Noise Certification of Supersonic Airplanes, 20431-20447 [2020-07039]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 85, Number 71 (Monday, April 13, 2020)]
[Proposed Rules]
[Pages 20431-20447]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-07039]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 21 and 36

[Docket No.: FAA-2020-0316; Notice No. 20-06]
RIN 2120-AL29


Noise Certification of Supersonic Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This action proposes to add new supersonic airplanes to the 
applicability of noise certification regulations, and proposes landing 
and takeoff noise standards for a certain class of new supersonic 
airplanes. There is renewed interest in the development of supersonic 
aircraft, and the proposed regulations would facilitate the continued 
development of airplanes by specifying the noise limits for the 
designs, providing the means to certificate the airplanes for subsonic 
operation in the United States.

DATES: Send comments on or before July 13, 2020.

ADDRESSES: Send comments identified by docket number FAA-2020-0316 
using any of the following methods:
     Federal eRulemaking Portal: Go to https://www.regulations.gov and follow the online instructions for sending your 
comments electronically.
     Mail: Send comments to Docket Operations, M-30; U.S. 
Department of Transportation (DOT), 1200 New Jersey Avenue SE, Room 
W12-140, West Building Ground Floor, Washington, DC 20590-0001.
     Hand Delivery or Courier: Take comments to Docket 
Operations in Room W12-140 of the West Building Ground Floor at 1200 
New Jersey Avenue SE, Washington, DC, between 9 a.m. and 5 p.m., Monday 
through Friday, except Federal holidays.
     Fax: Fax comments to Docket Operations at 202-493-2251.
    Privacy: In accordance with 5 U.S.C. 553(c), DOT solicits comments 
from the public to better inform its rulemaking process. DOT posts 
these comments, without edit, including any personal information the 
commenter provides, to https://www.regulations.gov, as described in the 
system of records notice (DOT/ALL-14 FDMS), which can be reviewed at 
https://www.dot.gov/privacy.
    Docket: Background documents or comments received may be read at 
https://www.regulations.gov at any time. Follow the online instructions 
for accessing the docket or go to Docket Operations in Room W12-140 of 
the West Building Ground Floor at 1200 New Jersey Avenue SE, 
Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, 
except Federal holidays. If you are submitting confidential business 
information as part of a comment, please consult section VI. A. of this 
document for the proper submission procedure.

FOR FURTHER INFORMATION CONTACT: For technical questions concerning 
this action, contact Sandy R. Liu, Office of Policy, International 
Affairs, & Environment, Noise Division (AEE-100), Federal Aviation 
Administration, 800 Independence Avenue SW, Washington, DC 20591; 
telephone 202-267-4748; email [email protected].

SUPPLEMENTARY INFORMATION: 

I. Executive Summary

    Current noise certification regulations do not include standards 
for supersonic airplanes other than the Concorde. In its 2018 
reauthorization,\1\ the FAA was directed to exercise leadership in the 
creation of Federal and international policies, regulations, and 
standards relating to the certification and the safe and efficient 
operation of civil supersonic aircraft. This rulemaking is a step in 
that process. The agency is proposing to amend the noise certification 
regulations in Title 14, Code of Federal Regulations (14 CFR) parts 21 
and 36 to provide for new supersonic airplanes, and to add subsonic 
landing and takeoff (LTO) cycle standards for supersonic airplanes that 
have a maximum takeoff weight no greater than 150,000 pounds and a 
maximum operating cruise speed up to Mach 1.8. This proposal is based 
in part on the Supersonic Transport Concept Airplane (STCA) studies 
performed by the National Aeronautics and Space Administration (NASA), 
information provided to the FAA by U.S. industry, and the continuing 
work of the International Civil Aviation Organization (ICAO) Committee 
on Aviation Environmental Protection (CAEP). These proposed 
certification standards would provide a means to certificate these 
airplanes for noise for subsonic operation domestically, but would not 
affect the prohibition in 14 CFR 91.817 on the creation of sonic booms 
(i.e., supersonic operations over land in the United States would 
remain prohibited).
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    \1\ Section 181, Public Law 115-254, FAA Reauthorization Act of 
2018 (October 5, 2018).
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    This proposed rule would (1) amend the applicability of part 36 to 
include new supersonic airplanes for which type certification is 
requested after a final rule takes effect, (2) revise the definition of 
supersonic airplane to include newly certificated airplanes but exclude 
the Concorde,\2\ (3) provide noise certification reference procedures 
to be used for all supersonic airplanes, and (4) establish noise limits 
for takeoff and landing that would apply to Supersonic Level 1 (SSL1) 
airplanes, as defined in the proposed regulation. The proposed 
standards include noise limits that are quieter than the Stage 4 limits 
at which most of the current subsonic jet fleet operates, though louder 
than the current certification level of Stage 5 for the same aircraft 
weights. The proposed standards would allow Variable Noise Reduction 
Systems (VNRS) to be used for noise certification testing, and if used 
for certification, would require the system to be activated during 
normal operations.
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    \2\ The Concorde type certificate remains valid, even though 
none are currently operating. The certification regulations in part 
36 that apply to the Concorde are limited to the Concorde model and 
need to remain in place. The FAA seeks to segregate the Concorde as 
a historical matter to prevent any confusion; the certification 
regulations proposed here would apply only to new supersonic 
airplanes. None of the proposed certification regulations affect the 
Concorde operating regulations already in place.
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II. Authority

    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 44715, Controlling aircraft 
noise and

[[Page 20432]]

sonic boom. Under that section, the FAA is charged with prescribing 
regulations to measure and abate aircraft noise. This rulemaking is 
also promulgated under the authority of Section 181 of the FAA 
Reauthorization Act of 2018, Public Law 115-254, which directs the FAA 
Administrator to exercise leadership in the creation of Federal 
policies, regulations, and standards related to the certification of 
and to the safe and efficient operation of civil supersonic aircraft. 
This regulation is within the scope of those authorities because it 
provides for the applicability of the regulations to a new class of 
supersonic airplanes, and sets the noise limits described in Sec.  
44715(a)(3) that are required to be in place before the FAA may issue a 
new type certificate.

III. Background

    Current noise certification regulations do not include standards 
for supersonic airplanes other than the Concorde. In 1978, the FAA 
promulgated its first rule addressing civil supersonic aircraft noise, 
establishing takeoff and landing noise standards in 14 CFR part 36 
specific to the Concorde airplane.\3\ That rule did ``not establish 
certification noise limits for future design [supersonic aircraft] 
since the technological feasibility of such standards is at present 
unknown.'' \4\ In addition, the FAA established operational noise 
limits applicable to civil supersonic airplanes.
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    \3\ Noise and Sonic Boom Requirements, 43 FR 28406 (Jun. 29, 
1978).
    \4\ Id.
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    However, the FAA anticipated that there would be future supersonic 
aircraft designs that could be economically viable and environmentally 
acceptable. In 1978, such an idea was only theoretical, but it was 
known that major advancements would need to be made. These advancements 
included improvements to noise reduction features, flexible performance 
requirements, and environmental acceptability.
    As technology continued to advance, the FAA expressed interest in 
amending its regulations to account for the development of supersonic 
aircraft other than the Concorde. In 1986, the FAA published an advance 
notice of proposed rulemaking (ANPRM) addressing the possibility of 
amending parts 36 and 91 to provide for noise type certification and 
civil operation of newer supersonic aircraft.\5\ The FAA subsequently 
published an NPRM in 1990 that would have required future supersonic 
aircraft to meet Stage 3 noise limits, which were then the maximum 
noise limits for subsonic airplanes.\6\ In 1994, the FAA withdrew the 
NPRM, stating that further research was necessary before developing a 
final rule.\7\
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    \5\ 51 FR 39663 (Oct. 30, 1986).
    \6\ Aircraft noise limits have varied over time from Stage 1 in 
the 1970s to current Stage 5 certification limits.
    \7\ Withdrawal: 59 FR 39711 (August 4, 1994).
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    In February 2018, the FAA Office of the Chief Counsel published an 
interpretation that addressed 14 CFR part 36, and whether it would 
apply to an application for type certification of a new supersonic 
airplane. The interpretation concluded that part 36 applies only to 
subsonic aircraft by its own terms (except for the Concorde, which was 
included by name in regulations from the 1970s). The interpretation 
also found that if no noise standards for a supersonic aircraft were in 
place at the time of an application for type certification, the FAA's 
statutory mandate would require the agency to create noise 
certification standards applicable to the aircraft before a type 
certificate could be issued, even if that set of noise standards only 
applied to one aircraft model. The full interpretation is available 
online \8\ and a copy has been placed in the docket for this 
rulemaking.
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    \8\ The interpretation is titled ``Applicability of part 36 to 
new supersonic aircraft.''
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    Currently, FAA regulations prohibit civil aircraft from operating 
at speeds exceeding Mach I over land in the United States. (14 CFR 
91.817). The FAA does not propose to change that prohibition with this 
rule. This proposal is limited to establishing procedures and noise 
levels for subsonic operation of supersonic aircraft during landing and 
takeoff.
    For a brief history of supersonic airplane operations in the United 
States, please consult the background section of the FAA's NPRM titled 
Special Flight Authorizations for Supersonic Aircraft, published in the 
Federal Register on June 28, 2019, at 84 FR 30961.

A. Statement of the Problem

    Several U.S. manufacturers have begun developing the next 
generation of supersonic airplanes. Current regulations do not include 
noise standards applicable to new supersonic airplanes, and the FAA's 
statutory authority requires that noise regulations be in place before 
a new aircraft type certificate may be issued.\9\ Accordingly, the FAA 
is proposing to amend its noise certification regulations to apply to 
supersonic airplanes, and to adopt noise certification procedures and 
noise limits that would apply during the LTO cycle of certain new 
supersonic airplanes. Manufacturers have indicated that they expect new 
supersonic-capable designs to enter service in the mid- to late-2020s. 
The FAA has a statutory duty to both protect the public health and 
welfare from aircraft noise and sonic boom,\10\ and when proposing 
noise standards, to consider whether the standard is economically 
reasonable, technologically practicable, and appropriate for the 
aircraft to which the standards apply.\11\ For more than a decade, 
aircraft developers have indicated their need for the FAA to establish 
reasonable, achievable supersonic LTO cycle noise limits in order to 
complete their designs with reasonable certainty that the aircraft will 
qualify for type certification in the United States.
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    \9\ 49 U.S.C. 44715(a)(3).
    \10\ 49 U.S.C. 44715(a).
    \11\ 49 U.S.C. 44715(b)(4).
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B. Scope of This Proposal

    All airplanes, including supersonic airplanes, operate at subsonic 
speed during the LTO cycle. Under part 36, the amount of noise allowed 
to be produced during these phases of flight is determined by aircraft 
weight.\12\ This rule proposes LTO cycle noise limits for supersonic 
airplanes that have a maximum takeoff weight of 150,000 pounds and a 
maximum operating cruise speed of Mach 1.8, defining this class of 
airplanes as SSL1. The primary reason for proposing a separate 
supersonic category and SSL1 airplane class is to account for the 
distinct design of the aircraft (discussed below in paragraph C.) and 
the resulting known source noise effects on certain noise measurements. 
As industry continues to develop supersonic capable airplane designs 
and can provide more data on airplane noise and performance, the FAA 
expects to adopt LTO cycle standards for aircraft of greater maximum 
takeoff weight and higher operational speeds.
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    \12\ Heavier aircraft require more lift, require more thrust, 
create more drag, and have larger aerodynamic surfaces that result 
in more noise, relative to smaller aircraft.
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    This proposed rule does not address any noise associated with 
normal flight at cruise altitudes or supersonic speeds. The FAA has not 
promulgated cruise altitude noise regulations for subsonic airplanes, 
and sufficient data are not currently available that would support 
rulemaking to develop such standards for supersonic airplanes. Before 
any changes to the operating rules could be proposed, more research is 
needed on the production of noise at supersonic

[[Page 20433]]

cruise speeds and the regulatory approaches that would be appropriate. 
Allowing civil airplane operation at speeds in excess of Mach 1 over 
land in the U.S. may become possible in the future, but it is not 
expected before the development of new technologies reducing the impact 
of sonic boom generation or eliminating sonic boom exposure. 
Accordingly, nothing about this proposal may be interpreted as 
affecting the existing prohibition on exceeding Mach 1 speed (thus 
producing a sonic boom) over land in the United States.\13\ The FAA, 
NASA, ICAO, and aviation stakeholders worldwide continue to study and 
evaluate the methods that would support the next phases of supersonic 
development, including the measurement of sonic boom noise and the 
effect on people on the ground.
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    \13\ 14 CFR 91.817.
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    As a part of the process to develop this proposed rule, the FAA has 
consulted with NASA and other interested parties in the aviation 
industry, and has continued its leadership roles at ICAO to assess the 
needs of the industry and the public, and the costs and benefits of 
introducing these new aircraft.
    When the FAA began to develop this rulemaking in 2018, the agency 
asked several entities whether they were developing supersonic airplane 
projects and whether they were interested in sharing data regarding the 
probable noise characteristics associated with those projects. The FAA 
is placing in the docket for this rulemaking the list of questions we 
sent interested entities, and a list of those who responded. The FAA 
has determined that the information we received in response to our 
questions is considered proprietary and subject to the Trade Secrets 
Act,\14\ and would be protected from release pursuant to the Freedom of 
Information Act (FOIA) under FOIA Exemption 4.\15\ The information we 
received was combined with the data from the NASA studies and ongoing 
ICAO efforts as part of the overall data set that informed this 
proposed rule.
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    \14\ 18 U.S.C. 1905.
    \15\ 5 U.S.C. 552(b)(4).
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C. Establishing Distinct Supersonic Standards

    The FAA is proposing noise certification levels specific to 
supersonic aircraft, as well as certain changes to existing reference 
procedures for measuring aircraft noise during certification. These 
proposed noise levels are different than the current Stage 5 noise 
levels for subsonic aircraft. This difference reflects the need to take 
into account the unique technological and design requirements for 
supersonic aircraft to maintain long-distance supersonic flight. As 
will be discussed below, the FAA has found that the technological 
differences between subsonic and supersonic airplanes require that a 
separate set of noise certification levels be established for 
supersonics since noise is an intrinsic function of these differences. 
This rule proposes standards for the use of airplane-specific noise 
abatement technical equipment and procedures (such as VNRS) that are 
central to establishing LTO cycle noise levels at certification. The 
traditional regulatory framework and the use of the well-understood, 
efficient subsonic airplane testing requirements are maintained in this 
proposed rule, including the existing means of acoustical measurements, 
data evaluation, reference (test) procedures, reference (atmospheric) 
conditions, and adjustment analyses for noise certification. The FAA 
expects that these proposed regulations would result in noise tests of 
new supersonic airplanes being conducted in much the same manner and 
under the same conditions as current subsonic airplanes.
    In order to achieve and maintain supersonic flight over long 
distances, different technologies need to be incorporated. They are 
most evident in the design and performance of (1) the fuselage and wing 
shape, and (2) the engine design. Each of those design characteristics 
has effects on airplane noise during subsonic operation. The FAA 
collected and reviewed data from U.S. manufacturers regarding their 
conceptual designs for new supersonic aircraft in an effort to identify 
appropriate subsonic LTO cycle noise limits for these airplanes. These 
data were also used to support the FAA's efforts to protect the public 
from noise and to propose standards that are reasonable. The noise 
limits proposed in this rule take into account the technological 
advancements that have been made since the Concorde was first flown 
commercially in the 1970s. The FAA anticipates that new supersonic 
airplane designs will produce LTO cycle noise similar to the fleet of 
subsonic airplanes currently in operation.
1. Wing and Fuselage Design
    The recognizable design of the Concorde, with its long, narrow 
fuselage and swept-back wings, is not simply about aesthetics. All 
aircraft experience drag, the resistance to moving air that requires 
power to overcome, similar to putting one's hand out the window of a 
moving car. When traveling at supersonic speeds, the amount of drag 
increases significantly due to wave drag attributed to shock wave 
formation when operating at speeds faster than Mach 1 (the speed of 
sound). As a consequence of the large increase in drag at supersonic 
speed, supersonic aircraft must have a relatively small cross-section 
to minimize the drag effect on the airframe. In practice, supersonic 
aircraft designs tend to look more like a dart with a smaller diameter 
fuselage than a traditional tube and wing shaped subsonic aircraft.
    Supersonic speeds also require a different wing design than the 
typical subsonic airplane. Wave drag, which also burdens subsonic 
airplanes, is a more significant contributor to total drag on 
supersonic designs because of shock waves that form at speeds greater 
than Mach 1. In order to minimize wave drag, the wings of a supersonic 
airplane are thinner (in cross-sectional thickness) and have a shorter 
swept wingspan (delta shaped) than a subsonic airplane. This wing 
design helps minimize wave drag at supersonic speeds; however, it does 
not generate lift as well as subsonic airplane wings at lower speeds. 
This difference is important when the airplane is taking off and 
landing. This difference in wing design requires supersonic airplanes 
to operate at higher speeds during takeoff and landing as compared to 
subsonic aircraft, requiring more thrust than subsonic airplanes to 
generate enough aerodynamic lift to take off and land safely. More 
thrust and speed at takeoff and landing results in more noise compared 
to a subsonic airplane of a similar weight.
2. Engine Design
    To take off and land safely, jet engines for supersonic aircraft 
require relatively greater thrust than subsonic aircraft of a similar 
weight, as well as a lower engine bypass ratio to reach and maintain 
supersonic speeds in excess of Mach 1. In addition, as discussed above, 
the aircraft and wing design are optimized to reduce drag, and the 
aircraft require increased thrust during takeoff and landing. An 
engine's bypass ratio is a measurement of the relationship between the 
diameter of the engine opening and the amount of air that flows through 
the fan of the engine and bypasses the core, compared to the amount of 
air that flows through the core. Over time, the bypass ratios for 
subsonic aircraft have greatly increased as a result of technology and 
materials improvements that also led to significant fuel efficiency 
improvements and noise reductions. There is limited

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opportunity to incorporate increased bypass ratios on engines that 
power supersonic aircraft. To reduce the increased drag already noted, 
the diameter of the engine inlet must be relatively small and well-
integrated into the airframe/wing design, making the high bypass ratios 
(and pod-on-wing design) of engines on modern subsonic aircraft not 
technologically feasible. As a result, new supersonic aircraft will 
need to utilize integrated lower bypass ratio engines, which are 
relatively louder than high bypass ratio engines.
3. A New Noise Category
    As part of its statutory duty to adopt standards that are 
economically reasonable, technologically practicable, and appropriate 
for a particular aircraft,\16\ the FAA first took into account the 
physical and technological differences between subsonic and supersonic 
airplanes described above. The FAA studied NASA's modeling efforts for 
modern supersonic design technologies, as well as data that 
manufacturers developing supersonic products provided to the FAA.\17\ 
Based on the available information, the FAA concluded that, to comply 
with Congress's statutory direction to enable a new generation of 
supersonic airplanes, the FAA needed to create a new category for 
purposes of noise certification.
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    \16\ 49 U.S.C. 44715(b)(4).
    \17\ Manufacturers submitted confidential or proprietary data.
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    The new category would account for the unique technology and design 
characteristics of supersonic airplanes. These unique characteristics 
fundamentally affect the way the noise is generated and measured, which 
makes comparison to subsonic airplanes neither appropriate nor helpful. 
In addition, the data available to the FAA indicate that a modern 
supersonic airplane would have little in common with the noise of the 
Concorde, and can be expected to incorporate developing technologies 
that would lessen the effect on the public of its expected landing and 
takeoff noise impacts.
    Based on the data available, the FAA proposes a new noise category 
for matters of supersonic noise certification in Part 36, and defines a 
first class of supersonic airplanes (defined by weight and maximum 
speed) that is expected to encompass most of the projects currently 
under design.\18\
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    \18\ If the FAA receives an application for an airplane that 
falls outside this class, both the agency and the airplane developer 
could use the first class (SSL 1) as a starting point for 
establishing an individual certification basis. Establishing this 
first class will inform the industry as to the agency's direction 
and serve as a foundation for future specific standards once the 
distinguishing characteristics of the next class (whatever they may 
be) emerge and can be taken into account.
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    The FAA proposes the first class, Supersonic Level 1 (SSL1), for 
airplanes capable of supersonic flight that have a maximum takeoff 
weight of 150,000 pounds and a maximum operating cruise speed of Mach 
1.8. The FAA chose this class definition because the agency anticipates 
that most of the designs currently under development will fit within 
these parameters. Because this regulatory structure is tailored to 
supersonic designs and technology currently under development, it will 
foster innovation in this new emerging class of airplanes. In addition, 
it will serve as a launching point for adopting appropriate standards 
for future classes that could encompass for example, heavier maximum 
takeoff weights and faster operating cruise speeds. The FAA does not 
intend for today's proposal to be a one-size fits all approach to 
emerging supersonic technology. To the contrary, today's proposal seeks 
to provide the regulatory certainty necessary to enable the generation 
currently under development. Current research suggests that supersonic 
airplanes with speeds above Mach 1.8 would have different design 
characteristics. These characteristics would affect aircraft noise and 
are expected to require different noise standards and different noise 
measurements.
4. Reference Procedure Changes
    The FAA's approach to reference procedures in this proposed rule is 
based in its long-established paradigm of noise certification that is 
broadly applicable. The proposed new supersonic category and proposed 
SSL 1 class reflect the FAA's need to accommodate the unique 
characteristics of supersonic airplanes. Consistent with the FAA's 
long-standing approach to noise certification, the FAA would evaluate 
supersonic airplanes under this proposed rule using a standard weight-
to-noise correlation, with the separate noise limits (the curve) needed 
to properly account for the inherent design differences and allow 
comparison of like products.
    In gathering noise data, an airplane is flown using Part 36 takeoff 
and approach reference procedures, which represent specific, repeatable 
conditions that ensure accurate noise measurement. This NPRM proposes 
using the same measurement locations contained in the existing part 36. 
However, to account for all of the differences between supersonic and 
subsonic airplanes described in this section, different reference 
procedures are proposed for takeoff speed and thrust.
    New supersonic designs are also expected to incorporate advanced 
technologies that control the engines and aerodynamic control surfaces 
automatically to reduce noise at takeoff and landing to the greatest 
extent possible, while still allowing the airplane to operate safely. 
The higher thrust needed for takeoff and the lower engine bypass ratio 
for supersonic airplanes both contribute to higher lateral noise 
levels. This proposed rule would allow for the use of Variable Noise 
Reduction Systems (VNRS), as part of the takeoff reference procedure. 
Inclusion of VNRS in the proposed standards is designed to allow 
maximum flexibility for manufacturers to present VNRS design options to 
the FAA that are appropriate for their airplanes. The FAA seeks to 
allow the maximum latitude for these designs while they are still in 
their infancy. The FAA seeks comment on whether there are other 
performance-based standards that could be included that would allow 
even greater design flexibilities.

D. International Standard Setting Activity

    The development of international supersonic noise standards for 
modern aircraft began in the early 2000s and continues today in ICAO. 
Since 1983, the ICAO CAEP has developed environmental standards and 
policies for international aviation. The United States is an active 
member of the CAEP. Work conducted by the CAEP Noise Technical Working 
Group was considered in many of the aspects of this proposed rule. The 
FAA continues to work with ICAO to develop an international civil 
supersonic LTO cycle noise standard that will allow supersonic 
airplanes to be certificated and accepted worldwide. This first 
proposal of supersonic noise certification regulations represents an 
exercise of the FAA's statutory direction to enable the safe commercial 
deployment of civil supersonic aircraft technology and the safe and 
efficient operation of civil supersonic aircraft. The United States 
understands the need for globally harmonized supersonic LTO cycle noise 
standards. The FAA is undertaking this rulemaking to respond to the 
demand from U.S. manufacturers to provide regulatory certainty while it 
continues to work with the international community to move forward with 
the international standard setting process for supersonic LTO cycle 
noise.

[[Page 20435]]

E. Analysis of Proposed Rule Text

    The following section contains a discussion of select portions of 
rule text. It does not repeat the rule text, but is designed to be read 
as a companion to the proposed rule language presented at the end of 
this document.
    Part 21, Sec.  21.93 Classification of changes in type design. The 
FAA is proposing to add supersonic airplanes to the list of aircraft in 
Sec.  21.93(b). That section provides that any voluntary change in the 
aircraft's type design that may increase noise levels (defined as an 
``acoustical change'') must meet the applicable requirements in part 36 
for design changes. Supersonic airplanes would be subject to acoustical 
change requirements equivalent to other aircraft types. None of the 
exceptions set forth in paragraphs (b)(2), (3), and (4) for subsonic 
jet airplanes, certain propeller-driven commuter or small airplanes, 
and helicopters, respectively, are appropriate for new supersonic 
airplanes. As discussed in subsequent sections, this proposed rule 
seeks to distinguish new supersonic airplanes from the Concorde model. 
As a result, this rule proposes to add the Concorde to Sec.  21.93 to 
preserve its place in the regulations.
    Part 36, Sec.  36.1 Applicability and definitions. The FAA is 
proposing to add supersonic airplanes, as defined in this NPRM, to the 
applicability of part 36. As discussed earlier in this preamble, the 
current applicability of part 36 is limited by its terms to subsonic 
aircraft. Expanding the applicability is necessary to include the noise 
limits for supersonic airplanes that the FAA is proposing in new 
subpart E and new appendix C to part 36.
    Throughout part 36, this proposed rule would add the term 
``subsonic'' before ``jet airplane'' when needed to distinguish between 
the part 36 requirements that are not applicable to both subsonic and 
supersonic jet airplanes.
    The FAA is proposing to amend the title of subpart B by inserting 
the word ``Subsonic'' before the word ``Jet'' to indicate that the 
regulations in that subpart do not apply to supersonic airplanes.
    The FAA is proposing to revise the definition of supersonic 
airplane in Sec.  36.1 and move it from paragraph (f) to new paragraph 
(j). The move will allow the definitions related to new supersonic 
airplanes to be grouped in one paragraph of Sec.  36.1. The revised 
definition would exclude the Concorde from the definition of supersonic 
airplane. The part 36 regulations that apply to the Concorde are 
specific to the Concorde and the FAA seeks to segregate them as a 
historical matter to prevent any confusion as to which standards apply 
to the Concorde as opposed to those for new supersonic airplanes being 
proposed here.
    The FAA is proposing a definition of SSL1 airplane that refers to 
proposed Appendix C, which would apply to supersonic airplanes with a 
maximum certificated takeoff weight of 150,000 pounds and a maximum 
operating speed of Mach 1.8 or less. This definition would include most 
of the proposed supersonic airplane design concepts that U.S. 
manufacturers have described to the FAA. The FAA anticipates that when 
data is available to establish LTO cycle noise standards for other 
weight and speed supersonic airplanes, other similar classes of 
airplane and noise level would be added to Sec.  36.1(j) with separate 
definitions.
    The FAA is proposing a definition of LTO cycle to specify that the 
proposed supersonic noise standards are associated with the departure 
and arrival of supersonic airplanes at subsonic speeds at airports. The 
LTO cycle noise levels consist of the flyover, lateral, and approach 
noise levels as specified in proposed Appendix C to part 36. The 
definition is necessary to distinguish that the noise limits proposed 
in Appendix C are not applicable to noise created during flight at 
supersonic speeds.
    The FAA is proposing a definition of VNRS and of Programmed Lapse 
Rate (PLR) to describe the function of various configuration controls 
that are intended to limit noise during the LTO cycle. Since these are 
new aircraft systems, the FAA specifically requests comment on the 
scope of these definitions and any suggested additions or changes that 
might be common to all developers of such systems.
    Part 36, Subpart D. The FAA is proposing to change the title only 
of Subpart D to indicate that the regulations presented in that subpart 
apply only to Concorde airplanes, removing the term supersonic from the 
subpart title. Although no Concorde airplanes are currently 
operational, the regulations on the Concorde would not be removed 
because the aircraft type certificate remains valid. Regulations that 
apply to new supersonic airplanes would be placed in a new Subpart E.
    Part 36, Subpart E. The FAA is proposing to add Subpart E to 
establish the noise measurement and evaluation requirements applicable 
to new supersonic airplanes. This new subpart would retain the familiar 
structure of other subparts in part 36, but apply only to new 
supersonic airplanes in accordance with the definition proposed in this 
rule. As discussed elsewhere in this rulemaking, the applicability of 
the regulations proposed for new subpart E is limited to SSL1 
airplanes.
    As a corollary to other aircraft types to which part 36 is 
applicable, the FAA is proposing a new Sec.  36.15 to add acoustical 
change requirements for supersonic airplanes. This is the companion 
regulation to the proposed change made in Sec.  21.93 that adds 
supersonic airplanes to the applicability of that section. As with 
other types of aircraft, a certificated supersonic airplane, after a 
change in the type design, would still be required to meet at least the 
noise level that was applicable to the design prior to the change.
    Section 36.1581, Manuals, markings, and placards. Several changes 
to this section are being proposed to address noise level information 
for new supersonic airplanes that must be made part of the Aircraft 
Flight Manual (AFM). Proposed paragraph (a)(4) establishes the general 
AFM requirements involving noise certification for supersonic 
airplanes.
    Paragraph (h) would restrict the maximum weight of the airplane to 
be the weight at which an LTO cycle noise level that complies with part 
36 was established.
    The proposed rule would also establish operating limitations in 
Sec.  36.1581(i) for supersonic airplanes. If applicable, the 
limitations must be included in the AFM. The FAA seeks comment 
specifically on Sec. Sec.  36.1581(i)(2) and (3). Proposed paragraph 
(i)(2) would require an operating limitation if a VNRS is used to show 
compliance with the proposed noise limits. The limitation would require 
the flight crew to verify that the VNRS is functioning properly before 
each takeoff. This verification of functionality prior to each takeoff 
is necessary because a malfunctioning or inoperable VNRS would present 
an immediate noise issue and indicate that the aircraft is not in 
compliance with part 36 as certificated.
    While a VNRS is not required, if a manufacturer chooses to 
incorporate a VNRS, the FAA proposes a requirement to verify that the 
VNRS is functioning properly. This requirement is a performance based 
standard: The FAA does not propose to prescribe the method or 
technology that a flight crew would use to conduct that verification. 
To the contrary, how a flight crew is able to verify that any VNRS 
system is functioning properly is dependent on its design. One way, but 
not the only way, to verify might be to require it to be part

[[Page 20436]]

of a flight crew checklist. Another way could include equipment or 
technology that would verify functionality prior to takeoff. The FAA 
intentionally declines to specify design standards to allow 
manufacturers flexibility and to allow for innovation.
    The FAA requests comment on whether developers have an equivalent 
means for flight crews to ensure the functionality of any certificated 
VNRS.
    The other proposed operating limitation on which the FAA seeks 
specific comment is in Sec.  36.1581(i)(3) regarding airplanes that 
incorporate PLR to limit thrust to a programmed level and decrease 
noise. To exceed PLR thrust after takeoff, the applicant must have 
demonstrated during testing that ending the programmed thrust does not 
produce a noise impact on the ground that exceeds the levels measured 
at the certification measurement points. Until the point at which no 
effect from increased thrust is determined, the PLR would need to 
remain in active operation. This point is not specified in these 
regulations because it is expected to be unique to each airplane 
design. The point determined for an individual PLR system would become 
an operating limitation for that airplane.
    The intent of the proposed limitation is to account for any noise 
issues that are unique to the design of a particular supersonic 
airplane model that may be caused by an increase in thrust when PLR use 
is completed.
    Appendix A to part 36, Aircraft Noise Measurement and Evaluation: 
Appendix A would be revised to make its procedures applicable to 
supersonic airplanes. Current Appendix A applies to transport category 
airplanes, subsonic jet airplanes, and the Concorde. Except as 
described below, the FAA proposes to require new supersonic airplanes 
to use the same noise measurement and evaluation conditions and 
procedures as these other aircraft. Based on the information provided 
by developers, new supersonic airplanes are expected to be sufficiently 
similar in design to other jet-powered fixed-wing aircraft such that 
the requirements in Appendix A remain appropriate for noise 
certification testing. The FAA seeks comment on whether any of the 
provisions in Appendix A would not be appropriate for new supersonic 
airplanes, including what alternative procedures would be appropriate.
    One proposed change to Appendix A for supersonic airplanes 
addresses VNRS reference procedures. When a VNRS (included in new 
Appendix C) is used to demonstrate compliance with part 36, Sec.  
A36.9.1.3 would require use of the integrated method of adjustment 
described in existing Sec.  A36.9.4. Rarely are certification flight 
test conditions ever identical to the reference atmospheric conditions 
prescribed. Appendix A requires that appropriate adjustments be made to 
the measured noise data using either a simplified or an integrated 
method of adjustment, as described in Sec.  A36.9. These methods adjust 
the noise results to account for differences in both the airplane to 
microphone distance, and the variations in atmospheric conditions 
between the actual test day and the prescribed reference day. Under 
current regulations that apply to all aircraft, if the simplified 
method results in either adjustments that exceed specified decibel 
levels or a final effective perceived noise evaluation metric level 
(EPNL) that falls within one decibel of the applicable noise limit, the 
integrated method of adjustment must instead be used to ensure 
accuracy. The simplified method adjusts noise only once, at the maximum 
peak, while the integrated method adjusts at each half-second of the 
entire noise segment of flight. The integrated method computes EPNL 
directly by recalculating, under reference conditions, the data points 
of the tone-corrected perceived noise level time history that 
corresponds to measured points obtained during testing. The FAA has 
found that the integrated method of adjustment accounts for the dynamic 
aspects of VNRS procedures more accurately than the simplified method 
of adjustment. For that reason, the FAA proposes that the integrated 
method always be used for supersonics that use VNRS. The simplified 
method is unable to provide sufficient data processing fidelity of the 
measured noise signal that is the expected result of VNRS influence in 
flight.
    Appendix C to part 36, ``Noise Levels for Supersonic Airplanes.'' 
This is a new appendix applicable to supersonic airplanes as defined in 
this proposed rule. The proposed appendix corresponds to existing 
Appendix B, which prescribes procedures for determining noise levels 
for transport category large airplanes, subsonic jet airplanes, and the 
Concorde. The FAA is proposing to incorporate into the new Appendix C 
many of the same technical requirements currently in Appendix B for 
subsonic airplanes, including the EPNL and the reference noise 
measurement points (lateral, flyover, and approach) because both the 
metric and reference measurement locations are appropriate in the 
demonstration of noise certification compliance. Except as noted 
before, new supersonic airplane designs are anticipated to be similar 
in their takeoff and landing characteristics as airplanes subject to 
Appendix B. The FAA seeks comment on whether any of the provisions from 
Appendix B that are being proposed for inclusion in new Appendix C are 
inappropriate for new supersonic airplanes, including what alternatives 
would be appropriate. The primary differences between the appendix 
requirements are as follows:
    Proposed Sec.  C36.5 sets the LTO cycle noise limits for SSL1 
airplanes. As noted previously in this preamble, the proposed limits 
are based primarily on NASA's Supersonic Transport Concept Airplanes 
(STCA) studies. The models and methodologies used in the STCA studies 
for estimating noise certification levels were developed by NASA using 
the most advanced physics-based scientific and engineering methods, and 
were supplemented with 2- and 3-engine supersonic design concepts and 
data from industry developers.
    In seeking to design a supersonic transport based on ``near-term 
technologies,'' the models produced by NASA researchers generally 
assumed design elements the researchers perceived as being economically 
viable and technologically practicable. For example, the notional 
engines equipped on each modeled aircraft is based on an ``off-the-
shelf'' subsonic turbofan. However, there are also a number of design 
and performance elements assumed into the notional aircrafts that were 
specifically or secondarily incorporated because of their noise-
abatement benefits. The research did not discuss the impacts to noise 
if these technologies were not included, nor did researchers discuss 
the cost impacts to design or operation if any of these processes or 
technologies were excluded.
    Relatedly, NASA researchers also explored alternative engine 
designs that included noise abatement mechanisms not ultimately 
included in their main noise impact projections. For example, NASA ran 
one alternative projection for an engine with a higher bypass ratio and 
second alternative projection for incorporating nozzle chevrons as a 
noise reduction technology to the original, lower bypass ratio engine. 
In both cases, NASA found the alternative technologies reduced the 
effective perceived noise level but came with a reduction in the flight 
range of the aircraft.
    Therefore, while the noise data sets generated by the NASA research 
indicates a range of potential noise outputs by these modeled aircraft, 
these noise assumptions are already

[[Page 20437]]

constrained by optional design elements the researchers did or did not 
choose to model as inputs for their final noise projections.
    Additional data provided to the FAA by U.S. industry and the 
ongoing work by the ICAO CAEP were also used to inform the agency's 
decision on noise limits. All of this technical information served as 
the basis for noise limits proposed in Sec.  C36.5. That section 
contains the noise limits for 2- or 3-engine supersonic airplanes with 
a maximum certificated takeoff weights of 150,000 pounds and a maximum 
operating speed of Mach 1.8 or less.
    The FAA proposes SSL1 noise limits and an applicability range using 
its established noise standard-setting process. The FAA based its 
proposal on the noise data sets from the NASA STCA program for that 
agency's 100,000 and 120,000 pound (45- and 55-metric ton) airplanes 
with two or three engines installed, as well as additional proprietary 
information from manufacturers developing supersonic airplanes. The FAA 
plotted these data sets, including associated design and modeling 
uncertainties, on a coordinate graph based on weight (in pounds) and 
noise (in EPNdB) for each airplane.
    Using this information plotted on the graph, the FAA developed a 
series of potential limit lines for airplanes of different weights and 
numbers of engines. The FAA evaluated these potential limit lines 
taking into account the FAA's statutory considerations of technological 
feasibility, economic reasonableness, and appropriateness for the 
aircraft type. This evaluation process relied on the FAA's expertise in 
noise evaluation of supersonic technologies and their qualitative 
assessment of the economic and social costs that weigh on the process 
to determine the intersection of elements that would result in a 
proposed noise limit line that addressed both industry design needs and 
agency statutory obligations. The novelty of the technology and the 
limited data sets result in an inherent uncertainty regarding whether 
these proposed noise standards fully optimize available noise reduction 
while considering what is economically reasonable and technologically 
practicable for modern supersonic aircraft. The FAA's intent in its 
approach is to set a standard that could require adoption of most or 
all known noise-abatement technologies to meet the noise limits, 
including ones that may cause marginal reductions in aircraft 
performance (e.g. reduce flight range), or marginal increases in the 
cost of manufacturing.
    This process resulted in the noise limits proposed in Sec.  C36.5. 
The proposed noise limits represent a range of applicability that takes 
into account the spectrum of information provided, while also 
addressing the FAA's statutory responsibilities regarding noise 
regulation.
    As the industry develops and more information becomes available, 
the FAA will consider whether to broaden the applicability of this 
proposed rule or establish a separate class for larger or faster 
supersonic airplanes.\19\ The proposed noise limits are consistent with 
the agency's statutory duty to control and abate aircraft noise while 
``consider[ing] whether the standard or regulation is economically 
reasonable, technologically practicable, and appropriate for the 
applicable aircraft, aircraft engine, appliance, or certificate.'' \20\
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    \19\ As noted previously, the FAA anticipates that the 
parameters for SSL1 noise standards will serve as the foundation for 
future generations of supersonic airplanes that may exceed the 
weight and speed limits set in this rule. That said, If the FAA 
receives an application for an airplane that exceeds the weight or 
speed limits for SSL1, both the agency and the airplane developer 
could use the SSL 1 standards as a starting point for establishing 
an individual certification basis.
    \20\ 49 U.S.C. 44715(b)(4).
---------------------------------------------------------------------------

    As discussed above, the FAA does not propose to change the 
fundamental approach to setting noise levels in its existing paradigm. 
Accordingly, in proposing the SSL1 noise limits, FAA relies on its 
existing approach, which uses weight as a correlating factor for noise 
levels. This means that noise limits are applied on a curve taking into 
account the fact that heavier aircraft will be louder, as weight is a 
fundamental component of aircraft noise generation. Consistent with the 
FAA's existing paradigm, the allowance for weight is not unlimited; the 
noise limits set for various aircraft categories take into account the 
entire range of aircraft in each category. The FAA does not propose to 
deviate from this paradigm for supersonic aircraft. Weight remains the 
correlating factor, without reference to the shape or thrust or other 
capacity of an individual model. The noise limits proposed in this 
rulemaking may be summarized as follows:
    A three-engine SSL1 airplane that has a maximum takeoff weight of 
150,000 pounds may not exceed 94.0 effective perceived noise decibel 
(EPNdB) at the flyover measurement point, 96.5 EPNdB at the lateral 
measurement point, and 100.2 EPNdB at the approach measurement point.
    A two-engine SSL1 airplane that has a maximum takeoff weight of 
150,000 pounds may not exceed 91.0 EPNdB at flyover, 96.5 EPNdB at the 
lateral measurement point, and 100.2 EPNdB at the approach measurement 
point.
    For SSL1 airplanes that seek certification at a lower maximum 
takeoff weight, the noise limit would decrease linearly with the 
logarithm of the airplane weight, at the rates set forth in proposed 
Sec. Sec.  C36.5(a), (b), and (c), and remain constant for airplanes at 
or below certain specified weights. This logarithmic decrease mirrors 
the current requirements applied to subsonic airplanes under Appendix 
B.
    As described above, the FAA does not propose to alter its 
fundamental paradigm for noise certification as a part of this rule. 
Accordingly, the FAA sets a proposed cumulative noise limit. The 
proposed cumulative noise limit is presented in Sec.  C36.5(e), which 
provides that the sum of the differences (i.e., the difference between 
the limits and maximum levels) at all three measurements points (i.e., 
flyover, lateral, and approach) may not be less than 13.5 EPNdB.
    Proposed Sec.  C36.6 specifies the requirements when a VNRS is 
included in an applicant's design and is used to show compliance with 
the LTO cycle requirements of part 36. The inclusion of VNRS is 
intended to enable the incorporation of advanced concepts and systems 
technologies that reduce noise using fully automated changeable 
properties or features. The two best known of the VNRS concepts are 
automated configuration changes, and Programmed Lapse Rate (PLR), as 
defined in proposed in Sec.  36.1. The FAA does not intend to limit the 
development of automated noise reduction systems, and under this 
regulatory provision will consider any design features presented at 
certification that seek to lessen the LTO cycle noise impacts of 
supersonic airplanes. When a VNRS is presented as part of an airplane 
design at certification, it must be accounted for in any reference 
procedures requested by the applicant, demonstrated, and approved by 
the FAA before the certification tests are conducted.
    Section C36.7 specifies the noise certification reference 
procedures and conditions that apply to supersonic airplanes, and 
includes alternative provisions when a VNRS is used. Reference 
procedures are required conditions and procedures for the measurement 
of noise at the three reference measurement points (lateral, flyover, 
and approach). For example, proposed Sec.  C36.7(b) specifies takeoff 
reference procedures that include the minimum height that an airplane 
must achieve and the engine thrust level that

[[Page 20438]]

must be used for the noise data to qualify for certification. Use of a 
VNRS allows the applicant to develop individual reference takeoff and 
approach procedures that must be approved by the FAA before noise 
certification testing if the VNRS is used to show compliance with part 
36. Each VNRS will likely be different, and the FAA does not yet know 
how these systems will be implemented in individual supersonic type 
designs. This proposed rule provides flexibility for the applicant to 
request alternative takeoff and approach procedures to accommodate 
varying VNRS designs. Applicants using VNRS must still comply with 
proposed Sec. Sec.  C36.7(d) VNRS Takeoff reference procedure and (e) 
VNRS Approach Reference Procedure when developing any alternative 
takeoff and approach procedures. Takeoff and approach reference 
profiles must be defined by applicants in accordance with these 
requirements so that the measured test data can be properly adjusted 
for deviations relative to the reference profile and recomputed for 
reference meteorological conditions. These requirements are intended to 
ensure that the procedures establish a common reference noise 
certification basis of standard adjustments and specified reference 
conditions that each applicant follows when using a VNRS. Such level-
setting procedures maintain fairness for all noise certification 
applicants in demonstrating compliance. As noted previously, use of 
VNRS to demonstrate compliance with part 36 will require its use during 
normal operations in accordance with Sec.  36.1581(i).
    Section C36.7(b) proposes the minimum cutback height and thrust 
requirements that are required for subsonic jet airplanes as a standard 
takeoff reference procedure. When VNRS (including PLR) is used, the 
takeoff reference procedure to be used prior to reaching minimum 
cutback height is presented in Sec.  C36.7(d).
    Section C36.7(c)(5) addresses the weight and configuration of the 
airplane during standard approach reference procedures. Weight and 
configuration for approach reference procedures using VNRS are 
addressed in Sec.  C36.7(e)(5). The FAA seeks specific comments 
regarding any additional considerations that would be appropriate for 
VNRS approach reference procedures, such as when and how VNRS is 
triggered on approach, and what indication will be used to show that it 
is functional and active on approach if used for noise certification. 
All suggested changes should be supported by additional data as 
appropriate.
    Section C36.8 addresses noise certification test procedures. Noise 
adjustments for speed and thrust from test to reference conditions 
follow the same methods of Appendix A, unless VNRS procedures and data 
adjustments are approved by the FAA.
    Interested persons are encouraged to review all of the proposed 
rule text in detail and submit comments regarding the organization and 
substance of the requirements for the LTO cycle noise certification of 
SSL1 airplanes.

IV. Regulatory Notices and Analyses

    Changes to Federal regulations must undergo several economic 
analyses. First, Executive Orders 12866 and 13563 direct that each 
Federal agency shall propose or 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), 
as codified in 5 U.S.C. 603 et seq., requires agencies to analyze the 
economic impact of regulatory changes on small entities. Third, the 
Trade Agreements Act of 1979 (Pub. L. 96-39), 19 U.S.C. Chapter 13, 
prohibits agencies from setting standards that create unnecessary 
obstacles to the foreign commerce of the United States. In developing 
U.S. standards, the Trade Agreements 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), as codified in 2 U.S.C. Chapter 25, requires agencies 
to prepare a written assessment of the costs, benefits, and other 
effects of proposed or final rules that include a Federal mandate 
likely to result in the expenditure by State, local, or tribal 
governments, in the aggregate, or by the private sector, of $100 
million or more annually (adjusted for inflation with base year of 
1995). The FAA has provided a more detailed Preliminary Regulatory 
Impact Analysis of this proposed rule in the docket of this rulemaking. 
This portion of the preamble summarizes this analysis.
    In conducting its analyses, FAA has determined that this proposed 
rule has benefits that justify its costs. This proposed rule is a 
significant regulatory action, as defined in section 3(f) of Executive 
Order 12866, as it raises novel policy issues contemplated under that 
Executive Order. This proposed rule is also significant under DOT's 
Regulatory Policies and Procedures for the same reason. The proposed 
rule would not have a significant economic impact on a substantial 
number of small entities, would not create unnecessary obstacles to the 
foreign commerce of the United States, and would not impose an unfunded 
mandate on State, local, or tribal governments, or on the private 
sector by exceeding the threshold.

A. Regulatory Evaluation

i. Baseline Problem and Statement of Need
    Without this proposal, aircraft developers would not be certain 
that their aircraft could qualify for type certification in the United 
States. As previously discussed, some U.S. manufacturers have begun 
developing the next generation of supersonic airplanes. Current 
regulations do not include noise standards applicable to supersonic 
airplanes, and the FAA's statutory authority requires that noise 
regulations be in place before a new aircraft type certificate may be 
issued. The FAA is proposing to amend its noise certification 
regulations to apply to new supersonic airplanes, and to adopt noise 
certification procedures and noise limits that would apply during the 
takeoff and landing (LTO) cycle of certain new supersonic airplanes. 
Aircraft developers have indicated their need for the FAA to establish 
noise limits in order to complete their designs with reasonable 
certainty that the aircraft will qualify for type certification in the 
United States.
ii. Enabled Supersonic Aircraft Potentially Qualifying for Type 
Certification
    As previously discussed, aircraft developers provided FAA with 
information and indicated that new supersonic-capable designs could 
enter service in the mid- to late-2020s. Based on this data and the 
proposed range of applicability, the FAA estimates two supersonic 
airplanes, one 2-engine and one 3-engine, with maximum certificated 
takeoff weight of 150,000 pounds and a maximum operating speed of Mach 
1.8, would qualify for type certification as a result of this proposal 
and potentially begin production by 2025.
    Based on data provided by aircraft developers and supersonic 
airplane studies, the FAA estimates a production of 25 airplanes per 
certificate for 50 total airplanes per year, a production period of ten 
years, and airplane life of 20 years. Aircraft developers indicate that 
50 percent or more of production would be sold to foreign operators. 
Therefore, the potential life cycle of the first U.S. civil supersonic 
fleet results in deliveries to U.S. operators of 25 airplanes per year 
(same to foreign operators) until the U.S. operating fleet reaches a 
potential peak of 250 airplanes

[[Page 20439]]

in 2034.\21\ We use these estimates to frame our analysis of future 
impacts. The FAA seeks comment on its estimate of the expected timing 
for development of supersonic aircraft and on its estimate of 
production volumes.
---------------------------------------------------------------------------

    \21\ By 2034, U.S. aircraft developers could potentially produce 
500 supersonic airplanes operating domestically and abroad.
---------------------------------------------------------------------------

    There is uncertainty with estimating a future U.S. civil supersonic 
fleet. The FAA acknowledges that data from current and future research 
and development of supersonic aircraft along with additional regulatory 
changes may expand the size of the future U.S. civil supersonic fleet. 
In addition, this proposal only provides a standard for potentially 
qualifying for type certification--it does not guarantee certification 
and does not fully enable or guarantee future production or domestic 
operation. The effect of current U.S. regulations may limit future 
operations. The existing prohibition on exceeding Mach 1 over land in 
the United States would limit any supersonic airplane to subsonic 
speeds while operated in the United States; the proposed regulations 
would cover only subsonic operation during departure and arrival at 
airports.
iii. Incremental Change of Proposed LTO Cycle Noise Limits
    The impact of the incremental change in the certificated noise 
level resulting from the proposed LTO cycle noise limits is low. The 
FAA looked at the average cumulative noise level of airplanes in the 
2034 subsonic fleet and the cumulative noise levels of the 2- and 3-
engine supersonic airplanes that would be covered under this proposed 
rule.
    The 2034 subsonic fleet has a median certificated noise level, 
expressed in EPNdB level, of 267.1 and a mean certificated noise level 
of almost the same at 267.0 with a standard deviation of 11.3.\22\ The 
anticipated certification noise levels of the 2-engine supersonic 
airplane is 269.3, a noise level at the 57th percentile of the subsonic 
fleet, meaning that 57 percent of the airplanes in the subsonic fleet 
in 2034 would have overall lower certification noise levels and 43 
percent have overall higher certification noise levels than the 2-
engine supersonic airplane. The anticipated certification noise level 
of the 3-engine supersonic airplane is 274.5, a noise level at the 74th 
percentile of the subsonic fleet. The noise level of the 2-engine 
supersonic is just one-fifth of a standard deviation above the mean of 
the airplanes in the subsonic fleet and the 3-engine supersonic 
airplane is just two-thirds of a standard deviation above the mean of 
the airplanes in the subsonic fleet. In addition, the number of 
supersonic airplanes potentially enabled by the proposal (i.e., those 
supersonic airplane models expected to be certificated as SSL1) is 
small and would represent less than three percent of the combined 
subsonic and supersonic U.S. fleet in 2034. Therefore, while the 
anticipated certification noise levels of the supersonic airplanes are 
higher than the average certificated level of airplanes in the subsonic 
fleet, the difference is moderate.
---------------------------------------------------------------------------

    \22\ When the mean and median are the same, it may imply a 
standard normal distribution and symmetry of the database 
distribution without significant outliers.
---------------------------------------------------------------------------

iv. Benefits and Costs
    For more than a decade, airplane producers interested in developing 
the next generation of supersonic airplanes have sought standards in 
the form of regulatory noise limits. Without such limits, potential 
producers are reluctant to expend millions of dollars on airplane 
designs that might ultimately fail to meet a future noise standard. The 
FAA has been unable to set such standards without knowing what is 
possible by way of noise mitigation for new designs.
    This proposed rule is the first step in bridging that gap. Aircraft 
developers have shared data on their designs and a range of expected 
noise levels. In turn, the FAA has used that information along with the 
work conducted by NASA to propose these LTO cycle noise limits for a 
certain size supersonic-capable airplane. Accordingly, the primary 
benefit of this proposed certification rule is that it reduces a 
current barrier to the development of the next generation of supersonic 
aircraft. This is accomplished through the establishment of a design 
and noise standard for developers and producers, providing them some 
reasonable certainty that their investments will result in airplanes 
that meet noise regulations that have been adopted by the FAA.
    The proposed rule supports future innovation in new supersonic 
designs that incorporate advanced technologies, such as VNRS, that 
reduce the noise at takeoff and landing to the greatest extent possible 
while allowing the airplane to operate safely. The proposed standards 
are designed to allow maximum flexibility for the manufacturers to 
enhance designs using advances in technology. The FAA seeks to allow 
the maximum latitude for these designs while they are still in their 
infancy.
    The FAA seeks comment on the following issues related to the 
impacts of the proposal:
     The potential noise effects of the proposed standard and 
how these might be analyzed;
     The expected time savings or other benefits to the 
travelling public from the ability to travel via supersonic airplane 
instead of subsonic airplane;
     The manufacturing costs of possible technologies that 
manufacturers are likely to use to meet the standard and their effects 
on performance, weight and safety; and
     The costs and benefits of alternative noise limits or 
reference procedures and their impacts on costs and benefits to 
manufacturers, airlines and the public, including the likely choice of 
alternative compliance technologies.
    The proposed rule has a positive effect on the development of U.S. 
standards and industry for both domestic and international markets. The 
proposal provides an initial benchmark for the international 
development of standards for supersonic LTO cycle noise that would have 
a positive effect on the innovation and expansion of the U.S. 
supersonic airplane and transport industry. As previously discussed, 
aircraft developers indicate that 50 percent or more of production 
would be delivered to foreign operators.
    The establishment of certification LTO cycle noise standards for 
subsonic operations of supersonic-capable airplanes allows industry and 
FAA to look at the impact of subsonic operations on noise with more 
certainty. When these aircraft are designed, certificated, and placed 
in service, knowledge of these noise limits will make it easier to 
determine the subsonic impacts at individual airports, which is 
necessary for approval of operations specifications within the United 
States.
    This proposal does not result in additional required regulatory 
costs. Issuance of a type certificate requires compliance with the 
applicable noise requirements of part 36. Full noise certification 
testing is required for each new aircraft type and for certain 
voluntary changes to type design that are classified as an acoustical 
change under Sec.  21.93(b). The noise certification costs occur for 
new type certification, or when a change to a type design results from 
an acoustical change. Because the requirements for noise certification 
already exist, any associated costs are not incremental costs of this 
proposal.\23\
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    \23\ In the Paperwork Reduction Act section of this proposal, 
the FAA provides estimates of changes to the paperwork related 
burden and the cost to comply with the existing information 
collection as required by the Paperwork Reduction Act and related 
Office of Management and Budget (OMB) guidance. These costs are not 
a result of a new collection requirement.

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[[Page 20440]]

    As previously discussed, this proposal would allow the use of VNRS 
during noise certification testing and during normal operation of 
certificated airplanes. Based on industry information, these systems 
are being developed without this rulemaking as part of the designs 
themselves to reduce the noise produced by these supersonic airplanes. 
Because no VNRS are currently certificated on airplanes, this proposal 
adds VNRS to part 36 as an option for producers to use in their 
designs. Because VNRS is not a requirement, it is not an additional 
cost of the proposal. Rather, the addition of VNRS incorporates current 
industry innovation, and the failure to allow this technology would 
result in costs to industry.
v. Alternatives Considered
    No Action. The alternative of ``no action'' would entail the 
foregone opportunity to develop civil supersonic airplanes with a 
subsonic LTO cycle noise certification that reduces noise at takeoff 
and landing to the greatest extent possible while allowing the airplane 
to operate safely. In addition, Congress directed the FAA to exercise 
leadership in the creation of policies, regulations, and standards 
relating to the certification and safe and efficient operation of civil 
supersonic aircraft.\24\ The FAA was directed to take action to advance 
the deployment of supersonic aircraft, both domestically and 
internationally, through the development of proposed noise 
certification standards to address the constraints of noise and enable 
supersonic flight. This proposed rule responds to this Congressional 
direction.
---------------------------------------------------------------------------

    \24\ Section 181 of the Federal Aviation Administration 
Reauthorization Act of 2018 (https://www.congress.gov/115/bills/hr302/BILLS-115hr302enr.pdf).
---------------------------------------------------------------------------

    No constraint on maximum certificated take-off weight and speed. 
The proposed rule applies only to supersonic airplanes with maximum 
certificated take-off weight of 150,000 pounds and maximum operating 
cruise speed of Mach 1.8. The FAA considered, but rejected, a proposed 
rule with no limit on maximum certificated take-off weight or Mach 
speed. Neither the NASA STCA analyses nor the aircraft data provided by 
industry were sufficient to provide a technically feasible basis to 
allow a reasonable estimate of certification noise limits for an open-
ended set of aircraft weights and Mach speeds; the goal remains a set 
of certification standards that would reduce noise to the greatest 
extent possible while allowing the airplane to operate safely.

B. Regulatory Flexibility Determination

    The Regulatory Flexibility Act of 1980 (Pub. L. 96-354) (RFA) 
establishes ``as a 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, not-for-profit organizations, and small 
governmental jurisdictions.
    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, 
Sec.  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.
    Based on industry information, the FAA estimates two U.S. aircraft 
developers to apply for part 36 LTO cycle noise certification under 
this proposed rule. These developers are large entities that have a 
variety of private and public partnerships and high levels of 
investment capable of designing and producing the next generation of 
technically advanced and high value supersonic aircraft.
    As discussed in the Regulatory Evaluation section, the FAA expects 
this proposed rule would have small certification costs on affected 
entities developing supersonic airplanes. In addition, this proposed 
rule would result in positive business impacts since it would establish 
a design and noise standard for entities developing and producing 
supersonic airplanes, providing them some reasonable certainty that 
their investments will result in airplanes that meet noise regulations.
    Therefore, as provided in Sec.  605(b), the head of the FAA 
certifies that this rulemaking will not have 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 this 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 proposed rule and 
determined that its purpose would be to allow supersonic-capable 
aircraft to be noise certificated in the United States, which will 
permit domestic subsonic LTO cycle operations and supersonic operations 
outside U.S. airspace and would not pose an unnecessary obstacle to the 
foreign commerce of the United States. Therefore, the rule would comply 
with the Trade Agreements Act.

D. Unfunded Mandate 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 proposed or final 
agency rule that may result in an expenditure of $100 million or more 
(in 1995 dollars) in any one year by State, local, and tribal 
governments, in the aggregate, or by the private sector; such a mandate 
is deemed to be a ``significant regulatory action.'' The FAA currently 
uses an inflation-adjusted value of $155.0 million in lieu of $100 
million.
    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. According to the 1995 
amendments to the Paperwork Reduction Act (5 CFR

[[Page 20441]]

1320.8(b)(2)(vi)), an agency may not collect or sponsor the collection 
of information, nor may it impose an information collection requirement 
unless it displays a currently valid OMB control number.
    This action contains the following proposed amendments to the 
existing information collection requirements previously approved under 
OMB Control Number 2120-0659. As required by the Paperwork Reduction 
Act of 1995 (44 U.S.C. 3507(d)), the FAA has submitted these proposed 
information collection amendments to OMB for its review.
    In accordance with the Paperwork Reduction Act of 1995, FAA invites 
public comments about our intent to request OMB approval to revise an 
existing information collection. The information is collected when an 
applicant seeking noise certification of aircraft demonstrates noise 
compliance in accordance with 14 CFR part 36. The demonstration of 
compliance by submitting noise test data was originally implemented 
under the Aircraft Noise Abatement Act of 1968, and is now part of the 
overall codification of aircraft noise authority in 49 U.S.C. 44715.
    You are asked to comment on any aspect of this information 
collection, including (a) whether the proposed collection of 
information is necessary for FAA's performance; (b) the accuracy of the 
estimated burden; (c) ways for FAA to enhance the quality, utility, and 
clarity of the information collection; and (d) ways that the burden 
could be minimized without reducing the quality of the collected 
information. The FAA will summarize and/or include your comments in the 
request for OMB's clearance of this information collection.
    Background: The aircraft noise certification regulations of 14 CFR 
part 36 currently include information collection requirements for the 
certification of subsonic airplanes (jet airplanes and subsonic 
transport category large airplanes). The information collected are the 
results of noise certification tests that demonstrate compliance with 
14 CFR part 36. The original information collection was implemented to 
show compliance in accordance with the Aircraft Noise Abatement Act of 
1968; that statute is now part of the overall codification of the FAA's 
regulatory authority over aircraft noise in 49 U.S.C. 44715.
    Appendix A to part 36, Sec.  A36.5.2, requires applicants to 
include test results in their noise certification compliance report. 
Aircraft certification applicants typically certificate an airplane 
model once. The current information collection estimate includes 14 
noise certification projects involving flight tests undertaken each 
year. For this NPRM, the FAA proposes to revise this PRA collection to 
include noise tests on supersonic aircraft, for an increased estimate 
of 16 total noise certification projects per year. The FAA estimates 
that there are two entities that would submit applications for 
certification of supersonic airplanes under this proposal. Each 
applicant's collected information is incorporated into a noise 
compliance report that is provided to and approved by the FAA. The 
noise compliance report is used by the FAA in making a finding that the 
airplane is in compliance with the regulations. These compliance 
reports are required only once when an applicant wants to certificate 
an aircraft type. Without this data collection, the FAA would be unable 
to make the required noise certification compliance finding. The 
proposed PRA data collection revisions are as follows:
    Respondents: Aircraft manufacturer/applicant seeking type 
certification;
    Frequency: Estimated 16 total applicants per year, which includes a 
proposed increase of 2 new supersonic airplane applications;
    Estimated Average Burden per Response: Estimated 200 hours per 
applicant for the compliance report; and
    Estimated Total Annual Burden: $25,000 per applicant or cumulative 
total $400,000 per year for 16 applicants.

F. International Compatibility

    In keeping with U.S. obligations under the Convention on 
International Civil Aviation, it is FAA policy to conform to 
International Civil Aviation Organization Standards and Recommended 
Practices to the maximum extent practicable. The FAA has reviewed the 
corresponding ICAO Standards and Recommended Practices and has 
identified no differences with these regulations; ICAO does not 
currently have standards for subsonic LTO cycle of supersonic capable 
airplanes.

G. Environmental Analysis

    In accordance with the provisions of regulations issued by the 
Council on Environmental Quality (40 CFR parts 1500-1508), FAA Order 
1050.1F identifies certain FAA actions that may be categorically 
excluded from the preparation of an Environmental Assessment or an 
Environmental Impact Statement. The FAA has determined that this NPRM 
is covered by the CATEX described in paragraph 5-6.6(d) of FAA Order 
1050.1F. Pursuant to FAA Order 1050.1F, paragraph 5-5.6(d), this 
rulemaking action qualifies for a categorical exclusion because no 
significant impacts to the environment are expected from publication of 
this NPRM. This CATEX finding applies only to this proposed rule. The 
FAA will initiate a separate review of any final rule, including the 
adoption of any supersonic airplane noise certification standards that 
would permit the subsonic operation of such airplanes in the United 
States.

V. Executive Order Determinations

A. Executive Order 13132, Federalism

    The FAA has analyzed this proposed rule under the principles and 
criteria of Executive Order 13132, Federalism (64 FR 43255, August 10, 
1999). The agency has determined that this action would 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, would not have federalism implications.

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

    The FAA analyzed this proposed rule under Executive Order 13211, 
Actions Concerning Regulations that Significantly Affect Energy Supply, 
Distribution, or Use (66 FR 28355, May 18, 2001). The agency has 
determined that it would not be a ``significant energy action'' under 
the executive order and would not be likely to have a significant 
adverse effect on the supply, distribution, or use of energy.

C. Executive Order 13609, Promoting International Regulatory 
Cooperation

    Executive Order 13609, Promoting International Regulatory 
Cooperation (77 FR 26413, May 4, 2012) 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 would have no effect on international regulatory 
cooperation.

D. Executive Order 13771, Reducing Regulation and Controlling 
Regulatory Costs

    This proposed rule is a deregulatory action under Executive Order 
13771, Reducing Regulation and Controlling Regulatory Costs (82 FR 
9339, February 3, 2017). Details on the enabling aspects

[[Page 20442]]

of this proposed rule that expand production and consumption options 
can be found in the Regulatory Evaluation.

VI. Additional Information

A. Comments Invited

    The FAA invites interested persons to participate in this 
rulemaking by submitting written comments, data, or views. The agency 
also invites comments relating to the economic, environmental, energy, 
or federalism impacts that might result from adopting the proposals in 
this document. The most helpful comments reference a specific portion 
of the proposal, explain the reason for any recommended change, and 
include supporting data. To ensure the docket does not contain 
duplicate comments, commenters should send only one copy of written 
comments, or if comments are filed electronically, commenters should 
submit only one time.
    The FAA will file in the docket all comments it receives, as well 
as a report summarizing each substantive public contact with FAA 
personnel concerning this proposed rulemaking. Before acting on this 
proposal, the FAA will consider all comments it receives on or before 
the closing date for comments. The agency may change this proposal in 
light of the comments it receives.
Confidential Business Information
    Confidential Business Information (CBI) is commercial or financial 
information that is both customarily and actually treated as private by 
its owner. Under the Freedom of Information Act (FOIA) (5 U.S.C. 552), 
CBI is exempt from public disclosure. If your comments responsive to 
this NPRM contain commercial or financial information that is 
customarily treated as private, that you actually treat as private, and 
that is relevant or responsive to this NPRM, it is important that you 
clearly designate the submitted comments as CBI. Please mark each page 
of your submission containing CBI as ``PROPIN.'' FAA will treat such 
marked submissions as confidential under the FOIA, and they will not be 
placed in the public docket of this NPRM. Submissions containing CBI 
should be sent to the person identified in the FOR FURTHER INFORMATION 
CONTACT section of this document. Any information the FAA receives that 
is not specifically designated as CBI will be placed in the public 
docket for this rulemaking.

B. Availability of Rulemaking Documents

    An electronic copy of rulemaking documents may be obtained from the 
internet by--
     Searching the Federal eRulemaking Portal (https://www.regulations.gov);
     Visiting the FAA's Regulations and Policies web page at 
https://www.faa.gov/regulations_policies; or
     Accessing the Government Publishing Office's web page at 
https://www.gpo.gov/fdsys/.
    Copies may also be obtained by sending a request to the Federal 
Aviation Administration, Office of Rulemaking, ARM-1, 800 Independence 
Avenue SW, Washington, DC 20591, or by calling (202) 267-9677. 
Commenters must identify the docket or notice number of this 
rulemaking.
    All documents the FAA considered in developing this proposed rule, 
including economic analyses and technical reports, may be accessed from 
the internet through the Federal eRulemaking Portal referenced above.

C. Small Business Regulatory Enforcement Fairness Act

    The Small Business Regulatory Enforcement Fairness Act of 1996 
(SBREFA) 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 identified 
in 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

14 CFR Part 21

    Aircraft, Aviation safety, Exports, Imports, Reporting and 
recordkeeping requirements.

14 CFR Part 36

    Aircraft, Noise control.

The Proposed Amendment

    In consideration of the foregoing, the Federal Aviation 
Administration proposes to amend chapter I of Title 14, Code of Federal 
Regulations as follows:

PART 21--CERTIFICATION PROCEDURES FOR PRODUCTS AND ARTICLES

0
1. The authority citation for part 21 is revised to read as follows:

    Authority:  42 U.S.C. 7572; 49 U.S.C. 106(f), 106(g), 40105, 
40113, 44701-44702, 44704, 44707, 44709, 44711, 44713, 44715, 45303; 
Pub. L. 115-254.

0
2. Amend Sec.  21.93 by revising paragraph (b)(2) and adding paragraph 
(b)(6) to read as follows:


Sec.  21.93  Classification of changes in type design.

* * * * *
    (b) * * *
    (2) Subsonic jet (Turbojet powered) airplanes (regardless of 
category) and Concorde airplanes. For airplanes to which this paragraph 
applies, ``acoustical changes'' do not include changes in type design 
that are limited to one of the following--
    * * *
    (6) Supersonic airplanes.
* * * * *

PART 36--NOISE STANDARDS: AIRCRAFT TYPE AND AIRWORTHINESS 
CERTIFICATION

0
3. The authority citation for part 36 is revised to read as follows:

    Authority:  42 U.S.C. 4321 et seq.; 49 U.S.C. 106(g), 40113, 
44701-44702, 44704, 44715; sec. 305, Pub. L. 96-193, 94 Stat. 50, 
57; E.O. 11514, 35 FR 4247, 3 CFR, 1966-1970 Comp., p. 902; Pub. L. 
115-254.

0
4. Amend Sec.  36.1 by
0
a. Adding paragraph (a)(6);
    b. Revising paragraph (c);
0
c. Revising the introductory text of paragraph (d);
0
d. Revising the introductory text of paragraph (f);
0
e. Revising paragraph (g);
0
f. Removing and reserving paragraph (f)(8); and
0
e. Adding paragraph (j).
    The additions and revisions read as follows:


Sec.  36.1  Applicability and definitions.

    (a) * * *
    (6) Type certificates, changes to those certificates, and standard 
airworthiness certificates, for supersonic airplanes.
* * * * *
    (c) Each person who applies under part 21 of this chapter for 
approval of an acoustical change described in Sec.  21.93(b) of this 
chapter must show that the aircraft complies with the applicable 
provisions of Sec. Sec.  36.7, 36.9, 36.11, 36.13, or 36.15 of this 
part in addition to the applicable airworthiness requirements of this 
chapter.
    (d) Each person who applies for the original issue of a standard 
airworthiness certificate for a transport category large airplane or 
for a subsonic jet airplane under Sec.  21.183 must, regardless of date 
of application, show compliance with the following

[[Page 20443]]

provisions of this part (including appendix B):
* * * * *
    (f) For the purpose of showing compliance with this part for 
transport category large airplanes and subsonic jet airplanes 
regardless of category, the following terms have the following 
meanings:
* * * * *
    (g) For the purpose of showing compliance with this part for 
transport category large airplanes and subsonic jet airplanes 
regardless of category, each airplane may not be identified as 
complying with more than one stage or configuration simultaneously.
* * * * *
    (j) For the purpose of showing compliance with this part, for 
supersonic airplanes regardless of category, the following terms have 
the meanings specified:
    Landing and Takeoff (LTO) cycle, as used in reference to a 
supersonic airplane, means the segments of subsonic flight that include 
flyover, lateral and approach noise levels prescribed in appendix C of 
this part.
    Programmed Lapse Rate (PLR) is a fully automated feature 
incorporated into the engine controls as part of the engine thrust 
rating structure as a means of reducing noise.
    Supersonic airplane means--
    (i) An airplane:
    (A) For which the maximum operating limit speed, Mmo, 
exceeds a Mach number of 1; and
    (B) That receives an original type certificate after [EFFECTIVE 
DATE OF FINAL RULE].
    (ii) Does not include any Concorde model airplane. No regulation in 
this part that references the Concorde applies to any non-Concorde 
supersonic airplane.
    Supersonic Level 1 (SSL1) noise level means a noise level at or 
below the noise limit prescribed in Sec.  C36.5 of appendix C to this 
part.
    Variable Noise Reduction System (VNRS) is a dynamic system 
integrated into the design of an aircraft that functions automatically 
to produce a change in the configuration of the aircraft to reduce 
noise. Such systems may include:
    (i) Hardware or software components that control engine parameters 
or airframe configuration; or
    (ii) Controls initiated through a flight management system as a 
means of noise reduction during normal operation.
0
5. Amend Sec.  36.7 by revising the section heading and paragraph (a) 
to read as follows:


Sec.  36.7  Acoustical change: Transport category large airplanes and 
subsonic jet airplanes.

    (a) Applicability. This section applies to all transport category 
large airplanes and subsonic jet airplanes for which an acoustical 
change approval is applied for under Sec.  21.93(b) of this chapter.
* * * * *
0
6. Add Sec.  36.15 to subpart A to read as follows:


Sec.  36.15  Acoustical change: Supersonic airplanes.

    (a) Applicability. This section applies to all supersonic airplanes 
for which an acoustical change approval is applied for under Sec.  
21.93(b) of this chapter.
    (b) General requirements. For supersonic airplanes, the acoustical 
change approval requirements are as follows:
    (1) In showing compliance, noise levels must be measured and 
evaluated in accordance with the applicable procedures and conditions 
prescribed in appendix A of this part.
    (2) Compliance with the SSL1 noise limits prescribed in Sec.  C36.5 
of appendix C of this part must be shown in accordance with the 
applicable provisions of Sec. Sec.  C36.7 and C36.8 of appendix C of 
this part.
    (c) If a supersonic airplane is an SSL1 airplane prior to a change 
in type design, after a change in type design it must remain an SSL1 
airplane as specified in Sec.  C36.5 of appendix C of this part.
0
7. Revise the heading of subpart B to read as follows.

Subpart B--Transport Category Large Airplanes and Subsonic Jet 
Airplanes

0
8. Amend Sec.  36.101 to read as follows:
    For subsonic transport category large airplanes and subsonic jet 
powered airplanes the noise generated by the airplane must be measured 
under appendix A of this part or under an approved equivalent 
procedure.
0
9. Revise the heading of subpart D to read as follows.

Subpart D--Noise Limits for Concorde Airplanes

0
10. Add subpart E to read as follows:

Subpart E --Noise Limits for Supersonic Airplanes

Sec.
36.401 Noise measurement and evaluation.
36.403 Noise limits.


Sec.  36.401  Noise measurement and evaluation.

    For supersonic airplanes, the noise generated by the airplane must 
be measured and evaluated in accordance with appendix A of this part or 
an approved equivalent procedure.


Sec.  36.403  Noise limits.

    For supersonic airplanes, compliance with this section is 
determined by:
    (a) Tests conducted in accordance with Sec.  36.401 of this part.
    (b) Demonstration of the noise levels produced using the reference 
procedures and conditions in Sec.  C36.7, and the test procedures of 
Sec.  C36.8 of appendix C of this part or an approved equivalent 
procedure.
    (c) For an airplane for which type certification application is 
made after [EFFECTIVE DATE OF FINAL RULE], the noise levels 
demonstrated may not exceed the SSL1 noise limits prescribed in Sec.  
C36.5(c) of appendix C of this part.
0
11. Amend Sec.  36.1581 by:
0
a. Revising paragraph (a)(1);
0
b. Adding paragraph (a)(4);
0
c. Revising paragraph (d);
0
d. Removing and reserving paragraph (g); and
0
e. Adding paragraph (h) and (i).
    The additions and revisions read as follows:


Sec.  36.1581  Manuals, markings, and placards.

    (a) * * *
    (1) For transport category large airplanes, subsonic jet airplanes, 
and the Concorde, the noise level information must be one value for 
each flyover, lateral, and approach as defined and required by appendix 
B of this part, along with the maximum takeoff weight, maximum landing 
weight, and configuration.
* * * * *
    (4) For supersonic airplanes, LTO cycle noise level information 
must:
    (i) Be determined in accordance with appendix C of this part;
    (ii) Be one value for each flyover, lateral, and approach condition 
as defined; and
    (iii) Correspond to the maximum takeoff weight, the maximum landing 
weight, and the configuration for each of these conditions.
* * * * *
    (d) For transport category large airplanes and subsonic jet 
airplanes, for which the weight used in meeting the takeoff or landing 
noise requirements of this part is less than the maximum weight 
established under the applicable airworthiness requirements, those 
lesser weights must be furnished, as operating limitations in the 
operating limitations section of the Airplane Flight Manual. Further, 
the maximum takeoff weight must not exceed the takeoff weight that

[[Page 20444]]

is most critical from a takeoff noise standpoint.
* * * * *
    (h) For supersonic airplanes, no maximum landing or takeoff weight 
may exceed the weight used to establish an LTO cycle noise level that 
shows compliance with this part.
    (i) The following conditions each require an operating limitation 
that must be included in the operating limitations section of the 
Airplane Flight Manual.
    (1) When any weight used in showing compliance with an LTO cycle 
noise requirement of this part is less than the maximum weight 
established under the applicable airworthiness requirements, the weight 
used to show compliance with a noise requirement of this part becomes 
an operating limitation.
    (2) When a VNRS has been used to show compliance with the SSL1 
noise limits of Sec.  C36.5 of appendix C of this part, or with the 
reference procedures of Sec. Sec.  C36.7(d) and C36.7(e) of appendix C 
of this part, the flight crew must ensure that the VNRS is functioning 
properly prior to takeoff;
    (3) When PLR has been used to show compliance with the SSL1 noise 
limits of Sec.  C36.5 of appendix C of this part, or with the reference 
procedures of Sec. Sec.  C36.7(d) and C36.7(e) of appendix C of this 
part, the airplane may not be programmed to exceed PLR thrust during 
normal operations except at specified thrust levels for which the 
airplane has been shown not to cause any significant noise impact on 
the ground.
0
12. In appendix A to part 36 revise the heading and Sec.  A.36.1.1 to 
read as follows:

Appendix A to Part 36--Aircraft Noise Measurement and Evaluation

* * * * *
    A36.1.1 This appendix prescribes the conditions under which 
airplane noise certification tests must be conducted and states the 
measurement procedures that must be used to measure airplane noise. 
This appendix also describes the procedures that must be used to 
determine the noise evaluation quantity designated as effective 
perceived noise level, EPNL, as referenced in Sec. Sec.  36.101, 36.401 
and 36.803.
* * * * *
0
c. Revise the note to Sec.  A36.2.1.1 to read as follows:
* * * * *

    Note:  Many noise certifications involve only minor changes to 
the airplane type design. The resulting changes in noise can often 
be established reliably without resorting to a complete test as 
outlined in this appendix. For this reason, the FAA permits the use 
of approved equivalent procedures. There are also equivalent 
procedures that may be used in full certification tests, in the 
interest of reducing costs and providing reliable results. Guidance 
material on the use of equivalent procedures in the noise 
certification of subsonic jet, propeller-driven large airplanes, and 
supersonic airplanes is provided in the current advisory circular 
for this part.

* * * * *
0
d. Revise paragraph A36.5.2(h)(1) to read as follows:
* * * * *
    A36.5.2.5 * * *
    (h) * * *
    (1) For subsonic jet airplanes and supersonic airplanes: engine 
performance in terms of net thrust, engine pressure ratios, jet exhaust 
temperatures and fan or compressor shaft rotational speeds as 
determined from airplane instruments and manufacturer's data for each 
test run;
* * * * *
0
e. Revise paragraph A36.9.1.3 to read as follows:
* * * * *
    A36.9.1.3 For supersonic airplanes, the integrated method of 
adjustment, described in Sec.  A36.9.4, must be used when VNRS 
reference procedures in C36.7(d) and C36.7(e) are used to demonstrate 
compliance with this part.
* * * * *
0
13. Revise the heading of appendix B to part 36, to read as follows.

Appendix B to Part 36--Noise Levels for Transport Category and Subsonic 
Jet Airplanes Under Sec.  36.103 and Concorde Airplanes Under Sec.  
36.301

0
14. Add appendix C to part 36 to read as follows:

Appendix C to Part 36--Noise Levels for Supersonic Airplanes

Sec.
C36.1 Noise Measurement and Evaluation.
C36.2 Noise Evaluation Metric.
C36.3 Reference Noise Measurement Points.
C36.4 Test Noise Measurement Points.
C36.5 Noise Limits.
C36.6 Use of a Variable Noise Reduction System (VNRS).
C36.7 Noise Certification Reference Procedures and Conditions.
C36.8 Noise Certification Test Procedures.
Section C36.1 Noise Measurement and Evaluation
    The procedures of appendix A of this part, or approved equivalent 
procedures, must be used to determine the noise levels of a supersonic 
airplane. The noise levels determined using these procedures must be 
used to show compliance with the requirements of this appendix.
Section C36.2 Noise Evaluation Metric
    The noise evaluation metric is the effective perceived noise level 
expressed in EPNdB, as calculated using the procedures of appendix A of 
this part.
Section C36.3 Reference Noise Measurement Points
    When tested using the procedures of this part, an airplane may not 
exceed the noise levels specified in Sec.  C36.5 at the following 
points on level terrain:
    (a) Lateral full-power reference noise measurement point: The point 
on a line parallel to and 1,476 feet (450 meters) from the runway 
centerline, or extended centerline, where the noise level after lift-
off is at a maximum during takeoff. When approved by the FAA, the 
maximum lateral noise at takeoff thrust may be assumed to occur at the 
point (or its approved equivalent) along the extended centerline of the 
runway where the airplane reaches 985 feet (300 meters) altitude above 
ground level. The altitude of the airplane as it passes the noise 
measurement points must be within + 328 to -164 feet (+100 to -50 
meters) of the target altitude.
    (b) Flyover reference noise measurement point: The point on the 
extended centerline of the runway that is 21,325 feet (6,500 meters) 
from the start of the takeoff roll;
    (c) Approach reference noise measurement point: The point on the 
extended centerline of the runway that is 6,562 feet (2,000 meters) 
from the runway threshold. On level ground, this corresponds to a 
position that is 394 feet (120 meters) vertically below the 3-degree 
descent path, which originates at a point on the runway 984 feet (300 
meters) beyond the threshold.
Section C36.4 Test Noise Measurement Points
    (a) If the test noise measurement points are not located at the 
reference noise measurement points, any corrections for the difference 
in position are to be made using the same adjustment procedures as for 
the differences between test and reference flight paths.
    (b) The applicant must use a sufficient number of lateral test 
noise measurement points to demonstrate to the FAA that the maximum 
noise level on the appropriate lateral line has been determined. For 
supersonic airplanes, simultaneous measurements must be made at one 
test noise measurement point at its symmetrical point on the other side 
of the runway. The measurement points are considered to be symmetrical 
if they are

[[Page 20445]]

longitudinally within 33 feet (10 meters) of each other.
Section C36.5 Noise Limits
    When determined in accordance with the noise evaluation methods of 
appendix A of this part, the noise levels of a Supersonic Level 1 
airplane may not exceed the following:
    (a) Flyover.
    (1) For an airplane with three engines:
    (i) For which noise certification is requested at a maximum 
certificated takeoff weight (mass) of 150,000 pounds (68,039 kilograms 
(kg)), the noise limit is 94.0 EPNdB.
    (ii) For which noise certification is requested at a maximum 
certificated takeoff weight of less than 150,000 pounds (68,039 kg), 
the noise limit begins at 94.0 EPNdB and decreases linearly with the 
logarithm of the airplane weight (mass) at the rate of 4 EPNdB per 
halving of weight (mass) down to 89 EPNdB at 63,052 pounds (28,600 kg) 
after which the limit is constant.
    (2) For an airplane with two engines or fewer:
    (i) For which noise certification is requested at a maximum 
certificated takeoff weight (mass) of 150,000 pounds (68,039 kg), the 
noise limit is 91.0 EPNdB.
    (ii) For which noise certification is requested at a maximum 
certificated takeoff weight (mass) of less than 150,000 pounds (68,039 
kg), the noise limit begins at 91.0 EPNdB and decreases linearly with 
the logarithm of the airplane weight (mass) at the rate of 4 EPNdB per 
halving of weight (mass) down to 89 EPNdB at 106,042 pounds (48,100 
kg), after which the limit is constant.
    (b) Lateral. Regardless of the number of engines, for an airplane 
at the reference noise measurement point:
    (1) For which noise certification is requested at a maximum 
certificated takeoff weight (mass) of 150,000 pounds (68,039 kg) the 
noise limit is 96.5 EPNdB.
    (2) For which noise certification is requested at a maximum 
certificated take-off weight (mass) of less than 150,000 pounds (68,039 
kg), the noise limit begins at 96.5 EPNdB and decreases linearly with 
the logarithm of the weight (mass) down to 94 EPNdB at 77,162 pounds 
(35,000 kg), after which the limit remains constant.
    (c) Approach. Regardless of the number of engines, for an airplane:
    (1) For which noise certification is requested at a maximum 
certificated takeoff weight (mass) of 150,000 pounds (68,039 kg) the 
noise limit is 100.2 EPNdB.
    (2) For which noise certification is requested at a maximum 
certificated takeoff weight (mass) of less than 150,000 pounds (68,039 
kg), the noise limit begins at 100.2 EPNdB and decreases linearly with 
the logarithm of the mass down to 98 EPNdB at 77,162 pounds (35.0k kg), 
after which the limit remains constant.
    (d) No airplane may exceed the noise limits described in this 
section at any measurement point.
    (e) The sum of the differences at all three measurement points 
between the maximum noise levels and the noise limits specified in 
Sec. Sec.  C36.5(a), C36.5(b) and C36.5(c) may not be less than 13.5 
EPNdB.
Section C36.6 Use of a Variable Noise Reduction System (VNRS)
    For any airplane that includes a VNRS as part of an airplane design 
for noise certification, the applicant must--
    (a) Submit reference procedures to be approved by the FAA as part 
of its noise certification test plan.
    (b) Demonstrate the approved VNRS reference procedures for takeoff 
as defined in Sec.  C36.7(d), or for approach as defined in C36.7(e), 
when conducting certification tests.
Section C36.7 Noise Certification Reference Procedures and Conditions
    (a) General conditions:
    (1) All reference procedures must meet the requirements of Sec.  
36.3 of this part.
    (2) Calculations of airplane performance and flight path must be 
made using the reference procedures and must be approved by the FAA.
    (3) Standard reference procedures--When using standard reference 
procedures, the following apply--
    (i) For takeoff, Sec.  C36.7(b);
    (ii) For lateral, Sec.  C 36.7(b)(3); and
    (iii) For approach, Sec.  C36.7(c).
    (4) VNRS reference procedures--For airplanes that use a VNRS, the 
following reference procedures apply--
    (i) For takeoff and lateral, Sec.  C36.7(d); and
    (ii) For approach, Sec.  C36.7(e).
    (5) The following reference conditions must be specified in the 
reference procedures. When used for the calculation of atmospheric 
absorption coefficients, the reference atmosphere is homogeneous in 
terms of temperature and relative humidity.
    (i) Sea level atmospheric pressure of 2,116 pounds per square foot 
(psf) (1013.25 hPa);
    (ii) Ambient sea-level air temperature of 77 [deg]F (25 [deg]C, 
i.e., ISA + 10 [deg]C);
    (iii) Relative humidity of 70 percent;
    (iv) Zero wind.
    (v) In defining the reference takeoff flight path(s) for the 
takeoff and lateral noise measurements, the runway gradient is zero.
    (b) Standard takeoff reference procedure:
    The takeoff reference flight path must be calculated using the 
following:
    (1) The takeoff thrust/power used must be the maximum specified by 
the applicant for normal takeoff operations (and is presumed to be less 
than maximum thrust/power for supersonic cruise speed) as listed in the 
performance section of the airplane flight manual under the reference 
atmospheric conditions given in Sec.  C36.7(a)(5). Average engine 
takeoff thrust or power must be used from brake release to the point 
where the minimum height above runway level is reached, as follows--
    The minimum height to be used--
    (i) For airplanes with three engines: 853 feet (260 meters).
    (ii) For airplanes with two engines or fewer: 984 feet (300 
meters).
    (2) Upon reaching the height specified in paragraph (b)(1) of this 
section, airplane thrust or power must not be reduced below that 
required to maintain the greater of--
    (i) A climb gradient of 4 percent; or
    (ii) For multi-engine airplanes, level flight with one engine 
inoperative.
    (3) To determine the lateral noise level, the reference flight path 
must be calculated using full takeoff power throughout the test run 
without a reduction in thrust or power.
    (4) The takeoff reference true airspeed is the all-engine operating 
takeoff climb speed using the procedures approved by the FAA--
    (i) For the shortest runway on which the airplane is approved to 
operate;
    (ii) When the aircraft reaches the measurement location distance 
from brake release.
    (iii) That is determined by the applicant when calculating the 
reference profile using the reference conditions stated in Sec.  
C36.7(5).
    (iv) The reference speed may not exceed 250 knots.
    (5) The takeoff configuration selected by the applicant and 
approved by the FAA must be maintained constantly throughout the 
takeoff reference procedure, except that the landing gear may be 
retracted.
    (6) The weight of the airplane at the brake release must be the 
maximum takeoff weight at which the noise certification is requested. 
This weight may be required as an operating limitation in accordance 
with Sec.  36.1581(i) of this part; and
    (7) The average engine is defined as the average of all the 
certification

[[Page 20446]]

compliant engines used during the airplane flight tests, up to and 
during certification, when operating within the limitations, and 
according to the procedures given in the Flight Manual. This will 
determine the relationship of thrust/power to control parameters (e.g., 
N1 or EPR). Noise measurements made during certification tests must be 
corrected using this relationship.
    (c) Standard approach reference procedure:
    The approach reference flight path must be calculated using the 
following:
    (1) The airplane is stabilized and following a 3-degree glide path;
    (2) A steady approach speed of Vref + 10 kts (Vref + 19 km/h) with 
thrust and power stabilized must be established and maintained over the 
approach measuring point.
    (3) The constant approach configuration used in the airworthiness 
certification tests, but with the landing gear down, must be maintained 
throughout the approach reference procedure;
    (4) The weight of the airplane at touchdown must be the maximum 
landing weight permitted in the approach configuration defined in 
paragraph (c)(3) of this section at which noise certification is 
requested. This weight may be required as an operating limitation in 
accordance with Sec.  36.1581(i) of this part; and
    (5) The weight at which certification is requested, with the 
airplane in the most critical configuration, defined as--
    (i) That which produces the highest noise level with normal 
deployment of aerodynamic control surfaces including lift and drag 
producing devices, and
    (ii) All equipment listed in Sec.  A36.5.2.5 of appendix A of this 
part that can be operated during normal flight.
    (d) VNRS Takeoff reference procedure:
    (1) The VNRS takeoff reference flight path is to be specified by 
the applicant using the following--
    (i) Maximum engine takeoff thrust or power (of an average engine) 
used to determine takeoff true airspeed from brake release to the 
activation of VNRS using the reference atmospheric conditions of Sec.  
C36.7(a)(5).
    (ii) The segment of the flight path from the activation of VNRS to 
the point at which VNRS is no longer active;
    (iii) The applicant must maintain climb power throughout the 
remaining segment of the reference flight path;
    (iv) The following minimum heights must be reached before engine 
cutback is initiated:
    (A) For airplanes with three engines: 853 feet (260 meters);
    (B) For airplanes with two engines or fewer: 984 feet (300 meters); 
and
    (v) Upon reaching the height specified in paragraph (d)(4) of this 
section, airplane thrust or power must not be reduced below that 
required to maintain either of the following, whichever is greater:
    (A) A climb gradient of 4 percent; or
    (B) In the case of multi-engine airplanes, level flight with one 
engine inoperative.
    (2) The VNRS reference flight path determined under paragraph 
(d)(1) of this section must be used when demonstrating and measuring 
the lateral noise level to show compliance with Sec.  C36.5 of this 
appendix.
    (3) The takeoff reference true airspeed to be used is calculated 
using the all engine operating takeoff climb speed, as determined 
using--
    (i) The shortest approved runway length;
    (ii) Maximum certificated takeoff weight at which the noise 
certification is requested, which may result in an operating limitation 
as specified in Sec.  36.1581(d);
    (iii) The reference conditions stated in Sec.  C36.7(5);
    (iv) The calculated true airspeed at the overhead measurement 
point, defined in Sec.  C36.3(b);
    (v) The takeoff reference true airspeed must be attained as soon as 
practicable after lift-off; and
    (vi) The takeoff reference true airspeed may not exceed 250 knots;
    (4) For all airplanes, noise values measured during testing must be 
corrected to the reference acoustic day takeoff speed.
    (5) The takeoff configuration selected by the applicant and 
approved by the FAA must be maintained throughout the takeoff reference 
procedure, except that the landing gear may be retracted; and
    (6) The weight of the airplane at brake release must be the maximum 
takeoff weight at which noise certification is requested. This weight 
may be required as an operating limitation in accordance with Sec.  
36.1581(i) of this part; and
    (7) As used in paragraph (d)(1)(i) of this section, average engine 
means the average of all the certification compliant engines used 
during the airplane flight tests, up to and during certification, when 
operating within the limitations and according to the procedures given 
in the Flight Manual. The average engine must be used to determine the 
relationship of thrust/power to control parameters (e.g., N1 or EPR).
    (e) VNRS Approach reference procedure:
    The VNRS approach reference flight path must be calculated using 
the following:
    (1) The airplane is stabilized and following a 3-degree glide path;
    (2) The approach reference speed is Vref + 10 kts (Vref + 19 km/h);
    (3) The applicant must use the approach configuration (landing gear 
down) established for normal operations as part of the airworthiness 
certification.
    (4) The weight of the airplane at touchdown, at which noise 
certification is requested, must be the maximum landing weight 
permitted in the approach configuration defined in paragraph (e)(3) of 
this section, in accordance with Sec.  36.1581(h) of this part; an
    (5) The weight at which certification is requested, with the 
airplane in the most critical configuration, defined as--
    (i) The configuration that produces the highest noise level with 
normal deployment of aerodynamic control surfaces including lift and 
drag producing devices; and
    (ii) All equipment listed in Sec.  A36.5.2.5 of appendix A of this 
part that can be operated during normal flight.
Section C36.8 Noise Certification Test Procedures
    (a) All test procedures must be approved by the FAA before 
certification tests are conducted.
    (b) The test procedures and noise measurements must be conducted 
and processed in an approved manner to yield the noise evaluation 
metric EPNL, in units of EPNdB, as described in appendix A of this 
part.
    (c) Acoustic data must be adjusted to the reference conditions 
specified in this appendix using the methods described in appendix A of 
this part. Adjustments for speed and thrust must be made as described 
in Sec.  A36.9 of this part, unless separate VNRS procedures and the 
data adjustments are approved.
    (d) If the airplane's weight during the test is different from the 
weight at which noise certification is requested, the required EPNL 
adjustment may not exceed 2 EPNdB for each takeoff and 1 EPNdB for each 
approach. Data approved by the FAA must be used to determine the 
variation of EPNL with weight for both takeoff and approach test 
conditions. The necessary EPNL adjustment for variations in approach 
flight path from the reference flight path must not exceed 2 EPNdB.
    (e) For approach, a steady glide path angle of 3 degrees 0.5 degree is acceptable.
    (f) If equivalent test procedures different from the reference 
procedures are used, the test procedures and all methods for adjusting 
the results to the reference procedures must be approved

[[Page 20447]]

by the FAA. The adjustments may not exceed 16 EPNdB on takeoff and 8 
EPNdB on approach. If the adjustment is more than 8 EPNdB on takeoff, 
or more than 4 EPNdB on approach, the resulting numbers must be more 
than 2 EPNdB below the noise limit specified in Sec.  C36.5.
    (g) During takeoff, lateral, and approach tests, the airplane 
variation in instantaneous indicated airspeed must be maintained within 
3% of the average airspeed between the 10 dB-down points. 
This airspeed is determined by the pilot's airspeed indicator. However, 
if the instantaneous indicated airspeed exceeds 3 kt 
(5.5 km/h) of the average airspeed over the 10 dB-down 
points, and is determined by the FAA representative on the flight deck 
to be due to atmospheric turbulence, then the flight so affected may 
not be used for noise certification purposes.

    Issued in Washington, DC, under the authority of 49 U.S.C. 
106(f), 44701(a)(5), 44715, and Sec.  181 of the FAA Reauthorization 
Act of 2018, on March 30, 2020.
Kevin W. Welsh,
Executive Director, Office of Environment & Energy.
[FR Doc. 2020-07039 Filed 4-10-20; 8:45 am]
 BILLING CODE 4910-13-P