83 FR 51623 - Special Conditions: Bell Helicopter Textron, Inc. (BHTI), Model 525 Helicopters; Flight Envelope Protection

DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration

Federal Register Volume 83, Issue 198 (October 12, 2018)

Page Range		51623-51624
FR Document		2018-22267

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.

Federal Register, Volume 83 Issue 198 (Friday, October 12, 2018)

[Federal Register Volume 83, Number 198 (Friday, October 12, 2018)]
[Rules and Regulations]
[Pages 51623-51624]
From the Federal Register Online  [www.thefederalregister.org]
[FR Doc No: 2018-22267]



========================================================================
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. 

========================================================================


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.

-----------------------------------------------------------------------

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

51623

Rules and Regulations Federal Register
Vol. 83, No. 198

Friday, October 12, 2018

This section of the FEDERAL REGISTER The BHTI Model 525 helicopter will conditions, the BHTI Model 525
contains regulatory documents having general be equipped with a four axis full helicopter must comply with the noise
applicability and legal effect, most of which authority digital FBW FCS that provides certification requirements of 14 CFR
are keyed to and codified in the Code of for aircraft control through pilot input part 36, and the FAA must issue a
Federal Regulations, which is published under and coupled flight director modes. The finding of regulatory adequacy under
50 titles pursuant to 44 U.S.C. 1510.
FBW FCS will contain an advanced § 611 of Public Law 92–574, the ‘‘Noise
The Code of Federal Regulations is sold by flight control system that will alter the Control Act of 1972.’’
the Superintendent of Documents. nominal flight control laws to ensure The FAA issues special conditions, as
that the aircraft remains in a defined in 14 CFR 11.19, in accordance
predetermined flight envelope. These with § 11.38, and they become part of
DEPARTMENT OF TRANSPORTATION Flight Envelope Protection (FEP) the type-certification basis under
features prevent the pilot or autopilot § 21.17(a)(2).
Federal Aviation Administration functions from making control
commands that would force the aircraft Novel or Unusual Design Features
14 CFR Part 29 to exceed its structural, aerodynamic, or
The BHTI Model 525 helicopter will
[Docket No.FAA–2017–1127; Notice No. 29–
operating limits. The design and
construction standards, specifically 14 incorporate the following novel or
044–SC] unusual design features: FBW FCS
CFR Section 29.779(a), require that
movement of the flight controls results incorporating FEP features. FEP is used
Special Conditions: Bell Helicopter to prevent the pilot or an autopilot from
Textron, Inc. (BHTI), Model 525 in a corresponding sense of aircraft
motion in the same axis. The making control commands that would
Helicopters; Flight Envelope force the rotorcraft to exceed its
Protection airworthiness standards for an
automatic pilot system in Section structural, aerodynamic, or operating
AGENCY: Federal Aviation 29.1329 covers design requirements for limits. To accomplish this envelope
Administration (FAA), DOT. basic operation of the system but does limiting, the FCS control laws change as
ACTION: Final special conditions. not address dynamic flight envelope the limit is approached or exceeded.
limitations imposed by the automatic Discussion
SUMMARY: These special conditions are pilot system. Currently there are no
issued for the BHTI Model 525 specific airworthiness requirements that These special conditions require the
helicopter. This helicopter will have a address FBW FCS FEP in rotorcraft. The minimum safety standard for the flight
novel or unusual design feature special conditions will require the envelope protection features. The FEP
associated with fly-by-wire flight minimum safety standard for the FEP features must meet requirements for
control system (FBW FCS) flight features. handling qualities, compatibility of
envelope protection. The applicable flight parameter limit values, response
airworthiness regulations do not contain Type Certification Basis to dynamic maneuvering, and failure
adequate or appropriate safety standards Under the provisions of 14 CFR 21.17, modes.
for this design feature. These special BHTI must show that the Model 525
helicopter meets the applicable Discussion of Comments
conditions contain the additional safety
standards that the Administrator provisions of part 29, as amended by Notice of proposed special conditions
considers necessary to establish a level Amendment 29–1 through 29–55 No. 29–044–SC for the BHTI Model 525
of safety equivalent to that established thereto. The BHTI Model 525 helicopter was published in the Federal
by the existing airworthiness standards. certification basis date is December 31, Register on June 6, 2018 (83 FR 26226).
DATES: These special conditions are 2013, the effective date of application to No comments were received, and the
effective November 13, 2018. the FAA. special conditions are adopted as
If the Administrator finds that the proposed.
FOR FURTHER INFORMATION CONTACT:
applicable airworthiness regulations
George Harrum, Aerospace Engineer, (i.e., 14 CFR part 29) do not contain Applicability
FAA, Rotorcraft Standards Branch, adequate or appropriate safety standards
Policy and Innovation Division, 10101 for the BHTI Model 525 because of a As discussed above, these special
Hillwood Pkwy., Fort Worth, TX 76177; novel or unusual design feature, special conditions are applicable to the BHTI
telephone (817) 222–4087; email conditions are prescribed under the Model 525 helicopter. Should BHTI
George.Harrum@faa.gov. provisions of § 21.16. apply at a later date for a change to the
SUPPLEMENTARY INFORMATION: Special conditions are initially type certificate to include another
applicable to the model for which they model incorporating the same novel or
Background unusual design feature, the special
are issued. Should the type certificate
On December 15, 2011, BHTI applied for that model be amended later to conditions would apply to that model as
khammond on DSK30JT082PROD with RULES

for a type certificate for a new transport include any other model that well.
category helicopter designated as the incorporates the same or similar novel Conclusion
Model 525. The Model 525 is a medium or unusual design feature, the special
twin-engine rotorcraft. The design conditions would also apply to the other This action affects only certain novel
maximum takeoff weight is 20,500 model under § 21.101. or unusual design features on one model
pounds, with a maximum capacity of 19 In addition to the applicable of rotorcraft. It is not a rule of general
passengers and a crew of 2. airworthiness regulations and special applicability.

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51624 Federal Register / Vol. 83, No. 198 / Friday, October 12, 2018 / Rules and Regulations

List of Subjects in 14 CFR Part 29 2. Be capable of initial counteraction FAA, Rotorcraft Standards Branch,
Aircraft, Aviation safety, Reporting of malfunctions without requiring Policy and Innovation Division, 10101
and recordkeeping requirements. exceptional pilot skill or strength; Hillwood Pkwy., Fort Worth, TX 76177;
3. Be controllable and maneuverable telephone (817) 222–4087; email
The authority citation for these
when operated with a degraded FCS, George.Harrum@faa.gov.
special conditions is as follows:
within a practical flight envelope SUPPLEMENTARY INFORMATION:
Authority: 49 U.S.C. 106(g), 40113, 44701, identified in the Rotorcraft Flight
44702, 44704. Manual; Background
The Special Conditions 4. Be capable of prolonged instrument On December 15, 2011, BHTI applied
flight without requiring exceptional for a type certificate for a new transport
Accordingly, pursuant to the category helicopter designated as the
authority delegated to me by the pilot skill;
5. Meet the controllability and Model 525. The Model 525 is a medium
Administrator, the following special twin-engine rotorcraft. The design
conditions are issued as part of the type maneuverability requirements of 14 CFR
part 29 Subpart B throughout a practical maximum takeoff weight is 20,500
certification basis for Bell Helicopter pounds, with a maximum capacity of 19
Textron, Inc., Model 525 helicopters: flight envelope; and
6. Be safely controllable following any passengers and a crew of 2.
Flight Envelope Protection additional failure or malfunction shown The BHTI Model 525 helicopter will
to not be extremely improbable be equipped with a four-axis full
The Flight Envelope Protection (FEP)
occurring within the approved flight authority digital FBW FCS that provides
features of the flight control system
envelope. for aircraft control through pilot input
(FCS) must meet the following and coupled flight director modes. The
requirements: Issued in Fort Worth, Texas, on October 3, current 14 CFR part 29 regulations do
a. Onset characteristics of each 2018.
not contain adequate standards for FBW
envelope protection feature must be Jorge Castillo, FCS with respect to control margin
smooth, appropriate to the phase of Acting Manager, Rotorcraft Standards awareness. The airworthiness standards
flight and type of maneuver, and not in Branch, Policy and Innovation Division, for controllability and maneuverability
conflict with the ability of the pilot to Aircraft Certification Services.
of the rotorcraft are contained in
satisfactorily change rotorcraft flight [FR Doc. 2018–22267 Filed 10–11–18; 8:45 am] § 29.143. These controllability
path, speed, or attitude within the BILLING CODE 4910–13–P requirements are compatible with most
approved flight envelope. FBW systems, while most of the
b. Limit values of protected flight
maneuverability requirements are not
parameters (and if applicable, associated DEPARTMENT OF TRANSPORTATION affected by FBW systems, except for the
warning thresholds) must be compatible
control margins. One of the purposes of
with: Federal Aviation Administration
1. Rotorcraft structural limits; the rule is to ensure that control margins
2. Safe and controllable maneuvering (at the rotor and the anti-torque system
14 CFR Part 29
of the rotorcraft; level) are sufficient in the defined flight
3. Margins to critical conditions. [Docket No.FAA–2017–1128; Notice No. 29– envelope to avoid loss of control (that is,
Dynamic maneuvering, airframe and 045–SC] the rotorcraft has adequate control
system tolerances (both manufacturing power for the pilot to exit potentially
Special Conditions: Bell Helicopter hazardous flight conditions). Implicit in
and in-service), and non-steady Textron, Inc. (BHTI), Model 525
atmospheric conditions—in any this purpose is that the pilot is provided
Helicopters; Control Margin with sufficient awareness of proximity
appropriate combination and phase of Awareness
flight—must not result in a limited to control limits. Because § 29.143 was
flight parameter beyond the nominal AGENCY: Federal Aviation written to address hydro-mechanical
design limit value that would cause Administration (FAA), DOT. flight control systems, through which
unsafe flight characteristics; pilot awareness of control margins is
ACTION: Final special conditions. provided by cyclic and pedal position
4. Rotor rotational speed limits;
5. Blade stall limits; and SUMMARY: These special conditions are relative to cockpit control stops, the rule
6. Engine and transmission torque issued for the BHTI Model 525 is inadequate for certification of a FBW
limits. helicopter. This helicopter will have a FCS, where there is no mechanical link
c. The aircraft must be responsive to novel or unusual design feature between the inceptor and the receptor.
pilot-commanded dynamic associated with the fly-by-wire flight Without a constant correlation between
maneuvering within a suitable range of control system (FBW FCS) in the area of cockpit control and main or tail rotor
the parameter limits that define the pilot awareness of the control margins actuator positions, the FCS may not
approved flight envelope. remaining while maneuvering the provide tactile control margin feedback
d. The FEP system must not create helicopter. The applicable airworthiness to the pilot through cockpit control
unusual or adverse flight characteristics regulations do not contain adequate or position relative to the control position
when atmospheric conditions or appropriate safety standards for this physical stop or limit, for all flight
unintentional pilot action causes the design feature. These special conditions conditions. The special conditions will
approved flight envelope to be contain the additional safety standards require the minimum safety standard to
exceeded. that the Administrator considers ensure awareness of proximity to
e. When simultaneous envelope necessary to establish a level of safety control limits at the main rotor and tail
khammond on DSK30JT082PROD with RULES

limiting is active, adverse coupling or equivalent to that established by the rotor is provided to pilots of the Bell
adverse priority must not result. existing airworthiness standards. Model 525 helicopter.
f. Following a single FEP failure
shown to not be extremely improbable, DATES: These special conditions are Type Certification Basis
the rotorcraft must: effective November 13, 2018. Under the provisions of 14 CFR 21.17,
1. Be capable of continued safe flight FOR FURTHER INFORMATION CONTACT: BHTI must show that the Model 525
and landing; George Harrum, Aerospace Engineer, helicopter meets the applicable

VerDate Sep<11>2014 16:22 Oct 11, 2018 Jkt 247001 PO 00000 Frm 00002 Fmt 4700 Sfmt 4700 E:\FR\FM\12OCR1.SGM 12OCR1

Document Created: 2018-10-13 10:07:33
Document Modified: 2018-10-13 10:07:33

Category		Regulatory Information
Collection		Federal Register
sudoc Class		AE 2.7: GS 4.107: AE 2.106:
Publisher		Office of the Federal Register, National Archives and Records Administration
Section		Rules and Regulations
Action		Final special conditions.
Dates		These special conditions are effective November 13, 2018.
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]
FR Citation		83 FR 51623
CFR Associated		Aircraft; Aviation Safety and Reporting and Recordkeeping Requirements

83 FR 51623 - Special Conditions: Bell Helicopter Textron, Inc. (BHTI), Model 525 Helicopters; Flight Envelope Protection

DEPARTMENT OF TRANSPORTATIONFederal Aviation Administration

Federal Register Volume 83, Issue 198 (October 12, 2018)

DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration