Document ID: FAA-2021-0065-0001
Agency: faa
Document Type: Proposed Rule
Title: Special Conditions: Bell Textron Inc., Model 525 Helicopter; Fly-By-Wire Flight Control System
Posted Date: 2021-01-29T05:00Z

[Federal Register Volume 86, Number 18 (Friday, January 29, 2021)]
[Proposed Rules]
[Pages 7516-7518]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-01958]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 29

[Docket No. FAA-2021-0065; Notice No. 29-054-SC]

Special Conditions: Bell Textron Inc., Model 525 Helicopter; Fly-
By-Wire (FBW) Flight Control System (FCS)

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This action proposes special conditions for the Bell Textron 
Inc. (Bell) Model 525 helicopter. This helicopter will have a novel or 
unusual design feature associated with a fly-by-wire (FBW) flight 
control system (FCS). 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 comments on or before March 15, 2021.

ADDRESSES: Send comments identified by Docket No. FAA-2021-0065 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 or 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 9 a.m. and 5 p.m., Monday 
through Friday, except Federal holidays.
     Fax: Fax comments to Docket Operations at 202-493-2251.
    Privacy: Except for Confidential Business Information (CBI) as 
described in the following paragraph, and other information as 
described in 14 CFR 11.35, 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).
    Confidential Business Information: CBI is commercial or financial 
information that is both customarily and actually treated as private by 
its owner. Under the Freedom of Information Act (FOIA) (5 U.S.C. 552), 
CBI is exempt from public disclosure. If your comments responsive to 
these proposed special conditions contain commercial or financial 
information that is customarily treated as private, that you actually 
treat as private, and that is relevant or responsive to these proposed 
special conditions, it is important that you clearly designate the 
submitted comments as CBI. Please mark each page of your submission 
containing CBI as ``PROPIN.'' The FAA will treat such marked 
submissions as confidential under the FOIA, and they will not be placed 
in the public docket of these proposed special conditions. Submissions 
containing CBI should be sent to John VanHoudt, FAA, Dynamic Systems 
Section, AIR-627, Technical Innovation Policy Branch, Policy and 
Innovation Division, Aircraft Certification Service, 10101 Hillwood 
Parkway, Fort Worth, TX 76177-98198; telephone and fax 817-222-5193; 
email John.G.Van.Houdt@FAA.Gov. Any commentary that the FAA receives 
which is not specifically designated as CBI will be placed in the 
public docket for this rulemaking.
    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 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: John VanHoudt, FAA, Dynamic Systems 
Section, AIR-627, Technical Innovation Policy Branch, Policy and 
Innovation Division, Aircraft Certification Service, 10101 Hillwood 
Parkway, Fort Worth, TX 76177-98198; telephone and fax 817-222-5193; 
email John.G.Van.Houdt@FAA.Gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA invites you to send any written relevant data, views, or 
arguments about this proposal. Send your comments to an address listed 
under ADDRESSES. Include ``Docket No. FAA-2021-0065; Notice No. 29-054-
SC'' at the beginning of your comments. The most helpful comments 
reference a specific portion of the special conditions, explain the 
reason for any recommended change, and include supporting data. The FAA 
will consider all comments received by the closing date and may amend 
these proposed special conditions because of those comments.

Background

    On December 15, 2011, Bell applied for a type certificate for a new 
14 CFR part 29 transport category helicopter designated as the Model 
525. Bell applied for multiple extensions, with the most recent 
occurring on November 12, 2020. The date of the updated type 
certification basis is December 31, 2016, based upon the applicant's 
proposed type certificate issuance date of December 31, 2021. 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 Bell 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 design of 
the Bell Model 525 FBW controls, which provides no direct hydro-
mechanical linkage between the primary cockpit flight controls or 
inceptors and the main and tail rotor

[[Page 7517]]

actuators, is a first for commercial rotorcraft use. Therefore, the 
regulations do not contain adequate or appropriate safety standards for 
this new design feature.
    The rotorcraft industry is producing new generations of 
helicopters, and gradually increasing size, speed, load capacity, and 
technical sophistication. In recent years, an accelerated trend has 
occurred using rotorcraft for a wide range of commercial and industrial 
applications. This has resulted in increased complexity of modern 
control systems and increased use of automation in flight control 
systems, including the implementation of advanced flight control 
systems such as FBW FCS.
    Title 14, Code of Federal Regulations (CFR), Sec.  29.671(c), which 
provides requirements for transport category rotorcraft control 
systems, does not contain adequate or appropriate safety standards for 
this new design feature. 14 CFR 29.671(c) requires, in part, a means to 
allow the pilot to determine that full control authority is available 
prior to flight. This command control authority is typically achieved 
by verifying movement of the control quadrant through an unassisted 
mechanical pilot-initiated manipulation of the primary flight controls 
prior to flight. Although this approach does not guarantee that 100% 
maximum control movement of the flight controls has been achieved prior 
to flight, it has been deemed appropriate for mechanical flight control 
systems.
    Unlike traditional mechanical flight control systems, the FBW FCS 
reduces the opportunity for jamming of the flight controls due to 
mechanical bind, improper servo adjustment resulting from faulty 
maintenance, or presence of a foreign object in the control mechanism 
that will impair safety. This reduced exposure for jams is due to the 
replacement of the mechanical linkages between the primary cockpit 
flight controls or inceptors and the main and tail rotor actuators with 
digital signal processing wiring. However, the FBW FCS does increase 
the potential for latent failures or faults that could impair full 
control authority, unless a means exists to ensure the FBW FCS is fully 
functional and free of control authority impairment prior to flight. A 
FBW system may have the ability to verify full control authority 
without having to move the primary flight controls.
    Although part 29 does not contain adequate or appropriate safety 
standards for this novel or unusual design feature, 14 CFR 25.671, 
amendment 25-23, provides these requirements for transport category 
airplanes. Accordingly, these proposed special conditions are based on 
Sec.  25.671 to provide requirements for a FBW FCS on the Bell Model 
525 helicopter. 14 CFR 25.671(c) provides the same level of safety as 
that intended by Sec.  29.671(c) when employing a FBW FCS by including 
requirements for jamming and failure analysis. The proposed special 
conditions would require a comprehensive safety analysis of the 
aircraft's FBW FCS to include failures due to command logic (software), 
mechanical and electronic interfaces to other systems, jamming and 
maintenance. Therefore, in conjunction with Sec.  29.671(a) and (b), 
the proposed special conditions incorporate provisions from Sec.  
25.671(c) to establish a level of safety equivalent to that established 
in the regulations.

Type Certification Basis

    Under the provisions of 14 CFR 21.17, Bell must show that the Model 
525 helicopter meets the applicable provisions of part 29, as amended 
by Amendments 29 through 55 thereto. The Bell Model 525 certification 
basis date is December 31, 2016.
    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 Bell 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 Bell Model 525 helicopter must comply with the 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 Bell Model 525 helicopter will incorporate the following novel 
or unusual design features: A FBW FCS.
    This new design feature has no direct hydro-mechanical linkage 
between the primary cockpit flight controls or inceptors and the main 
and tail rotor actuators, thereby eliminating the more complex elements 
of either a manual movement of the controls by the pilot, or another 
manual means.

Discussion

    The proposed special conditions would require that a means be 
available to show full control authority for all powered control 
systems.
    The 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.

Applicability

    As discussed above, these special conditions are applicable to the 
Bell Model 525 helicopter. Should Bell apply at a later date for a 
change to the type certificate to include aother 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 the Bell Model 525 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:

    Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701-44702, 44704.

The Proposed Special Conditions

    Accordingly, the Federal Aviation Administration (FAA) proposes the 
following special conditions in lieu of Sec.  29.671(c) as part of the 
type certification basis for the Bell Textron Inc. Model 525 
helicopter:
    The rotorcraft must be shown by analysis, tests, or both, to be 
capable of continued safe flight and landing after any of the following 
failures or jamming in the flight control system within the normal 
flight envelope, without requiring exceptional piloting skill or 
strength. Probable failures must have only minor effects.
    (1) Any single failure not shown to be extremely improbable, 
excluding jamming.
    (2) Any combination of failures not shown to be extremely 
improbable, excluding jamming.
    (3) Any jam in a control position normally encountered during 
hover, takeoff, climb, cruise, normal turns,

[[Page 7518]]

descent, and landing, unless the jam is shown to be extremely 
improbable or can be alleviated.

    Issued in Fort Worth, Texas.
Jorge Castillo,
Manager, Strategic Policy Rotorcraft Section, Policy and Innovation 
Division, Aircraft Certification Service.
[FR Doc. 2021-01958 Filed 1-28-21; 8:45 am]
BILLING CODE 4910-13-P