Document ID: FAA-2021-0710-0016
Agency: faa
Document Type: Notice
Title: Noise Certification Standards: Matternet Model M2 Aircraft
Posted Date: 2022-09-12T04:00Z

[Federal Register Volume 87, Number 175 (Monday, September 12, 2022)]
[Notices]
[Pages 55878-55887]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-19639]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

[Docket No.: FAA-2021-0710]

Noise Certification Standards: Matternet Model M2 Aircraft

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule; rule of particular applicability.

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SUMMARY: The Federal Aviation Administration (FAA) is promulgating 
noise certification standards that apply only to the Matternet Model M2 
quadcopter unmanned aircraft (UA) because no generally applicable noise 
standards were available for this aircraft at the time the aircraft was 
presented for certification. Therefore, to complete the Matternet Model 
M2's type certification process for noise, the FAA adopts the standards 
in this rule for the Matternet Model M2.

DATES: This rule of particular applicability is effective September 9, 
2022.

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

FOR FURTHER INFORMATION CONTACT: For technical questions concerning 
this action, contact Hua (Bill) He, Federal Aviation Administration, 
Office of Environment and Energy, 800 Independence Ave. SW, Room 900 
West, Washington, DC 20591; telephone (202) 267-3565; email 
[email protected].

SUPPLEMENTARY INFORMATION:

I. Authority for This Rulemaking

    The FAA's authority to issue rules on aviation safety is found in 
Title 49 of the United States Code. Subtitle I, section 106 describes 
the authority of the FAA Administrator. Subtitle VII, Aviation 
Programs, describes in more detail the scope of the agency's authority.
    This rulemaking is promulgated under the authority described in 
subtitle VII, part 447, and section 44715. Section 44715(a)(3) states 
that an original type certificate for an aircraft may be issued only 
after the Administrator of the FAA prescribes noise standards and 
regulations under that section that apply to the aircraft. This 
regulation is within the scope of that authority.

II. Good Cause

    The Administrative Procedure Act (5 U.S.C. 551 et seq.) requires 
the publication or service of any substantive rule not less than 30 
days before its effective date, except as otherwise provided by the 
agency for good cause found and published with the rule. (5 U.S.C. 
553(d)). The FAA finds good cause exists to make this rule immediately 
effective because delaying the effective date is unnecessary. This rule 
applies to a single certification applicant (Matternet), and no other 
person will be affected by the requirements. FAA understands that 
Matternet likely is able to meet the standards when they become 
effective. The notice that would be provided by delaying the effective 
date is unnecessary. Moreover, delaying the effective date would 
negatively impact Matternet, the only party impacted by this rule, by 
delaying its ability to type certificate the Matternet Model M2, due to 
the lack of effective noise certification standards. Accordingly, the 
FAA finds that good cause exists to make this rule effective in less 
than 30 days.

III. Background

A. Need for This Rulemaking

    Section 44704 of Title 49 of the United States Code requires that 
the FAA issue a type certificate to an applicant that presents a 
qualified design. Section 44715(a)(3) requires the FAA to prescribe 
noise standards for an aircraft before a type certificate may be 
issued.
    Matternet applied for type certification of its aircraft on May 18, 
2018. The aircraft is a quadcopter design unmanned aircraft (UA) with a 
maximum takeoff weight of 29 pounds, including a 4-pound payload, and a 
proposed operating altitude of 400 feet or lower. To fulfill the 
statutory requirement of section 44715(a)(3), the FAA is adopting the 
set of noise certification standards described in this rule of 
particular applicability that will apply only to the Matternet Model 
M2, as the current noise certification standards cannot be applied 
effectively to this aircraft.

B. Related Actions

    This is the first rule of particular applicability establishing a 
noise certification basis for a single model of aircraft. At present, 
the FAA does not have a sufficient database of information about the 
noise generated by most UA models to establish generally applicable 
noise standards due to their novelty and variety. The FAA will continue 
to receive information about noise characteristics as it engages with 
certification applicants, and expects to use data collected through 
this rule to inform future rules of particular applicability and 
generally applicable standards. The FAA will consider similar 
rulemaking actions for other noise certification applicants while it 
develops the generally applicable standards for UA.

C. Summary of the NPRM

    On August 27, 2021, the FAA published a notice of proposed 
rulemaking (NPRM) setting out the noise certification test standards 
and noise limit that would apply to the Matternet Model M2 (86 FR 
48281). The NPRM proposed that the requirements of 14 CFR 36.3 and 36.6 
would apply to the Matternet Model M2 except as described in the rule, 
and proposed specific noise limits and testing procedures to be applied 
to the Matternet Model M2 aircraft. The comment period for the NPRM 
closed September 27, 2021.
    The NPRM was not intended to affect the airworthiness certification 
of this aircraft model or any operational approvals.\1\ The FAA, in 
accordance with the applicable airworthiness standards and operating 
rules, makes those findings separately.
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    \1\ As is true for all noise certification, this rule neither 
assesses the environmental impacts of any eventual operation of the 
subject aircraft, nor constitutes any environmental review that may 
be required by the FAA before granting operational approval. Any 
such environmental review would be completed in advance of granting 
operational approval(s).
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IV. Discussion of Comments and Final Rule

    The FAA received submissions from 14 commenters. The commenters 
included five individuals, two engineering firms, four aircraft 
manufacturers and operators (Bell Textron, Inc., Zipline International, 
Inc., Ameriflight, LLC, and UPS Flight Forward, Inc.), and three 
aviation industry trade groups (Commercial Drone Alliance (CDA), 
Robotic Skies, and the Small UAV Coalition).
    The aircraft manufacturers, aircraft operators, and aviation 
industry trade groups supported the proposed certification standards as 
being appropriate for the Matternet Model M2. Three individual 
commenters found the

[[Page 55879]]

proposed noise limit unreasonable but presented no support for their 
comments or any alternatives. One individual expressed concern about UA 
noise impacts in general. As discussed in more detail in the following 
paragraphs, five commenters suggested specific changes in the noise 
measurement procedures for the Matternet Model M2. Three commenters 
suggested changes to noise test procedures that should apply to all UA 
rather than specifically to the Matternet Model M2.
    One anonymous commenter suggested changes to the format of the 
proposed rule.

A. Comments Regarding the Proposed Noise Certification Standards for 
the Matternet Model M2

1. Noise Limit Objections
    Three commenters expressed dissatisfaction regarding the 78 dBA 
noise limit specified for the Matternet Model M2. These commenters 
described other noise metrics with lower values, but the metrics 
suggested were not relevant to the certification of an individual 
aircraft. In one case, the commenter appeared to reference the sound 
level applied for compatible land use planning around airports, 
however, the sound level referenced would not be applicable to an 
individual aircraft model. This sound level, known as day-night average 
sound level (DNL) 65 dB, is an average of all flights over a certain 
area. Although the FAA uses DNL 65 dB as the significance threshold 
when it performs environmental planning reviews, DNL 65 dB is not the 
appropriate threshold here because it applies to the average noise of 
all aircraft in a particular area, as opposed to a single aircraft, the 
Matternet Model M2. Another commenter suggested a limit of 30 dB, but 
did not provide justification for the suggestion, or indicate how the 
limit should be used. The FAA makes no change to the proposed noise 
limit for the Matternet Model M2 in this final rule.
2. Noise Limit Clarification
    One individual commenter expressed concern with the FAA's 
explanation of the 78 dB noise limit. The FAA clarifies below the 
approach in setting the limit at 78dB, as the intent is to maintain a 
consistent noise certification approach that includes aircraft of all 
sizes, including UA.
    In the absence of historical data regarding most models of UA, the 
FAA began its analysis by using the existing noise limits in the 
regulations and extrapolating those limits to a lower-weight aircraft 
tested at a lower altitude. The FAA used established limit data from 
the appendices (including A and J) to part 36 where practicable, and 
FAA applied accepted, well-known noise certification principles and 
adjustment methods in developing this rule. Since the Matternet Model 
M2 is a quadcopter, the FAA used as its starting point the simplified 
helicopter noise limit found in part 36 appendix J that applies to 
smaller helicopters (Sec.  J36.305 (a)(2)). One key assumption of this 
method is that fundamental rotorcraft physics and associated noise are 
scalable for lighter-weight UA. For the subject aircraft, the Stage 3 
noise limit of appendix J was extrapolated to the maximum takeoff 
weight (MTOW) to correspond to a 527-pound aircraft. A secondary noise 
adjustment was applied to account for the adjusted reference altitude 
of 250 feet for the Matternet Model M2, rather than the 492-foot 
reference altitude in appendix J. These two adjustments account for the 
size and the expected operational altitudes of the Matternet Model M2. 
These adjustments provide the basis for the constant 78 dB limit for 
the Matternet Model M2. No change was made to this final rule based on 
this comment.
3. Noise Measurement Procedure--Atmospheric Attenuation Limit in 
Paragraph (9)(b)
    Acoustical Analysis Associates, Inc. stated that the atmospheric 
absorption limitation of 10 dB per 100 meters at 8 kHz in paragraph 
(9)(b) is unnecessarily restrictive, because sound propagation paths 
during the noise test of UA will be shorter than they are for light 
helicopters tested under appendix J. The commenter suggested that the 
limit be relaxed to allow atmospheric absorption up to 12dB per 100 
meters. Although the FAA proposed the atmospheric absorption limit from 
appendix J without change, the agency considers the recommended change 
reasonable as a less stringent and more flexible approach when 
considering the test environment for UA. Therefore, in this final rule, 
the FAA has revised paragraph (9)(b) to reflect an atmospheric 
absorption limitation of 12dB per 100meters.
4. Supplemental Noise Test
    The Small UAV Coalition stated that any ``voluntary'' test, in this 
case the voluntary hover test Matternet agreed to conduct, should not 
be an element in setting a noise certification basis, and that data 
from a voluntary test ``should not be an element in setting a noise 
certification basis.'' \2\
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    \2\ See Small UAV Coalition comment at p. 2.
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    The FAA reiterates that the data collected during the voluntary 
hover tests will not be used to inform the applicant's airworthiness or 
type certification basis, or be evaluated against any noise limits or 
regulatory criteria for noise certification purposes. This supplemental 
test is designed to gather further information on an aircraft that is 
capable of hovering. This approach will enable the FAA to create a 
larger database of UA reference noise data. The FAA is seeking the data 
so that the agency can understand and more accurately describe relevant 
factors of UA noise generation, and to use them to inform future rules 
of general applicability for UA. Finally, as described in the NPRM 
preamble, Matternet has agreed to conduct another test and give the 
resulting data to the FAA to inform the larger database of noise 
experience with UA. No change was made to this final rule based on this 
comment.
5. Technological Practicability and Economic Reasonableness
    The Small UAV Coalition expressed general concern that the test 
procedures proposed for the Matternet Model M2 were unnecessarily 
complex, making them costly and ``economically unreasonable'' for many 
smaller UA manufacturers. Zipline International, Inc. expressed a 
similar concern. Neither Small UAV Coalition nor Zipline International, 
Inc. presented any information regarding how the proposed test 
requirements could be made less complex or less economically burdensome 
and still meet the requirements for certificating a new aircraft model.
    The FAA agrees with comments that the testing requirements should 
be the simplest, most appropriate means of meeting noise requirements. 
The FAA's statutory authority requires that the agency consider whether 
proposed standards are ``economically reasonable, technologically 
practicable, and appropriate for the applicable aircraft.'' See 49 
U.S.C. 44715(b)(4). Thus, in formulating the standards for the 
Matternet Model M2, the FAA started with the simplest and most 
appropriate means of noise certification testing established in 
existing regulation (14 CFR part 36, appendix J), and, as described 
above, extrapolated down to values appropriate for a much smaller 
aircraft. The FAA then developed test procedures intended to function 
more

[[Page 55880]]

closely to the anticipated operating envelope for the Matternet Model 
M2.
    As previously noted, commenters did not present any suggestions for 
how the proposed test procedures could be made less complex or less 
economically burdensome and still meet noise certification 
requirements. Further, these comments express concern regarding 
standards for future certification projects rather than the Matternet 
Model M2 standards. Accordingly, no change is made to this final rule 
based on these comments.

B. Comments Regarding Noise Certification for Unmanned Aircraft: 
General

1. Elimination of Duration Adjustment
    Acoustical Analysis Associates Inc. suggested eliminating the 
duration adjustment, contained in the data correction procedure 
(paragraph (27)(c)). The correction procedure compensates for off-
reference ambient temperature conditions (also referred to as tip Mach 
airspeed correction) because this adjustment, originally developed for 
lighter weighted helicopters in part 36 appendix J, is not well suited 
to UA designs.
    The FAA will consider this suggestion in developing future 
generally applicable UA noise certification standards as more 
certification data is collected and the agency's understanding of UA 
noise propagation is improved. At this time, the FAA concludes that 
there is insufficient data to justify making the change suggested by 
the commenter.
2. Use of Ground Microphone
    An anonymous commenter and Josephson Engineering suggested either 
the use of a ground microphone on a hard surface, or the use of an 
inverted microphone placed on a ground board, as used in appendix G to 
part 36 (applicable to small airplanes) procedures for noise 
certification measurement. The proposed standards for the Matternet 
Model M2 proposed placing the microphone on a tripod or pole at 4 feet 
above the ground for UA noise certification measurements. The commenter 
stated that a ground microphone placement would help to reduce 
measurement uncertainty inherent in the 4-foot microphone placement.
    Although the FAA understands the commenter's concerns, a pole-
placed microphone is relatively simple and less costly to deploy in 
noise certification measurement when compared to a ground-plane 
microphone. In order to develop a testing method more widely applicable 
to UA noise certification, the FAA will continue to compile data and 
research results to inform future generally applicable rulemaking for 
testing procedures for UA noise certification. The FAA may make further 
changes to these procedures as the research matures. No change was made 
to this final rule based on this comment.
3. Use of Multiple Microphones for Hover Noise Measurement
    Bell Textron, Inc. suggested the use of multiple microphones for 
hover noise testing to reduce testing time and improve efficiency. The 
FAA identified such hover test requirements in paragraph (16) of the 
proposed and final rule as supplemental hover test conditions. The 
proposed rule was designed to be simpler for UA by using fewer 
microphones, decreasing the cost and workload associated with using 
more. If any applicant finds that the use of more microphones has an 
advantage, the FAA would review and approve their use. No change is 
made to this final rule based on the comment.
4. Noise Limit Varying With UA Weight
    Bell Textron, Inc. commented on the noise limit generally, not 
specifying a noise limit change specific to the Matternet Model M2. The 
commenter recommended that the FAA develop a noise limit that would 
change with the maximum takeoff weight (MTOW) for higher-weight UA. The 
FAA acknowledges that a noise limit corresponding with weight is a 
recognized standard convention applied to other aircraft in part 36 and 
by Annex 16 to the Convention on International Civil Aviation, 
Environmental Protection, Volume I, Aircraft Noise. As the commenter 
did not offer any rationale, supporting information, or data for the 
FAA to consider with regard to UA noise certification for UA at 
different weights, or the Matternet Model M2's specific weight, the FAA 
retains the proposed constant 78 dB SEL noise limit for the Matternet 
Model M2 in this final rule. Until more noise data become available for 
UA at specific weights, the FAA will continue to extrapolate noise 
limits on a case-by-case basis.

C. Rule Structure

    An anonymous commenter suggested that the FAA revise the proposed 
rule structure (paragraph numbers 1 to 33) to a shorter and simpler 
section numbering approach to help the reader, citing appendix J to 
part 36 as an appropriate example. In choosing a format, the FAA 
considered the UA applicant's relative inexperience with noise testing. 
Because the regulations in appendix J are complex, the FAA chose an 
approach that would allow all noise testing requirements to be 
contained in a single source. The FAA will consider alternative 
formatting as experience with the noise certification of UA continues. 
No change was made to this final rule based on this comment.

D. Corrections for the Final Rule

    The FAA identified errors in referencing paragraph numbers in the 
proposed regulatory text. The following table identifies the paragraphs 
where the errors occurred and the corrections made in the final rule:

----------------------------------------------------------------------------------------------------------------
      Referenced in paragraph:             NPRM language                      Final rule language
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(2).................................  paragraphs (7) through   paragraphs (7) through (22).
                                       (23).
(3).................................  paragraphs (7) through   paragraphs (7) through (24).
                                       (23).
(3)(b)..............................  paragraphs (24) through  paragraphs (25) through (27).
                                       (26).
(10)(a).............................  paragraph (17).........  paragraph (18).
(10)(b).............................  paragraph (26).........  paragraph (27).
(15)................................  paragraphs (17) through  paragraphs (17) through (22).
                                       (21).
(16)................................  (a) through (f)........  (a) through (g).
(28)................................  paragraphs (7) through   paragraphs (7) through (27).
                                       (26).
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    In addition, citations in the proposed rule to Sec.  36.6 are not 
included in this final rule. Section 36.6 contains descriptions of 
material that has been incorporated by reference (IBR) in part 36. The 
IBR process is necessary only for rules of general applicability; it, 
therefore, has no function in this rule. Material referenced in the 
text of this rule is accepted by the applicant when it uses such 
material as its means of compliance at the time of certification.

[[Page 55881]]

    Except for the aforementioned change to paragraph (9)(b), the 
corrections to certain cross-references in the proposed regulatory 
text, and the removal of the reference to Sec.  36.6, the NPRM is 
adopted as proposed.

V. Regulatory Notices and Analyses

A. Regulatory Evaluation

    This rule of particular applicability is not subject to review 
under Executive Order 12866, Regulatory Planning and Review, as that 
Executive Order applies only to rules of general applicability.

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, 
section 605(b) of the RFA provides that the head of the agency may so 
certify, and a regulatory flexibility analysis is not required.
    This rule only impacts Matternet, which is considered a small 
business based on the U.S. Small Business Administration (SBA) size 
standards. The SBA lists small business size standards based on the 
North American Industry Classification System (NAICS). NAICS code 
336411 is titled ``Miscellaneous Aircraft Manufacturing,'' and includes 
the manufacture of unmanned and robotic aircraft. The SBA defines 
industries within this code to be small if they employ 1,500 employees 
or less.
    The FAA expects that under this rule of particular applicability 
Matternet will incur small costs to conduct noise testing and gather 
data but will benefit Matternet by enabling a noise certification basis 
for it to complete the type certification it seeks. The FAA expects 
this rule will not have a significant economic impact on Matternet.
    If an agency determines that a rulemaking will not result in a 
significant economic impact on a substantial number of small entities, 
the head of the agency may so certify under section 605(b) of the RFA. 
Therefore, based on the foregoing discussion, as provided in section 
605(b), the head of the FAA certifies that this rulemaking will not 
result in a significant economic impact on a substantial number of 
small entities.

C. International Trade Impact Assessment

    The Trade Agreements Act of 1979 (Pub. L. 96-39), as amended by the 
Uruguay Round Agreements Act (Pub. L. 103-465), prohibits Federal 
agencies from establishing standards or engaging in related activities 
that create unnecessary obstacles to the foreign commerce of the United 
States. Pursuant to these Acts, 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 
determined this rule would not present any obstacle to foreign commerce 
of the United States. In addition, this rule is not contrary to 
international standards since no international standards for UA noise 
certification exist.

D. Unfunded Mandates Assessment

    Title II of the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-
4) requires each Federal agency to prepare a written statement 
assessing the effects of any Federal mandate in a 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 million in lieu of $100 
million. This rule does not contain such a mandate; therefore, the 
requirements of Title II of the Act do not apply.

E. Paperwork Reduction Act

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

F. International Compatibility

    The FAA remains actively involved in the International Civil 
Aviation Organization's (ICAO) Committee on Aviation Environmental 
Protection (CAEP) and CAEP's Working Group 1 that addresses aircraft 
noise. Working Group 1 began activities to address noise from UA in 
2013. There are, at present, no noise or other environmental standards 
for UA that have been adopted into ICAO Annex 16. The FAA has 
determined that there are no ICAO Standards and Recommended Practices 
that correspond to the rule so as to require conformance.
    While the FAA has begun type and noise certification of UA, the 
European Union Aviation Safety Agency (EASA) has focused on operational 
regulations. In March 2020, EASA published its Easy Access Rules for 
Unmanned Aircraft (Regulation 2019/947 and delegated regulation 2019/
945), which contain the applicable rules and procedures for the 
operation of UA in the EU. While the regulations contain some 
requirements for noise measurement depending on the operating 
environment of the UA, they are limited to operations in the EU and are 
not a certification standard as established by this rule.

G. Environmental Analysis

    FAA Order 1050.1F identifies FAA actions that are categorically 
excluded from preparation of an environmental assessment or 
environmental impact statement under the National Environmental Policy 
Act in the absence of extraordinary circumstances. The FAA has 
determined this rulemaking action qualifies for the categorical 
exclusion identified in paragraph 5-6.6 (d) (Categorical Exclusions for 
Regulatory Actions) for regulations since it is a rulemaking action 
that proscribes a certification test standard, and would not presume 
the acceptability of operation of any particular aircraft in any 
location. No extraordinary circumstances are involved.

[[Page 55882]]

VI. Executive Order Determinations

A. Executive Order 13132, Federalism

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

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

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

VII. How To Obtain Additional Information

A. Rulemaking Documents

    An electronic copy of a rulemaking document may be obtained by 
using the internet--
    1. Search the Federal eRulemaking Portal at www.regulations.gov;
    2. Visit the FAA's Regulations and Policies web page at 
www.faa.gov/regulations_policies; or
    3. Access the Government Printing Office's web page at 
www.GovInfo.gov.
    Copies may also be obtained by sending a request (identified by 
notice, amendment, or docket number of this rulemaking) to the Federal 
Aviation Administration, Office of Rulemaking, ARM-1, 800 Independence 
Avenue SW, Washington, DC 20591, or by calling (202) 267-9677.

B. Comments Submitted to the Docket

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

The Noise Certification Basis

    In consideration of the foregoing, and under the authority of Title 
49 of the United States Code, section 44715(a), the Federal Aviation 
Administration (FAA) establishes the following standards and procedures 
as the noise certification basis of the Matternet Model M2 unmanned 
aircraft (UA).
    All statutory references in this Rule of Particular Applicability 
(rule) refer to Title 49 of the United States Code. All regulatory 
references refer to Title 14 of the Code of Federal Regulations, part 
21 or part 36 and its appendices, unless otherwise cited.

Noise Certification Requirements for the Matternet Model M2

    (1) General: The requirements and limitations of 14 CFR 36.3 apply 
to the Matternet Model M2, except as described herein.
    (a) Limitations (Reference Sec.  36.5, as modified): Pursuant to 49 
U.S.C. 44715(b)(4), the noise level in this Rule of Particular 
Applicability (rule) has been determined to be as low as is 
economically reasonable, technologically practicable, and appropriate 
for this aircraft. No determination is made that these noise levels are 
or should be acceptable or unacceptable for operation at, into, or out 
of, any airport, landing or launch pad, community, or any other 
environment that may be impacted or is sensitive to noise.
    (b) Acoustical Change (Reference Sec.  36.9 as modified): If, after 
type certification using the requirements stated herein, the aircraft 
incorporates a change in type design, the changed design is subject to 
an acoustical change analysis and approval in accordance with Sec.  
21.93(b). After such change in design, the aircraft may not 
subsequently exceed the noise limits specified in this rule.
    (2) Noise Measurement (Reference Sec.  36.801, as modified): The 
noise generated by the aircraft must be measured at the noise measuring 
point and under the test conditions prescribed in paragraphs (7) 
through (23) of this rule, or using an equivalent procedure approved by 
the FAA before testing. Any procedure not approved by the FAA before a 
test is performed is subject to disapproval and may require the 
aircraft to be retested using an approved procedure.
    (3) Noise Evaluation (Reference Sec.  36.803, as modified): The 
noise measurement data required by paragraph (2) of this rule must be 
obtained using the test procedures in paragraphs (7) through (24) of 
this rule, and:
    (a) Corrected to the reference conditions contained in paragraphs 
(5) and (6) of this rule; and
    (b) Evaluated using the procedures in paragraphs (25) through (27) 
of this rule, or using an FAA-approved equivalent procedure. Any 
procedure not approved by the FAA before a test is performed is subject 
to disapproval and may require the aircraft to be retested using an 
approved procedure.
    (4) Noise Limits (Reference Sec.  36.805, as modified): Compliance 
with the noise limits prescribed in paragraphs (28) and (29) of this 
rule must be shown for this aircraft for which application for issuance 
of a type certificate in the special class is made under part 21.
    (5) Reference Conditions--General (Reference part 36 appendix J, 
section J36.1, as modified): Paragraphs (6) through (29) of this rule 
prescribe the noise certification requirements for this aircraft, 
including:
    (a) The conditions under which each noise certification test must 
be conducted and the measurement procedure that must be used to measure 
the aircraft noise during the test;
    (b) The procedures that must be used to correct the measured data 
to the reference conditions, and to calculate the noise evaluation 
quantity designated as the A-weighted Sound Exposure Level (SEL, 
denoted by symbol LAE); and
    (c) The noise limit with which compliance must be shown.
    (6) Reference Conditions--Test (Reference part 36 appendix J, 
section J36.3, as modified):
    (a) Meteorological Conditions--The following are the noise 
certification reference atmospheric conditions that are assumed to 
exist from the surface to the aircraft altitude:
    i. Sea level pressure of 2,116 pounds per square foot (76 
centimeters of mercury);
    ii. Ambient temperature of 77 degrees Fahrenheit (25 degrees 
Celsius);
    iii. Relative humidity of 70 percent; and
    iv. Zero wind.
    (b) Reference test site. The reference test site is flat and 
without line-of-sight obstructions, including any area across the 
flight path that is long enough to encompass the 10 dB down points of 
the A-weighted time history.
    (c) Level flyover reference profile. For UA, the reference flyover 
profile is a level flight, 250 feet (76.2 meters) above ground level as 
measured at the noise measuring station. The reference flyover profile 
has a linear flight track and passes directly over the noise monitoring 
station. The applicable reference airspeed is stabilized and maintained 
throughout the measured portion of the flyover. Rotor speed is normal 
operating RPM throughout the 10 dB-down time interval. For UA, 
applicable reference airspeeds are:

[[Page 55883]]

    i. Vmax ~ 0.9VNE, where VNE is the 
never-exceed airspeed (at empty weight).
    ii. Vcruise ~ VH, where VH is the 
maximum performance airspeed (at maximum certificated takeoff weight 
(MTOW)),
    (d) Two series of flyover tests are required. Each series must be 
flown at the weight and applicable reference speed conditions as 
follows:
    i. MTOW (inclusive of payload) and Vcruise; and
    ii. Empty weight (no payload) and Vmax.
    (7) Noise Measurement Procedures--General (Reference part 36, 
appendix J, section J36.101(a) as modified): Paragraphs (8) through 
(10) of this rule prescribe the conditions under which the aircraft 
noise certification tests must be conducted, and the measurement 
procedures that must be used to measure the aircraft noise during each 
test.
    (8) Test site requirements (Reference: part 36, appendix J, section 
J36.101(b), as modified):
    (a) The noise measuring station must be surrounded by terrain 
having no excessive sound absorption characteristics, such as might be 
caused by thick, matted, or tall grass, shrubs, wooded areas, or loose 
soil. Grass is acceptable if mowed to 3 inches or less in a 25-foot 
radius around any sound measuring stations.
    (b) During the period when the flyover noise measurement is within 
10 dB of the maximum A-weighted sound level, no obstruction that 
significantly influences the sound field from the aircraft may exist 
within a conical space above the noise measuring position (the point on 
the ground vertically below the microphone). The cone is defined by an 
axis normal to the ground and by half-angle 80 degrees from this axis.
    (9) Weather restrictions (Reference: part 36, appendix J, section 
J36.101(c) as modified): Each test must be conducted under the 
following atmospheric conditions:
    (a) No rain or other precipitation.
    (b) Ambient air temperature between 36 degrees and 95 degrees 
Fahrenheit (2 degrees and 35 degrees Celsius), inclusively, and 
relative humidity between 20 percent and 95 percent inclusively, except 
that testing may not take place where combinations of temperature and 
relative humidity result in a rate of atmospheric attenuation greater 
than 12 dB per 100 meters (36.6 dB per 1,000 feet) in the one-third 
octave band centered at 8 kiloHertz.
    (c) Wind velocity that does not exceed 10 knots (19 km/h) and a 
crosswind component that does not exceed 5 knots (9 km/h). The wind 
must be determined using a continuous averaging process of no greater 
than 30 seconds.
    (d) Measurements of ambient temperature, relative humidity, wind 
speed, and wind direction must be made between 4 feet (1.2 meters) and 
33 feet (10 meters) above the ground. Unless otherwise approved by the 
FAA, ambient temperature and relative humidity must be measured at the 
same height above the ground.
    (e) No anomalous wind conditions (including turbulence) or other 
anomalous meteorological conditions that could significantly affect the 
noise level of the aircraft when the noise is recorded at the noise 
measuring station.
    (f) If the measurement site is within 6,560 feet (2,000 meters) of 
a fixed meteorological station (such as those found at airports or 
other facilities), the weather measurements reported at that station 
may be used for temperature, relative humidity and wind velocity, when 
approved by the FAA before the test is conducted. The use of 
measurements reported at a fixed meteorological station, if not 
approved by the FAA before a test is performed, may cause the test to 
be disapproved and require that the aircraft be retested.
    (10) Aircraft test procedures (Reference part 36, appendix J, 
section J36.101(d), as modified):
    (a) The aircraft test procedures and noise measurements must be 
conducted and processed in a manner that yields the noise evaluation 
measure designated LAE, as defined in paragraph (18) of this 
rule.
    (b) The aircraft height relative to the noise measurement point 
sufficient to make corrections required in paragraph (27) of this rule 
must be determined by an FAA-approved method that is independent of 
normal flight instrumentation, such as a Differential Global 
Positioning System (DGPS), or photographic scaling techniques. The 
aircraft position in three dimensions relative to the microphone must 
be monitored and recorded at all times during the test and data 
collection, with correlation via time synchronization to the acoustic 
noise data collection. The accuracy of the aircraft location system, 
and all sources of inaccuracy, along with possible error introduction 
when correlating to measured and recorded noise (inaccuracies of timing 
devices and methods), must be determined and reported. A description of 
the aircraft location system and its accuracy must be included as part 
of the noise test plan required by paragraph (31) of this rule, and 
approved by the FAA before use.
    (c) If an applicant demonstrates that the design characteristics of 
the aircraft would prevent flight from being conducted in accordance 
with the reference test conditions prescribed in paragraph (6) of this 
rule, then the applicant may request a variance in reference test 
conditions to be used. Any variance from standard reference test 
conditions is limited to that required for the subject aircraft design 
characteristics that make compliance with the reference test conditions 
impossible.
    (11) Flyover Test Conditions (Reference part 36, appendix J, 
section J36.105(a), as modified): Paragraphs (12) through (15) of this 
rule prescribe the flight test conditions and allowable random 
deviations for flyover noise tests conducted to demonstrate compliance 
with this rule.
    (12) Level flight height and lateral path tolerances (Reference 
part 36, appendix J, section J36.105(b), as modified): A test series 
must consist of at least six flights. The number of level flights made 
with a headwind component must be equal to the number of level flights 
made with a tailwind component over the noise measurement station:
    (a) In level flight and in cruise configuration;
    (b) At the test height above the ground level over the noise 
measuring station as defined in paragraph (6) of this rule. For the 
selected height, the vertical tolerance of this height should be  10% value; and
    (c) Within 10 degrees from the zenith.
    (13) Airspeed and Controls (Reference part 36, appendix J, section 
J36.105(c), as modified): Each flyover noise test flight must be 
conducted:
    (a) At the reference airspeed specified in paragraph (6)(c) of this 
rule; and
    (b) With the flight controls stabilized during the period when the 
measured aircraft noise level is within 10 dB of the maximum A-weighted 
sound level (LAmax).
    (14) Aircraft weight (Reference part 36, appendix J, section 
J36.105(d), as modified): For the weight at which noise certification 
is requested, the aircraft test weight for each flyover test series 
must be specified for:
    (a) MTOW (inclusive of payload); and
    (b) Empty weight (no payload).
    (15) Flyover height adjustment (Reference part 36, appendix J, 
section J36.105(e), as modified): If ambient noise at the measurement 
station, measured in accordance with paragraphs (17) through (22) of 
this rule, is found to be within 15 A-weighted decibels (dB(A)) of the 
A-weighted

[[Page 55884]]

aircraft noise level (LAmax), measured at the same location, 
the applicant may request the FAA approve an alternate flyover height. 
If an alternate flyover height is approved, the results must be 
adjusted to the reference flyover height specified in paragraph (6)(c) 
of this rule using an FAA-approved method.
    (16) Supplemental hover test conditions--This is a supplemental 
test to collect data for assessment of community noise impacts, and to 
inform later general noise and test standards for UA. This supplemental 
test does not require compliance with a noise limit and does not affect 
the noise certification findings for the subject aircraft.
    The aircraft is required to hover at different spatial locations 
relative to the microphone in accordance with subparagraphs (a) through 
(g) of this paragraph.
    (a) The aircraft must be at MTOW, inclusive of maximum payload 
weight of cargo.
    (b) To ensure that the widest dimensional profile of the noise 
source is captured in the recordings, for each aircraft attitude 
heading (0, 90, 180 and 270 degrees) relative to the microphone 
position for hover conditions described in paragraphs (16)(c) and (d) 
of this rule, stabilize the aircraft in hover and record the sound in 
accordance with paragraph (16)(f) of this rule.
    (c) Hover condition #1 (sound elevation angle at zero degrees): The 
aircraft maintains a hover condition at a lateral distance of 20 feet 
to the microphone and at 4 feet above ground level (rotors in the same 
plane as the microphone). Test when the conditions are optimal for 
minimal influence of wind on the noise recording.
    (d) Hover condition #2 (sound elevation angle at 45 degrees): The 
aircraft maintains a hover condition at a lateral distance of 20 feet 
to the microphone position and at 20 feet AGL. Test when the conditions 
are optimal for minimal influence of wind on the noise recording.
    (e) Hover condition #3 (overhead, or sound elevation angle at 90 
degrees): The aircraft maintains a hover condition at 20 feet AGL and 
hold centered within a one-foot radial over the microphone location.
    (f) For the noise measurements at each hover condition, record the 
value of the equivalent sound level (Leq) and sound pressure level in 
\1/3\ octave bands for a minimum of 30 seconds for each of the test 
conditions (paragraphs 16(c) through (e) of this rule).
    (g) The tolerance of the hover height or lateral distance is within 
+/-1 ft., and the tolerance of the headings is within +/-5 degrees.
[GRAPHIC] [TIFF OMITTED] TN12SE22.002

    (17) Measurement of aircraft noise received on the ground--General 
(Reference: part 36, appendix J, section J36.109(a), as modified): 
Aircraft noise measurements made for the purpose of noise certification 
in accordance with the requirements of this rule must be obtained 
using:
    (a) The noise evaluation metric prescribed in paragraph (18) of 
this rule;
    (b) Acoustic equipment that meets the specifications prescribed in 
paragraphs (19) and (20) of this rule; and
    (c) The calibration and measurement procedures prescribed in 
paragraphs (21) and (22) of this rule.
    (18) Measurement of aircraft noise received on the ground--Noise 
unit definition (Reference part 36, appendix J, section J36.109(b), as 
modified):
    (a) The sound exposure level, as expressed in LAE, is 
defined as the level, in decibels, of the time integral of squared `A'-
weighted sound pressure (PA) over a given time period or 
event, with reference to the square of the standard reference sound 
pressure (P0) of 20 micropascals and a reference duration of 
one second.
    (b) The sound exposure level in units of decibels (dB) is defined 
by the expression:

[[Page 55885]]

[GRAPHIC] [TIFF OMITTED] TN12SE22.003

    Where T0 is the reference integration time of one second 
and (t2-t1) is the integration time interval.
    (c) The integral equation of paragraph (18)(b) can also be 
expressed as:
[GRAPHIC] [TIFF OMITTED] TN12SE22.004

    Where LA(t) is the time varying A-weighted sound level.
    (d) The integration time (t2-t1) in practice 
must not be less than the time interval during which LA(t) 
first rises to within 10 dB(A) of its maximum value (LAmax) 
and last falls below 10 dB(A) of its maximum value.
    (19) Measurement of Aircraft Noise Received on the Ground--
Measurement System (Reference part 36, appendix J, section J36.109(c), 
as modified):
    (a) Acoustical measurement system instrumentation must be 
equivalent to the following and approved by the FAA:
    i. A microphone system with frequency response that is compatible 
with the measurement and analysis system accuracy prescribed in 
paragraph (20) of this rule;
    ii. Tripods or similar microphone mountings that minimize 
interference with the sound energy being measured; and
    iii. Recording and reproducing equipment with characteristics, 
frequency response, and dynamic range that are compatible with the 
response and accuracy requirements of paragraph (20) of this rule.
    (b) The calibration and checking of measurement systems must be 
accomplished in accordance with the procedures described in part 36, 
appendix A, section A36.3.9.
    (20) Measurement of Aircraft Noise Received on the Ground--Sensing, 
Recording, and Reproducing Equipment (Reference part 36, appendix J, 
section J36.109(d), as modified):
    (a) The sound pressure time-history (audio) signals obtained from 
aircraft flyovers under this paragraph must be recorded digitally at a 
minimum sample rate of 44 kilohertz (kHz) for a minimum bandwidth of 20 
hertz (Hz) to 20 kHz, and encoded using a minimum of 16-bit linear 
pulse code modulation (or equivalent) during analog to digital 
conversion. Digital audio recording must also meet the additional 
requirements specified in part 36, appendix A, section A36.3.6 
``Recording and Reproducing Systems.''
    (b) The LAE value from each flyover and A-weighed Leq 
(LAeq) values from each hover test flight condition may be 
determined directly from an integrating sound level meter that meets 
the specifications of International Electrotechnical Commission (IEC) 
Standard 61672-1 (2013) for a Class 1 instrument set at ``slow'' 
response.
    (c) The acoustic signal from the aircraft, along with the 
calibration signals specified in paragraph (21) and the background 
noise signal required by paragraph (22) of this rule, must be recorded 
in a digital audio format as specified in paragraph (20)(a) of this 
rule for subsequent analysis for an integrating sound level meter 
identified in paragraph (20)(b) of this rule. The record/playback 
system must conform to the requirements prescribed in part 36, appendix 
A, section A36.3.6 ``Recording and Reproducing Systems.'' The recorder 
must comply with the specifications of IEC standard 61265 2nd edition 
(2018).
    (d) The characteristics of the complete system must meet the 
specifications of IEC standard 61672-1 for the microphone, amplifier, 
and indicating instrument characteristics.
    (e) The response of the complete system to a plane, progressive 
wave of constant amplitude must lie within the tolerance limits 
specified for Class 1 instruments in IEC standard 61672-1 for weighting 
curve ``A'' over the frequency range of 45 Hz to 20 kHz.
    (f) A windscreen must be used with the microphone during each 
measurement of the aircraft flyover noise. Correction for any insertion 
loss produced by the windscreen, as a function of the frequency of the 
acoustic calibration required by paragraph (21) of this rule, must be 
applied to the measured data, and each correction applied must be 
included in the test report.
    (21) Measurement of Aircraft Noise Received on the Ground--
Calibrations (Reference part 36, appendix J, section J36.109(e), as 
modified):
    (a) For the aircraft acoustic signal recorded for subsequent 
analysis, the measuring system and components of the recording system 
must be calibrated as prescribed in Title 14 CFR, part 36, appendix A.
    (b) If the aircraft acoustic signal is measured directly using an 
integrating sound level meter:
    i. The overall sensitivity of the measuring system must be checked 
before and after the series of flyover tests and at intervals (not 
exceeding a two-hour duration) during the flyover tests using an 
acoustic calibrator generating a sinusoidal signal at a known sound 
pressure level and at a known frequency.
    ii. The performance of equipment in the system is considered 
satisfactory if, during each day's testing, the variation in the 
measured value for the acoustic calibrator does not exceed 0.5 dB. The 
LAE data collected during the flyover tests must be adjusted 
to account for any variation in the calibration value.
    iii. A performance calibration analysis of each piece of 
calibration equipment, including acoustic calibrators, reference 
microphones, and voltage insertion devices, must have been made during 
the six calendar months preceding the beginning of the aircraft flyover 
series. Each calibration must be traceable to the National Institute of 
Standards and Technology.
    (22) Measurement of Aircraft Noise Received on the Ground--Noise 
measurement procedures (Reference part 36, appendix J, section 
J36.109(f), as modified):
    (a) The microphone must be of a pressure-sensitive capacitive type 
designed for nearly uniform grazing incidence response. The microphone 
must be mounted with the center of the sensing element 4 feet (1.2 
meters) above the local ground surface and must be oriented for grazing 
incidence such that the sensing element (diaphragm) is substantially in 
the plane defined by the nominal flight path of the aircraft and the 
noise measurement station. A microphone that satisfies the requirements 
of this paragraph must be used when determining compliance

[[Page 55886]]

with the noise limit prescribed in paragraph (29) of this rule.
    (b) For each aircraft acoustic signal recorded for subsequent 
analysis, the frequency response of the electrical system must be 
determined at a level within 10 dB of the full-scale reading used 
during the test.
    (c) The background noise, including both ambient acoustical sound 
present at the microphone site and electrical noise of the measurement 
systems, must be determined in the test area and the system gain set at 
levels which will be used for aircraft noise measurements. If aircraft 
sound levels do not exceed the background sound levels by at least 15 
dB(A), flyovers at an FAA-approved lower height may be used; the 
results must be adjusted to the reference measurement point by an FAA-
approved method.
    (d) When an integrating sound level meter is used to measure the 
aircraft noise, the instrument operator must monitor the continuous A-
weighted (slow response) noise levels throughout each flyover to ensure 
that the A-weighted sound exposure level (LAE) integration 
process includes, at minimum, all of the noise signal between the 
LAmax and the 10 dB down points in the flyover time history. 
The instrument operator must note the actual dB(A) levels at the start 
and stop of the LAE integration interval and document these 
levels along with the value of LAmax and the integration 
interval (in seconds) for inclusion in the noise data submitted as part 
of the reporting requirements in paragraph (23) of this rule.
    (23) Data Reporting--General (Reference part 36, appendix J, 
section J36.111(a), as modified): Data representing physical 
measurements, and corrections to that measured data, including 
corrections to measurements for equipment response deviations, must be 
recorded in permanent form and appended to the test reports required by 
this rule. Each correction is subject to FAA approval.
    (24) Data Submission (Reference part 36, appendix J, section 
J36.111(b), as modified): After the completion of all certification 
tests required by this rule, the following must be submitted to the 
FAA:
    (a) A test report containing the following:
    (i) Measured and corrected sound levels obtained with equipment 
conforming to the standards prescribed in paragraphs (17) through (22) 
of this rule;
    (ii) A description of the equipment and systems used for 
measurement and analysis of all acoustic, aircraft performance and 
flight path, and meteorological data;
    (iii) The atmospheric environmental data required to demonstrate 
compliance with this rule, as measured throughout the test period;
    (iv) Conditions of local topography, nearby ground cover (if any), 
or events that may have interfered with a sound recording;
    (v) The following aircraft information:
    (A) Type, model, and serial numbers, if any, of aircraft, engine(s) 
and rotor(s) and/or propellers tested;
    (B) Gross dimensions of aircraft, location of engines or motors, 
rotors or propellers, number of blades for each rotor or propeller, and 
the range of rotational speeds of the rotors;
    (C) MTOW at which certification under this rule is requested;
    (D) Aircraft configuration, including landing gear positions;
    (E) Aircraft Airspeeds: VNE and Vmax for both 
empty weight and maximum payload configuration, or for maximum range, 
whichever is greatest, and applicable as reference and operational 
airspeeds;
    (F) Aircraft gross weight for each test run;
    (G) Indicated and true airspeed for each test run; if indicated and 
true airspeed for each run are not available, then ground speed as 
measured from a DGPS, or from an alternate method, may be approved by 
the FAA;
    (H) Ground speed, if measured, for each run;
    (I) Aircraft engine performance as determined from aircraft 
instruments and manufacturer's data; and
    (J) Aircraft flight path above ground level, referenced to the 
microphone position of the noise measurement station, in feet, 
determined using an FAA-approved method that is independent of normal 
flight instrumentation, such as DGPS or photo scaling techniques at the 
microphone location;
    (vi) Aircraft position and performance data necessary to make the 
adjustments prescribed in paragraph (27) of this rule and to 
demonstrate compliance with the performance and position restrictions 
prescribed in paragraphs (11) through (16) of this rule; and
    (vii) The aircraft position in three dimensions and orientation 
(for hover) relative to the microphone must be monitored and recorded 
at all times during the test and data collection, with correlation via 
time synchronization to the acoustic noise data collection.
    (b) All of the recorded audio data from all phases of all flight 
tests used to demonstrate compliance with this rule.
    (c) All recordings and data collected during the measurement 
activity required by paragraph (16) of this rule. These data will not 
affect the outcome of this certification findings intended to 
demonstrate compliance with this rule and may be submitted separately 
from data that affects certification.
    (25) Noise Evaluation and Calculations--Noise Evaluation Expressed 
in LAE (Reference: part 36, appendix J, section J36.201, as 
modified): The noise evaluation measure must be expressed as the 
LAE in units of dB(A) as prescribed in paragraph (18) of 
this rule. The LAE value for each flyover may be determined 
directly using an integrating sound level meter. Specifications for the 
integrating sound level meter and requirements governing the use of 
such instrumentation are prescribed in paragraphs (17) through (22) of 
this rule.
    (26) Noise Evaluation and Calculations--Calculation of Noise Levels 
(Reference part 36, appendix J, section J36.203, as modified):
    (a) To demonstrate compliance with the noise level limits specified 
in paragraph (29) of this rule, the LAE noise levels from 
each valid flyover, corrected as necessary to reference conditions in 
accordance with paragraph (27) of this rule, must be arithmetically 
averaged to obtain a single LAE dB(A) mean value for each 
flyover series. No individual flyover run may be omitted from the 
averaging process, unless approved by the FAA.
    (b) The minimum sample size acceptable for the aircraft flyover 
certification measurements is six. The number of samples must be 
sufficient to establish statistically a 90 percent confidence limit 
that does not exceed 1.5 dB(A).
    (c) All data used and calculations performed under this paragraph, 
including the calculated 90 percent confidence limits, must be 
documented and provided in accordance with the data reporting and 
submission requirements of paragraphs (23) and (24) of this rule.
    (27) Data Correction Procedures (Reference part 36, appendix J, 
section J36.205, as modified):
    (a) When certification test conditions measured in accordance with 
paragraphs (7) through (23) of this rule differ from the reference test 
conditions prescribed in paragraph (6) of this rule, appropriate 
adjustments must be made to the measured noise data in accordance with 
the methods set out in paragraphs (27)(b) and (c) of this rule. At 
minimum, appropriate adjustments in accordance with paragraph (27)(b) 
of this rule must be made for off-reference altitude and for any 
difference between reference airspeed and adjusted

[[Page 55887]]

reference airspeed in accordance with paragraph (27)(c) of this rule.
    (b) The adjustment for off-reference altitude may be approximated 
from:
[GRAPHIC] [TIFF OMITTED] TN12SE22.005

    Where J1 is the quantity in decibels that must be 
algebraically added to the measured LAE noise level to 
correct for an off-reference flight path, HT is the height, 
in feet, of the test aircraft when directly over the noise measurement 
point, and the constant (12.5) accounts for the effects on spherical 
spreading and duration from the off-reference altitude.
    (c) The adjustment for the difference between reference airspeed 
and adjusted reference airspeed is calculated from:
[GRAPHIC] [TIFF OMITTED] TN12SE22.006

    Where J3 is the quantity in decibels that must be 
algebraically added to the measured LAE noise level to 
correct for the influence of airspeed on the integration duration of 
the measured flyover event as received at the noise measurement 
station; VR is the reference airspeed as prescribed in 
paragraph (6)(c) of this rule, and VRA is a speed adjustment 
applied to the reference airspeed to allow flying at an airspeed that 
provides the reference tip Mach speed. The reference airspeed must be 
adjusted for the atmospheric conditions on-site.
    (d) All data used and calculations performed under this paragraph 
must be documented and submitted in accordance with paragraphs (22) and 
(23).
    (28) Noise Limit Compliance--Noise Measurement, Evaluation, and 
Calculation (Reference part 36, appendix J, section J36.301, as 
modified): In demonstrating compliance with this rule, the aircraft 
noise levels must be measured, evaluated, and calculated in accordance 
with paragraphs (7) through (27) of this rule.
    (29) Noise Limit (Reference part 36, appendix J, section J36.305, 
as modified): The calculated noise levels of the aircraft, at the 
measuring point described in paragraphs (7) through (10) of this rule, 
must be shown to not exceed 78.0 decibels LAE at the 
reference altitude of 250 feet.
    (30) Manuals, Markings, and Placards (Reference part 36 Sec. Sec.  
36.1501 and 36.1581, as modified):
    (a) All procedures, weights, configurations, and information or 
data used to obtain the certified noise levels required to demonstrate 
compliance with this rule, including equivalent procedures used for 
flight, testing, and analysis, must be approved by the FAA.
    (b) Noise levels achieved during type certification must be 
included in the approved portion of each Unmanned Aircraft Flight 
Manual for the subject aircraft. If an Unmanned Aircraft Flight Manual 
is not approved, the procedures and information must be furnished in a 
combination of manual material, markings, and placards approved by the 
FAA. The noise level information that must be included is as follows:
    i. The noise level information must be one value for flyover as 
defined and required by these specifications; the value is determined 
at the maximum reference speed, weight and configuration in accordance 
with paragraph (6)(c) of this rule. The noise level value must also 
indicate the series from which it was determined.
    ii. If supplemental operational noise level information is included 
in the approved portion of the Unmanned Aircraft Flight Manual, it must 
be segregated, identified as information that is provided in addition 
to the certificated noise levels, and clearly distinguished from the 
information required by paragraph (30)(b)(i) of this rule.
    iii. The following statement must be included in each approved 
manual near the listed noise level:
    No determination has been made by the Federal Aviation 
Administration that the noise levels of this aircraft are or should be 
acceptable or unacceptable for operation at, into, or out of any 
location or environment that may be affected by operational noise.
    (31) Test Plan Preparation and Approval: Prior to conducting any 
testing and data collection required by this rule, the applicant must 
prepare a test plan and obtain FAA approval of it from the FAA's 
Aircraft Certification Service, Policy & Innovation Division (P&I) (or 
another FAA employee designated by the P&I division)
    (32) Test Witnessing: The FAA P&I Division (or another FAA employee 
designated by the P&I Division) must witness the test and data 
collection required by this rule for the results to be valid for 
certification. Other acoustic focals from FAA's Aircraft Certification 
Office and Acoustic Engineer(s) from the Office of Environment and 
Energy or US DOT Volpe National Transportation Systems Center may also 
be present to observe the tests.
    (33) Test Report Preparation and Approval: The applicant must 
prepare a report that includes all of the findings and data required 
under this rule. The report must be approved by the FAA P&I Division 
(or another FAA employee designated by the P&I division) as a part of 
the aircraft certification record.

    Issued in Washington, DC, on September 7, 2022.
Augustus Bradley Mims,
Deputy Administrator.
[FR Doc. 2022-19639 Filed 9-9-22; 8:45 am]
BILLING CODE 4910-13-P