[Federal Register Volume 83, Number 198 (Friday, October 12, 2018)]
[Rules and Regulations]
[Pages 51623-51624]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2018-22267]
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Rules and Regulations
Federal Register
________________________________________________________________________
This section of the FEDERAL REGISTER contains regulatory documents
having general applicability and legal effect, most of which are keyed
to and codified in the Code of Federal Regulations, which is published
under 50 titles pursuant to 44 U.S.C. 1510.
The Code of Federal Regulations is sold by the Superintendent of Documents.
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Federal Register / Vol. 83, No. 198 / Friday, October 12, 2018 /
Rules and Regulations
[[Page 51623]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 29
[Docket No.FAA-2017-1127; Notice No. 29-044-SC]
Special Conditions: Bell Helicopter Textron, Inc. (BHTI), Model
525 Helicopters; Flight Envelope Protection
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions.
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SUMMARY: These special conditions are issued for the BHTI Model 525
helicopter. This helicopter will have a novel or unusual design feature
associated with fly-by-wire flight control system (FBW FCS) flight
envelope protection. 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: These special conditions are effective November 13, 2018.
FOR FURTHER INFORMATION CONTACT: George Harrum, Aerospace Engineer,
FAA, Rotorcraft Standards Branch, Policy and Innovation Division, 10101
Hillwood Pkwy., Fort Worth, TX 76177; telephone (817) 222-4087; email
[email protected].
SUPPLEMENTARY INFORMATION:
Background
On December 15, 2011, BHTI applied for a type certificate for a new
transport category helicopter designated as the Model 525. The Model
525 is a medium twin-engine rotorcraft. The design maximum takeoff
weight is 20,500 pounds, with a maximum capacity of 19 passengers and a
crew of 2.
The BHTI Model 525 helicopter will be equipped with a four axis
full authority digital FBW FCS that provides for aircraft control
through pilot input and coupled flight director modes. The FBW FCS will
contain an advanced flight control system that will alter the nominal
flight control laws to ensure that the aircraft remains in a
predetermined flight envelope. These Flight Envelope Protection (FEP)
features prevent the pilot or autopilot functions from making control
commands that would force the aircraft to exceed its structural,
aerodynamic, or operating limits. The design and construction
standards, specifically 14 CFR Section 29.779(a), require that movement
of the flight controls results in a corresponding sense of aircraft
motion in the same axis. The airworthiness standards for an automatic
pilot system in Section 29.1329 covers design requirements for basic
operation of the system but does not address dynamic flight envelope
limitations imposed by the automatic pilot system. Currently there are
no specific airworthiness requirements that address FBW FCS FEP in
rotorcraft. The special conditions will require the minimum safety
standard for the FEP features.
Type Certification Basis
Under the provisions of 14 CFR 21.17, BHTI must show that the Model
525 helicopter meets the applicable provisions of part 29, as amended
by Amendment 29-1 through 29-55 thereto. The BHTI Model 525
certification basis date is December 31, 2013, the effective date of
application to 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 BHTI Model 525 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 BHTI Model 525 helicopter must comply with the noise
certification requirements of 14 CFR part 36, and the FAA must issue a
finding of regulatory adequacy under Sec. 611 of Public Law 92-574,
the ``Noise Control Act of 1972.''
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. 21.17(a)(2).
Novel or Unusual Design Features
The BHTI Model 525 helicopter will incorporate the following novel
or unusual design features: FBW FCS incorporating FEP features. FEP is
used to prevent the pilot or an autopilot from making control commands
that would force the rotorcraft to exceed its structural, aerodynamic,
or operating limits. To accomplish this envelope limiting, the FCS
control laws change as the limit is approached or exceeded.
Discussion
These special conditions require the minimum safety standard for
the flight envelope protection features. The FEP features must meet
requirements for handling qualities, compatibility of flight parameter
limit values, response to dynamic maneuvering, and failure modes.
Discussion of Comments
Notice of proposed special conditions No. 29-044-SC for the BHTI
Model 525 helicopter was published in the Federal Register on June 6,
2018 (83 FR 26226). No comments were received, and the special
conditions are adopted as proposed.
Applicability
As discussed above, these special conditions are applicable to the
BHTI Model 525 helicopter. Should BHTI apply at a later date for a
change to the type certificate to include another model incorporating
the same novel or unusual design feature, the special conditions would
apply to that model as well.
Conclusion
This action affects only certain novel or unusual design features
on one model of rotorcraft. It is not a rule of general applicability.
[[Page 51624]]
List of Subjects in 14 CFR Part 29
Aircraft, Aviation safety, Reporting and recordkeeping
requirements.
The authority citation for these special conditions is as follows:
Authority: 49 U.S.C. 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 Bell Helicopter Textron, Inc., Model
525 helicopters:
Flight Envelope Protection
The Flight Envelope Protection (FEP) features of the flight control
system (FCS) must meet the following requirements:
a. Onset characteristics of each envelope protection feature must
be smooth, appropriate to the phase of flight and type of maneuver, and
not in conflict with the ability of the pilot to satisfactorily change
rotorcraft flight path, speed, or attitude within the approved flight
envelope.
b. Limit values of protected flight parameters (and if applicable,
associated warning thresholds) must be compatible with:
1. Rotorcraft structural limits;
2. Safe and controllable maneuvering of the rotorcraft;
3. Margins to critical conditions. Dynamic maneuvering, airframe
and system tolerances (both manufacturing and in-service), and non-
steady atmospheric conditions--in any appropriate combination and phase
of flight--must not result in a limited flight parameter beyond the
nominal design limit value that would cause unsafe flight
characteristics;
4. Rotor rotational speed limits;
5. Blade stall limits; and
6. Engine and transmission torque limits.
c. The aircraft must be responsive to pilot-commanded dynamic
maneuvering within a suitable range of the parameter limits that define
the approved flight envelope.
d. The FEP system must not create unusual or adverse flight
characteristics when atmospheric conditions or unintentional pilot
action causes the approved flight envelope to be exceeded.
e. When simultaneous envelope limiting is active, adverse coupling
or adverse priority must not result.
f. Following a single FEP failure shown to not be extremely
improbable, the rotorcraft must:
1. Be capable of continued safe flight and landing;
2. Be capable of initial counteraction of malfunctions without
requiring exceptional pilot skill or strength;
3. Be controllable and maneuverable when operated with a degraded
FCS, within a practical flight envelope identified in the Rotorcraft
Flight Manual;
4. Be capable of prolonged instrument flight without requiring
exceptional pilot skill;
5. Meet the controllability and maneuverability requirements of 14
CFR part 29 Subpart B throughout a practical flight envelope; and
6. Be safely controllable following any additional failure or
malfunction shown to not be extremely improbable occurring within the
approved flight envelope.
Issued in Fort Worth, Texas, on October 3, 2018.
Jorge Castillo,
Acting Manager, Rotorcraft Standards Branch, Policy and Innovation
Division, Aircraft Certification Services.
[FR Doc. 2018-22267 Filed 10-11-18; 8:45 am]
BILLING CODE 4910-13-P