[Federal Register Volume 88, Number 115 (Thursday, June 15, 2023)]
[Rules and Regulations]
[Pages 39152-39161]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-12454]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No.: FAA-2019-0218; Amdt. No. 25-148]
RIN 2120-AL15


High Elevation Airport Operations

AGENCY: Federal Aviation Administration (FAA), Department of 
Transportation (DOT).

ACTION: Final rule.

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SUMMARY: This final rule amends certain airworthiness regulations 
applicable to cabin pressurization systems and oxygen dispensing 
equipment on transport category airplanes, to facilitate certification 
of those airplanes, systems, and equipment for operation at high 
elevation airports. This rule eliminates the need for certain 
equivalent level of safety findings and exemptions.

DATES: Effective July 17, 2023.

ADDRESSES: For information on where to obtain copies of rulemaking 
documents and other information related to this final rule, see ``How 
To Obtain Additional Information'' in the SUPPLEMENTARY INFORMATION 
section of this document.

FOR FURTHER INFORMATION CONTACT: Robert Hettman, Aircraft Systems 
Section, AIR-623, Technical Innovation Policy Branch, Policy and 
Innovation Division, Aircraft Certification Service, Federal Aviation 
Administration, 2200 S 216th Street, Des Moines, Washington, 98198; 
telephone and facsimile 206-231-3171; email [email protected].

SUPPLEMENTARY INFORMATION: 

Authority for This Rulemaking

    The FAA's authority to issue rules on aviation safety is found in 
Title 49 of the United States Code. Subtitle I, section 106 describes 
the authority of the FAA Administrator. Subtitle VII, Aviation 
Programs, describes in more detail the scope of the agency's authority.
    This rulemaking is promulgated under the authority described in 
Subtitle VII, part A, subpart III, section 44701, ``General 
Requirements.'' Under that section, the FAA is charged with promoting 
safe flight of civil aircraft in air commerce by prescribing 
regulations and minimum standards for the design and performance of 
aircraft that the Administrator finds necessary for safety in air 
commerce. This regulation is within the scope of that authority. It 
prescribes new safety standards for the design and operation of 
transport category airplanes.

I. Overview of Final Rule

    This final rule amends two sections of title 14, Code of Federal 
Regulations (14 CFR), part 25.
    First, the rule amends Sec.  25.841, ``Pressurized cabins,'' for 
airplanes equipped with cabin pressurization systems intended for 
operations at airports with elevations at or above 8,000 feet. The FAA 
considers airports with elevations greater than 8,000 feet as ``high 
elevation airports.'' Section 25.841(a) still requires that cabin 
pressure altitudes do not exceed 8,000 feet under normal operating 
conditions, while the revisions allow cabin pressure altitudes to 
exceed 8,000 feet during takeoff and landing at high elevation 
airports. In addition, changes to Sec.  25.841(b)(6) allow applicants 
to increase the threshold for activation of cabin pressure altitude 
warnings to altitudes above 10,000 feet, to prevent nuisance warnings 
to the flightcrew during takeoff and landing at high elevation 
airports.
    Second, this rule amends Sec.  25.1447, ``Equipment standards for 
oxygen dispensing units,'' for airplanes equipped with passenger oxygen 
systems intended for operations into or out of airports with elevations 
above 13,000 feet. The revisions to Sec.  25.1447(c)(5) allow 
applicants to raise the automatic presentation altitude for oxygen 
masks located throughout the passenger cabin to altitudes above 15,000 
feet while operating out of or into airports with elevations exceeding 
13,000 feet.
    This final rule affects manufacturers, modifiers, and operators of 
transport category airplanes. The amendments to Sec. Sec.  25.841 and 
25.1447 eliminate the burden on applicants and the FAA that results 
from the processing of project-specific equivalent level of safety 
(ELOS) findings and grants of exemption that are currently necessary 
for the FAA to approve the designs of cabin pressurization systems and 
oxygen dispensing units on airplanes intended to be used for operations 
into or out of high elevation airports.

II. Background

A. Summary of the Problem

    Current FAA regulations require that the cabin pressure altitude on 
transport category airplanes remain at or below 8,000 feet in normal 
operating conditions, and that supplemental oxygen be automatically 
presented to passengers before the cabin pressure altitude reaches 
15,000 feet. While these standards provide an acceptable level of 
safety for normal operating conditions, they can hinder or conflict 
with operations at high elevation airports.
    To enable such operations, applicants develop specialized design 
modifications that often cannot comply with cabin pressurization and 
supplemental oxygen requirements in FAA regulations. In order to 
approve such modifications and enable operation into high elevation 
airports, the FAA typically must make and document an ELOS finding. The 
FAA must typically also grant an exemption from the automatic oxygen 
mask presentation requirements for operations into or out of airports 
with elevations at or above 13,000 feet.
    Transport airplane operators currently utilize seven airports in 
the United States that have an elevation between 8,000 and 10,000 feet. 
While no airports in the U.S. supporting transport airplane operations 
are at an elevation higher than 10,000 feet, the FAA is aware of at 
least five airports in other parts of the world that support transport 
airplane operations and are at elevations that exceed 13,000 feet. 
Therefore, it is for operations at these airports that applicants seek 
either an ELOS or an exemption in order to obtain certification of 
cabin pressurization and oxygen systems.

B. Discussion of Current Regulatory Requirements

    Current regulatory requirements for cabin pressurization systems of 
transport category airplanes are contained in Sec.  25.841(a) and (b). 
Section 25.841(a) requires cabin pressurization systems to maintain the 
interior cabin pressure so that the maximum cabin

[[Page 39153]]

pressure altitude does not exceed 8,000 feet. While an airplane is 
operating on the ground before takeoff or after landing, however, the 
interior cabin pressure must be equal to the outside ambient air 
pressure, or airport pressure altitude. Otherwise, should the need for 
an emergency evacuation arise, the pressure differential between 
interior cabin and airport pressure altitude may be too high to allow 
cabin attendants to open the doors. For airports above 8,000 feet, the 
regulatory requirement of Sec.  25.841(a) to equip the airplane to keep 
its cabin pressure altitude from exceeding 8,000 feet, and the 
practical requirement for cabin pressure altitude to equal the airport 
pressure altitude for takeoff and landing, are in direct conflict. This 
creates a need for specialized design modifications and certification 
approaches to accommodate these operations.
    When a transport category airplane takes off from an airport with 
an elevation below 8,000 feet, its cabin pressure altitude does not 
normally exceed 8,000 feet. The cabin pressure nominally starts at the 
ambient pressure altitude of the airport, and gradually increases as 
the airplane climbs until the cabin pressure altitude stabilizes at an 
altitude not exceeding 8,000 feet.
    However, when a transport category airplane takes off from an 
airport with an elevation at or above 8,000 feet, the cabin pressure 
altitude necessarily exceeds 8,000 feet. The cabin pressure starts at 
the airport's ambient pressure altitude at 8,000 feet or greater, and 
then, if it is equipped with a system that complies with Sec.  
25.841(a), decreases until it is not more than 8,000 feet. During the 
time between takeoff and the point when cabin pressure altitude reaches 
8,000 feet, the airplane's pressurization system is not in compliance 
with the regulation. Similarly, when a transport category airplane is 
landing at a high elevation airport, the interior cabin pressure 
altitude will initially be at or below 8,000 feet, as required by Sec.  
25.841(a), and then rise as the airplane descends, until the interior 
cabin pressure altitude is the same as the ambient pressure altitude at 
the airport. Since the maximum cabin pressure altitude of 8,000 feet is 
exceeded to accommodate the operation into a high elevation airport, 
the cabin pressurization system would again briefly not comply with the 
8,000 foot limit in Sec.  25.841(a).
    Furthermore, Sec.  25.841(b)(6) requires a warning indication at 
the pilot or flight engineer station to indicate when the safe or 
preset pressure differential and cabin pressure altitude limits are 
exceeded. As described in Sec.  25.841(b)(6), appropriate warning 
markings on the cabin pressure differential indicator meet the warning 
requirement for pressure differential limits, and an aural or visual 
signal (in addition to cabin altitude indicating means) meets the 
warning requirement for cabin pressure altitude limits, if they warn 
the flightcrew when the cabin pressure altitude exceeds 10,000 feet. To 
support high elevation airport operations and avoid nuisance alerts, 
airplane designers incorporate modifications to raise the cabin 
pressure altitude at which the cabin pressure high altitude warning 
indication occurs.
    Currently, when an airplane designer applies to the FAA for 
certification of an airplane with a cabin pressurization system 
intended for operations at high elevation airports, the cabin 
pressurization and cabin pressure altitude warning systems cannot meet 
the design standards in Sec.  25.841(a) and (b)(6). To obtain FAA 
approval of such designs, the airplane designer will typically include 
compensating elements that provide an equivalent level of safety to 
that intended by the regulations.\1\ For the design standards provided 
by Sec.  25.841(a) and (b)(6), the FAA has found that compensating 
factors such as the flightcrew's use of oxygen and minimizing the time 
that the cabin pressure altitude may be above 8,000 feet can provide an 
ELOS during high elevation airport operations. The FAA documents its 
finding in a memorandum that communicates the agency's rationale to the 
public.\2\ Processing an ELOS finding (i.e., evaluating the request, 
analyzing the design, making the determination, and creating the 
memorandum) creates an administrative burden on both the applicant and 
the FAA during the certification process.
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    \1\ The authority for the agency to make an ELOS finding is 
provided in 14 CFR 21.21(b). Paragraph (b) of Sec.  21.21 specifies 
that the FAA must find the proposed design meets the applicable 
airworthiness requirements of subchapter C of chapter I of title 14 
of the Code of Federal Regulations or that any airworthiness 
provisions not complied with are compensated for by factors that 
provide an equivalent level of safety.
    \2\ ELOS memorandums are available electronically to the public 
in the FAA's Dynamic Regulatory System (DRS) at https://drs.faa.gov/browse.
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    Section 25.1447(c)(1) requires airplanes certified for operations 
above 30,000 feet to include oxygen dispensing equipment that is 
automatically presented to each of the airplane's occupants in the 
event of depressurization, before the cabin pressure altitude reaches 
15,000 feet. To avoid unnecessary presentations of the supplemental 
oxygen equipment and the maintenance costs of servicing the system 
afterward, applicants typically incorporate design features to 
temporarily raise the automatic presentation altitude for oxygen masks 
during high elevation airport operations. Currently, applicants whose 
designs incorporate these features must submit a petition for an 
exemption from Sec.  25.1447(c)(1).\3\ This creates an administrative 
burden for both applicants who develop the petition and the FAA in the 
evaluation and analysis of each petition.
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    \3\ The Administrator's exemption authority is provided by 49 
U.S.C. 44701(f) and implemented in accordance with 14 CFR part 11.
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C. Summary of the Notice of Proposed Rulemaking (NPRM)

    The FAA published an NPRM (84 FR 13565) on April 5, 2019, that 
proposed to amend Sec. Sec.  25.841, ``Pressurized cabins,'' and 
25.1447, ``Equipment standards for oxygen dispensing units.'' The FAA 
proposed these revisions to provide design standards for cabin 
pressurization systems and oxygen dispensing equipment on transport 
category airplanes intended for operation at airports with elevations 
at or above 8,000 feet, also referred to in this preamble as ``high 
elevation airports.''
    In the NPRM, the FAA proposed adding new Sec.  25.841(c), as an 
exception to Sec.  25.841(a), for systems designed to support 
operations at high elevation airports. Proposed Sec.  25.841(c) would 
have allowed the airplane's cabin pressure altitude to be equal to or 
less than the airport elevation while the airplane is at or below 
25,000 feet, provided the cabin pressurization system is designed to 
minimize the time that passenger cabin occupants would be exposed to 
cabin pressure altitudes exceeding 8,000 feet in flight.
    The FAA also proposed adding new Sec.  25.841(d) as an exception to 
Sec.  25.841(b)(6). This would have allowed an applicant to change the 
threshold for the cabin pressure altitude warning indication from 
10,000 feet to either 15,000 feet or 2,000 feet above the airport 
elevation, whichever is greater, when operating into or out of a high 
elevation airport and the airplane is at or below 25,000 feet. The FAA 
proposed 2,000 feet above the airport elevation in order to allow for 
system flexibility while maintaining a level of safety consistent with 
previously issued ELOS determinations.
    In the NPRM, the FAA also proposed to add new Sec.  25.1447(c)(5) 
as an exception to Sec.  25.1447(c)(1) to allow approval of passenger 
cabin oxygen dispensing units that automatically

[[Page 39154]]

deploy at 15,000 feet, or 2,000 feet above the airport elevation, 
whichever is greater, during operations into or out of high elevation 
airports. Similarly, the FAA proposed a variation of 2,000 feet above 
the airport elevation to allow for system flexibility while maintaining 
a level of safety consistent with previously-issued exemptions and to 
harmonize with European Union Aviation Safety Agency (EASA) guidance.
    The revisions proposed in the NPRM intended to eliminate 
administrative tasks and analyses associated with the preparation and 
processing of ELOS determinations and exemptions to accommodate 
transport category airplane operations at high elevation airports, 
without compromising safety. The FAA invited comments to the proposal, 
and the comment period closed on June 4, 2019.

D. General Overview of Comments

    The FAA received ten sets of comments. Three commenters were 
airplane manufacturers: Boeing, Bombardier, and Embraer. The Aerospace 
Industries Association and the General Aviation Manufacturers 
Association (AIA/GAMA) commented collectively. One civil aviation 
authority, the Transport Canada Civil Aviation Authority (TCCA), 
provided comment. Three individuals commented, and three Health 
Sciences majors submitted a collective comment.
    The majority of the comments from industry were requests to revise 
regulatory text for clarification and consistency. An individual also 
described the need to make clear distinctions and utilize consistent 
terminology. Another individual supported the economic cost savings, 
but requested further information on new airplane designs. The three 
Health Sciences majors opposed the proposed regulation because they 
stated that the health risks of flying into high elevation airports 
outweigh the economic benefits. Another commenter recommended not 
approving high elevation operations and proposed the removal of 
airports located at elevations greater than 7,500 feet for safety and 
environmental reasons. A detailed discussion of the comments and 
resulting regulatory changes is provided in section III.

E. Advisory Material

    AIA/GAMA and Boeing suggested that the FAA develop and publish an 
Advisory Circular (AC) on high elevation airport operations to provide 
specific guidance on how to design cabin pressurization systems to 
minimize the amount of time that passenger cabin occupants are exposed 
to higher cabin pressure altitudes, to reduce the risk of hypoxia. The 
FAA is providing additional discussion of this topic in this final rule 
and does not consider it necessary to publish separate guidance.

III. Discussion of Public Comments and Final Rule

    The FAA has made changes to this final rule in response to comments 
made by the public. Some of the changes are to terminology to improve 
clarity, while other changes are in response to technical comments 
related to design of cabin pressurization systems. Summaries of the 
comments and the FAA's responses are grouped by category in the 
following subsections.

A. Clarification of Terminology

    Six commenters recommended that the FAA use the term ``cabin 
pressure altitude'' in the regulatory language and preamble, in lieu of 
the term ``cabin pressure'' as used in the NPRM including proposed 
changes to Sec.  25.841. ``Cabin pressure'' is a measurement of 
pressure, typically pounds per square inch, while ``cabin pressure 
altitude'' is an equivalent measurement expressed in height above sea 
level, typically feet. The FAA agrees that the suggested change would 
promote clarity and consistency, and in this final rule uses ``cabin 
pressure altitude'' instead of ``cabin pressure'' when referring to the 
condition in the airplane cabin.

B. Cabin Pressure Altitude at the Maximum Operating Altitude

    Section 25.841(a) limits the cabin pressure altitude to not more 
than 8,000 feet at the maximum operating altitude of the airplane under 
normal operating conditions. In the NPRM, the FAA proposed revising 
Sec.  25.841(a) to remove the phrase ``at the maximum operating 
altitude of the airplane.'' As discussed in the NPRM, the FAA did not 
intend Sec.  25.841(a) to imply that the cabin pressure altitude could 
exceed 8,000 feet under normal operating conditions provided the 
airplane was below the maximum operating altitude.
    In response to the NPRM, TCCA asked if the FAA would update any 
advisory materials to clarify the intent of the term ``under normal 
operating conditions.'' The FAA does not intend to update or add any 
advisory materials for this rulemaking and notes that the term ``normal 
operating conditions'' currently in Sec.  25.841(a) is not being 
changed by this rule. As the term relates to Sec.  25.841(a), the FAA 
considers normal operating conditions to mean that the cabin 
pressurization system is operating normally, rather than under some 
alternative mode due to system failure. The FAA considers operating at 
the maximum operating altitude of the airplane a normal operating 
condition. In the context of this rulemaking, the FAA also considers 
operations into or out of a high elevation airport a normal operating 
condition.

C. Cabin Pressurization Limits

    In the NPRM, the FAA proposed changes to Sec.  25.841(a) related to 
operations at airports with elevations exceeding 8,000 feet. When 
issuing the NPRM, the FAA did not consider airports that may be planned 
or under construction which would exceed an elevation of 15,000 feet. 
AIA/GAMA and Boeing requested that the FAA add an exception to Sec.  
25.841(a) to account for probable pressurization failures that could 
occur while operating at airports with elevations exceeding 15,000 
feet. When operating at such airports, a probable pressurization system 
failure could occur while the cabin pressure altitude is above 15,000 
feet, and the airplane pressurization system would not comply with 
current Sec.  25.841(a). The commenters suggested that the FAA should 
also consider the effects of probable failures of a cabin 
pressurization system during operations into or out of airports with 
elevations that exceed 15,000 feet.
    The FAA agrees with the commenters. Under normal operating 
conditions into or out of airports with elevations near 15,000 feet, 
the cabin pressure altitude is likely to be near or above 15,000 feet 
for short durations. The FAA still considers any probable failure of 
the cabin pressurization system during this timeframe to be a system 
failure, even if the airplane's cabin pressure altitude is already 
above 15,000 feet due to operation at the airport. The closer the 
airplane is to the airport, the closer the cabin pressure altitude will 
be to the airport pressure altitude. If the cabin pressure altitude 
were already above 13,000 feet while the airplane is near the high 
elevation airport, a probable cabin pressurization failure would not 
result in significant changes in cabin pressure altitude that would 
increase passenger risk of hypoxia. The FAA is therefore adding in this 
final rule an exception to Sec.  25.841(a)(1) to allow certification of 
systems despite probable cabin pressurization system failures \4\ 
resulting in cabin pressure altitudes which exceed 15,000 feet. In the 
event

[[Page 39155]]

of such failures, new Sec.  25.841(c)(1) specifies that the cabin 
pressure altitude cannot exceed either 15,000 feet or 2,000 feet above 
the airport elevation, whichever is higher. These exceptions 
accommodate operations into or out of airports with elevations near 
15,000 feet.
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    \4\ A probable failure condition is a failure condition having 
an average probability per flight hour greater than the order of 
1x10E-5.
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D. Cabin Pressure Altitudes Exceeding 8,000 Feet

    In the NPRM, the FAA proposed new Sec.  25.841(c)(1) to allow cabin 
pressure altitude during operations at high elevation airports to be 
equal to or less than the airport elevation provided the airplane is at 
or below 25,000 feet.
    AIA/GAMA, Boeing, Bombardier, and TCCA suggested removing the 
proposed restriction of this allowance to altitudes at or below 25,000 
feet, due to concerns over passenger discomfort that may result from 
the rapid changes in cabin pressure altitude that might occur with 
systems designed to meet this restriction. They noted that the 
restriction would limit design options and could inadvertently result 
in designs that employ rapid increases in cabin pressure altitude in 
excess of those typically necessary to accommodate operations into high 
elevation airports.
    The commenters cited a scenario that assumed an average airplane 
descent rate of 2,500 ft/min, which results in a descent time of 
approximately four minutes from 25,000 feet to an airport with an 
elevation of 15,000 feet. Assuming an initial cabin pressure altitude 
of 8,000 feet when the airplane descends through 25,000 feet, the 
pressurization systems would begin commanding the cabin pressure 
altitude to increase to reach the airport elevation of 15,000 feet in 
this timeframe. This results in a cabin pressure altitude ascent rate 
in excess of 1,000 ft/min. A similar cabin pressure altitude descent 
rate would be required during the climb phase after takeoff from a 
15,000-foot elevation airport.
    While this rate of cabin pressure altitude change would meet the 
FAA's objective to minimize the time the cabin pressure altitude is 
above 8,000 feet, the FAA acknowledges that rapid changes in pressure 
could cause passenger discomfort, and injury to the eardrum, if the 
pressure difference between the middle and outer ear continues to 
rapidly increase. As discussed by the commenters, typical operations 
utilize a change in cabin pressure altitude on average around 500 ft/
min. Although using a slower airplane descent or ascent rate may be a 
viable option for some high elevation airport operations, it is not 
always possible at some high elevation airports due to surrounding 
terrain, and may cause issues for air traffic control and flight 
planning.
    For these reasons, the FAA agrees with the commenters, and in this 
final rule has revised proposed Sec.  25.841(c)(1) to eliminate the 
restriction that the cabin pressure altitude may only be above 8,000 
feet while the airplane is at or below 25,000 feet, when undertaking 
operations at high elevation airports. This decision is consistent with 
ELOS determinations made by the FAA in which the proposed design 
required the flightcrew to configure the cabin pressurization system 
for high elevation airport operations while the airplane was at the top 
of descent, rather than at or below 25,000 feet.
    Conversely, three Health Sciences majors collectively expressed 
concern with increased health risks to passengers at cabin pressure 
altitudes above 8,000 feet. Another individual recommended not 
approving high elevation airport operations, and removal of airports 
over 7,500 feet for safety and to ``reduce development in these fragile 
zones.'' The group of three individuals suggested that the potential 
health risks outweigh the economic benefits to the airline industry 
from the proposed regulations. They noted that the flying public might 
not be aware of potential health issues associated with low cabin air 
pressure, and under this new rule may be less able to make fully 
informed choices about the potential risks posed to them by flying. 
They filed information concerning the health risks of high cabin 
pressure altitudes and the effects of hypoxia on primarily elderly and 
infants.
    The FAA acknowledges the possibility of increased health risks to 
some passengers exposed to cabin pressure altitudes above 8,000 feet 
for extended periods of time. However, this rulemaking is only 
applicable to airplane designs and systems seeking approval for 
operations at high elevation airports, not all airplane designs. For 
some passengers, there may be increased health risks with flight in 
general because their blood oxygen saturation may reach levels 
considered hypoxic during exposure to typical cabin pressure altitudes 
experienced during flight. The FAA has sponsored research on this 
subject \5\ to enhance the awareness of the public and medical 
communities of these risks. The FAA expects that passengers travelling 
to high elevation airports do so intentionally and accept the potential 
health risks of visiting or living at high altitude. Areas surrounding 
these high elevation airports are sufficiently inhabited that the need 
for airplane service has arisen. High elevation airports allow 
transportation to areas that may otherwise be difficult to reach. Air 
travel to these areas allows for easier transportation of not only 
people, but also supplies such as medical equipment and other cargo.
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    \5\ National Air Transportation Center of Excellence for 
Research in the Intermodal Transport Environment (RITE)/Airliner 
Cabin Environment Research (ACER) Program, Report No. RITE-ACER-CoE-
2011-1, Health Effects of Aircraft Cabin Pressure for Older and 
Vulnerable Passengers, dated November 2011, Final Report. https://www.faa.gov/data_research/research/med_humanfacs/cer/media/HealthEffectsVulnerablePassengers.pdf.
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    Since travel to these areas is necessary, the FAA is adopting, as 
proposed, the condition in Sec.  25.841(c)(2) that the system minimize 
the time that the cabin pressure altitude is above 8,000 feet. The FAA 
expects that the cabin pressurization system design will automatically 
control the cabin pressure altitude once descent into the high 
elevation airport is initiated, to ensure that the cabin pressure 
altitude is equal to the pressure altitude at the airport when the 
airplane lands. As such, the FAA expects the cabin pressure altitude to 
be above 8,000 feet for no more than 15 to 20 minutes during most high 
elevation airport operations. For example, assuming a constant airplane 
descent rate of 2,500 ft/min, a descent from 40,000 feet to an airport 
elevation of 15,000 feet would take approximately 10 minutes. Assuming 
a constant change in cabin pressure altitude of 500 ft/min, a change in 
cabin pressure altitude from 8,000 feet to 15,000 feet would take 
approximately 14 minutes. The FAA recognizes that many variables are 
associated with flights into or out of specific high elevation 
airports, so descent rates and cabin pressure altitude changes will 
vary. However, in accordance with Sec.  25.841(c)(2), the design must 
minimize the time that the cabin pressure altitude may be above 8,000 
feet during high elevation airport operations. The FAA's intent is that 
manufacturers optimize the airplane flight manual procedures and cabin 
pressurization system to minimize the time that the cabin pressure 
altitude is above 8,000 feet to safely support high elevation airport 
operations.

E. Cabin Pressure High Altitude Warning System

    Section 25.841(b)(6) requires a warning indication at the pilot or 
flight engineer station to indicate when the safe or preset pressure 
differential and cabin pressure altitude limits are exceeded. The FAA 
did not propose any changes to this section, but TCCA recommended 
clarifying it by replacing

[[Page 39156]]

``warning indication at the pilot or flight engineer station'' with 
``warning indication at the flightcrew station.'' The purpose of that 
requirement is to provide warning to the flightcrew at the appropriate 
time, not to prescribe a location within the flight deck to receive 
such a warning. Therefore in this final rule the FAA has revised Sec.  
25.841(b)(6) to require a warning indication for the flightcrew when 
the safe or preset pressure differential or cabin pressure altitude 
limit is exceeded.
    The NPRM proposed adding new Sec.  25.841(d) as an exception to 
Sec.  25.841(b)(6) to allow for changes to the threshold for activation 
of the cabin pressure high altitude warning alert from 10,000 feet, so 
that it is provided at either 15,000 feet or 2,000 feet above the 
airport elevation, whichever is greater, when the airplane is operating 
at a high elevation airport and at or below 25,000 feet. Because of 
multiple comments, the FAA has revised the structure of Sec.  25.841(d) 
from what was proposed in the NPRM. The FAA revised the introductory 
paragraph of Sec.  25.841(d), as detailed below, to accommodate the 
varied nature of the designs of cabin pressure altitude warning 
systems. The NPRM proposed in Sec.  25.841(d)(1), that if the threshold 
for activation of the cabin pressure high altitude warning is shifted 
above 10,000 feet, an alert is provided to the flightcrew. This final 
rule moved the requirement to Sec.  25.841(d)(2) and, as explained in 
more detail below, revised it to refer to an indication rather than an 
alert. In this context, the cabin pressure high altitude warning alert 
is referring to the system that provides warning to the flight crew 
that the safe or pre-set cabin pressure altitude has been exceeded. 
Section 25.841(d)(2) in this final rule requires that indication is 
provided to the flight crew when the cabin pressure high altitude 
warning alert is shifted above 10,000 feet.
    The FAA received multiple requests that the FAA not adopt the 
proposed condition that the activation altitude for the cabin pressure 
high altitude warning alert could only be raised above 10,000 feet once 
the airplane was at or below 25,000 feet. In response, the FAA has 
revised Sec.  25.841(d)(1) to include the following alternative 
conditions for when the activation altitude for the cabin pressure high 
altitude warning alert can be raised.
    As previously discussed, the NPRM proposed adding new Sec.  
25.841(d) as an exception to Sec.  25.841(b)(6). This would have 
allowed for adjustment to the cabin pressure high altitude warning 
alert to be provided at 15,000 feet, or 2,000 feet above the airport 
elevation, whichever is greater, when the airplane is operating into or 
out of a high elevation airport and at or below 25,000 feet. AIA/GAMA, 
Boeing, and TCCA requested that the FAA clarify Sec.  25.841(d) to 
explain that the cabin pressure high altitude warning alert should be 
provided at cabin pressure altitudes ``up to'' 15,000 feet or 2,000 
feet above the airport elevation. The exception proposed in the NPRM 
would have allowed for certification of a system that raised the 
activation threshold for the cabin pressure high altitude warning alert 
from the 10,000 feet in the current rule, to 15,000 feet. However, that 
proposal would not have accommodated designs where the cabin pressure 
high altitude warning alert could vary as a function of airport 
elevation and activate at some point between 10,000 and 15,000 feet. As 
described by the commenters, some cabin pressure high altitude warning 
systems are a function of the pressure altitude data entered into the 
flight computer and not an analog pressure switch. For these types of 
systems, the cabin pressure high altitude warning system may have a 
unique setting that varies as a function of pressure altitude rather 
than a simple step up from 10,000 feet to 15,000 feet. The FAA does not 
intend for applicants to change the cabin pressure high altitude 
warning system unless it is necessary to prevent nuisance warnings 
during operations into or out of high elevation airports. As a result, 
in this final rule Sec.  25.841(d) allows the cabin pressure high 
altitude warning alert to be triggered at elevations ``up to'' 15,000 
feet or 2,000 feet above the airplane's maximum takeoff and landing 
altitude, whichever is greater, when operating into or out of a high 
elevation airport.
    AIA/GAMA and Boeing also requested that the FAA revise Sec.  
25.841(d) to allow the cabin pressure high altitude warning alert to 
activate at up to 15,000 feet or within 2,000 feet of the airplane's 
maximum takeoff and landing altitude during high elevation airport 
operations, rather than 2,000 feet above the airport elevation. For 
example, high elevation airports in Tibet have a maximum pressure 
altitude of approximately 15,400 feet; therefore, an airplane operating 
into this area would need to have a cabin pressure high altitude 
warning alert activated before the cabin pressure altitude reaches 
17,400 feet to avoid a nuisance warning. If the same airplane were used 
for operations into an airport with an elevation of 14,000 feet, the 
cabin pressure high altitude warning alert would need to be provided 
before the cabin pressure altitude reached 16,000 feet. As such, the 
rule proposed in the NPRM would require either a system specifically 
designed for each airport, or a system that could change the cabin 
pressure high altitude warning alert as a function of the pressure 
altitude at the airport. The commenters also noted that there is still 
a large portion of the airplane fleet which utilizes an analog pressure 
switch to activate the cabin pressure altitude warning alert, and 
therefore implementing a variable system is either not possible or 
would be extremely costly to implement for derivative airplane models.
    The FAA agrees with the commenters and revised Sec.  25.841(d) to 
state that when operating into or out of airports with elevations 
exceeding 8,000 feet, the cabin pressure altitude warning alert may be 
provided up to 15,000 feet, or 2,000 feet above the airplane's maximum 
takeoff and landing altitude, whichever is greater. For reference, the 
maximum takeoff and landing altitude is defined in the applicable 
flight manual as an operational limitation of the airplane. This change 
to the final rule will accommodate various designs of the cabin 
pressure altitude warning system and prevent unnecessary warning alerts 
while still including provisions intended to maintain an acceptable 
level of safety during operations into and out of high altitude 
airports. The provision in Sec.  25.841(d)(1) is intended to minimize 
the time that the cabin pressure altitude is above 8,000 feet as well 
as minimize the time that the cabin altitude warning alert for the 
flight crew is shifted above 10,000 feet. Section 25.841(d)(2) requires 
indication to the flight crew that the altitude for the cabin pressure 
altitude warning system alert has been changed for high altitude 
operations. Section 25.841(d)(3) requires one of two different methods 
intended to protect the flight crew from the effects of hypoxia during 
high altitude airport operations. The first option requires an 
additional alert to notify the flight crew when to don oxygen in 
accordance with their applicable operating regulations. Such a system, 
if installed, provides the same intended function as the cabin altitude 
warning alert. The second option is to have approved procedures in the 
airplane flight manual that would require at least one pilot to don 
oxygen when the cabin pressure altitude warning alert is shifted for 
high altitude operations. Such provisions are consistent with 
previously issued ELOS determinations depending on the specific 
aircraft design that was being considered.

[[Page 39157]]

    As previously discussed, the FAA is not adopting the condition, 
originally proposed for Sec.  25.841(c)(1), that the cabin pressure 
altitude of the airplane may only be above 8,000 feet during operations 
into or out of high elevation airports while the airplane is at or 
below 25,000 feet. In the NPRM, the FAA also proposed Sec.  25.841(d), 
which would have allowed the cabin pressure high altitude warning alert 
to be activated at cabin pressure altitudes above 10,000 feet during 
high elevation airport operations provided the airplane was at or below 
25,000 feet. AIA/GAMA, Boeing, and TCCA suggested raising or 
eliminating the 25,000 foot operating condition on the increased 
activation altitude for the cabin pressure high altitude warning alert 
when the cabin pressurization system is configured either automatically 
or by the flightcrew for high elevation airport operations, to avoid 
potential nuisance alerts during descent. The FAA agrees with the 
commenters. When the cabin pressurization system is configured for high 
elevation airport operations, either manually by the flightcrew or 
automatically as dictated by the design, during descent the cabin 
pressure altitude may reach 10,000 feet before the airplane passes 
25,000 feet. Such a condition may unnecessarily activate the cabin 
pressure high altitude warning alert certified to existing regulations. 
In this final rule, the FAA has therefore revised Sec.  25.841(d) to 
remove the condition that the activation altitude for the cabin 
pressure high altitude warning alert could only exceed 10,000 feet 
while the airplane was at or below 25,000 feet.
    In addition, in this final rule, the FAA adds Sec.  25.841(d)(1) to 
require that during landing, the activation altitude for the cabin 
pressure high altitude warning alert may not be changed to exceed 
10,000 feet before the start of descent into the high elevation 
airport. Following takeoff from a high elevation airport, the cabin 
pressure altitude warning must be reset to 10,000 feet, either 
automatically or manually by the flightcrew, before beginning cruise 
operation. Both requirements ensure that the cabin pressure high 
altitude warning alert remains at 10,000 feet during cruise while 
allowing operational flexibility during climb out of and descent into 
high elevation airports. This is consistent with ELOS determinations 
that the FAA has made, approving systems for which the cabin pressure 
high altitude warning alert is changed to exceed 10,000 feet for high 
elevation airport operations once the aircraft enters descent, rather 
than below 25,000 feet.
    AIA/GAMA and Boeing also requested that the FAA revise the 
condition requiring a flightcrew alert that the activation altitude for 
the cabin pressure high altitude warning has shifted to above 10,000 
feet in proposed Sec.  25.841(d)(1) to refer to an ``indication'' 
system instead of an ``alert'' system. As described in the preamble for 
Sec.  25.1322, amendment 25-131 (75 FR 67209, November 2, 2010) (Sec.  
25.1322), the word ``alert'' describes a flight deck indication meant 
to attract the attention of the flightcrew and identify a non-normal 
operational or airplane system condition. For high elevation airport 
operations, the alert originally proposed in Sec.  25.841(d)(1) was for 
a normal operating condition, not for a non-normal condition. Thus, 
requiring that an alert be provided for a normal operating condition is 
not appropriate.
    The FAA agrees with the commenters, and this final rule revises 
Sec.  25.841(d) to refer to an indication system rather than an alert 
system. Revised Sec.  25.841(d)(2) requires an indication to be 
provided to the flightcrew that the activation altitude for the cabin 
pressure high altitude warning alert has shifted above 10,000 feet 
cabin pressure altitude. The FAA considers the required indication to 
be in support of normal operations and flightcrew action may not 
necessarily be required. However, depending on which certification 
method in Sec.  25.841(d)(3) the applicant follows, flight procedures 
may still require the pilot to don oxygen when the indication denotes 
that the cabin pressure high altitude warning has shifted above 10,000 
feet cabin pressure altitude.
    In the NPRM, the FAA proposed that Sec.  25.841(d)(2) require that 
if the system shifts the cabin pressure high altitude warning above 
10,000 feet automatically, it must also alert the flightcrew to take 
action should the automatic shift function fail. AIA/GAMA, Boeing, and 
Bombardier suggested removal of this additional alert. The commenters 
suggested that such an alert is unnecessary and the need to provide 
crew alerts is already addressed through compliance with Sec. Sec.  
25.1309(c) and 25.1322.
    The FAA agrees with the commenters. For any system that an 
applicant proposes to reconfigure for high elevation airport 
operations, Sec.  25.1309 would be applicable and require the applicant 
to conduct a hazard analysis that includes system failure. The FAA is 
not adopting the proposal that Sec.  25.841(d)(2) require an additional 
alert to the flightcrew. An additional alert may or may not be 
necessary depending on the hazard analysis that must still be conducted 
in accordance with Sec.  25.1309.

F. Automatic Presentation of Oxygen Masks

    The NPRM proposed adding Sec.  25.1447(c)(5) as an exception to 
Sec.  25.1447(c)(1) to allow approval of passenger cabin oxygen 
dispensing units that are automatically presented at 15,000 feet or 
within 2,000 feet of the airport elevation, whichever is higher, 
provided the airplane is being operated at altitudes at or below 25,000 
feet. This change was meant to relieve applicants and the FAA from the 
burden of preparing and processing exemptions from the passenger oxygen 
mask automatic presentation altitude requirement in Sec.  
25.1447(c)(1). During operations into some high elevation airports, 
increasing the cabin pressure altitude at which passenger cabin oxygen 
dispensing units are automatically presented is required in order to 
avoid unnecessary presentations.
    AIA/GAMA and Boeing requested that new Sec.  25.1447(c)(5) allow 
automatic oxygen mask presentations at up to 15,000 feet or within 
2,000 feet of the airplane's maximum takeoff and landing altitude, 
rather than within 2,000 feet of the airport elevation. They noted that 
many in-production airplanes, which an applicant may seek to certify 
for operation at high elevation airports, utilize an analog pressure 
switch to automatically deploy the oxygen masks. Implementing a 
variable system is either not possible or would be extremely costly to 
implement on airplanes with this type of design, according to the 
commenters. AIA/GAMA, Boeing, and Bombardier commented that the 
proposed rule would have required either an automatic oxygen mask 
presentation system unique for each airport, or a system that would 
automatically change the oxygen mask presentation altitude as a 
function of the airport elevation. In addition, landing at a high 
elevation airport, which is below the airplane's maximum certified 
takeoff and landing altitude, will have a negligible difference between 
when masks might be automatically presented due to a sudden loss of 
cabin pressure, and when the airplane lands. The FAA agrees with the 
commenters, and Sec.  25.1447(c)(5) allows automatic oxygen mask 
presentations at up to 15,000 feet or within 2,000 feet of the 
airplane's maximum takeoff and landing altitude, to accommodate the 
variation in design and potential unnecessary presentation of the 
oxygen masks.

[[Page 39158]]

    In addition, AIA/GAMA and Boeing suggested that the FAA not adopt 
the requirement proposed in the NPRM that the passenger oxygen mask 
presentation altitude could only be reset during high elevation 
operations when the airplane is below 25,000 feet. As discussed by the 
commenters, not allowing the flightcrew to reset the oxygen mask 
presentation altitude until the airplane is below 25,000 feet creates 
additional crew workload, which could be avoided if the airplane is 
allowed to be configured at the top of descent. Reduction in crew 
workload during the critical descent phase allows the crew to focus on 
other tasks. The FAA agrees with the commenters and Sec.  25.1447(c)(5) 
omits the condition proposed in the NPRM that the oxygen mask 
presentation altitude only be revised when the airplane is at or below 
25,000 feet.
    In the discussion of Sec.  25.1447(c)(5) in the NPRM, the FAA 
proposed raising the automatic presentation altitude for passenger 
oxygen masks during operations into all airports above 8,000 feet. 
However, the intent of this rulemaking, in part, is to eliminate the 
need for processing exemptions to Sec.  25.1447(c)(1) to avoid nuisance 
oxygen mask presentations while operating at airports with elevations 
that would otherwise cause oxygen mask presentations. When operating 
into airports with elevations at or below 13,000 feet, the automatic 
presentation altitude for the oxygen masks could still be below 15,000 
feet, the required presentation altitude in Sec.  25.1447(c)(1), and 
avoid inadvertent oxygen mask presentations. As a result, the FAA has 
not granted exemptions to the automatic oxygen mask presentation 
requirements in Sec.  25.1447(c)(1) for airplanes proposed to be 
approved for operations at airports with elevations at or below 13,000 
feet. As a result of all related comments, Sec.  25.1447(c)(5), as 
adopted in this final rule, states that when operating into or out of 
airports with elevations above 13,000 feet, the dispensing units 
providing the required oxygen flow must be automatically presented to 
the occupants within 2,000 feet of the airplane's maximum takeoff and 
landing altitude.
    In addition, an individual commenter described various operational 
considerations that should be made by operators when operating into 
high elevation airports, such as the potential need to provide oxygen 
to passengers that may need it while the airplane is on the ground or 
when cabin pressure altitudes are above 8,000 feet. The FAA agrees that 
there are many operational issues to consider when operating into and 
out of high elevation airports. However, this rulemaking is limited to 
approval of new airplane type designs with cabin pressurization systems 
and oxygen systems intended for operations into and out of high 
elevation airports. Operational considerations are outside the scope of 
this rulemaking activity.
    The FAA also received comments to revise specific preamble text of 
the NPRM. The specific preamble text from the NPRM is not restated in 
this final rule, so specific editorial suggestions to the preamble text 
of the NPRM are not applicable. No changes were made to this final rule 
in this regard.

IV. Regulatory Notices and Analyses

A. Regulatory Evaluation

    Changes to Federal regulations must undergo several economic 
analyses. First, Executive Order 12866 and Executive Order 13563, as 
amended by Executive Order 14094 (``Modernizing Regulatory Review''), 
direct that each Federal agency shall adopt a regulation only upon a 
reasoned determination that the benefits of the intended regulation 
justify its costs. Second, the Regulatory Flexibility Act of 1980 (Pub. 
L. 96-354) requires agencies to analyze the economic impact of 
regulatory changes on small entities. Third, the Trade Agreements Act 
(Pub. L. 96-39) prohibits agencies from setting standards that create 
unnecessary obstacles to the foreign commerce of the United States. In 
developing U.S. standards, the Trade Act requires agencies to consider 
international standards and, where appropriate, that they be the basis 
of U.S. standards. Fourth, the Unfunded Mandates Reform Act of 1995 
(Pub. L. 104-4) requires agencies to prepare a written assessment of 
the costs, benefits, and other effects of proposed or final rules that 
include a Federal mandate that may result in the expenditure by State, 
local, and tribal governments, in the aggregate, or by the private 
sector, of $100 million or more (adjusted annually for inflation) in 
any one year. The current threshold after adjustment for inflation is 
$177 million using the most current (2022) Implicit Price Deflator for 
the Gross Domestic Product. This portion of the preamble summarizes the 
FAA's analysis of the economic impacts of this final rule.
    In conducting these analyses, FAA has determined that this final 
rule (1) has benefits that justify its costs; (2) is not an 
economically ``significant regulatory action'' as defined in section 
3(f) of Executive Order 12866, as amended; (3) will not have a 
significant economic impact on a substantial number of small entities; 
(4) will not create unnecessary obstacles to the foreign commerce of 
the United States; and (5) will not impose an unfunded mandate on 
state, local, or tribal governments, or on the private sector by 
exceeding the threshold identified previously. These analyses are 
summarized below.
    Currently, the FAA processes ELOS memorandums to document ELOS 
findings when an airplane manufacturer or modifier requests 
certification of airplane cabin pressurization systems used for 
operations into or out of airports with elevations at or above 8,000 
feet. The FAA also processes exemptions to the automatic oxygen mask 
presentation requirements for operations into or out of airports with 
elevations at or above 13,000 feet. The final rule will eliminate the 
need to continue performing the administrative tasks and analyses 
associated with the processing of an ELOS or exemption to accommodate 
operations at high elevation airports for transport category airplanes 
without compromising safety.
    This final rule will result in small quantifiable cost savings. The 
FAA issues on average four ELOS findings and two exemptions per year 
related to high elevation airports, devoting between 20 to 100 
engineering hours for each ELOS or exemption processed. The FAA 
estimates industry organizations seeking certification expend the same 
range of engineering hours for each ELOS and exemption processed. Using 
the loaded wage rate of $83.86 for aerospace engineer,\6\ the FAA 
estimates the total annual cost savings of this final rule could range 
from $20,126 to $100,632 for both industry and FAA.
---------------------------------------------------------------------------

    \6\ $59.12 is the average wage salary cost for aerospace 
engineer, which accounts 70.5% of employer costs; and $24.74 or 
29.5% is the fringe benefits. https://www.bls.gov/news.release/pdf/ecec.pdf (accessed on 12/20/22).
---------------------------------------------------------------------------

    As a result, this rulemaking will reduce the cost of airplane 
certification without reducing the current level of safety. The 
expected outcome will be a minimal economic impact resulting in a small 
regulatory burden relief. The FAA requested comments with supporting 
justification about the FAA determination of minimal economic impact. 
No such comments were received. Therefore, the FAA has determined that 
this final rule is not a ``significant regulatory action'' as defined 
in section 3(f) of Executive Order 12866, as amended, and is not 
``significant'' as defined in DOT's Regulatory Policies and Procedures.

B. Regulatory Flexibility Determination

    The Regulatory Flexibility Act of 1980 (Pub. L. 96-354) (RFA) 
establishes ``as a

[[Page 39159]]

principle of regulatory issuance that agencies shall endeavor, 
consistent with the objectives of the rule and of applicable statutes, 
to fit regulatory and informational requirements to the scale of the 
businesses, organizations, and governmental jurisdictions subject to 
regulation.'' To achieve this principle, agencies are required to 
solicit and consider flexible regulatory proposals and to explain the 
rationale for their actions to assure that such proposals are given 
serious consideration. The RFA covers a wide range of small entities, 
including small businesses, and not-for-profit organizations.
    Agencies must perform a review to determine whether a rule will 
have a significant economic impact on a substantial number of small 
entities. If the agency determines that it will, the agency must 
prepare a regulatory flexibility analysis as described in the RFA. 
However, if an agency determines that a rule is not expected to have a 
significant economic impact on a substantial number of small entities, 
section 605(b) of the RFA provides that the head of the agency may so 
certify and a regulatory flexibility analysis is not required. The 
certification must include a statement providing the factual basis for 
this determination, and the reasoning should be clear.
    The final rule relieves the industry from requesting that the FAA 
make a determination that an ELOS exists for certification of airplane 
cabin pressurization systems used for operations into or out of 
airports with elevations at or above 8,000 feet above sea level. This 
final rule also relieves industry from petitioning for exemptions to 
the automatic oxygen mask presentation requirements for operations into 
and out of airports with elevations above 13,000 feet above sea level. 
This expected outcome will be a minimal economic impact with small 
burden relief and savings for any small entity affected by this 
rulemaking action.
    If an agency determines that a rulemaking will not result in a 
significant economic impact on a substantial number of small entities, 
the head of the agency may so certify under section 605(b) of the RFA. 
Therefore, as provided in section 605(b), the head of the FAA certifies 
that this final rulemaking will not result in a significant economic 
impact on a substantial number of small entities.

C. International Trade Impact Assessment

    The Trade Agreements Act of 1979 (Pub. L. 96-39) prohibits Federal 
agencies from establishing standards or engaging in related activities 
that create unnecessary obstacles to the foreign commerce of the United 
States. Pursuant to these Act, the establishment of standards is not 
considered an unnecessary obstacle to the foreign commerce of the 
United States, so long as the standard has a legitimate domestic 
objective, such as the protection of safety, and does not operate in a 
manner that excludes imports that meet this objective. The statute also 
requires consideration of international standards and, where 
appropriate, that they be the basis for U.S. standards. The FAA has 
assessed the effect of this final rule and determined that its purpose 
is to protect the safety of U.S. civil aviation. Therefore, the final 
rule is in compliance with the Trade Agreements Act.

D. Unfunded Mandates Assessment

    Title II of the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-
4) requires each Federal agency to prepare a written statement 
assessing the effects of any Federal mandate in a final agency rule 
that may result in an expenditure of $100 million or more (adjusted 
annually for inflation) in any one year. The current threshold after 
adjustment for inflation is $177 million using the most current (2022) 
Implicit Price Deflator for the Gross Domestic Product. This final rule 
does not contain such a mandate; therefore, the requirements of Title 
II of the Act do not apply.

E. Paperwork Reduction Act

    The Paperwork Reduction Act of 1995 (44 U.S.C. 3507(d)) requires 
that the FAA consider the impact of paperwork and other information 
collection burdens imposed on the public. The FAA has determined that 
there is no new requirement for information collection associated with 
this final rule.

F. International Cooperation

    (1) In keeping with U.S. obligations under the Convention on 
International Civil Aviation, it is FAA's policy to conform to 
International Civil Aviation Organization (ICAO) Standards and 
Recommended Practices to the maximum extent practicable. The FAA has 
reviewed the corresponding ICAO Standards and Recommended Practices and 
has found no differences with these final regulations.
    (2) European Union Aviation Safety Agency (EASA) certification 
requirements related to oxygen dispensing units in CS 25.1447(c)(1) are 
similar to those in Sec.  25.1447(c)(1). In amendment 18 of 
Certification Specifications and Acceptable Means of Compliance for 
Large Aeroplanes, CS-25,\7\ the EASA describes an acceptable means of 
compliance (AMC) in AMC 25.1447(c)(1). Specifically, AMC 25.1447(c)(1) 
states: ``The design of the automatic presentation system should take 
into account that when the landing field altitude is less than 610 m 
(2,000 feet) below the normal preset automatic presentation altitude, 
the automatic presentation altitude may be reset to landing field 
altitude plus 610 m (2,000 feet).'' Thus, the FAA's change to Sec.  
25.1447 is consistent with guidance provided by EASA.
---------------------------------------------------------------------------

    \7\ Amendment 18 of European Aviation Safety Agency, 
``Certification Specifications and Acceptable Means of Compliance 
for Large Aeroplanes,'' CS-25, dated June 22, 2016, can be found at 
this web address: https://www.easa.europa.eu/document-library/certification-specifications/cs-25-amendment-18.
---------------------------------------------------------------------------

    (3) EASA has not published advisory material to accommodate 
operations into or out of high elevation airports in consideration of 
the cabin pressure altitude and warning requirements in CS 25.841.

G. Environmental Analysis

    FAA Order 1050.1F, ``Environmental Impacts: Policies and 
Procedures,'' identifies FAA actions that are categorically excluded 
from preparation of an environmental assessment or environmental impact 
statement under the National Environmental Policy Act in the absence of 
extraordinary circumstances. The FAA has determined this rulemaking 
action qualifies for the categorical exclusion identified in paragraph 
5-6.6 of Order 1050.1F and involves no extraordinary circumstances.

V. Executive Order Determinations

A. Executive Order 13132, Federalism

    The FAA has analyzed this final rule under the principles and 
criteria of Executive Order 13132, ``Federalism.'' The agency 
determined that this action will not have a substantial direct effect 
on the States, or the relationship between the Federal Government and 
the States, or on the distribution of power and responsibilities among 
the various levels of government, and, therefore, does not have 
federalism implications.

B. Executive Order 13175, Consultation and Coordination With Indian 
Tribal Governments

    Consistent with Executive Order 13175, Consultation and 
Coordination with Indian Tribal Governments,\8\ and

[[Page 39160]]

FAA Order 1210.20, American Indian and Alaska Native Tribal 
Consultation Policy and Procedures,\9\ the FAA ensures that Federally 
Recognized Tribes (Tribes) are given the opportunity to provide 
meaningful and timely input regarding proposed Federal actions that 
have the potential to affect uniquely or significantly their respective 
Tribes. At this point, the FAA has not identified any unique or 
significant effects, environmental or otherwise, on tribes resulting 
from this proposed rule.
---------------------------------------------------------------------------

    \8\ 65 FR 67249 (Nov. 6, 2000).
    \9\ FAA Order No. 1210.20 (Jan. 28, 2004), available at https://www.faa.gov/documentLibrary/media/1210.pdf.
---------------------------------------------------------------------------

C. Executive Order 13211, Regulations That Significantly Affect Energy 
Supply, Distribution, or Use

    The FAA analyzed this final rule under Executive Order 13211, 
Actions Concerning Regulations that Significantly Affect Energy Supply, 
Distribution, or Use (May 18, 2001). The agency has determined that it 
is not a ``significant energy action'' under the Executive order and it 
is not likely to have a significant adverse effect on the supply, 
distribution, or use of energy.

D. Executive Order 13609, International Cooperation

    Executive Order 13609, Promoting International Regulatory 
Cooperation, promotes international regulatory cooperation to meet 
shared challenges involving health, safety, labor, security, 
environmental, and other issues and to reduce, eliminate, or prevent 
unnecessary differences in regulatory requirements. The FAA has 
analyzed this action under the policies and agency responsibilities of 
Executive Order 13609, and has determined that this action will not 
effect on international regulatory cooperation.

VI. How To Obtain Additional Information

A. Rulemaking Documents

    An electronic copy of a rulemaking document may be obtained by 
using the internet--
    1. Search the Federal eRulemaking Portal (www.regulations.gov);
    2. Visit the FAA's Regulations and Policies web page at 
www.faa.gov/regulations_policies/; or
    3. Access the Government Printing Office's web page at 
www.GovInfo.gov.
    Copies may also be obtained by sending a request (identified by 
notice, amendment, or docket number of this rulemaking) to the Federal 
Aviation Administration, Office of Rulemaking, ARM-1, 800 Independence 
Avenue SW, Washington, DC 20591, or by calling (202) 267-9680.

B. Comments Submitted to the Docket

    Comments received may be viewed by going to https://www.regulations.gov and following the online instructions to search the 
docket number for this action. Anyone is able to search the electronic 
form of all comments received into any of the FAA's dockets by the name 
of the individual submitting the comment (or signing the comment, if 
submitted on behalf of an association, business, labor union, etc.).

C. Small Business Regulatory Enforcement Fairness Act

    The Small Business Regulatory Enforcement Fairness Act (SBREFA) of 
1996 requires FAA to comply with small entity requests for information 
or advice about compliance with statutes and regulations within its 
jurisdiction. A small entity with questions regarding this document, 
may contact its local FAA official, or the person listed under the FOR 
FURTHER INFORMATION CONTACT heading at the beginning of the preamble. 
To find out more about SBREFA on the internet, visit https://www.faa.gov/regulations_policies/rulemaking/sbre_act/.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Navigation (air), Reporting and 
recordkeeping requirements.

The Amendments

    In consideration of the foregoing, the Federal Aviation 
Administration amends 14 CFR part 25 as follows:

PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES

0
1. The authority citation for part 25 continues to read as follows:

    Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701, 44702 and 
44704.


0
2. Amend Sec.  25.841 by revising paragraphs (a) introductory text, 
(a)(1), and (b)(6) and adding paragraphs (c) and (d) to read as 
follows:


Sec.  25.841  Pressurized cabins.

    (a) Except as provided in paragraph (c) of this section, 
pressurized cabins and compartments to be occupied must be equipped to 
provide a cabin pressure altitude of not more than 8,000 feet under 
normal operating conditions.
    (1) If certification for operation above 25,000 feet is requested, 
the airplane must be designed so that occupants will not be exposed to 
cabin pressure altitudes in excess of 15,000 feet after any probable 
failure condition in the pressurization system except as provided in 
paragraph (c) of this section.
* * * * *
    (b) * * *
    (6) Warning indication to the flightcrew when the safe or preset 
pressure differential or cabin pressure altitude limit is exceeded. 
Appropriate warning markings on the cabin pressure differential 
indicator meet the warning requirement for pressure differential 
limits. An alert meets the warning requirement for cabin pressure 
altitude limits if it warns the flightcrew when the cabin pressure 
altitude exceeds 10,000 feet, except as provided in paragraph (d) of 
this section.
* * * * *
    (c) When operating into or out of airports with elevations at or 
above 8,000 feet, the cabin pressure altitude in pressurized cabins and 
occupied compartments may be up to, or greater than, the airport 
elevation by 2,000 feet, provided--
    (1) In the event of probable failure conditions of the cabin 
pressurization system, the cabin pressure altitude must not exceed 
15,000 feet, or 2,000 feet above the airport elevation, whichever is 
higher; and
    (2) The cabin pressurization system is designed to minimize the 
time in flight that occupants may be exposed to cabin pressure 
altitudes exceeding 8,000 feet.
    (d) When operating into or out of airports with elevations at or 
above 8,000 feet, the cabin pressure high altitude warning alert may be 
provided at up to 15,000 feet, or 2,000 feet above the airplane's 
maximum takeoff and landing altitude, whichever is greater, provided:
    (1) During landing, the change in cabin pressure high altitude 
warning alert may not occur before the start of descent into the high 
elevation airport and, following takeoff, the cabin pressure high 
altitude warning alert must be reset to 10,000 feet before beginning 
cruise operation;
    (2) Indication is provided to the flightcrew that the cabin 
pressure high altitude warning alert has shifted above 10,000 feet 
cabin pressure altitude; and
    (3) Either an alerting system is installed that notifies the 
flightcrew members on flight deck duty when to don oxygen in accordance 
with the applicable operating regulations, or a limitation is provided 
in the airplane flight manual that requires the pilot flying the 
airplane to don oxygen when the cabin pressure altitude warning has 
shifted above 10,000 feet, and requires other flightcrew members on 
flight deck

[[Page 39161]]

duty to monitor the cabin pressure and utilize oxygen in accordance 
with the applicable operating regulations.


0
3. Amend Sec.  25.1447 by revising paragraph (c)(1) and adding 
paragraph (c)(5) to read as follows:


Sec.  25.1447  Equipment standards for oxygen dispensing units.

* * * * *
    (c) * * *
    (1) There must be an oxygen dispensing unit connected to oxygen 
supply terminals immediately available to each occupant wherever 
seated, and at least two oxygen dispensing units connected to oxygen 
terminals in each lavatory. The total number of dispensing units and 
outlets in the cabin must exceed the number of seats by at least 10 
percent. The extra units must be as uniformly distributed throughout 
the cabin as practicable. Except as provided in paragraph (c)(5) of 
this section, if certification for operation above 30,000 feet is 
requested, the dispensing units providing the required oxygen flow must 
be automatically presented to the occupants before the cabin pressure 
altitude exceeds 15,000 feet. The crewmembers must be provided with a 
manual means of making the dispensing units immediately available in 
the event of failure of the automatic system.
* * * * *
    (5) When operating into or out of airports with elevations above 
13,000 feet, the dispensing units providing the required oxygen flow 
must be automatically presented to the occupants at cabin pressure 
altitudes no higher than 2,000 feet above the airplane's maximum 
takeoff and landing altitude.

    Issued under authority provided by 49 U.S.C. 106(f), 44701(a), 
and 44703 in Washington, DC.
Billy Nolen,
Acting Administrator.
[FR Doc. 2023-12454 Filed 6-14-23; 8:45 am]
BILLING CODE 4910-13-P