Notice2022-19639
Noise Certification Standards: Matternet Model M2 Aircraft
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
September 12, 2022
Effective
September 9, 2022
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
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.
Full Text
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<title>Federal Register, Volume 87 Issue 175 (Monday, September 12, 2022)</title>
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[Federal Register Volume 87, Number 175 (Monday, September 12, 2022)]
[Notices]
[Pages 55878-55887]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[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
<a href="/cdn-cgi/l/email-protection#adc5d8cc83c5c8edcbcccc83cac2db"><span class="__cf_email__" data-cfemail="355d40541b5d50755354541b525a43">[email protected]</span></a>.
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:
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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 <a href="http://www.regulations.gov">www.regulations.gov</a>;
2. Visit the FAA's Regulations and Policies web page at
<a href="http://www.faa.gov/regulations_policies">www.faa.gov/regulations_policies</a>; or
3. Access the Government Printing Office's web page at
<a href="http://www.GovInfo.gov">www.GovInfo.gov</a>.
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 <a href="https://www.regulations.gov">https://www.regulations.gov</a> 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 L<INF>AE</INF>); 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. V<INF>max</INF> ~ 0.9V<INF>NE,</INF> where V<INF>NE</INF> is the
never-exceed airspeed (at empty weight).
ii. V<INF>cruise</INF> ~ V<INF>H</INF>, where V<INF>H</INF> 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 V<INF>cruise</INF>; and
ii. Empty weight (no payload) and V<INF>max</INF>.
(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 L<INF>AE,</INF> 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 <plus-
minus> 10% value; and
(c) Within <plus-minus>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 (L<INF>Amax</INF>).
(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 (L<INF>Amax</INF>), 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 L<INF>AE</INF>, is
defined as the level, in decibels, of the time integral of squared `A'-
weighted sound pressure (P<INF>A</INF>) over a given time period or
event, with reference to the square of the standard reference sound
pressure (P<INF>0</INF>) 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 T<INF>0</INF> is the reference integration time of one second
and (t<INF>2</INF>-t<INF>1</INF>) is the integration time interval.
(c) The integral equation of paragraph (18)(b) can also be
expressed as:
[GRAPHIC] [TIFF OMITTED] TN12SE22.004
Where L<INF>A</INF>(t) is the time varying A-weighted sound level.
(d) The integration time (t<INF>2</INF>-t<INF>1</INF>) in practice
must not be less than the time interval during which L<INF>A</INF>(t)
first rises to within 10 dB(A) of its maximum value (L<INF>Amax</INF>)
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 L<INF>AE</INF> value from each flyover and A-weighed Leq
(L<INF>Aeq</INF>) 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
L<INF>AE</INF> 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 (L<INF>AE</INF>) integration
process includes, at minimum, all of the noise signal between the
L<INF>Amax</INF> 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 L<INF>AE</INF> integration interval and document these
levels along with the value of L<INF>Amax</INF> 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: V<INF>NE</INF> and V<INF>max</INF> 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 L<INF>AE</INF> (Reference: part 36, appendix J, section J36.201, as
modified): The noise evaluation measure must be expressed as the
L<INF>AE</INF> in units of dB(A) as prescribed in paragraph (18) of
this rule. The L<INF>AE</INF> 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 L<INF>AE</INF> 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 L<INF>AE</INF> 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 <plus-minus>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 <DELTA>J1 is the quantity in decibels that must be
algebraically added to the measured L<INF>AE</INF> noise level to
correct for an off-reference flight path, H<INF>T</INF> 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 <DELTA>J3 is the quantity in decibels that must be
algebraically added to the measured L<INF>AE</INF> 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; V<INF>R</INF> is the reference airspeed as prescribed in
paragraph (6)(c) of this rule, and V<INF>RA</INF> 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 L<INF>AE</INF> 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
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