~OEING John A. Hamilton 

Lead Administrator 

Regulatory Administration 

Commercial Airplanes 

The Boeing Company 

P.O. Box 3707 MC 03-56 

Seattle, WA 98124-2207 

MAR -4 2013 

RA-13-00845 

U.S. Department of Transportation 

Docket Operations 

West Building Ground Floor, Room W 12-140 

1200 New Jersey Avenue, S.E. 

Washington, D.C. 20590 

Subject: 

Model: 

RA Project No.: 

EASA Project No.: 

EASA Level: 

Branch/Panel No.: 

Branch/Panel Name: 

Response Due: 

Reference(s): 

Special Instructions: 

This letter is to submit: 

Petition for Exemption from 14 CFR 

25.841 (a)(2) and (a)(3), Pressurized CabinsUncontained Engine Failure 

767-2C 

PS09-0863 

N/A 

N/A 

ANM-106B 

Certification Services 

June 4, 2013 

(a) PS-ANM-03-112-16, Interim Policy on High 

Altitude Cabin Decompression 

N/A 

(X) Petition for Exemption 

This letter is being sent for: 

(X) Posting to the Federal Docket 

;,.,.,.,\ 

j 

en 

J> 

.(J'j 

The Boeing Company hereby petitions for an exemption for relief from 

14 CFR 25.84I(a)(2) and (a)(3), as amended by Amendment 25-87, with respect 

to uncontained engine failure. This petition is made in accordance with the 

reference (a) FAA Policy. 

Waiver.from Public Comment 

As allowed by 14 CFR 11.87, The Boeing Company respectfully requests a 

waiver from the publication and public comment period of the Exemption 
rzi-aoEI.IVG 

Page2 

Mr. A. Xidias 

RA-13-00845 

requirements of 14 CFR 11.85 and 1 J .89 as this petition wi II not set a precedent 

and the relief requested is identical to exemptions previously granted. 

To supp01t the 767-2C program schedule, The Boeing Company respectfully 

requests that the enclosed information be processed by June 4, 2013. 

Furthermore, The Boeing Company requests to be notified when the enclosed 

petition processing has completed. 

Please contact this office or the following individuals if you have further 

questions: 

Project Administrator (PA): 

Program Manager 

Cert.ification Specialist: 

S. Gordon 

P. Guilford 

T. Howorth 

N. Jolly 

425-23 7-6068 

425-237-5981 

425-717-9847 

425-266-7499 

The information being forwarded to the FAA by or with this correspondence is 

for the exclusive purpose of support of applications for or amendments to Type 

Ce1tificates. 

Sincerely, 

For Douglas M. Lane 

ODA Deputy Lead Administrator 

(425) 23 7-1383, MC 03-56 

FAX: (425) 294-9340 

Enclosures: Petition for Exemption 

cc 

Name 

Jim Cashdollar 

Angelos Xidias 

Letter 

EDT 

EDT 

Enclosures Comments 

EDT ANM-IOOB 

EDT ANM-1008 
RA-13-00845 

Enclosure (A) 

Page I of 17 

Petition for Exemption from Title 14 Code of Federal Regulations 25.841, Amendment 25-87 

N arne and Address of the Petitioner 

Doug Lane, Director, Regulatory Administration Deputy Lead Administrator 

The Boeing Company , 

PO Box 3707 

Seattle, Washington, 98124 

Section(s) of the Regulations from which Relief is Sought 

§§ 25.841(a)(2) and 25.84l(a)(3) With Respect to Uncontained Engine Failures. 

§ 25.841 

(a)(2) 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 2minutes; or 

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

(a)(3) Fuselage structure, engine and system failures are to be considered in 

evaluating the cabin decompression. 

The Extent ofReliefSought and Reason(s) 

Regulation Requires: Relief is Necessary because: 

§ 25.84l(a)(2) and (a)(3) Compliance to be shown with Direct compliance would limit maximum 

Amendment 25-87 cabin pressure altitude limits aircraft altitude to less than 40,000ft and 

for uncontain~d engine failure would: 

A) create an economic impact to 

operators associated with higher 

fuel bum 

B) have an environmental impact 

due to increased engine emissions 

associated with higher fuel bum 

C) reduce competitiveness of the 

767-2C in the aircraft 

marketplace 

1 
RA-13-00845 

Enclosure (A) 

Page 2 of 17 

Description of Issue 

The 767-2C aircraft is being designed to operate at a maximum cruise altitude of 40,100 ft. 

Amendment 25-87, Reference (1), established new requirements in§ 25.841(a) intended to 

upgrade the airplane and equipment airworthiness standards for subsonic transport airplanes 

operated above 40,000 feet. These were hased in part on special conditions that had been used on 

type certification of executive business airplanes for many years. Specifically, Amendment 

25-87 created three requirements in§§ 25.841(a)(2)(i), 25.841(a)(2)(ii), and 25.841(a)(3) 

governing the cockpit/cabin environment: 

§ 25.841(a) subpart; 

(2) The airplane must be desigried 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. 

(3) Fuselage structure, engine and system failures .are to be considered in evaluating the 

cabin decompression. 

The Boeing Company respectfully submits that compliance with§§ 25.841(a)(2), and 

25.841 (a)(3) as written, with respect only to the consideration of an uncontained engine failure, 

provides no increase in safety with respect to modern transport category jet aircraft when 

considering the safety record of the fleet over the last 53 years. The fleet has a demonstrated 

safety record with millions of hours at altitudes similar to the maximum cruise altitude proposed 

for the 767-2C. Despite the improved descent capability of the 767-2C over previously 

certificated aircraft of similar category and class, compliance with§ 25.841(a)(2)(i) following an 

uncontained engine failure would limit the 767-2C maximum certificated altitude. In addition, 

The Boeing Company assessment of the§ 25.841(a), Amendment 87, impact on overall fleet 

safety raised concerns about several unintended consequences. One such consequence is higher 

density air traffic at altitudes below 40,000 feet as a result of limiting new aircraft with wing 

mounted engines to altitudes below 40,000 feet. This may result in additional cost to maintain an 

adequate level of safety for the air traffic system. 

The 767-2C is designed to fly at cruise altitudes that will maximize fuel efficiency. The 

reduction in maximum cruise altitude resulting from compliance with§§ 25.841(a)(2) and 

25.841(a)(3) for uncontained engine failure would significantly impact the marketability of the 

767-2C. This concern is 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 767-2C incorporates new technology, lessons learned from previous and current production 

airplanes, and complies with the latest airworthiness standards (except as noted in 767-2C 

Certification Basis) throughout to provide a safer, more efficient transportation option for 

operators and occupants. Grant of this petition provides the public the benefits of the 767-2C 

airplane. 

.. 2 
RA-13-00845 

Enclosure (A) 

Page 3 of17 

As stated in the Mechanical Systems Harmonization Working Group (MSHWG) report, there is 

an inherent physiological risk to humans when exposed to high cabin altitudes. In the 767-2C 

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

requirements, proven design methodologies and operational considerations regardless ofthe 

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 25.841(a)(3) as cuJ;Tently written. In the following, The Boeing Company 

provides:· 

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

• a review of the safety history ofhigh altitude commercial flight 

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

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

existing rule, as related to economics, environmental, and air traffic considerations 

• proposed risk mitigation 

• statements addressing public interest and no adverse impact to safety 

Background on 14 CFR 25.841(a)(2)(3), Amendment 25-87 

Amendment 25-87 to § 25.841(a) was made effective July 5, 1996. The focus ofthe rule was to 

codify the special conditions formerly used in the certification of high altitude operation, 

generally applied to general aviation and transport category business jets covering operation up 

to 51,000 feet. This section was changed without being harmonized with the Joint Aviation 

Authorities (JAA) or now the European Aviation Safety Agency (EASA). It is noteworthy that 

the JAA and EASA have not adopted the same regulations as levied in 14 CFR 25.841(a) as 

promulgated in Amendment 25-87 and lists§ 25.841(a) as a significant difference for concurrent 

FAA/ JAA or FAAJEASA certification programs. The JAA INT/POL/25/16, Issue 1, Date: 

0 1.06.03, "Airworthiness Standards for Subsonic Transport Aeroplanes to be operated above an 

altitude of 41,000 ft," states, with respect to evaluation of engine rotor burst, "It is JAA opinion 

that turbine engine installations failures should be assessed against the specific requirement of 

JAR 25.903(d) and should not be part of the present Special Conditions, this is to allow a 

consistent approach at the aircraft level..." 

The provisions of§§ 25.841(a)(2) and 25.841(a)(3) of Amendment 25-87 effectively limit new 

transport category airplanes with wing-mounted engines to operating altitudes well below 40,000 

feet. This has major cost impacts since new airplane models may not be able to compete with 

existing certificated airplanes or derivative airplanes, which do not have§ 25.841(a), 

Amendment 25-87 as part of their certification basis. The existing airplanes can cruise at 

altitudes above 40,000 feet where they are more fuel-efficient. 

The Aerospace Industries Association (AlA) and European Association of Aerospace 

Industries/ Association Europeenne des Constructeurs de Materiels Aeronautique (AECMA) 

petitioned the Federal Aviation Administration to amend 14 CFR 25.841(a), Amendment 25-87, 

pressurized cabins, and the associated Advisory Circular 25-20. It was suggested that the 

proposed amendment be addressed through the auspices of the Aviation Rulemaking Advisory 

·3 
RA-13-00845 

Enclosure (A) 

Page 4 of 17 

Committee (ARAC). The petitioners recommended that harmonization with the Joint 

Airworthiness Requirements and Transport Canada's standards be accomplished simultaneously 

through the ARAC process. 

The petitioners represented the manufacturers of transport category airplanes in the United States 

and Europe. As such, they have an interest in this rulemaking proposal because new and 

derivative airplanes designed to meet 14 CFR Part 25 as amended at Amendment 25-87 will 

have significantly higher design and operating costs than currently certificated airplanes, with no 

measurable increase in safety. These higher costs, impact the ability of manufacturers to develop 

new airplanes that can compete with previously approved airplanes. The petitioners also 

identified that the economic evaluation conducted by the FAA did not consider the costs 

associated with applying this new standard to changes to existing type certificates (derivative 

models) when assessing the costs and benefits accruing from the amendment, nor whether the 

new requirement itself could be met by any practical means for any new or derivative airplane. 

In July 2001, the FAA assigned the ARAC and the Mechanical Systems Harmonization Working 

Group (MSHWG) the task of addressing various concerns with the regulation, raised by industry, 

and of reaching a consensus among medical experts, representatives from the FAA, JAA, Air 

Transport Association (ATA), ALP A, AF A and Aircraft Manufacturers (members with 

representation in the AlA, AECMA or GAMA). The MSHWG agreed that the existing .standard 

may be conservative relative to engine related failures when considering the associated risks and 

exposure to safety. The issuance of an FAA Interim Policy, March 2006, Reference (2) is · 

consistent with this position, as is the MSHWG working group report, Reference (3), which 

identified the existing requirements as being conservative relative to safety. In consideration of 

comments received on the draft Interim Policy and the acceptance of the MSHWG report by 

TAEIG, the FAA worked with manufacturers to establish appropriate criteria for§ 25.841(a) 

with respect to an uncontained engine failure. The following proposal is consistent with those 

criteria and similar to exemptions granted for the 787-8, 747:.8, 747-8F, A380, ERJ 170, and 

ERJ 190. 

Safety History 

The original§§ 25.841(a)(2) and 25.841(a)(3) had the goal of ensuring that no fatalities or 

permanent physiological harm occurred following a rapid depressurization event. However, the 

MSHWG believed that there is an inherent risk to occupant health and safety associated with any 

rapid depressurization event. The MSHWG concluded that all occupants are at some level of risk 

during· a decompression event and the resulting emergency descent, flight, and landing. Fatalities 

may occur during the initial event (i.e., from impact of uncontained engine debris or from being 

ejected from the airplane). In addition, some cases of permanent physiological harm could result 

from hypoxia among those occupants at increased risk due to pre-existing health factors (e.g., 

age, chronic and acute medical conditions, etc.). The following is presented to establish the 

demonstrated risk to safety due to rapid depressurizations is non-sigilificant when compared to 

other risks to· safety. · · 

Previously certificated large transport aircraft incorporating established design practices have 

safely operated at altitudes in excess of 40,000 feet for more than 30 years, representing many 

4 
RA-13-00845 

Enclosure (A) 

Page 5 of 17 

millions of flight hours. Historically, relatively few accidents or incidents have occurred during 

cruise. According to the statistics, for the period 1959- 1996, only 6.8 percent of accidents in the 

worldwide commercial fleet history have occurred during cruise; even though the highest 

percentage of the flight time (57%) is at cruise (Reference (4)). See Figure 1-1. More recent 

statistics, show only 6.0 percent of accidents have occurred during cruise for the period 1994-

2003, (Reference (5)) and 11 percent of accidents have occurred during cruise for the period 

2002-2011 (Reference (16)). See Figure 1-2 and 1-3 respectively. 

Fatalities 

Worldwide Commercial Jet Fleet-1959-1996 

Exposure percentage based on flight duration of 1. 5 hours 

Load, 

taxi, 

unload 

2.0% 

18.3% 

~------ Percentage of fatalnies 

Takeoff lnnial Climb Cruise 

climb 

7.3% 11.0% 17.4% 6.8% 

/ 

~Flaps retracted 

1% 1% 14% 57% 

22.6% 

Descent lnnial 

.... ~ 

Final Landing 

approach approach 

11.7% 21.2% 18.2% 4.4% 

~~ 

~ ~--~ Nav fb< Outer marker I 

11% 1 12% I 3% 1% 

Exposure, percentage of flight time 4,

578 

Figure 1-1, Fatalities, Worldwide Commercial Jet Fleet -1959 -1996 

5 
RA-13-00845 

Enclosure (A) 

Page 6 of 17 

Accidents and Onboard Fatalities by Phase of Flight 

Hull Loss and/or Fatal Accidents- Worldwide Commercial Jet Fleet -1994-2003 

17% 

-~ FataiiUes ~;: 0% ... ~-=- 8% l 1~: 

100 

Hull· 80 

loss 

and/or ao 

fatal 

accldents40 

20 

r----.. :.~--/1 

1% 1% 

Percentage of accidents/fatalities 

51% 

Climb 

(flaps up) 

8% 

Cruise 

6% 

Descent 

3% 

Initial Final I 

approach ; approach Landing 

I . 

7% J 6% 45% 

12% 

I I 

Exposure= percentage of flight time 

based on flight duration of 1.6 hours 

Initial 

approach fix 

14% 57% 11% v 

Distribution of accidents and fatalities 

1 619 

·- ~--·~;;-r···--;·;;··-·· 

18% 

I 

J 1% 

93 

Descent Initial Final Landing 

approach approach 

ll Hull loss andlor fatal accidents 0 Onboand fatalities 

2000 

1500 

Fatal lUes 

1000 

500 

16 

2003 STATISTICAL SUMMARY, MAY 2004 rlJ.-,HIIEI,NG 

Figure 1-2, Fatalities, Worldwide Commercial Jet Fleet -1994-2003 

6 
RA-13-00845 

Enclosure (A) 

Page 7 of17 

Fatal Accidents and Onboard Fatalities by Phase of Flight 

Worldwide Commercial Jet Fleet- 2002 Through 2011 

Taxi, load/ 16% Percentage of fat"! accidents and onboard f~talitie~ 

unload~ 

par1<ed, tn~ial Climb 

tow Takeoff climb (flaps up) 

Fatal accidenls 11% 10% 1 6% 6% 

Onboard fat a lilies Oo/o 10% 

Exposure 

· (Percent8ge offlight 

time estimated for a 

1.5 hour flight) ! 1% 1% I 14% .. J 

Cruise I Descent 

11% 4% 

+ 

22% 2% 

57% 

37% 

100 r-----------------------------------------------------------~~ 

so 

Fatal 60 

11ccidents 

40 

D felolecciderts 

00nboordfaloliies 

Distnoulion of fatal accidents and onboard fatalities 

1001 

1500 

Onboard 

1000 fatalities 

20 lOll STAJISTIC!<l SlMofJIRY.JUHE2011 

Figure 1-3, Fatalities, Worldwide Commercial Jet Fleet- 2002-2011 

Figure 2 shows fatal accidents by category for the world commercial jet fleet for the period of 

1992 to 2001. Note for this period, of the 7,171 fatalities from all causes, none were due to 

hypoxia resulting from in-flight rapid decompression events at altitudes greater than 25,000 feet. 

Relative to other causes, decompressions resulting in hypoxic fatalities are not a significant 

accident contributor. 

7 
RA-13-00845 

Enclosure (A) 

Page 8 of 17 

2,500 

2,000 

:! '"1,500 

!.1,000 

500 

Fatalities by Accident Categories 

Fatal Accidents· World Commercial Jet Fleet -1992 Through 2001 

ja Total fatalities • 2001 fatalities J 

Sources: Boeing Airplane Safety Engineering (ASE) and Safety Information System (SIS), National Transportation Safety Board (NTSB) 

Figure 2: Fatal Accidents by Category 

Additionally, an assessment of decompressions since the 2001 completion of the above study 

through 2011, confirmed there were no additional fatalities due to hypoxia resulting from inflight rapid decompression. There were 121 additional fatalities related to hypoxia from a single 

event; the Helios Airways Flight HCY522 accident which was not a decompression event, but a 

failure of the flight crew to properly configure the pressurization system and a subsequent failure 

to recognize that the aircraft was not pressurized after takeoff, Reference (15). There were no 

additional deaths or injuries resulting in permanent physiological harm and only two additional 

incidents were recorded as having resulted in minor barotrauma injuries. 

It should also be noted that very few rapid decompression events, if any, have exposed aircraft 

occupants to cabin pressure altitude profiles that run the risk of permanent harm to occupants. 

Industry experience shows that very few cases of decompressions at high altitude resulting in 

death or permanent physiological harm have occurred. The FAA cited 3 cases as examples of 

uncontained engine failure for consideration. In one case, a DC-1 0 (cruise flight near 

Albuquerque, New Mexico) reported several cases of initial decompression sickness apparently 

with no permanent injuries. However, it was noted that 24 passengers and crewmembers were 

brought to the hospital at Kirtland AFB for treatment of symptoms including, barotraumas (ear 

problems), minor abrasions, and smoke inhalation. Because there was no known follow-up on 

these occupants, there is no way to assess the extent of physiological injuries sustained during 

this decompression event. The NTSB report, (Reference (6), NTSB report NTSB-AAR-75-2) 

concluded that the rotor burst occurred due to the fact that "The flight crew (was), in effect, 

performing an untested failure analyses on the auto throttle system." In the second case (Sioux 

City, Iowa), the aircraft damage was aft of the pressure bulkhead, thus no rapid decompression 

occurred. The FAA cites this event to estimate the damage if the debris field had been forward of 

the pressure bulkhead. In the third case (Pensacola, Florida), the airplane was performing a 

takeoff (not cruise) when the event occurred and the flight deck crew successfully performed a 

rejected takeoff. Thus, this case did not encounter a rapid decompression. It should be noted that 

8 
RA-13-00845 

Enclosure (A) 

Page 9 of 17 

the FAA cited these three cases (Reference (7)) because they were "data rich" events. In addition 

to the "data rich" events discussed above, there have been nine other uncontained engine failures 

at cruise identified to the FAA, Reference (8), however, none of these other events caused a 

cabin decompression. 

The events experienced to date as discussed above were associated with 1st generation engine 

technology. 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 2nd /3rd generation engine 

design practices have resulted in a reduction in uncontained engine failure events. The 

uncontained engine failure rates of2nd;3rd generation engines compared to 1st generation engines 

has improved by approximately 95% based on historical Boeing data on uncontained engine 

failures. · · 

As noted previously regarding the three "data rich events" (the Albuquerque, Sioux City, and 

Pensacola events), only the Albuquerque event resulted in a decompression. Furthermore, the 

Albuquerque event remains an inappropriate event as a "decompression" model, particularly 

since the NTSB noted that "The flight crew was, in effect, performing an untested failure 

analyses on the autothrottle system" prior to the engine failure, Reference (6), NTSB report 

NTSB-AAR-75-2. 

Figure 3 depicts pressurization events by cause. Note that uncontained engine failure is an 

insignificant contributor to the total number of events. 

4.00E-06 

3.50E-06 

3.00E-06 

2.50E-06 

2.00E-06 

1.50E-06 

1.00E-06 

5.00E-07 

O.OOE+OO 

Decompression Events by Cause 

Pressurization Events per Hour an.d per Flight, by Cause 

I C # Ev/Hr • # Ev/Fit I 

Sources: Boeing Airplane Safety Engineering (ASE) and Safety lnfonnatlon Syetem (SIS), National Transportation Safety Board (NTSB) 

Engine Events Are Rare Contributors To Decompression Events 

~.BDEIND'" 

Figure 3, Pressurization Events by Cause per Flight Hour 

9 
RA-13-00845 

Enclosure (A) 

Page 10 of 17 

In conjunction with the above data, it should be noted that very few decompression events 

exposed the aircraft occupants to cabin pressure altitude profiles which run the risk of permanent 

physiological harm. Figure 4 summarizes significant transport category decompression events 

resulting in fatalities or incapacitation (in red). Note that while fatalities were incurred, none 

would have been prevented by the intent of§ 25.841(a), Amendment 25-87 which was 

promulgated in large part to prevent death or permanent physiological harm from hypoxia as a 

result of a rapid decompression caused by a large hole in the pressure vessel from an uncontained 

engine failure. The only fatal event since this data was taken has been the previously discussed 

Helios event. 

CD 

"0 

:I 

:1::: 

5i 

c 

:a 

I'll 

u 

E 

:I 

E 

';( 

I'll 

:E 

45,000 

40,000 

35,000 

30,000 

25,000 

20,000 

15,000 

10,000 

5,000 

0 

• 

• 

All Pressurization Events with associated 

Fatality, Incapacitation or Injury 

J• Fatality/Incapacitation • lnjuryJ 

• ...... • • _A 

• 

•••• ~___. 

... • : l • A • ·: ' .. -..-."-rl> ;-.-t-& • • • 

• 

I 

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 45,000 50,000 

Event Altitude 

Figure 4: Pressurization Events with Fatality, Incapacitation or Injury 

Notes: Total of2866 pressurization events reported 1959-2001. Transport Category 

Airplanes over 60,000 lbs. Event Altitude and Cabin Altitude were reported 

for 873 events. 

Sources: Boeing Airplane Safety Engineering (ASE) and Safety Information System 

(SIS), National Transportation Safety Board (NTSB) 

Of the 18 events that resulted in fatalities, 1 0 events were at cabin altitude exposures less than 

those altitudes addressed by§ 25.841(a)(2), Amendment 25-87.ln four of the remaining eight 

events, fatalities were due to injury directly attributed to the event rather than from hypoxia (one 

catastrophic structure loss, two engine failures, and one wheel burst). The remaining four events 

were attributed to crew error, un-annunciated loss of pressurization, and oxygen system failure. 

Current generation aircraft, (1980s through 2000s) introduced higher performance permitting 

higher altitude flight in response to the need for increased fuel efficiency and avoidance of 

increasingly crowded airspace at altitudes below 40,000 feet. The MSHWG report, Reference (3) 

concluded for the world commercial jet fleet for the period of 1992 to 2001, no hypoxia related 

fatalities were due to in-flight decompression events. This saf~ty record has been maintained 

10 
RA-13-00845 

Enclosure (A) 

Page 11 of 17 

even as newer airplanes fly at these higher altitudes more often than older airplanes (see Figure 

5). As stated previously, an assessment of decompressions since the 2001 completion of the 

above study through 2011 confirmed there were no additional fatalities or permanent 

physiological harm due to hypoxia resulting from in-flight rapid decompression, and only two· 

additional incidents resulting in minor barotrauma injuries. As discussed previously, the Helios 

Airways Flight HCY522 accident was not a decompression event, but a failure of the flight crew 

to properly configure the pressurization system and a subsequent failure to recognize that the 

aircraft was not pressurized after takeoff. Based on these facts, the MSHWG report conclusions 

remain valid. Three separate studies have recently been made to illustrate the extent of air traffic 

operations at high altitUde in today's air traffic system. While today's numbers are significant, 

the new generation of airplanes as exemplified by the 767-2C are being designed to cruise at 

altitudes above 37,000 feet for even longer portions of their mission. 

45% 

40% 

35% 

30% 

t! 25% 

0 

Q. 

~ 20% 

15% 

10% 

5% 

0% 

Altitude Reports By Airplane Model 

FAA's Enhanced Traffic Management System (ETMS) Reports for U.S. 

Commercial Aircraft above 28,000 feet ... ---- --·· ···-· 

i 

r-

; I IJAbove 40,000 ft I IJ Above 37,000 ft 

~ First Flight of Type Prior to 1980 ~ - 1-

~ 

1-

rr- r- r-

,_ r- 1- - r--

r- -

i-- ·- 1- 1- -

I r- '-- I r- r- r- ,_ -

_n rE n n I.-- ill ill 

~~~~~~~,~~-~~~~,,~,/ <§1 Q ~ .... ' 

• Data represents reports from one week in Sept 2000 

• Based on position reports every 3 minutes. 

,...-

Figure 5: Frequency of Flights above 37,000 ft. and 40~000 ft. Altitude of New Design 

Aircraft vs. Older Design Aircraft. 

Aerospace Hypoxia Physiology Data 

The FAA, and other qualified experts 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 Aeromedical Institute (CAMI), which were based on the concept of"Time of 

Safe Unconsciousness" (TSU)documented by James G. Gaume in his 1970 paper. The study 

concluded with the statement that,"" ... a plea must be made for collection of better data." 

11 
RA-13-00845 

Enclosure (A) 

Page 12 of 17 

Gaume's 1970 paper is only one source in establishing safety basis. It should be understood that 

the proposed TSU criteria was established as a compensating consideration to the elimination of 

the passenger oxygen system. Today's commercial transport are required to provide an 

emergency oxygen system providing additional margin of safety. 

The MSHWG agreed additional data based on further study would benefit the establishment of 

new standards. In lieu of new data the MSHWG established physiological exposure limits that 

are conservative with respect to the data available. The MSHWG considered the available 

physiological exposure research which included several papers that have been circulated in the 

aerospace medical community, all with the objective of establishing 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 documented its recommendations in 

the Reference (3) TAEIG accepted report. The following are summaries ofthe reports from . 

recognized Aerospace Medical Doctors addressing physiological information that was 

considered by the MSHWG: 

- ·James Gaume (Aerospace Medicine) authored a paper substantiating the new rule. 

According to Gaume, during an emergency descent from 42,000 feet to 5,000 feet for 

adequate recovery of unconscious passengers without any supplemental emergency 

oxygen to the occupants, with an aircraft emergency descent of 6200 feet per minute 

and with cabin altitude exceeding 33,000 feet, no more than 1 minute and 42 seconds 

is considered acceptable. Reference (9): "Factors Influencing the Time of Safe Unconsciousness (TSU) for Commercial Jet Passengers Following Cabin 

Decompression" by James Gaume, Aerospace Medicine, April 1970. 

- Dr. Stanley R. Mohler, a former director ofCAMI (FAA's Civil Aeromedical 

Institute), analyzed a number of actual decompression cases, including data from 

studies by Barron, Reference (10), and Gaume. He concluded that brain damage in 

the absence of oxygen starts after about four minutes, and that three minutes above 

25,000 feet is a reasonable limit to protect against permanent physiological damage 

from a cabin decompression occurring at up to 45,000 feet. Reference (11): "Sudden 

High Altitude Cabin Decompression Immediately Threatens Safety of Aircraft Crew 

and Passengers" by Dr. Stanley Mohler, Flight Safety Foundation, Human Factors & 

Aviation Medicine, December 1994. 

Dr. Robert Gamer, Research ·Physiologist, Protection and Survival Laboratory at 

CAMI, agrees that limiting cabin altitude exposure to 25,000 feet for up to three 

minutes and never allowing it to exceed 45,000 feet would provide an acceptable 

level of safety. His views on this matter have been communicated to the FAA 

Transport Standards Staff. 

DraftWhite paper issued by CAMI- FAA Civil Aerospace Medical Altitude Rule: 

presented in the MSHWG in July 2002, Reference (12), Page 13, states that exposure: 

if unprotected, passengers to a 41,000 feet altitude would be approximately equal to 

exposure at a 40,000 feet altitude. · 

12 
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Enclosure (A) 

Page 13 of 17 

- "Neurological Study of Simulated Decompression in Supersonic Transport Aircraft," 

Aerospace Medicine, J.B. Brierley and A. N. Nicholson, August, 1969, Reference 

(13), concluded that cabin altitude exposure above 10,000 feet not more than eight 

minutes up to peak of 36,000 feet does not cause brain damage. 

"Neurological Sequelae of Prolonged Decompression," Aerospace Medicine, A. N. 

Nicholson and J.R. Emsting, April1967, Reference (14) concluded that cabin altitude 

exposure above 40,000 feet with time exposure of 1 minute and 30 seconds caused 

brain damage. 

In consideration of the above studies, comments received on the draft Interim Policy, and the 

acceptance of the MSHWG report by TAEIG,the FAA established appropriate criteria for 

§ 25.841(a) with respect to an uncontained engine failure. These criteria are more conservative 

than those established by MSHWG report. In lieu of any other standard, Boeing will comply 

with these criteria as presented in the Proposed Risk Mitigation discussion provided later in this 

petition. 

Impacts of Compliance with the Uncontained Engine Failure Aspect of Rule 

The Boeing Company's 767-2C will fully comply with the latest airworthiness standards (except 

. as noted in the 767-2C Certification Basis) including§§ 25.841(a)(2) and 25.841(a)(3), 

Amendment 25-87 in all regards, except as related to an uncontained engine failure event as 

defined herein. 

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) economic which lead to (2) reduced potential for overall safety improvements 

and (3) environmental. · 

(1) While it is difficult to place an exact dollar amount on the impact of these new 

requirements on the 767-2C, it is clear that not granting the proposed exemption would 

have severe impact. This conclusion is based on the reduction in maximum cruise altitude 

that compliance with§§ 25.841(a)(2) and 25.841(a)(3), Amendment 25-87 as it relates to 

uncontained engine failure would result in. This reduction in maximum cruise altitude 

would result in significantly higher operating costs~ based on the significant increased 

fuel burn due to operations at altitudes not optimum for these airplanes. These higher 

costs will adversely impact the ability of the Boeing 767-2C to compete with previously 

certificated airplanes which can operate at the more economical cruise altitudes typically 

in excess of 37,000 feet. In addition, restricting airplane operations to lower altitudes will 

increase traffic congestion. Three separate studies have shown that the number of 

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 

tum will result in higher cost ·of safety in order to maintain established air traffic vertical 

and horizontal separation requirements. 

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Enclosure (A) 

Page 14 of 17 

(2) Since the release of Amendment 25-87, a number of amendments to 14 CFR 25 have 

been released. Each of these amendments has the intent of an increase in aviation safety. 

The Boeing 7 67-2C will meet the latest amendments in effect at the time of application, 

except as noted in the 767-2C Certification Basis. The net result is that the 767-2C 

incorporates the safety-advancements as intended within these later amendments. Any 

significant impact to the marketability of the 767-2C will, at a minimum, result in a 

reduced number 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 model 

series of aircraft. In either case, Amendment 25-87 results in a reduced potential for 

overall aviation safety improvements. 

(3) As stated in (1) above, the restriction to maximum cruise altitude imposed upon the 

767-2C due to compliance with§§ 25.841(a)(2) and 25.841(a)(3), Amendment 25-87 as 

it relates to uncontained engine failure has a significant adverse impact on 767-2C fuel 

bum. This additional fuel bum not only increases 767-2C operating costs, but will also 

increase engine emissions (e.g. C02). 

Proposed Risk Mitigation 

It is The Boeing Company assessment that the risk to safety which is attempted to be mitigated 

by the new rule§§ 25.841(a)(2) and 25.841(a)(3), creates unintended consequences. The existing 

fleet has demonstrated safe operations via millions of hours of flight at altitudes similar to those 

proposed for the 767-2C. The risk of rapid depressurization following an uncontained engine 

failure is better mitigated by a combination of proven design practices established through years 

of airplane industry experience combined with today's improved technical capabilities. I~ is 

intended that the proposed risk mitigation measures augment this exemption request and address 

the intended concern for safety without the non-commensurate impacts driven by current · 

requirements of§§ 25.841(a)(2) and 25.84l(a)(3). 

It must be reiterated that this request for exemption for§§ 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 25-87. All mechanical and/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 of the 767-2C design. The 

Boeing Company design practices refine the requirements into sub-requirements for systems, 

structures, aerodynamics, and performance in order to assure airplane level compliance. 

Other threat minimization philosophies employed in the 767-2C design include an automatic 

pressure demand mask for the pilots which will be certified to§ 25.1441(d), separation and 

redundancy of key systems such as electrical power, cabin pressure control and spoiler actuation. 

The following more specifically addresses The Boeing Company proposed means of compliance 

for rapid depressurizations related to uncontained engine failures. Using the FAA established 

criteria (Reference (2)), The Boeing Company proposes to mitigate the risk to occupants from 

14 
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Enclosure (A) 

Page 15 of17 

exposure to high cabin altitudes resulting from uncontained engine failure, in part, by 

implementing the following design requirements on the 767-2C airplane: 

• Design Requirement 

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 engine 

failure condition not shown to be extremely improbable: 

(i) Forty-five thousand (45,000)feetfor 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 (JO,OOO)feetfor more than six minutes. 

In calculating the descent capability of the airplane in order to meet the cabin altitude 

requirements, the loss of the failed engine's contribution as a source of power to the systems 

enabling the descent need be considered. (i.e. If losing power on one engine results in loss of a 

hydraulic system, and that in tum reduces the number of spoilers that are available, the descent 

rate must be based on the capabilities of the degraded system.) Systems degradation due to debris 

damage from an Uncontained Engine Failure need not be considered. 

References 

1) Amendment 25-87 Final Rule, Docket 26070, Federal Register Volume 61, Number 

109, June 5, 1996 

2) FAA Interim Policy, ANM-03-112-16, Subject: Interim Policy on High Altitude 

Cabin Decompression (Reference Amendment 25-87) Issued March 24, 2006 

3) Mechanical Systems Harmonization Working Group (MSHWG) Final Report on 

FAR 25.841(a)(2,3), dated August 2003, submitted to FAA October 21,2003 

4) Statistical Summary of Commercial Jet Airplane Accidents, Worldwide Operations, 

1959-2002, Published by Boeing Commercial Airplane, May, 2003 

5) St3;tistical Summary of Commercial Jet Airplane Accidents, Worldwide Operations, 

1959-2003, Published by Boeing Commercial Airplane, May, 2004 

6) NTSB-AAR-75-2, AIRCRAFT ACCIDENT NATIONAL AIRLINES, INC.,DC-10-

10, N60NA NEAR ALBUQUERQUE, NEW MEXICO, November 3,1973 

7) Uncontained Engine Failure Fuselage Hole Analysis, Draft Technical Note, October 

2001 

8) Uncontained Engine Damage Database, ACCESS 2000 Database, FAA UED vOO 1, 

June 10, 2002 

9) Factors influencing the time of Safe Unconsciousness (TSU) for commercial 

passengers Following Cabin Decompression, Gaume, J., 1970. Aerospace Medicine, 

April1970, 382-385 

10)Barron, C . .and Cook, T.,-Effects of Variable Decompressions to 45000 feet, 

Aerospace Medicine, May 1965,425.430 

11) Mohler, Dr. Stanley, "Sudden High Altitude Cabin Decompression Immediately 

Threatens Safety of Aircraft Crew and Passeng~rs," Flight Safety Foundation, Human 

Factors & Aviation Medicine, December 1994 

15 
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Enclosure (A) 

Page 16 of 17 

12) Draft White paper issued by CAMI - FAA Civil Aerospace Medical Altitude Rule: 

presented in the MSHWG in July 2002 

13) ''Neurological Study of Simulated Decompression in Supersonic Transport Aircraft," 

Aerospace Medicine, J.B. Brierley and A.N. Nicholson, August, 1969 

14) "Neurological Sequelae of Prolonged Decompression," Aerospace Medicine, A.N. 

Nicholson and J.R. Emsting, April1967 

15) Hellenic Republic Ministry of Transport & Communications, AAIASB Aircraft 

Accident Report, Helios Airways Flight HCY522, Boeing 737-31S At Grammatiko, 

Hellas on 14 August 2005, Dated 1112006 

16) Statistical Summary of Commercial Jet Airplane Accidents, Worldwide Operations, 

1959-2011, To be published by Boeing Commercial Airplane 

Statement of Public Interest 

The Boeing Company Model 767-2C fully complies with the latest airworthiness standards 

(except as noted in 767-2C Certification Basis) including§§ 25.841(a)(2) and 25.841(a)(3), 

Amendment 25-87 in all regards, except as related to an uncontained engine failure event as 

defined herein. Specific features ofthe 767-2C design mitigate the safety risk to occupants due to 

a decompression resulting from an uncontained engine failure. Improvements in engine 

technology, application oflessons learned, and 2nd 13rd generation engine design practices have 

resulted in a reduction in uncontained engine failure events and the risk of a rapid 

depressurization. As stated above, the Boeing 767 -2C will meet all the latest amendments in 

effect at the time of application, except as noted in the 767-2C Certification Basis. The net result 

is that the 767-2C incorporates the safety advancements as intended within these later 

amendments. The 767-2C, therefore, offers a higher level of safety than do previously 

certificated transport category airplanes. 

In addition, the 767-2C will provide industry-leading operating economics, and environmental 

improvements. Granting this petition of exemption is in the public interest because it will 

improve safety relative to previously certificated airplanes, while reducing operational costs by 

reducing the amount of fuel consumed. The cost of maintaining the level of safety within the 

existing air traffic management system will not be adversely impacted by continuing to allow 

operation in the less congested altitudes typically well above 37,000 feet. The reduction in fuel 

consumed will also result in reduced emissions: These benefits will accrue with no decrease in 

safety. 

Statement of No Adverse Effect on Safety 

The exemption requested will not adversely affect safety. As previously discussed, the 767-2C 

will comply with§ 25.841(a) in all other aspects of a rapid depressurization. In the unlikely 

event of an uncontained engine failure, the 767-2C design incorporates a high level of safety due 

to its descent capability and other design features. As concluded herein, and based on the 

MSHWG report (Reference (3)), and the Interim Policy (Reference (2)), the world commercial 

jet fleet has had no hypoxia related fatalities due to in-flight decompression events caused by an 

uncontained engine failure. This safety record has been maintained even as newer airplanes fly at 

higher altitudes more often than older airplanes. In keeping with time-above-altitude FAA 

16 
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Enclosure (A) 

Page 17 of 17 

guidance and the recommendat"ions of the MSHWG report, as adopted by TAIEG, Boeing has 

incorporated design features that appropriately address the risk to safety following an 

uncontained engine failure. Therefore, granting of the exemption will not compromise safety to 

the airplane occupants. 

Request to 'Waive Publication and Comment' 

Boeing requests to waive the requirement for publication and comment based on sim'ilar 

exemptions granted to the following aircraft: 787-8, 747-8, 747-8F, A380, ERJ 170, and ERJ 

190. 

Privileges of the Exemption Outside the United States 

Per§ 11.81(h), Boeing requests that the privileges of this exemption be extended outside the 

United States. This extension of privileges is necessary for operations based within foreign 

countries having bilateral agreements with the United States accepting FAA 14 CFR part 25 as 

their airworthiness standards for transport category aircraft. The 767-2C is intended for the 

global market place. 

Conclusion 

The information in this petition for exemption provides evidence that compliance with§§ 

25.841(a)(2), and 25.841(a)(3), with respect to an uncontained engine failure, provides no 

increase in safety. The 767-2C provides advancements in technology and safety relative to 

previously certified aircraft. Grant of this petition provides the public the benefits of the 767-2C 

airplane. Operators will be able to operate the 767-2C where it is most efficient and therefore 

will not face higher operating costs due to increased fuel burn. Furthermore, reduced fuel bum 

will lead to lower engine emissions resulting in positive impact to the environment. By granting 

this petition for exemption the true benefits of'767-2C will be realized, causing no adverse effect 

on safety. 

Summary to be Published in the Federal Register 

PETITIONER: Boeing Commercial Airplanes 

SECTION OF 14 CFR AFFECTED: 14 CFR 25.841(a)(2)(3) . > 

DESCRIPTION OF RELIEF SOUGHT: To allow relieffrom the requirements pertaining to 

cabin decompression following certain extremely rare uncontained engine failures for the Boeing 

Model 767-2C. 

17