[Federal Register Volume 89, Number 89 (Tuesday, May 7, 2024)]
[Rules and Regulations]
[Pages 37969-37971]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-09825]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 29
[Docket No. FAA-2021-1143; Special Conditions No. 29-055-SC]
Special Conditions: Airbus Helicopters Model H160-B Helicopter;
Extended Duration of Flight After Loss of Main Gearbox Lubrication
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions.
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SUMMARY: These special conditions are issued for the Airbus Helicopters
(Airbus) Model H160-B helicopter. This helicopter has a novel or
unusual design feature when compared to the state of technology
envisioned in the airworthiness standards for helicopters. This design
feature is the extended duration of continued safe flight and landing
beyond 30 minutes after indication to the flightcrew of the loss of
main gearbox lubrication. The applicable airworthiness regulations do
not contain adequate or appropriate safety standards for this design
feature. These special conditions contain the additional safety
standards that the Administrator considers necessary to establish a
level of safety equivalent to that established by the existing
airworthiness standards.
DATES: Effective June 6, 2024.
FOR FURTHER INFORMATION CONTACT: Kamron Dowlatabadi, Mechanical
Systems, AIR-623, Technical Policy Branch, Policy and Standards
Division, Aircraft Certification Service, 10101 Hillwood Parkway, Fort
Worth, TX 76177; telephone (817) 222-5219; email
[email protected].
SUPPLEMENTARY INFORMATION:
Background
On July 10, 2023, Airbus applied for an amendment to Type
Certificate No. R00009RD for the Model H160-B helicopter to include
continued safe flight and landing beyond 30 minutes after indication to
the flightcrew of the loss of main gearbox lubrication.
The Airbus Model H160-B helicopter is a transport-category, twin-
turboshaft-engine helicopter certificated under 14 CFR part 29. This
helicopter has a maximum takeoff weight of 13,436 lbs. with seating for
12 passengers and 2 flightcrew members. The Airbus Model H160-B
helicopter is also characterized by the integration of composite
materials in its airframe, five main rotor blades (Blue Edge
technology), a Fenestron tail rotor, and a Helionix avionics suite.
Type Certification Basis
Under the provisions of 14 CFR 21.101, Airbus must show that the
Model H160-B helicopter meets the applicable provisions of the
regulations listed in Type Certificate No. R00009RD, or the applicable
regulations in effect on the date of application for the change, except
for earlier amendments as agreed upon by the FAA.
If the Administrator finds that the applicable airworthiness
regulations (i.e., 14 CFR part 29) do not contain adequate or
appropriate safety standards for the Airbus Model H160-B helicopter
because of a novel or unusual design feature, special conditions are
prescribed under the provisions of Sec. 21.16.
Special conditions are initially applicable to the model for which
they are issued. Should the type certificate for that model be amended
later to include any other model that incorporates the same or similar
novel or unusual design feature, the special conditions would also
apply to the other model under Sec. 21.101.
In addition to the applicable airworthiness regulations and special
conditions, the Airbus Model H160-B helicopter must comply with the
noise certification requirements of 14 CFR part 36.
The FAA issues special conditions, as defined in 14 CFR 11.19, in
accordance with Sec. 11.38, and they become part of the type-
certification basis under Sec. 21.101.
Novel or Unusual Design Features
The Airbus Model H160-B helicopter will incorporate the following
novel or unusual design feature:
Extended duration of continued safe flight and landing beyond 30
minutes after indication to the flightcrew of the loss of main gearbox
lubrication.
Discussion
Current regulations do not prescribe a duration for continued safe
flight and landing to be specifically called out in the rotorcraft
flight manual when a loss of main gearbox lubrication is indicated to
the flightcrew. Although Sec. 29.927(c)(1) requires a 30-minute test
to show that the rotor drive system, which is defined in Sec.
29.917(a) and includes the main gearbox, is operational for 30 minutes
following the indication to the flightcrew of a loss of lubrication,
the associated bench test conditions may not be representative of
aircraft flight conditions because a 30-minute bench test of the main
gearbox may not translate to 30 minutes of continued safe flight and
landing.
The novel or unusual design feature of the Airbus Model H160-B
helicopter is intended to enable the helicopter to continue safe flight
and landing, for a minimum of 30 minutes, to the intended destination
or to a safe landing location after the indication to the flightcrew of
a loss of main gearbox lubrication. To meet this minimum 30 minutes of
continued safe flight and landing, the Airbus Model H160-B helicopter
main gearbox is designed with a redundant lubrication system. This main
gearbox redundant lubrication system would allow continued safe
operation after the failure of a single lubrication system. Current
regulations do not address a redundant lubrication system that allows
operation after the failure of a single lubrication system because at
the time the existing regulations were issued, the agency did not
envision that a flight duration of more than 30 minutes after the
indication to the flightcrew of the loss of main gearbox lubrication
was needed. Accordingly, these special conditions provide testing
criteria to ensure the reliability of the redundant lubrication system
to provide an extended period for safe flight and landing beyond 30
minutes after indication to the flightcrew of the loss of the main
gearbox lubrication.
These special conditions add new requirements in lieu of the
existing airworthiness standards in Sec. Sec. 29.917(a) and 29.927(c)
and add a requirement to Sec. 29.1585.
At the time of the issuance of the existing regulations, the FAA
did not envision the evolving operations for these types of aircraft
and the regulations did not include the main gearbox lubrication system
components in the required design assessment of the rotor drive system.
Accordingly, these special conditions include requirements for
addressing ``any associated lubrication system components including oil
coolers'' in the design assessment required by Sec. 29.917(b).
These special conditions add a safety margin over the current 30-
minute rotor drive system test specified in Sec. 29.927(c)(1) by
requiring a test duration of more than 30 minutes to
[[Page 37970]]
ensure that the rotor drive gearbox system has an in-flight operational
endurance capability of at least 30 minutes following a failure of any
one pressurized, normal-use lubrication system. The 30-minute test
interval starts when the lubrication-failure indication to the
flightcrew is triggered and the engine is at maximum continuous power.
These special conditions require a bench test of the rotor drive system
main gearbox for a minimum of 30 minutes to establish a maximum period
of in-flight operation following loss of main gearbox lubrication, and
to ensure that the main gearbox continues to operate safely for at
least 30 minutes after an indication to the flightcrew of a loss of
lubrication.
The term ``confidence'' specified in Category A and B in these
special conditions necessitates the applicant provide supporting data
with respect to the mechanical behavior of the main gearbox and must
reflect the applicant's confidence in the repeatability of the
certification test data. Test loading, in the context of these special
conditions, refers to the engine, main gearbox, clutch system, and
rotors (or similar test apparatus) interconnected and operating in
unison, as this combination of mechanical elements pertains to power
input transmitted to the main gearbox and subsequent reaction torques
simulating operating conditions.
These special conditions add a requirement that the maximum
duration of operation after a failure, which results in a loss of main
gearbox lubrication and an associated indication to the flightcrew,
must be furnished in the rotorcraft flight manual, and the duration
must not exceed the maximum period of in-flight operational endurance
capability substantiated.
These special conditions contain the additional safety standards
that the Administrator considers necessary to establish a level of
safety equivalent to that established by the existing airworthiness
standards.
Discussion of Comments
The FAA issued Notice of Proposed Special Conditions No. 29-21-01-
SC for the Airbus Model H160-B helicopter, which was published in the
Federal Register on May 12, 2023 (88 FR 30680). The FAA received
several comments from Leonardo Helicopters regarding the proposed
special conditions.
Leonardo Helicopters requested the FAA generally maintain
harmonization and alignment with the EASA certification specifications
(CS) 29 requirements by implementing the same changes to part 29 that
were introduced by EASA rulemaking task RMT.0608, following notice of
proposed amendment (NPA) 2017-07, Rotorcraft gearbox loss of
lubrication, through Amendment 5.
This request relating to the pursuit of future rulemaking for part
29 is beyond the scope of these special conditions. No change was made
to these special conditions as a result of this comment.
Leonardo Helicopters stated that EASA's CS-29 requirements and
acceptable means of compliance (AMC) clearly define how to establish
the operational endurance capability through the application of
reduction factors. However, the correlation between 30 and 60 minutes,
and the criteria for defining this correlation, is not clear in the
proposed special conditions. Leonardo Helicopters requested the FAA
revise the proposed special conditions to define the proposed reduction
factors and allow the public to comment. The FAA infers that Leonardo
Helicopters is also requesting clarification regarding the correlation
between 30 and 60 minutes for the bench test.
The FAA disagrees with the commenter's request to include reduction
factors and related material in these special conditions. The FAA
considers the details referenced by Leonardo Helicopters, including the
correlation between the test duration and substantiated safe operation
duration, to be related to the means of compliance for these special
conditions. Means of compliance for these special conditions are
defined separately between the FAA and the applicant via the FAA issue
paper process, which is outside the scope of these special conditions.
However, to address the Leonardo Helicopters comment, the FAA has
clarified language in the discussion section. Specifically, the FAA
removed the previous reference in these special conditions to a 60-
minute bench test scenario, since it is not a requirement under
29.927(c), but rather an example to illustrate how applicants translate
the time duration of a bench test into 30 minutes of substantiated
operation for continued safe flight and landing. In addition, the term
``reduction factor'' has been removed from the discussion section and
replaced with language to define the term ``confidence'' used in these
special conditions.
Additionally, Leonardo Helicopters stated that EASA CS-29 does not
have a similar requirement for a test duration of at least 60 minutes,
and therefore the special conditions are not harmonized with the EASA
requirements. The FAA infers Leonardo Helicopters is requesting that
the FAA revise the proposed special conditions to address an alleged
contradiction and lack of harmonization with the related EASA CS-29
requirements.
The FAA does not agree to revise the proposed special conditions to
address a possible contradiction because the FAA does not find that a
contradiction exists. The commenter suggests that these special
conditions contain a 60-minute testing requirement. There is no
specific requirement in these special conditions for a 60-minute test.
However, in the preamble of the proposed special conditions, the FAA
discussed a scenario where it may be necessary for an applicant to
perform a 60-minute test, depending on reduction factors. As explained
previously, this language has been removed to address the related
public comment and replaced with language to describe the context of
the word ``confidence'' used in these special conditions. The details
related to the test duration and maximum period of in-flight operation
following loss of main gearbox lubrication are associated with the
means of compliance for these special conditions. As previously
explained, the means of compliance are established between the FAA and
applicant through the FAA issue paper process and the FAA's acceptance
of a specific means of compliance is beyond the scope of these special
conditions. No changes were made to these special conditions as a
result of this comment. However, the FAA has made minor editorial
changes to these special conditions to ensure consistency in the
language of the requirements.
Applicability
As discussed above, these special conditions are applicable to the
Airbus Helicopters Model H160-B helicopter. Should Airbus Helicopters
apply at a later date for a change to the type certificate to include
another model incorporating the same novel or unusual design feature,
these special conditions would apply to that model as well.
Conclusion
This action affects only a certain novel or unusual design feature
on one model of helicopter. It is not a rule of general applicability.
List of Subjects in 14 CFR Part 29
Aircraft, Aviation safety, Reporting and recordkeeping
requirements.
Authority Citation
The authority citation for these special conditions is as follows:
[[Page 37971]]
Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701-44702, 44704.
The Special Conditions
Accordingly, pursuant to the authority delegated to me by the
Administrator, the following special conditions are issued as part of
the type certification basis for the Airbus Helicopters Model H160-B
helicopter. Unless stated otherwise, all requirements in Sec. Sec.
29.917, 29.927, and 29.1585 still apply.
In lieu of Sec. 29.917(a), the following special condition
applies:
(a) Design: General. The rotor drive system includes any part
necessary to transmit power from the engines to the rotor hubs. This
includes gearboxes, shafting, universal joints, couplings, rotor brake
assemblies, clutches, supporting bearings for shafting, any attendant
accessory pads or drives, any cooling fans, and any associated
lubrication-system components including oil coolers that are a part of,
attached to, or mounted on the rotor drive gearbox system.
In lieu of Sec. 29.927(c), the following special condition
applies:
(c) Lubrication system failure. For rotor drive gearbox systems
featuring a pressurized, normal-use lubrication system, the following
requirements for continued safe flight and landing apply:
(1) Category A. Confidence must be established that the rotor drive
gearbox system has an in-flight operational endurance capability of at
least 30 minutes following a failure of any one pressurized, normal-use
lubrication system.
(i) For each rotor drive gearbox system necessary for continued
safe flight or safe landing, the applicant must conduct a test that
simulates the effect of the most severe failure mode of the
pressurized, normal-use lubrication system, as determined by the
failure analysis required by Sec. 29.917(b). The duration of the test
must be dependent on the number of tests and the component condition
after each test.
(ii) The test must begin when the indication to the flightcrew
shows a lubrication failure has occurred, and its loading must be
consistent with 1 minute at maximum continuous power, followed by the
minimum power needed for continued flight at the rotorcraft maximum
gross weight.
(iii) The test must end with a 45-second out-of-ground-effect (OGE)
hover to simulate a landing phase. Test results must substantiate the
maximum period of operation following a loss of lubrication by means of
an extended test duration or multiple test specimens, or another
approach prescribed by the applicant and accepted by the FAA.
(2) Category B. Confidence must be established that the rotor drive
gearbox system has an in-flight operational endurance capability to
complete an autorotation descent and landing following a failure of any
one pressurized, normal-use lubrication system.
(i) For each rotor drive gearbox system necessary for safe
autorotation descent or safe landing, the applicant must conduct a test
of at least 16 minutes and 15 seconds, following the most severe
failure mode of the pressurized, normal-use lubrication system, as
determined by the failure analysis required by Sec. 29.917(b).
(ii) The test must begin when the indication to the flightcrew
shows that a lubrication failure has occurred, and its loading must be
consistent with 1 minute at maximum continuous power. Thereafter, the
input torque should be reduced to simulate autorotation for a minimum
of 15 minutes.
(iii) The test must be conducted using an input torque to simulate
a minimum power landing for approximately 15 seconds.
In addition to Sec. 29.1585, the following special condition
applies:
(h) Power Plant limitations. The maximum duration of operation
after a failure, resulting in any loss of lubrication of a rotor-drive-
system gearbox and an associated oil-pressure warning, must be
furnished in the rotorcraft flight manual, and must not exceed the
maximum period substantiated in accordance with Sec. 29.927(c) of
these special conditions.
Issued in Kansas City, Missouri, on April 29, 2024.
Patrick R. Mullen,
Manager, Technical Policy Branch, Policy and Standards Division,
Aircraft Certification Service.
[FR Doc. 2024-09825 Filed 5-6-24; 8:45 am]
BILLING CODE 4910-13-P