. 

Finally, Boeing requests relieffrom § 25.84 I(a)(3), which requires that an airplane manufacturer 

consider fuselage structure, engine, and system failures when evaluating the cabin pressure 

altitude following a decompression due to one of these failure events. As noted in the preamble 

to this regulation: 

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Possible modes of failure to be evaluated include malfunctions and damage from external 

sources such as tire burst, wheel failure, uncontained engine failure, engine fan, 

compressor or turbine multi blade failure, and loss of antennas ... 

The FAA's analysis shows that Boeing did consider these failures in its analysis. Therefore, the 

petitioner complies with § 25.841 (a)(3), eliminating the need for an exemption from it. 

2. Analysis under FAA policy 

The FAA reviewed this petition, in the context of the MSHWG Final Report on§ 25.84l(a)(2) 

and FAA policy memorandum ANM-03-112- 16, dated March 24, 2006, on Amendment 25-87 

requirements. The policy applies only to decompression events that are due to uncontained 

engine-rotor failure. The basis of the policy is data from research on the response of humans and 

other primates to changes in ambient pressure. Evaluation of this data indicates a direct 

correlation between the alveolar partial pressure of oxygen time integral and the likelihood of 

fatalities or permanent physiological damage to those exposed to such pressure changes. That is, 

as the value of the integral increases, the likelihood of fatalities or permanent physiological 

damage also increases. The FAA policy contains a table of altitudes and cumulative exposure 

times in lieu of the pressure-time integral. The values of altitude and time in the table, and the 

results of the pressure-time integral method, are in agreement. 

Accordingly, our policy focuses on minimizing the likelihood that, if a person is exposed to 

high-altitude cabin pressure from any failure not shown to be extremely improbable, they will 

suffer permanent physiological damage. To analyze petitions for exemption from§ 25.84l(a)(2), 

the FAA requires information about emergency descent rates, any design features that increase 

such rates, other design features that offset the inherent increased risk of exposure to highaltitude cabin pressure, and operational procedures. 

As stated above and in the policy, the FAA acknowledges a lack of relevant data on the effects of 

exposure to high-altitude cabin pressure following decompression and, particularly, those effects 

on people of various ages, people with circulatory or respiratory diseases, or certain other 

medical conditions. 

Our review of the Boeing petition indicates that Boeing used the criteria recommended in the 

FAA's policy. Boeing's design incorporated these limits to ensure airplane descent performance. 

This methodology is conservative because it assumes a lower partial pressure of oxygen than 

would likely be present during decompression at 41,100 feet. 

Boeing provided descent profiles for the Model 787-10 airplane, based on conservative estimates 

of descent performance for failure scenarios, as described in the FAA's policy; descent profiles 

indicate that the Model 787-10 airplane can descend rapidly from 41,100 feet to below 25,000 

feet. 

Boeing also performed a depressurization analysis on both types of engines used on the Model 

787-10 airplane, Rolls-Royce Trent and General Electric GEnx engines, which were based upon 

maximum cruise flight conditions. It defined the envelope of vulnerability of passengers 

following fai lures that result in a decompression. In addition, Boeing identified design and 

operational features of the Model 787-10 airplane that would mitigate the effects of an increase 

in cabin pressure altitude. 

6 
The decompression analysis used several measures recommended in the MSHWG Final Report. 

Specifically, Boeing estimated the severity of exposure to high-altitude cabin pressure for 

occupants, based on calculation of a DEI. The analysis also considered the relationship between 

cabin pressure and the DSI, a measure of the partial pressure of oxygen. The analysis indicates 

that the physiological effect of a slight increase in the length of time spent above 25,000 feet is 

within the uncertainty band of available physiological data. The Boeing analysis also shows that, 

for the failure modes reviewed for this exemption, resultant DSI levels were much less than the 

critical value recommended by the MSHWG. 

The FAA reviewed information Boeing provided about design features and operational 

procedures that would mitigate the threat of a high-altitude rapid decompression as it relates to 

maintaining the descent capability of the Model 787-10 airplane and to ensure occupant survival. 

We concluded that the design features and operational procedures associated with rapid 

decompression, followed by an emergency descent, support a finding that granting the exemption 

would not adversely affect safety. 

3. Review of historical data and research 

The FAA reviewed databases from its National Aviation Safety Data Analysis Center, covering 

1959 to 2012. Approximately 3,000 instances of loss of cabin pressure have occurred since 1959. 

System failures, such as cabin-pressurization-controller failures and valve failures; and structural 

failures, such as door-seal failures, have caused the vast majority of these events, which typically 

have been recognized at low altitude within a few minutes after takeoff. Pilot error has also 

contributed to the number of events. The majority of these events have not subjected the 

occupants to exposures above 25,000 feet (an altitude considered physiologically significant). 

The cabin pressure altitude in most events did not exceed 15,000 feet (the cabin pressure altitude 

at which passenger oxygen masks are deployed). 

Similarly, uncontained engine-rotor-burst failures tend to be very rare. A simple calculation 

shows that grouping all engines and transport airplanes together yields an average probability of 

an uncontained engine failure at cruise of approximately 1 x 1 o-7 per engine hour. New engine 

designs appear to reduce this probability by an order of magnitude. We found, as noted in the 

MSHWG report on§ 25.841 (a), that no fatalities from hypoxia were due to in-flight rapid 

decompression events as envisioned by Amendment 25-87. The data indicate that decompression 

is not a significant cause of fatalities. It is because these events are so rare that the FAA 

considers the risk to be acceptable. 

In addition, Boeing provided the FAA with proprietary data from its analysis of uncontained 

engine-rotor failures, and the size and number of holes in the fuselage resulting from such 

failures. Using historical service data and theoretical values, Boeing performed decompression 

analysis for several scenarios. Boeing analyzed the probability of uncontained engine-rotor 

failure and of penetration of the fuselage of the Model 787-1 0 airplane from fragments of various 

sizes, from both engines, resulting from such failures. This analysis was used to assess the threat 

of such an event to occupants ofthe airplane. The FAA did not agree with Boeing's exclusion of 

data in their analysis that concerned large holes in the fuselage causing decompression. 

However, Boeing's analysis was conducted in a manner consistent with the recommendations 

within the MSHWG report, and their data showed that even for the largest survivable hole, the 

Model 787-1 0 airplane would be able to meet the FAA's policy criteria. 

7 
The 17 J\J\ concurs with the petitioner that uncontained engine-rotor failures arc rare events. 

Furthermore, our analysis in this case is similar to our analysis of an earlier petition for 

exemption, from a different applicant, for an airplane with an intended cruise altitude of 41,000 

teet. The petition submitted by this previous applicant included estimates or the probability or 

occurrence of an uncontained engine-rotor fa ilure. In that case. the altitude excursion above 

40.000 feet was less than 1.000 feet. We concluded that the risk associated with exposure of the 

occupants to the slightly higher altitude was essentially the same as the risk of exposure at 

40.000 teet. In other words. the risk tl·om exposure at altitude was essentially the same with or 

without the grant of the exemption. Therefore. the rarity of uncontained engine-rotor failures did 

not signi ticantly enter into consideration regarding the previous grant of exemption. 

4. Usc of supplementa l oxygen 

As discussed below. the r J\J\ has analyzed the Boeing petition in the context or the MSHWG 

recommendations, the part 25 requirements pertaining to supplemental oxygen. and certain 

technical standards for supplemental-oxygen equipment. Section 25.1441 (d) requires approval or 

oxygen equipment for airplanes that are approved to operate above 40.000 feet altitude. Section 

25.1443 specifi es the minimum mass tlow or supplemental oxygen for f1ightcrew and passenger 

oxygen systems up to a cabin altitude of 40.000 feet. Part 25 does not contain standards for 

oxygen systems above 40.000 feet. However, FAA Technical Standard Orders (TSOs) provide 

requirements for tlightcrew di Iuter demand pressure breathing regulators (TSO-C89a) and 

tlightcrew demand oxygen masks (TSO-C78a) up to 45.000 feet. In addition. the Society of 

Automoti ve Engineers (SJ\E) Standard AS 8027 provides specifications for diluter demand 

pressure breathing regulators used by the flightcrew up to 45,000 feet. 

As part or the certification for the Model 787-10 airplane. Boeing must substantiate the adequacy 

of the t1 ightcrev,, supplemental-oxygen system for operation above 40.000 feet. 

Flightcrcw pressure-breathing equipment is generally used to provide hypoxia protection at high 

cabin pressure altitudes and requires training to ensure eftective use. Pressure breathing requires 

physical effort to exhale and minimal effort to inhale. This reversal of the normal breathing cycle 

can lead to hyperventilation. The fAA considers the training of passengers to use pressure 

breathing equipment safely to be impractical. The FAA determined that an acceptable means of 

compliance for the fixed and portable oxygen systems used by Oight attendants and passengers 

would be to install oxygen equipment that is certificated to 40.000 feet and limit exposure to the 

reduced pressure environment above 40.000 feet via airplane-descent performance. The FAA 

believes that. ultimately. occupant survival during a decompression event depends upon swift 

descent to a lower altitude. In its review of the petitioner's airplane-descent profile. the FA/\ 

finds that the Model 787- 10 airplane can descend at acceptable rates. 

5. Conclusion ofF AA analysis 

Permitting airplanes to tly above 40.000 feet offers real and tangible benefits to the aerospace 

industry, the traveling public. and the U.S. economy by reducing congestion, improving fuel 

economy. and reducing pollution. If compliance with § 25.841 at Amendment 25-87 were to 

limit airplane operations to a maximum altitude of 40.000 feet, it would impose a significant 

disadvantage on newly designed airplanes that have many sa fety advantages over older airplanes 

currently allowed to operate at higher altitudes. This would delay the introduction of these 

airplanes and the safety benefits of their more-advanced technology. 

8 
Based upon evaluation of the data and analysis Boeing provided. the FAA has determined that 

granting this exemption would not adversely affect safety. is in the public interest, and therefore 

that there is sufficient justification for a partial grant of exemption from * 25.84 1 (a)(2)(i) 

and (ii). 

This partial grant or exemption does not provide relief from 14 CFR 25.841 (a) for any other 

system and structural fa il ure events not shown to be extremely improbable. The petitioner must 

demonstrate compliance for those failure events. and this partial grant is predicated on the 

condition that the petitioner successfull y demonstrates compli ance for the Boeing Model 787- 10 

airplane. As noted in the MSHWG report on § 25 .84 l(a). a tire burst in flight is not extremely 

improbable. as demonstrated by historic data. The ground loads for tires are not applicable in 

tlight and for this condition tires are extremely robust. According to the preamble of 

§ 25. 729(1)( I) and historic data. tire bursts occur in fl ight. It is very difficult to demonstrate that 

tires cannot be burst in case of overheat. It cannot be demonstrated that tires do not burst in highaltitude fl ight. Therefore, the tire-burst event must be considered in the depressurization analysis. 

In addition. pressure-vessel openings resulting from loss of antennas or stall warning vanes. or 

any system f~1 ilure conditions that are not shown to be extremely improbable. must be 

considered. The effects of such damage. while operating under maximum norma l cabin pressure 

di tTerenti al, must be evaluated. Also, structural cracks must be addressed as per the existi ng 

Amendment 25-87 preamble, i.e., 

The maximum pressure-vessel opening resulting from an initially detectable crack 

propagating lor a period encompassing four normal inspection intervals. Mid panel 

cracks and cracks th rough skin stringer and ski n l'rame combinations must be evaluated. 

In addition. this partial grant of exemption is predicated on the requirement that the Boeing 

Model 787-10 airplane successfully demonstrates compliance to§§ 25.144 1. 25. 1443,25.1445, 

25.1 44 7 and 25. 1449. 

This partial grant of exemption takes into account operating rules in 14 CFR parts 91, 121. and 

135 which require (a) that one pilot wear and use an oxygen mask when operating above 4 1.000 

feet altitude and (b) that an adequate quantity of oxygen is provided for crew operations. 

This partial grant of exemption is also premised on the conditions that: 

I. The certifi cation tlight test conducted. to provide data that corroborate the descent profiles 

used in the applicant· s analysis. and to show that. after decompression at an airplane indicated 

operating pressure altitude of 41, I 00 feet, the cabin pressure altitude will not exceed 25.000 feet 

for more than 3 minutes or 40,000 feet for more than I minute, should be conducted with the 

engine-power setting of the railed engine set at idle. Due to the uncertainty of' the state of an 

engine fo llowing an uncontained engine fa ilure, it is not possible to accurately simulate the 

resulting aerodynamic engine-nacell e drag as would occur in !light. Rather than require multiple 

flight tests or analyses to address this issue, the FAA has dctcnnined that setting the failed 

engine to idle thrust provides an acceptable configuration. 

2. If dispatch is deemed appropriate with a malfunctioning system that is required to ensure that 

the airplane is capable of pcrfonning an emergency descent (i.e .. spoil ers full y deployed. if 

appropriate: maximum descent rate: maximum operating limit VMo/Mi\·Jo speed). the Master 

9 
Minimum Equipment List (MMEL) must limit dispatch to a maxinwm flight altitude of 40,000 

feet. unless other regulations or limitations require a lower altitude. 

Though V ;..,ofMt-1o is normally the best speed for a rapid decompression descent, the pilots 

should follow the recommended emergency descent procedures in the Airplane Flight Manual 

(/\FM). Rather than place an MMEL dispatch limitation as an explicit condition of granting the 

exemption. the FAA has determined that it is appropriate for the FAA Flight Operations 

Evaluation Board to evaluate the matter of dispatch with a malfunctioning system that is required 

to ensure that the airplane is capable of performing an emergency descent. 

3. The applicable rapid decompression procedures tor the tlightcrew must be included in the 

emergency procedures section ofthe Af M. This information should also be included in the 

13oeing Flight Crew Operating Manual. Note that initial and recurrent emergency training for all 

crcwmembers. in accordance with §§ 12 1.397. 121.417. and 12 1.427. must include training lor a 

rapid decompression and donning of oxygen masks. 

Regarding the provisions of§ 25.841 (a)(3). the petitioner included in its analysis consideration 

of engine failures. In addition. as part of the normal certification process, the petitioner will 

consider fuselage structure and system failures. Therefore, relief from this requirement is not 

necessary. 

The partial grant of exemption from § 25.841 (a)(2)(ii) permits cabin pressure altitude to exceed 

40.000 feet lor one minute (but not to exceed 41.1 00 feet for any duration) after decompression 

from any uncontained engine failure condition not shown to be extremely improbable. The 

partial grant of exemption fi·om ~ 25.841 (a)(2)(i) permits cabin pressure altitude to exceed 

25,000 feet lor more than 2 minutes (but not more than three minutes) after decompression from 

any uncontained engine-failure condition not shown to be extremely improbable. allowing time 

for the airplane to descend from an altitude of 4l.l 00 feet to 25.000 feet. 

The FAA's decision 

In consideration of the foregoing. I find that a partial grant of exemption is in the public interest 

regarding 14 CFR 25.84 1 (a)(2)(i) and 25.84 1 (a)(2)(ii). as amended by Amendment 25-87. 

Theretore. pursuant to the authority contained in 49 U .S.C. 401 13 and 44 701. delegated to me by 

the Administrator. the petition or Boeing for an exemption from the requirements of 

~§ 25.84 l(a)(2)(i). and 25.84 1 (a)(2)(ii). as amended by Amendment 25-87. is granted for Boeing 

lode! 787-10 airplanes. 

This partial grant of exemption is subject to the following conditions: 

I . The Airplane Flight Manual for the Boeing Model 787-1 0 airplane must indicate that the 

maximum indicated operating pressure altitude is 4 1.1 00 feet. 

2. The Airplane Flight Manual must contain applicable fli ghtdeck crew procedures for a 

rapid decompression event. The section of the Airplane Flight Manual tor the Boeing 

Model 787-10 airplane. which pertains to actions in the event or a decompression. must 

state that the flightdeck crew should initiate a descent at the maximum rate of descent and 

safe descent speed. which is typically the maximum operating speed (V Mo/Mr-..,o). 

assuming structural integrity of the airplane. 

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3. The petitioner must submit certi lication tlight-tcst data lor the Boeing Model 787 -I 0 that 

corroborate the descent profiles used in the analysis, to show that after decompression at 

an airplane indicated operating pressure altitude of 4 1.1 00 feet. the cabin pressure altitude 

will not exceed 25,000 feet for more than 3 minutes or 40.000 teet for more than 

I minute. 

JAN 1 2 2016 

Michael Kaszycki 

Acting Manager. Transport Airplane Directorate 

Aircraft Certilication Service 

1 1