Document ID: FAA-2021-0710-0001
Agency: faa
Document Type: Notice
Title: Noise Certification Standards: Matternet model M2 aircraft
Posted Date: 2021-08-27T04:00Z

[Federal Register Volume 86, Number 164 (Friday, August 27, 2021)]
[Notices]
[Pages 48281-48290]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-17769]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

[Docket No.: FAA-2021-0710; Notice No. 21-01]

Noise Certification Standards: Matternet Model M2 Aircraft

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

ACTION: Notice of proposed rulemaking (NPRM), rule of particular 
applicability.

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SUMMARY: The Federal Aviation Administration (FAA) proposes noise 
certification standards that would apply only to the Matternet model M2 
quadcopter unmanned aircraft because there are currently no generally 
applicable noise certification standards for this aircraft.

DATES: Send comments on or before September 27, 2021.

ADDRESSES: Send comments identified by docket number FAA-2021-0710 
using any of the following methods:
     Federal eRulemaking Portal: Go to http://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 www.regulations.gov, as described in the system 
of records notice (DOT/ALL-14 FDMS), which can be reviewed at 
www.dot.gov/privacy.
    Docket: Background documents or comments received may be read at 
http://www.regulations.gov at any time. Follow the online instructions 
for accessing the docket or go to the 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.

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 
hua.he@faa.gov.

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 issued under the authority described in subtitle 
VII, chapter 447, 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. 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.
    The current noise standards are contained in 14 CFR part 36. Within 
part 36, aircraft are distinguished by type, including jet airplanes, 
large turboprop airplanes, small airplanes, helicopters, and 
tiltrotors. When the FAA began issuing type certificates for unmanned 
aircraft (UA) several years ago, it used the noise standards for the 
type of manned aircraft that was most like the UA seeking type 
certification and that were compatible with the type classification. In 
the first two certifications, the FAA applied the small airplane 
standards under subpart F and appendix G. The small helicopter 
standards of subpart H and appendix J might also be found as applicable 
based on the design of an aircraft presented for certification.
    The increase of low-altitude UA operations, and the increased 
demand for commercial operation using them, has caused the FAA to re-
evaluate whether the requirements for certain categories of aircraft 
(e.g., helicopters, tilt-rotors, small propeller-driven fixed wing) 
described in part 36 remain appropriate for the noise certification of 
particular UA designs like the Matternet M2. The FAA has recently begun 
to consider not only the means of propulsion and flight, but the amount 
and type of noise generated by UA, which in many cases are small in 
size, electrically (battery) powered, and may include distributed 
propulsion features or vertical takeoff and landing capabilities. As a 
result, it is possible that these aircraft generate less noise than was 
contemplated when part 36 was promulgated.
    A significant consideration is the expected operating environment 
for UA. Manned airplanes and helicopters normally operate from airports 
or helipads that include property that serves as a primary buffer from 
the general population. The methods of testing and determining proper 
noise limits used these proximities to the population as their bases, 
with testing done at large airport test locations and at altitudes 
representative of takeoff and landing. The UA addressed in this 
proposal, however, is an aircraft that is intended to operate in closer 
proximity

[[Page 48282]]

to people, such as delivering packages in residential areas. These uses 
are expected to have an impact on persons and property from much closer 
distances than traditional piloted aircraft.
    When tested under the current requirements of part 36 for manned 
aircraft, the noise generated by many UA could be lost in the ambient 
background noise at the reference altitude of 492 feet required in part 
36 appendix J, while the noise in their proposed operating environments 
would be more apparent to persons near it.
    The use of distributed electric propulsion and a high level of 
automated control at each rotor allow UA to operate with a variety of 
profiles, unlike those of larger manned aircraft. The complex vortex 
field created by the interaction of the rotors, combined with the 
airframe, can cause such aircraft to exhibit highly tonal spectral 
content and unique noise directivity patterns that are often coupled 
with the vehicle flight dynamics and flight profiles. Such noise 
characteristics and flight profiles have not been considered previously 
under the standards and testing contained in part 36 and its 
appendices. These noise characteristics and flight profiles are 
examples of the factors that caused the FAA to test these aircraft and 
gather consistent data as a means to understand their relevance and 
eventual use in informing future standards generally applicable to UA.
    Effective generally applicable noise rules require a base of data 
gathered from a test environment common for all aircraft, and 
certifications of unmanned aircraft such as this one represent the 
early stages of such data gathering. 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. While small UA have operated under part 107 
for several years, those aircraft do not have type or airworthiness 
certificates, and did not require noise testing; only limited noise 
data on those smaller models has been collected, and most of the 
collected data was acquired in a manner inconsistent with formal noise 
certification test conditions.
    As industry seeks both type and airworthiness certification for UA 
to allow operation under part 91 or commercial operation under part 
135, a commensurate shift in the noise certification paradigm is 
occurring as a means to capture new operational concepts that will be 
reflected in future regulations. While the FAA will continue to build a 
database of noise characteristics as it engages with certification 
applicants, such data gathering takes time and requires input about a 
number of models and designs before the influences of design on noise 
can be fully understood. FAA expects to use data collected through this 
proposed rule to inform future particularly and generally applicable 
standards.
    Matternet applied for type certification of its aircraft on May 18, 
2018. The aircraft is a quadcopter design UA with a maximum takeoff 
weight of 29 pounds including a 4-pound payload, and a proposed 
operating altitude of 400 feet or lower. Since the FAA has found that 
the current noise certification standards cannot be effectively applied 
to the Matternet Model M2 UA, in order to fulfill the statutory 
requirement under section 44715(a)(3), the FAA is proposing a set of 
noise certification standards described in this Rule of Particular 
Applicability that would apply only to the Matternet model M2.
    Without this proposed rule, Matternet would be unable to 
certificate its aircraft until such time as the FAA was able to 
establish a rule of general applicability for UA noise certification. 
The benefits of this proposal include establishing a noise 
certification basis for Matternet to seek type certification, the 
fulfillment of the FAA's obligation to provide noise standards under 49 
U.S.C. 44715, and the collection of additional data that will be used 
to inform the development of a larger UA noise database from which 
future standards of general applicability may be developed.

III. Discussion of the Proposal

    This proposed rule presents only the noise certification basis for 
one new model of UA seeking type certification, the Matternet M2. 
Nothing in this proposed rule is intended to affect the airworthiness 
certification of this aircraft model or any operational approvals.\1\ 
Those findings are made separately by the FAA in accordance with the 
applicable aircraft certification and operating rules.
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    \1\ In addition, 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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    When an applicant presents an aircraft (of any type) for 
certification, the FAA must determine which among its many regulations 
apply to the aircraft presented. This is true for airworthiness 
standards and noise standards. This is an iterative process, during 
which the FAA determines the standards and processes that apply, taking 
into account any new or novel features of the aircraft. The FAA works 
closely with the applicant to ensure that the applicant understands 
what standards apply, and what must be demonstrated during 
certification.
    As previously discussed, in the case of the Matternet model M2 UA, 
the FAA reviewed part 36, including its appendices, and determined that 
while the subject aircraft has some characteristics that are similar to 
a small helicopter that would be noise certificated under appendix J, 
the differences require noise certification test criteria and standards 
tailored to the size and features of the UA. The FAA then worked with 
Matternet to understand the novel features and expected operating 
environment of the aircraft so that the FAA could determine the 
appropriate modifications and additions to the limits and procedures to 
develop a complete noise certification basis that would effectively 
profile the aircraft. The results of the agency's assessments are 
presented in this proposed rule. The proposed rule text is annotated at 
the beginning of each paragraph to indicate similar requirements in 
appendix J for those unfamiliar with noise certification requirements. 
The requirements presented in this proposal stand alone for 
certification of the M2 aircraft.
    In addition to the data gathered for noise certification of the 
model M2, the applicant has agreed to conduct another test and give the 
resulting data to the FAA to inform the larger database of noise 
experience with UA. Data from the supplemental test are not part of the 
type or airworthiness certification basis of the aircraft and will not 
be evaluated against any noise limits or regulatory criteria for noise 
certification purposes.
    The supplemental test is designed to gather further information on 
an aircraft that is capable of hovering. The FAA developed the 
supplemental testing procedure with a consideration toward minimal test 
efforts; for example, no new or extra equipment is required. 
Additionally, rather than placing microphones at different spatial 
locations, the microphone is placed at height 4 feet above the ground 
in accordance with paragraph (22) of this proposed rule and remains in 
place.

Differences From Generally Applicable Noise Regulations

    As stated above, the FAA began its determination of the noise 
certification basis for the Matternet M2 aircraft using the outline of 
standards and procedures for small helicopters. To compensate for

[[Page 48283]]

the novel aircraft design features, including the size, propulsion 
system, and proposed flight operations, the FAA proposes the following 
new standards for inclusion in the M2 noise certification basis:
    1. The reference altitude for the level flyover test is 250 feet 
(rather than 492 feet in appendix J), item 6 in the proposed standard. 
This lower reference altitude addresses the nominal altitude for this 
UA, and was determined to be representative of the lowest cruise 
altitude for this UA based on operational data provided by the 
applicant. A major consideration in choosing reference altitude was the 
ability to collect sufficient noise signals that exceeded the 
background (ambient) noise at a typical test site (maintaining an 
acceptable signal-to-noise ratio). As tests are conducted, an applicant 
may be directed by the FAA to fly the aircraft at an altitude lower 
than the reference height to achieve a signal-to-noise ratio that meets 
the certification test requirements. If that occurs, the noise data 
collected at the actual test altitude would be mathematically adjusted 
to the reference altitude after the testing is complete. All such 
adjustments would be included in the test report.
    2. The reference airspeeds for flyover testing are: (a) Maximum 
flight speed at empty weight; and (b) highest cruise speed at maximum 
takeoff weight, (rather than a single reference speed as is used for 
small helicopters), paragraph (6)(c) in the proposed rule. Although 
both speed and aircraft weight contribute to noise generation, the FAA 
does not have sufficient data regarding these two factors to know which 
dominates in UA designs such as the Matternet model M2. The proposed 
rule requires the aircraft to be tested at two sets of reference 
conditions to address the potential noise conditions over a range of 
operations determined to be representative of the aircraft operation.
    3. The sound exposure level limit is 78 dB at the prescribed new 
reference level flyover altitude of 250 feet. Two considerations 
resulted in this new limit. The first consideration accounts for the 
lower reference altitude, which, without a consideration for weight, 
would increase the noise to 85.7 dB, or 3.7 dB higher than 82 dB in 
appendix J for a small helicopter weighting less than 3,215 lbs. and 
flying at reference altitude of 492 ft. The second consideration is for 
aircraft weight. The curve that flattens out at 82 dB in appendix J 
applies to small manned helicopters weighing between 0 and 3,125 lbs.; 
this curve was simplified to include the possibility of manned 
ultralight helicopters of unknown weight. In evaluating the Matternet 
M2 noise, the noise curve section reduced at a constant, resulting in 
the limit proposed here, which is 7.7 dB lower. The two adjustments 
together yields the new noise limit of 78 dB (78 = 82 + 3.7-7.7).
    This proposed rule also contains updated terminology, equipment 
references, recording standards, and relevant best practices that have 
become standard in the industry since appendix J was first adopted in 
1992 and are used in current noise certification. As an example, the 
FAA included more detailed requirements for the area immediately 
surrounding a test microphone regarding the condition of the ground 
surface, which is expected to be more sensitive to smaller aircraft 
with a single microphone arrangement. Such additions were sourced from 
FAA guidance materials and agency orders.
    This proposed rule also includes the requirement to create and get 
approval for a test plan, which is used during certification testing 
but may be unfamiliar to newer certification applicants. An applicant 
seeking noise type certification must prepare a test plan when testing 
is required to demonstrate compliance to the regulations. The applicant 
should submit the test plan early enough to allow the FAA time to 
review and approve the test plan before the planned start of testing. A 
test plan typically contains descriptions of the aircraft, equipment, 
calibration procedures, and test procedures.
    The FAA seeks specific input from interested persons concerning the 
considerations the agency used to select the proposed reference test 
height of 250 feet AGL for flyover noise testing of UAS, as discussed 
here. Commenters are encouraged to submit any data that supports the 
use of different considerations that would be appropriate for aircraft 
of this type.

IV. Regulatory Notices and Analyses

A. Executive Order 12866, Regulatory Planning and Review

    This proposed 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 Act

    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 proposed 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 proposed 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 proposed 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 this proposed rule of particular applicability 
would have small costs for Matternet to conduct tests and gather data. 
These would be one-time test costs representing a very small cost 
relative to the overall costs of seeking of type certification. This 
proposed rule would benefit Matternet by enabling a noise certification 
basis for it to complete the type certification it seeks. The FAA 
expects this proposed rule would 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. The FAA requests comments on this certification.

[[Page 48284]]

C. International Trade Impact

    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 proposed rule would not present any obstacle to foreign 
commerce of the United States. In addition, this proposed rule is not 
contrary to international standards since no international standards 
for UA noise certification exist.

D. Unfunded Mandates Reform Act

    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 proposed 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 
this proposed rule does not impose any new requirement for information 
collection covered by the Act.

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 these proposed regulations 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 unmanned aircraft 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 is proposed here.

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) since it is a rulemaking action that proposes a 
certification test standard, and would not presume the acceptability of 
operation of any particular aircraft in any location. No extraordinary 
circumstances are involved.

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. 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 (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.

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 FAA will consider comments filed 
after the comment period has closed if it is possible to do so without 
incurring expense or delay. 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.'' The 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 Hua (Bill) He, Federal Aviation Administration, Office of 
Environment and Energy, 800 Independence Ave. SW, Room 900

[[Page 48285]]

West, Washington, DC 20591; telephone (202) 267-3565; email 
hua.he@faa.gov. Any commentary that the FAA receives which 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--
    1. Searching the Federal eRulemaking Portal (www.regulations.gov);
    2. Visiting the FAA's Regulations and Policies web page at 
www.faa.gov/regulations_policies or
    3. Accessing the Government Printing Office's web page at 
www.GovInfo.gov.
    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) 267-9680. 
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 in item 
(1) above.

The Proposed 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 proposes that the following standards and procedures 
apply as the noise certification basis of the Matternet M2 model 
aircraft.
    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 M2 Model 
Aircraft:
    (1) General: The requirements and limitations of 14 CFR 36.3 and 
36.6 apply to the Matternet M2 model aircraft, 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 (23) 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 (24) through (26) 
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:
    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

[[Page 48286]]

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 10 dB per 100 meters (30.5 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 (17) of this 
rule.
    (b) The aircraft height relative to the noise measurement point 
sufficient to make corrections required in paragraph (26) 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 (21) of 
this rule, is found to be within 15 A-weighted decibels (dB(A)) of the 
A-weighted 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 
(f) 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

[[Page 48287]]

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 AGL (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 SPL 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] TN27AU21.007

    (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 regulation 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:
[GRAPHIC] [TIFF OMITTED] TN27AU21.008

    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:

[[Page 48288]]

[GRAPHIC] [TIFF OMITTED] TN27AU21.009

    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 PCM 
(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 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

[[Page 48289]]

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 regulation.
    (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 reference airspeed 
in accordance with paragraph (27)(c) of this rule.
    (b) The adjustment for off-reference altitude may be approximated 
from:

>delta< J1 = 12.5 log10(HT/250) (dB)

Where >deltaAE 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:

>delta< J3 = 10 log10(VRA/VR) (dB);

Where >deltaAE 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

[[Page 48290]]

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 (26) 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 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 (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 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.
Kevin Welsh,
Executive Director, Office of Environment and Energy.
[FR Doc. 2021-17769 Filed 8-26-21; 8:45 am]
BILLING CODE 4910-13-P