Page 1 of 1 October 1 st , 2012

AW-BD5/12/530

Mr. D. Turnbull Director, National Aircraft Certification Branch Transport Canada, (AARD)

3 rd Floor, Tower “C”, Place de Ville, 330 Sparks Street, Ottawa, Ontario K1A 0N8

Attention: Mr. Jacques Levesque, Sr. Project Manager

Subject : CSeries airplane models BD-500- 1A10 (CS100) & BD-500-1A11 (CS300) – Petition for Exemption per 14CFR § 11.61(b) from 14CFR § 25.841(a)(2) with respect to Uncontained Engine Failures.

References: (1) BA Letter AW-BD5/11/693, titled “BD-500-1A10 & 1-A11 (CSeries CS100 & CS300) – Petition for Exemption from CAR 521.30(1)(e) for 14CFR § 25.841(a)(2) with respect to Uncontaine d Engine Failures”, dated 2011-10-19. (2) Title 14 Code of Federal Regula tions (14CFR) § 11.81, titled “What information must I include in my petition for an exemption?”, Docket No. 1999–6622, 65 FR 50863, dated 2000-08-21. (3) FAA Memo PS-ANM-03-112-16, “Interim Policy on High Altitude Cabin Decompression (Reference Amendment 25-87)” , Federal Register Doc. 03- 13541, dated 2006-03-24. (4) Aviation Rulemaking Advisory Comm ittee (ARAC) Transport Airplane Engine Issues Group (TAEIG) Mechanic al Systems Harmonization Working Group (MSHWG), “ Final Report on 14CFR 25.841(a)(2) and (3)” , dated 2003-07-31, submitted to the FAA on 2003-10-21. (5) Aviation Rulemaking Advisory Comm ittee (ARAC) Transport Airplane Engine Issues Group (TAEIG ) Meeting, held 2003-10-15.

Dear Mr. Levesque,

Further to a similar petition for exemption subm itted to TCCA [see reference (1)], Bombardier Aerospace (BA) respectfully requests that TCCA submit to the FAA on BA’s behalf this petition for exemption of the CSeries aer oplane models BD-500-1A10 & 1- A11 from the requirements of 14CFR § 25.841 (a)(2)(i) and (a)(2 )(ii) at Amdt 25-87, with resp ect to Uncontained Engine Failures. This petition for Exemption is made in accordance with 14CFR § 11.81 [see reference (2)], is in line with th e applicable FAA policy memorandum [s ee reference (3)], and is based on the Mechanical Systems Harmonization Worki ng Group (MSHWG) report [see reference (4)] HEADQUARTERS

BOMBARDIER AEROSPACE 400 CÔTE-VERTU ROAD WEST DORVAL, QUÉBEC CANADA H4S 1Y9

TEL. 514-855-5000

FAX. 514-855-7401

www.bombardier.comPage 2 of 2 which was accepted by the Transport Airplane and Engine Issues Group (TAEIG) [see reference (5)].

Enclosed with this letter is the Exemption Request Form which has been completed in accordance with 14CFR § 11.81. This petition is s upported by additional proprietary information that will be submitted separately to the FAA Ne w York Aircraft Certif ication Office (NYACO).

Should you require additional information, pl ease contact Hagop Kazarian at (514) 855-5000 x59083 or hagop.kazarian@aero.bombardier.com.

Yours truly,

Keith Barnett Airworthiness Manager, CSeries Bombardier AerospaceBombardier Airworthiness Coordination Sheet

Page 1 of 2 Subject: BA letter AW-BD5/12/530, titled “CSeries airplane models BD-500-1A10 (CS100) & BD-500-1A11 (CS300) – Pe tition for Exemption per 14CFR § 11.61(b) from 14CFR § 25.841(a)(2) with respect to Uncontained Engine Failures”, dated 2012-10-01.

Reference(s) : 1. Airworthiness – CSeries Cert ification eRoom Action Item #2545.

DISCIPLINE NAME APPROVAL DATE

Environmental Systems C. Lima

Environmental Systems K. Ayre

Propulsion Systems G. Armstrong

RM&S Focal F. Godin

Airworthiness Focal H. Kazarian

Airworthiness Manager K. BarnettEXEMPTION REQUEST FORM

Page 1 of 14 REQUEST MADE BY:
Bombardier Inc.
400 Côte-Vertu Road West Dorval, Québec, Canada H4S 1Y9
Contact Person: Keith Barnett
Email: keith.barnett@aero.bombardier.com Tel: (514) 855-7567 Fax: (514) 855-7301

REQUEST MADE TO: Federal Aviation Administration (FAA)
New York Aircraft Cer tification Office (NYACO)

DATE REQUEST MADE: 2012-10-01 (in accordance with 14CFR § 11.63(d) )

DATE WE REQUIRE THIS EXEM PTION TO TAKE EFFECT: 2013-10-01 (currently scheduled F AA Type Certification date)

14CFR PROVISION: 14CFR § 11.61(b)

SPECIFIC SECTIONS OF 14CFR FROM WHICH WE SEEK AN EXEMPTION: 14CFR § 25.841(a)(2)(i) and (a)(2)(ii)

We would also request the permission to exerci se the privileges of this exemption outside the United States, most notably since the CSeries will operate internationall y, and the basic design requirements, and any exemptions therefrom, should therefore be applicable worldwide, notwithstanding any additional foreign authority requirements that might also be applicable.

THE EXTENT OF RELIEF WE SEEK:

14CFR § 25.841(a)(2) at Amendment 25-87 1 requires that the cabin a ltitude does not exceed the limits specified in the sub-parts followi ng various failures co nditions, and 14CFR § 25.841(a)(3) at Amendment 25-87 further requires additional c onsiderations for an unc ontained engine failure (UEF) which punctures and/or tears the fuselage creating a very large hole (bigger than the critical hole size).

1 Amendment 25-87 Final Rule, Docket 26070, Federal Register Volume 61, Number 109, June 5th, 1996.EXEMPTION REQUEST FORM

Page 2 of 14 The Bombardier Aerospace (BA) CSeries aerop lane models BD-500-1A10 & BD-500-1A11 are designed to cruise at a maximum altitude of 41,000 ft pressure altitude. Should an UEF occur at the maximum cruising altitude, it is possible th at the cabin pressure could exceed the limits contained in current regulations since the fusela ge hole size generated by the engine debris will exceed the allowable cabin altitudes, maki ng it non-compliant to the above-mentioned certification requirements.

THE REASON WE SEEK RELIEF: Other airplane manufacturers have had similar difficulties meeting this certification requirement. In fact, no aircraft designs whic h incorporate a wing mounted engine lay-out have been certified to fully comply with this certification require ment and each manufacturer of such designs has elected to request an Exempti on for aeroplanes where Special C onditions -Airworthiness – or the equivalent to 14CFR § 25.841(a) at Amendm ent 25-87 – have been in the basis of
certification. 2,3,4

EASA CS-25 is not harmonized with the AWM a nd 14CFR, and has allowe d large airplanes to operate above 40,000 ft without requiri ng a similar request for Exemption. 5

Furthermore, Industry data is available to suppor t the number of engine rotor burst incidents and the resulting cabin decompressions in othe r manufacturer’s petitions for Exemptions. 2,3,4

BA requests an exemption from compliance wi th 14CFR § 25.841(a)(2)(i) and (ii) for cabin depressurization that can occur from UEFs that result in larg e fragment penetration causing a very large hole in the fuselage. BA notes that the FAA Interim Policy 6 allows Exemptions from 14CFR § 25.841(a) regarding the worst-case fa ilures caused by an UEF, provided alternate criteria (time limits) can be met, and additional m itigating factors are present in the design of the airplane.

The CSeries design will meet the requirements of 14CFR § 25.841(a)(2)(i) and (ii) for all system and structural failures but not for all types of engine failures: for some UEFs that result in pressure vessel penetration by fragments causing a very large hole, the design of the CSeries does not meet the requirements of 14CFR § 25.841(a )(2)(i) and (ii). Theref ore, BA requests the exemption be granted for altitudes up to the CSeries maximum cruise altitude of 41,000 ft. A grant of exemption from this regulation woul d allow the CSeries to operate up to 41,000 ft,

2 FAA Exemption No. 8160 for the Embraer E170. Available online at http://rgl.faa.gov/Regulatory_and_Guidance_Librar y/rgEX.nsf/0/cae639b1350ae04586256dce006727a6/$FILE/8160.pdf

. 3 FAA Exemption No. 8857 for the Boeing B787-8. Available online at http://rgl.faa.gov/Regulatory_and_Guidance_Library/ rgEX.nsf/0/ee62f9861e47dee9862572b90052aaef/$FILE/8857.pdf

. 4 FAA Exemption No. 8695A for the Airbus A380. Available online at http://rgl.faa.gov/Regulatory_an d_Guidance_Library/rgEX.nsf/0/26b96 ca49ea7c03c862573db005abc08/$FILE/8695A.pdf

. 5 EASA, “Book 1 – Airworthiness Code”, Certification Specifications for Large Aeroplanes CS-25, Amendment 7

, Annex to ED Decision 2009/013/R, October 21 st , 2009. Available online at http://www.easa.europa.eu/agencymeasures/certification- specifications.php#CS-25

. 6 FAA Memo (HAPPENY, Steve), ANM-03-112-16 “Interim Policy on High Altitude Cabin Decompression (Reference Amendment 25-87)” , Federal Register Doc. 03- 13541, March 24 th , 2006.EXEMPTION REQUEST FORM

Page 3 of 14 which could briefly expose cabin occupants to this altitude in the event of a worst-case decompression.

Specifically, BA requests relief from 14CFR § 25.841(a)(2)(ii) which specifies that cabin pressure altitude may not exceed 40,000 ft for a ny duration after decompression from any failure condition not shown to be extremely improbable. A grant of exemption from this regulation
would allow the CSeries cabin pressure altitude to exceed 40,000 ft following a decompression due to an UEF causing a very large hole in the fuselage.

BA also requests relief from 14CFR § 25.841(a)(2)(i) which specifies that cabin pressure altitude may not exceed 25,000 ft for more than 2 minutes after decompression from any failure condition not shown to be extremely improbable. A grant of exemption from this regulation
would allow the CSeries to take longer than 2 minutes to de scend from 41,000 ft to 25,000 ft following a decompression due to an UEF cau sing a very large hole in the fuselage.

Technical Information in Support of the Petition for Exemption: BA offers the following justification in support of its petition for exemption (some of this justification is based on cabin decompressi on evaluations performed and reported by the Mechanical Systems Harmonization Working Group (MSHWG) under the auspices of the Aviation Rulemaking Advisory Committee (ARAC) 7,8 ):

1. The rule as written will force the CSeries to have an altit ude limitation imposed which will be less than the 41,000 ft altit ude being sought. The lay-out of the CSeries is conventional
and thus is no less safe than other manufactur er’s aircraft which we re certified prior to 14CFR amendment 25-87 and operated above 40, 000 ft. Furthermore, BA submits that the
current rule and its associated limitations ar e not in the public’s best interest, since compliance with the current requirements may limit airplanes to a maximum operating altitude of less than 40,000 ft, and there will be an economic impact because of the increased fuel use and longer routes due to more congested airspace at lower altitudes, thus making the
aircraft less attractiv e for potential sales.

The CSeries is designed to fly at cruise al titudes that will maximize fuel efficiency. The
reduction in maximum cruise a ltitude resulting from comp liance with 14CFR § 25.841(a)(2) for UEF is a concern shared by other manufact urers of airplanes with wing-mounted engines seeking new or amended Type certification. No transport category airplane with wingmounted engines certificated today for operation above 39,000 ft can meet the new cabin

7 Aviation Rulemaking Advisory Committee (ARAC) Transport Airplane Engine Issues Group (TAEIG). Mechanical Systems Harmonization Working Group (MSHWG), Final Report on 14CFR 25.841(a)(2) and (3)

, dated August 2003, submitted to FAA on October 21 st , 2003. Available online at http://www.faa.gov/avr/arm/ar ac/aractasks/tae_mshwg3.doc

. Note: This final report was approved by a majority of the members of ARAC: seven members of TAEIG voted to submit the report as a recommendation to the FAA, tw o members voted against submitting the report, and one
member abstained.

8 Aviation Rulemaking Advisory Committee (ARAC) Transport Airplane Engine Issues Group (TAEIG) Meeting,
held 2003-10-15. Minutes available online at http://www.faa.gov/avr/ar m/arac/aracmin/oct_15_16 _2003/meeting_minutes.doc

.EXEMPTION REQUEST FORM

Page 4 of 14 altitude limits within the current 14C FR § 25.841(a)(2) without an exemption.

2. In addition, BA observes that ne ither the Joint Airworthiness Authorities nor the European Aviation Safety Administration has implemented similar restrictions in their certification requirements. 5

3. The CSeries complies with the latest Canadian, US, and European requirements and therefore offers a significantly higher basic level of safe ty than previously certified transport category
aircraft.

4. UEFs are rare events, and UEFs causing rapid depressurization are even rarer. BA believes, based on fleet service expe rience, that UEFs are rare events. 9 Modern transport category aircraft have a 45 year safety record with millions of hours and more than 30 years
at altitudes similar to the maximum crui se altitude proposed for the CSeries.

Data from previous accidents involving UEFs were compiled from many different sources:

4.1. BA’s internal computerized Air Safety, Continuning Airworthiness, and FRACAS
databases.

4.2. Canadian Transportation Safety Board (TSB) accident reports.

4.3. US National Transportation Safety Board (N TSB) accident reports, special reports, and computerized databases.

4.4. Society of Automotive Engineers (SAE) A ccident Investigati on Reports (AIR):
4.5. British Department of Transport Air Accident s Investigation Branch (AAIB) accident
reports.
4.6. US FAA’s online Lessons Learned from Tr ansport Airplane Accidents database 10

. 4.7. Communications with safety representatives of major aircraft ma nufacturers, including reports and data they have provided 11

. 4.8. Communications with safety representatives of major engine manu facturers, including reports and data they have provided.
4.9. Previous similar exemption requests.

In 1974, the NTSB published a special study 12 of turbine engine rotor disk failures from 1962 to 1973,” which presents data on 41 cases of engi ne disk failures in public transport aircraft. This was primarily focused on low bypass engines, but did include six (6) 1 st generation high bypass engine events. The NTSB safety recommendations focused on a goal of disk
containment. The NTSB database covers the years 1962 to present containing all the

9 According to SAE AIR4770, the probability of an UEF is ~1.6x10 -7 per flight hour for the world fleet.

10 FAA Lessons Learned From Transport Airplane Accidents database, available online at: http://accidentsll.faa.gov/ll_main.cfm?TabID=3&CategoryID=12

11 Boeing Commercial Airplanes, “Statistical Summary of Commercial Jet Airplane Accidents, Worldwide Operations, 1959-2002” , May 2003. Boeing Commercial Airplanes, “Statistical Summary of Commercial Jet Airplane Accidents, Worldwide Operations,
1959-2003” , May 2004.

12 NTSB, NTSB-AAS-74-4 – Special Study - Turbine Engine Rotor Disk failures , Published 1974.EXEMPTION REQUEST FORM

Page 5 of 14 information on the accident report from NTSB 6120.4 or its predecessor. The files contain additional information not pub lished in the cause report.

Society of Automotive Engineers (SAE) Invest igation Reports (AIR) titled “Report on Aircraft Engine Containment” provide the mo st concise information on the causes of such failures and are invaluable in pred icting the occurrence rate of UEFs:

4.10. SAE AIR 1537 13 , covering the period of 1962 through 1975.

4.11. SAE AIR 4003 14 , covering the period of 1976 through 1983.

4.12. A third report, SAE AIR 4770 15 , covering the period of 1984 through 1989, was prepared but never published.

These reports focused on the location of the failure (turbine, fan, compressor, etc.), the flight stage at failure (takeoff, climb, cruise, etc.), and when determinable, the cause of the failure (fatigue, material defect, etc.), for the entire commercial transport fleet. They contain limited data on airplane effects, and do not address th e development of events after failures leading to catastrophic loss of the aircraft.

Delucia, Salvino, Fenton et al produced a se ries of statistical reports on “Aircraft Gas Turbine Engine Rotor Failures” covering US commercial aviation in the late 1980s. The reports’ definition of “rotor failure” encompa ssed many kinds of turbomachinery failures, and the reports are therefore less specific.

The SAE AIR reports provide enough data to es timate the probability of UEFs using fault tree analysis (FTA). An alternate method is failure modes and effect analyses (FMEA), but
FTA is found to be a more suitable me thod according to section 2.2. of the 1997 FAA DOT/FAA/AR-96/95 report on UEF debris 16

.

Although it is considered difficult to quantify precisely using 2 nd generation data (the
CSeries uses 3 rd generation engines), the CSeries UEF rate can be conservatively assessed
to be on the order of < 1 ×10 -7 per engine hour.

The CSeries has: 2 engines, and the probability of an UEF event at cruise is 14% (FAA AC20-128), therefore the CSeries UEF rate at high altitude = 2 × 0.14 × 1×10 -7 = 2.8×10 -8
per aircraft hour.

Even considering the subsequent probability that the uncontained debris strikes the fuselage and creates a large hole causing a rapid cabin depressurization (generally approximated using a 0.1 multiplier,), BA and other engine and airplane manufacturers still can not declare that
the event is less than 1×10 -9 certification requirement, as such cases are potentially

13 SAE AIR 1537, Report on Aircraft Engine Containment: 1962 to 1975 , dated 1977.

14 SAE AIR 4003, Report on Aircraft Engine Containment: 1976 to 1983 , dated 1987.

15 SAE AIR 4770 Draft, Report on Aircraft Engine Containment: 1984 to 1989 , dated 1994.

16 FAA DOT/FAA/AR-96/95 , Final Report: The Potential for Fuel Tank Fire and Hydrodynamic Ram From Uncontained Aircraft Engine Debris , dated January 1997.EXEMPTION REQUEST FORM

Page 6 of 14 catastrophic. However such cases are approach ing extremely improbable and that the design is what is technologically practical for wing-mounted engine airplanes.

Notwithstanding the above, the CS eries uses state-of-the-art 3 rd generation Pratt & Whitney

PurePower® PW1500G series Geared TurbofanTM (G TF) engines which incorporate improvements in engine technol ogy (e.g. enhanced vibration/tre nd monitoring) and state-ofthe art 3 rd generation engine design practices which apply lessons learned with respect to UEFs, all of which can be expect to further in crease the reliability and decrease the risk of UEFs for the CSeries family of airplanes.

Furthermore, BA will provide TCCA with calcula tion of the probability for the CSeries of an UEF during cruise causing a large hole in the fuselage and lead ing to rapid de pressurization.
BA believes the likelihood for the CSeries is lower than similar previously certificated transport category airplane with wing-mounted engines.

5. Rapid depressurization events rare ly result in risk to occupants: BA notes that very few, if a ny, rapid depressurization events ha ve exposed an airplane cabin to pressure altitude profiles whic h pose a risk of injury to occ upants. Industry history reveals that few cases of catastrophic d ecompressions at high altitude ha ve occurred (see 4 above for those a summary of those caused by a UEF), and those that have occurred have typically involved small business jets. BA observes that the FAA has c ited a few cases of UEFs in
cruise 10,17 . In one such instance, the crew of a DC-10 crossing New Mexico reported several cases of initial decompression sickness, apparently with no permanent injuries 18 . However,
the UEF in that case was believed to have been induced by crew action.

Furthermore, the MSHWG report 7 concluded for the world co mmercial jet fleet for the period of 1992 to 2001, that none of the known de pressurization events have resulted in severe cases of occupant hypoxia

.

6. Aerospace hypoxia physiology data shows no d ifference between 40,000 feet or 41,000 feet: Several research papers have been circulated in the aerospace medical community generating controversy regarding the abso lute physiological limits to occupants following cabin depressurization. However, the consensus is th at the physiological limits are not significantly affected if cabin depressurization occurs at 40,000 feet or 41,000 feet.

The FAA and other qualified e xperts agree that the severity of hypoxia exposure to rapid depressurization is determined by the pressure field and duration of the event. This is predicated on observations made from flight physiological and medical experiments. The
cabin altitude limits in Amendment 25-87 were developed by the FAA based in part on
recommendations from the FAA’s Civil Aerome dical Institute (CAMI), which were based on the concept of “Time of Safe Unconsciousne ss” (TSU) documented by James G. Gaume in

17 Uncontained Engine Damage Database, ACCESS 2000 Database , FAA UED v001, June 10 th , 2002.

18 NTSB-AAR-75-2, Aircraft Accident, National Airlines Inc., DC-10, N60NA near Albuquerque, New Mexico,
November 3 rd , 1973.EXEMPTION REQUEST FORM

Page 7 of 14 his 1970 paper. The study concluded with the st atement that, “[...] a plea must be made for
collection of better data” 19 . Gaume’s 1970 paper is only one so urce in establishing adequate safety basis. It should be unde rstood that the proposed TSU criteria was established as a compensating consideration to the elimina tion of the passenger oxygen system. Today’s commercial transport are requi red to provide an emerge ncy oxygen system providing additional margin of safety. The MSHWG agr eed additional data based on further study
would benefit the establishment of new sta ndards. In lieu of new data, the MSHWG established physiological exposur e limits that are conservativ e with respect to the data
available. The MSHWG considered the avai lable physiological exposure research which included several papers that have been circ ulated in the aerospace medical community, all with the objective of estab lishing physiological limits to occupants following cabin decompression. It was based on these papers, and consideration of the overall risk to decompression exposure that the MSHWG docum ented its recommendations in the TAEIG accepted report 7 . The following are summaries of th e reports from recognized Aerospace Medical Doctors addressing physio logical information that wa s considered by the MSHWG:

6.1. James G. Gaume (Aerospace Medicine) authored a paper substantiating the new rule. According to Gaume, during an emergency descent from 42,000 ft to 

### 5,000 ft for adequate recovery 

### of unconscious passengers without any supplemental emergency oxygen to the occupants, with an aircraft emergency descent of 

### 6,200 ft per minute and with cabin altitude exceeding 33,000 ft, no more than 

### 1 minute and 42 seconds 

### is considered acceptable. 19

6.2. Dr. Stanley R. Mohler, a form er director of the FAA’s CA MI, analyzed a number of actual depressurization cases, incl uding data from studies by Barron 20 , and Gaume 19 . He concluded that brain damage in the absence of oxygen starts after about four minutes, and that three minutes above 25,000 ft is a reas onable limit to protect against permanent physiological damage from a cabin de pressurization occurring at up to 

### 45,000 ft. 21

6.3. Dr. Robert Garner, Research Physiologist, Protection and Su rvival Laboratory at the FAA’s CAMI, agrees that limiting cabin a ltitude exposure to 25,000 ft for up to three minutes and never allowing it to exceed 45,000 ft would provide an acceptable level of safety. His views on this matter have b een communicated to the FAA Transport
Standards Staff.

6.4. Draft White paper issu ed by the FAA’s CAMI - FAA Civil Aerospace Medical Altitude Rule: presented in the MSHWG in July 2002, states that exposure: if unprotected, passengers to a 41,000 ft altitude would be a pproximately equal to exposure at a 40,000
ft altitude. 22

19 GAUME, James G., “Factors influencing the Time of Safe Unconsciousness (TSU) for commercial passengers Following Cabin Decompression”, Aerospace Medicine , April 1970, 382-385.

20 BARRON, C. and COOK, T., “Effects of Variable Decompressions to 45,000 feet”, Aerospace Medicine , May 1965, 425-430.

21 MOHLER, Dr. Stanley, “Sudden High Altitude Cabin Decompression Immediately Threatens Safety of Aircraft Crew and Passengers”, Flight Safety Foundation, Human Factors & Aviation Medicine , December 1994.

22 CAMI & FAA, “Draft White paper on Civil Aerospace Medical Altitude Rule” , presented in the MSHWG in July 2002, p.13.EXEMPTION REQUEST FORM

Page 8 of 14 6.5. J.B. Brierley and A. 

### N. Nicholson concluded in a 1969 study that cabin altitude exposure above 10,000 ft not more than eight minutes up to peak of 36,000 ft does not cause brain damage. 23

6.6. A. N. Nicholson and J.R. Ernsting conc luded in a 1967 study that cabin altitude exposure above 40,000 ft with time exposure of 1 minute and 30 seconds caused brain damage. 24

In consideration of the above studies, co mments received on the FAA Interim Policy 6 , and the acceptance of the MSHWG report 7 by TAEIG, the FAA establis hed appropriate criteria for 14CFR § 25.841(a) with respect to an UEF. Thes e criteria are more c onservative than those established by the MSHWG report. In lieu of a ny other standard, BA will comply with these criteria as presented in the Proposed Conditions by Party Making the Request, to Show How the Exemption Would Provide a Level of Safet y At Least Equal to the Existing Rule: section, which need to be confirmed by the FAA as appropriate.

HOW OUR REQUEST WOULD BENEFIT THE PUBLIC AS A WHOLE:

Permitting the CSeries to fly above 40,000 ft does offer real and tangible benefits to the aerospace industry, the traveling pub lic, and the economy, and is ther efore in the public interest:

a) Lower air traffic management costs. Three separate studies have shown that the number of operations above 37,000 ft are significant today and the trend is for newer airp lanes to cruise at these altitudes for even longer portions of their mission. Limiting opera tion of new generation airplanes to lower
altitudes will result in higher traffic density, which in turn wi ll result in higher cost of safety
in order to maintain established air traffic vertical and horizontal separation requirements, which is not in the public interest. Conversely, the cost of maintaini ng the level of safety within the existing air traffic management system will not be adversely impacted by continuing to allow operation in the less congest ed altitudes, typically well above 37,000 ft.

b) Better fuel economy and lower operating costs.
The CSeries uses state-of-the-art 3 rd generation Pratt & Whitney PurePower® PW1500G series Geared TurbofanTM (GTF) engines whic h have been designed to offer double-digit improvements in fuel burn at higher altitudes, and associated lower operating costs. In fact, initial fuel burn improvements — gate-to-gate — have been estimated at 16% versus today’s
best 2 nd generation turbofan engines. With the benef its of a new, advanced airplane such as the CSeries, the fuel burn be nefit can be even greater — over 20% versus today’s best aircraft. That can be a significant savings to airlines and airline passengers. Therefore, granting this exemption is clearl y in the interest of the public since it allows the CSeries to

23 BRIERLEY, J.B. and NICHOLSON, A.N., “Neurological Study of Simulated Decompression in Supersonic Transport Aircraft”, Aerospace Medicine , August 1969.

24 NICHOLSON, A.N. and ERNSTING, J.R., “Neurological Sequelae of Prolonged Decompression”, Aerospace
Medicine , April 1967.EXEMPTION REQUEST FORM

Page 9 of 14 operate on routes and generate significantly lo wer emissions and noise than other aircraft types that are currently operating on those same routes.

Furthermore, limiting CSeries operations to lowe r than 40,000 ft will result in significantly increased fuel burn since operations at lower altitudes in certai n environmental conditions are not optimum for these aeroplanes and engines. Since additional fuel is required for an otherwise identical route, this ultimately increas es CSeries operating costs, which is clearly not in the interest of airlines and airline passengers.

c) Lowering noise and emissions.
The CSeries uses state-of-the-art 3 rd generation Pratt & Whitney PurePower® PW1500G series Geared TurbofanTM (GTF) engines whic h have been designed to offer double-digit improvements in environmental emissions (e.g. CO 2 , NO

x ) and noise when compared to

current 2 nd generation turbo-fan engines. In fact, the use of those engines on the CSeries cuts carbon emissions by over 3,000 metric tonnes — equal to planting over 700,000 trees — per aircraft per year, and slashes aircraft noise footprints by up to 75% — a big relief to communities. At up to 20 decibels below today’s most stringent standard, it is the quietest engine in its class: meaning lower noise f ees, shorter flight tracks, extended curfew operation, and quieter cabins: this is clearly in the interest of airlines and passengers. In addition, Pratt & Whitney’s TALONTM X combus tor slashes NOx exhaust gases 50% below CAEP/6. Since preserving a clean atmosphe re, reducing green house gas emissions, and lowering community noise is in everyone’s best in terest, granting this ex emption is clearly in the interest of the public since it allows th e CSeries to operate on routes and generate significantly lower emissions and noise than othe r aircraft types that are currently operating
on those same routes.

d) Fostering a competitive aviation industry.
A reduction in maximum cruise altitude would also adversely impact the ability of the CSeries to compete with previously certificat ed airplanes which can operate at the more economical cruise altitudes typically in exce ss of 37,000 ft. If compliance with 14CFR § 25.841(a) limited airplanes operations to a maximum altitude of 40,000 ft, this would impose a significant disadvantage on ne wly designed airplanes that ha ve many safety advantages over older airplanes currently a llowed to operate at higher alti tudes. This would delay the introduction of these airplanes and the be nefits of their more advanced technology. Therefore, denial of this peti tion would deny the public some of the benefits of a new family of airplanes. The CSeries fa mily of airplanes will inco rporate new technology, lessons learned from previous and cu rrent production airplanes, and comply with the latest airworthiness standards throughout to provide a safer, more effi cient transportation option for airlines and airline passengers.

e) Lower cost of air travel for the public. The CSeries will provide industry-leading operating economics, and environmental improvements. Granting this petition of exempti on is in the public interest because it will improve safety relative to pr eviously certificated airplanes, while reducing noise, emissions, operational costs (fuel burn due to better engine s, air traffic management service fees forEXEMPTION REQUEST FORM

Page 10 of 14 airlines due to less crowded airspace), and ultimately making air transport more accessible, more efficient, and less costly for the travelling public.

These benefits will accrue with no decrease in safety.

REASONS WHY THE EXEMPT ION WOULD NOT ADVERSELY AFFECT SAFETY: Permitting the CSeries to fly above 40,000 ft doe s not adversely affect aviation safety.

a) Since the release of Amendment 25-87, a numbe r of amendments to 14 CFR 25 have been
released. Each of these amendm ents has the intent of increasing aviation safety. The CSeries will meet the latest amendments in effect at the time of application and therefore offers a higher level of safety than do previously certif icated transport categor y airplanes. The net

result 

### is that the CSeries incorporates all the safety advancements as intended within these later amendments. Any significant impact to th e marketability of the CSeries will, at a minimum, result in a reduced numbe r of aircraft with this higher level of safety as compared with the previous generation of aircraft, or at a maximum, preclude the manufacture of this new generation of aircraft, which adve rsely affects global aviation safety.

b) The CSeries fully complies with the latest airworthiness standard s including 14CFR § 25.841 (a)(2) and (3) in all regards, except as related to an UEF as defined he rein. Specific features have been incorporated into the CSeries design to mitigate the safety risk to occupants due to a decompression resulting from an UEF. Improve ments in engine technology, application of lessons learned, and 3 rd generation engine design practices have resulted in a reduction in
UEF events and the risk of a rapid depressurization.

c) Restricting airplane operations to lower alt itudes will increase traffic congestion at the detriment of aviation safety. Since higher traffic densities result in higher air traffic controller and pilot workloads, which in turn increase the risk of accidents, the granting of this exemption provides for increased aviation safety from an air traffic management standpoint.

d) In the unlikely event of an UEF, the CSeries pres erves an even higher leve l of safety relative to previously certificated airplanes due to its higher descent capability and other design
features. As concluded herei n, and based on the MSHWG report 7 , the world commercial jet fleet has had no hypoxia related fa talities due to in-flight deco mpression events caused by an UEF. This safety record has been maintained even as newer airplanes fly at higher altitudes more often than older airplanes. In keepi ng with time-above-altitude FAA guidance and the recommendations of the MSHWG report 7 , BA has incorporated design features that appropriately address the risk to safety following an UEF. Therefore, granting of the exemption will not compromise safety to the airplane occupants.EXEMPTION REQUEST FORM

Page 11 of 14 PROPOSED CONDITIONS BY PARTY MAKI NG THE REQUEST, TO SHOW HOW
THE EXEMPTION WOULD PROVIDE A LEVEL OF SAFETY AT LEAST EQUAL TO
THE EXISTING RULE: BA believes that although 14CFR § 25.841(a)(2) a nd (3) intend to mitigat e certain risks to safety, they also create unintended consequen ces. The existing word-wide fleet of transport category aeroplanes has demonstrated safe opera tions during millions of hours of flight at altitudes similar to or higher th an those proposed for the CSeries. Therefore, as outlined in the FAA Interim Policy 6 , the risk 

### of rapid depressurization following an UEF is better mitigated by a combination of proven design practices establishe d through years of airpla ne industry experience combined with today’s improved te chnical capabilities. It is intended that the following proposed risk mitigation measures augment this exempti on request and address the intended concern for safety without the non-commensurate impacts driven by current requirements of 14CFR § 25.841(a)(2).

a) It must be reiterated that this request for exemption from compliance to 14CFR § 25.841(a)(2) is limited to UEFs, and the CSeries will fully comply with the latest
airworthiness standards includi ng 14CFR § 25.841(a)(2) and (3) fo r other sources of rapid depressurization, including system failures and specific structural failures, except as related

to an UEF. All mechanical and/or functional interf aces that could potentially violate the physiological limits imposed by 14CFR § 25.841(a) are considered. Robust structural and systems design and the ability for the airplane to rapidly descend ar e key to assuring the safety of airplane occupant s and are an inherent part 

### of the CSeries design. BA design practices refine the requirements into s ub-requirements for systems, structures, aerodynamics, and performance in order to assure airplane level compliance (for example, it is still our overall design objective to de scend below 25,000 ft in under 2 minutes for UEF cases). Furthermore, the CSeries design ensu res separation and redundancy of key systems that are required for the emergency descent, such as electrical pow er, flight crew and passenger oxygen, cabin pressure control, and spoiler actuation.

b) The Airplane Flight Manual (AFM) will clearly st ate that the CSeries is limited to operate up to 41,000 ft pressure altitude, and will include appropriate procedures for emergency descent following loss of cabin altit ude or an engine failure.

c) Other threat minimization philosophies empl oyed on the CSeries include an automatic pressure demand mask 

### (FAA approved for 41,000 ft) for the pilots which will be certified to comply with 14CFR § 25.1441(d).

d) In consideration of the above studies and the acceptance of the MSHWG report 7 by TAEIG, the FAA established appropriate criteria for 14C FR § 25.841(a) with respect to an UEF in its Interim Policy 6 . BA notes that these criteria are more conservative than those established by MSHWG report 7 . Therefore, in lieu of any other standard, BA will comply with the following alternate criteria to be considered for the UEF case only:

Criteria for rapid decompression following an UEF:EXEMPTION REQUEST FORM

Page 12 of 14 

### The airplane must be designed 

### so that occupants will not be exposed to a cabin pressure altitude that exceeds the follo wing after decompression from any engine failure condition not shown to be extremely improbable: (i) 

### Forty-five thousand (45,000) feet for any duration; or (ii) 

### Forty thousand (40,000) feet for one minute; or (iii) 

### Twenty-five thousand (25,000) feet for more than three minutes; or (iv) 

### Ten thousand (10,000) feet fo r more than six minutes.

e) In calculating the descent capability 

### of the aeroplane in order to meet the revised cabin altitude conditions in d), pilot recognition a nd reaction time will be considered. There is a
consensus in the MSHWG that a value of 17 sec onds is the acceptable va lue to recognize the
failure and initiate descent.

f) In calculating the descent capability 

### of the aeroplane in order to meet the revised cabin altitude conditions in d), the loss of the failed engine’s contribution as a source of power to the systems enabling the descent will be consider ed (i.e. if losing power on one engine results in loss of one hydraulic system engine-driven- pump, the descent rate will be based on the capabilities of the remaining hydraulic systems with the back up power sources, such as the ACMP or PTU). Systems degradation due to debris damage from the actual UEF (e.g. hydraulic line rupture, wiring dama ge, etc...) will not be considered.

g) In calculating the descent capability 

### of the aeroplane in order to meet the revised cabin altitude conditions in d), various dispatch conditions will also be considered.

h) The CSeries will have an Emergency Descent Mode (EDM) which will provide an additional margin of safety by initiating a descent auto matically if there is no flight crew action following a loss of cabin pressure or when the flight crew pushes the EDM button. This feature will be shown to comply with all app licable certification re quirements, however the CSeries will fully comply with the latest airworthiness standards including AWM 525.841(a)(2) and (3) for rapid depressurization w ithout taking certification credit for this
feature.

SUMMARY THAT CAN BE PUBLISHED IN THE FEDERAL REGISTER:

14CFR § 25.841(a)(2) at Amendment 25- 87 requires that the cabin altitude for commercial airplanes not exceed the limits specified in th e sub-parts following various failures conditions,
and 14CFR § 25.841(a)(3) at Amendment 25-87 further requires additional considerations for an uncontained engine failure (UEF) which punctures a nd/or tears the fuselage creating a very large hole (bigger than the critical hole size).

The Bombardier Aerospace (BA) CSeries aerop lane models BD-500-1A10 & BD-500-1A11 are designed to cruise at a maximum altitude of 41,000 ft pressure altitude. Should an UEF occur at the maximum cruising altitude and should the engi ne debris create a very large hole in theEXEMPTION REQUEST FORM

Page 13 of 14 fuselage, it is possible that the cabin pressu re could exceed the limits contained in current regulations, making it non-compliant to the a bove-mentioned certification requirements.

Other airplane manufacturers have had similar difficulties meeting this certification requirement. In fact, no aircraft designs whic h incorporate a wing mounted engine lay-out have been certified to fully comply with this certification require ment and each manufacturer of such designs has elected to request an Exemption. Furthermore, EASA CS-25 is not harmonized with the AWM and 14CFR, and has allowed large airplanes to operate above 40,000 ft without requiring a similar request for Exemption: therefore, airplane s built and operated in Europe have not had to consider similar requirements for UEFs.

BA requests an exemption from compliance wi th 14CFR § 25.841(a)(2)(i) and (ii) for cabin depressurization that can occur from UEFs that result in larg e fragment penetration causing a very large hole in the fuselage. BA notes that the FAA Memo PS-ANM-03-112-16
titled “Interim Policy on High Altitude Cabin Decompression (Reference Amendment 25-87)” (Federal Register Doc. 03-13541, dated 2006-03 -24) allows Exemptions from 14CFR § 25.841(a) regarding the worst-case failures caused by an UEF, provi ded alternate cr iteria (time limits) can be met, and additional mitigating factors are present in the design of the airplane.

BA submits that this petition for Exemption w ould benefit the public as a whole since it would lead to lower air traffic management costs, be tter fuel economy, lower operating costs, and lower noise and emissions, and consequently lead to lowe r cost of air travel for the public and therefore foster a competitive aviation industry.

BA also submits that this petition for Exempti on would not adversely a ffect safety since the CSeries fully complies with the latest airworthine ss standards includi ng 14CFR § 25.841 (a)(2) and (3) in all regards, except as related to an UEF as defined herein. BA has incorporated design features that appropriately addr ess the risk to safety following an UEF, as recommended by the FAA Interim Policy above. In the unlikely event of an UEF, the CSeries preserves an even higher level of safety relative to previously ce rtificated airplanes due to its higher descent capability (in line with the time-above-altitude FAA guidance and the recommendations of the ARAC), and other design feature such as an Emergency Descent Mode (EDM) which will provide an additional margin of safety by initiati ng a descent automatically if there is no flight crew action following a loss of cabin pressure, as well as an automatic pressure demand mask (FAA approved for 41,000 ft) for the pilots which will be certified to comply with 14CFR § 25.1441(d). Improvements in engine technology, application of lessons learned, and 3 rd
generation engine design practices have also resulted in a redu ction in UEF events. In addition, the world commercial jet fleet has had no hypoxia related fatalities due to in-flight decompression events caused by an UEF, and this safety record has been maintained even as newer airplanes fly at higher altitudes more ofte n than older airplanes. Since the CSeries will
meet the latest amendments in e ffect at the time of application a nd therefore offers a higher level of overall safety than do previous ly certificated transport cate gory airplanes, granting of the exemption will not compromise safety to the airp lane occupants. Furthermore, BA notes that refusing this exemption and restricting airplane ope rations to lower altitudes will increase traffic congestion at the detriment of aviation safety: since higher traffic densities result in higher airEXEMPTION REQUEST FORM

Page 14 of 14 traffic controller and pilot workloads, which in tu rn increase the risk of accidents, the granting of this exemption provides for increa sed aviation safety from an ai r traffic manage ment standpoint.