83 FR 26226 - Special Conditions: Bell Helicopter Textron, Inc. (BHTI), Model 525 Helicopters; Flight Envelope Protection

DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration

Federal Register Volume 83, Issue 109 (June 6, 2018)

Page Range		26226-26228
FR Document		2018-12077

This action proposes special conditions 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 proposed 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 109 (Wednesday, June 6, 2018)

[Federal Register Volume 83, Number 109 (Wednesday, June 6, 2018)]
[Proposed Rules]
[Pages 26226-26228]
From the Federal Register Online  [www.thefederalregister.org]
[FR Doc No: 2018-12077]


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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: Notice of proposed special conditions.

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SUMMARY: This action proposes special conditions 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 proposed 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: Send your comments on or before July 23, 2018.

ADDRESSES: Send comments identified by docket number [FAA-2017-1127] 
using any of the following methods:
     Federal eRegulations Portal: Go to http://www.regulations.gov and follow the online instructions for sending your 
comments electronically.
     Mail: Send comments to Docket Operations, M-30, U.S. 
Department of Transportation (DOT), 1200 New Jersey Avenue SE., Room 
W12-140, West Building Ground Floor, Washington, DC 20590-0001.
     Hand Delivery of Courier: Take comments to Docket 
Operations in Room W12-140 of the West Building Ground Floor at 1200 
New Jersey Avenue SE, Washington, DC, between 8 a.m., and 5 p.m., 
Monday through Friday, except Federal holidays.
     Fax: Fax comments to Docket Operations at 202-493-2251.
    Privacy: The FAA will post all comments it receives, without 
change, to http://www.regulations.gov, including any personal 
information the commenter provides. Using the search function of the 
docket website, anyone can find and read the electronic form of all 
comments received into any FAA docket, including the name of the 
individual sending the comment (or signing the comment for an 
association, business, labor union, etc.). DOT's complete Privacy Act 
Statement can be found in the Federal Register published on April 11, 
2000 (65 FR 19477-19478), as well as at http://DocketsInfo.dot.gov.
    Docket: Background documents or comments received may be read at 
http://www.regulations.gov at any time. Follow the online instructions 
for accessing the docket or go to the Docket Operations in Room W12-140 
of the West Building Ground Floor at 1200 New Jersey Avenue SE, 
Washington, DC, between 9 a.m., and 5 p.m., Monday through Friday, 
except Federal holidays.

FOR FURTHER INFORMATION CONTACT: George Harrum, Aerospace Engineer,

[[Page 26227]]

FAA, Rotorcraft Standards Branch, Policy and Innovation Division, 10101 
Hillwood Pkwy, Fort Worth, TX 76177; telephone (817) 222-4087; email 
[email protected].

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite interested people to take part in this rulemaking by 
sending written comments, data, or views. The most helpful comments 
reference a specific portion of the special conditions, explain the 
reason for any recommended change, and include supporting data.
    We will consider all comments we receive on or before the closing 
date for comments. We will consider comments filed late if it is 
possible to do so without incurring expense or delay. We may change 
these special conditions based on the comments we receive.

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 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 Sec.  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 
proposed 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 section 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

    The proposed special conditions will 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.

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.

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 Proposed Special Conditions

    Accordingly, the Federal Aviation Administration (FAA) proposes the 
following special conditions 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 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

[[Page 26228]]

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 May 24, 2018.
Jorge Castillo,
Acting Manager, Rotorcraft Standards Branch, Policy and Innovation 
Division, Aircraft Certification Services.
[FR Doc. 2018-12077 Filed 6-5-18; 8:45 am]
BILLING CODE 4910-13-P

Federal Register / Vol. 83, No. 109 / Wednesday, June 6, 2018 / Proposed Rules 26227

FAA, Rotorcraft Standards Branch, helicopter meets the applicable unusual design feature, the special
Policy and Innovation Division, 10101 provisions of part 29, as amended by conditions would apply to that model as
Hillwood Pkwy, Fort Worth, TX 76177; Amendment 29–1 through 29–55 well.
telephone (817) 222–4087; email thereto. The BHTI Model 525
Conclusion
George.Harrum@faa.gov. certification basis date is December 31,
SUPPLEMENTARY INFORMATION: 2013, the effective date of application to This action affects only certain novel
the FAA. or unusual design features on one model
Comments Invited If the Administrator finds that the of rotorcraft. It is not a rule of general
We invite interested people to take applicable airworthiness regulations applicability.
part in this rulemaking by sending (i.e., 14 CFR part 29) do not contain
List of Subjects in 14 CFR Part 29
written comments, data, or views. The adequate or appropriate safety standards
most helpful comments reference a for the BHTI Model 525 because of a Aircraft, Aviation safety, Reporting
specific portion of the special novel or unusual design feature, special and recordkeeping requirements.
conditions, explain the reason for any conditions are prescribed under the The authority citation for these
recommended change, and include provisions of § 21.16. special conditions is as follows:
supporting data. Special conditions are initially
We will consider all comments we Authority: 49 U.S.C. 106(g), 40113, 44701,
applicable to the model for which they 44702, 44704.
receive on or before the closing date for are issued. Should the type certificate
comments. We will consider comments for that model be amended later to The Proposed Special Conditions
filed late if it is possible to do so include any other model that Accordingly, the Federal Aviation
without incurring expense or delay. We incorporates the same or similar novel Administration (FAA) proposes the
may change these special conditions or unusual design feature, the special following special conditions as part of
based on the comments we receive. conditions would also apply to the other the type certification basis for Bell
Background model under § 21.101. Helicopter Textron, Inc., Model 525
In addition to the applicable helicopters:
On December 15, 2011, BHTI applied airworthiness regulations and special
for a type certificate for a new transport conditions, the BHTI Model 525 Flight Envelope Protection
category helicopter designated as the helicopter must comply with the noise
Model 525. The Model 525 is a medium The Flight Envelope Protection (FEP)
certification requirements of 14 CFR features of the FCS must meet the
twin-engine rotorcraft. The design part 36, and the FAA must issue a
maximum takeoff weight is 20,500 following requirements:
finding of regulatory adequacy under a. Onset characteristics of each
pounds, with a maximum capacity of 19 section 611 of Public Law 92–574, the
passengers and a crew of 2. envelope protection feature must be
‘‘Noise Control Act of 1972.’’ smooth, appropriate to the phase of
The BHTI Model 525 helicopter will The FAA issues special conditions, as
be equipped with a four axis full flight and type of maneuver, and not in
defined in 14 CFR 11.19, in accordance conflict with the ability of the pilot to
authority digital FBW FCS that provides with § 11.38, and they become part of
for aircraft control through pilot input satisfactorily change rotorcraft flight
the type-certification basis under path, speed, or attitude within the
and coupled flight director modes. The § 21.17(a)(2).
FBW FCS will contain an advanced approved flight envelope.
flight control system that will alter the Novel or Unusual Design Features b. Limit values of protected flight
nominal flight control laws to ensure The BHTI Model 525 helicopter will parameters (and if applicable, associated
that the aircraft remains in a incorporate the following novel or warning thresholds) must be compatible
predetermined flight envelope. These unusual design features: FBW FCS with:
Flight Envelope Protection (FEP) incorporating FEP features. FEP is used 1. Rotorcraft structural limits;
features prevent the pilot or autopilot to prevent the pilot or an autopilot from 2. Safe and controllable maneuvering
functions from making control making control commands that would of the rotorcraft;
commands that would force the aircraft force the rotorcraft to exceed its 3. Margins to critical conditions.
to exceed its structural, aerodynamic, or structural, aerodynamic, or operating Dynamic maneuvering, airframe and
operating limits. The design and limits. To accomplish this envelope system tolerances (both manufacturing
construction standards, specifically 14 limiting, the FCS control laws change as and in-service), and non-steady
CFR 29.779(a), require that movement of the limit is approached or exceeded. atmospheric conditions—in any
the flight controls results in a appropriate combination and phase of
corresponding sense of aircraft motion Discussion flight—must not result in a limited
in the same axis. The airworthiness The proposed special conditions will flight parameter beyond the nominal
standards for an automatic pilot system require the minimum safety standard for design limit value that would cause
in § 29.1329 covers design requirements the flight envelope protection features. unsafe flight characteristics;
for basic operation of the system but The FEP features must meet 4. Rotor rotational speed limits;
does not address dynamic flight requirements for handling qualities, 5. Blade stall limits; and
envelope limitations imposed by the compatibility of flight parameter limit 6. Engine and transmission torque
automatic pilot system. Currently there values, response to dynamic limits.
are no specific airworthiness maneuvering, and failure modes. c. The aircraft must be responsive to
daltland on DSKBBV9HB2PROD with PROPOSALS

requirements that address FBW FCS pilot-commanded dynamic
Applicability maneuvering within a suitable range of
FEP in rotorcraft. The proposed special
conditions will require the minimum As discussed above, these special the parameter limits that define the
safety standard for the FEP features. conditions are applicable to the BHTI approved flight envelope.
Model 525 helicopter. Should BHTI d. The FEP system must not create
Type Certification Basis apply at a later date for a change to the unusual or adverse flight characteristics
Under the provisions of 14 CFR 21.17, type certificate to include another when atmospheric conditions or
BHTI must show that the Model 525 model incorporating the same novel or unintentional pilot action causes the

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Document Created: 2018-06-06 00:53:57
Document Modified: 2018-06-06 00:53:57

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		Proposed Rules
Action		Notice of proposed special conditions.
Dates		Send your comments on or before July 23, 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 26226
CFR Associated		Aircraft; Aviation Safety and Reporting and Recordkeeping Requirements

83 FR 26226 - Special Conditions: Bell Helicopter Textron, Inc. (BHTI), Model 525 Helicopters; Flight Envelope Protection

DEPARTMENT OF TRANSPORTATIONFederal Aviation Administration

Federal Register Volume 83, Issue 109 (June 6, 2018)

DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration