83 FR 26225 - Special Conditions: Bell Helicopter Textron, Inc. (BHTI), Model 525 Helicopters; Control Margin Awareness

DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration

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

This action proposes special conditions for the BHTI Model 525 helicopter. This helicopter will have a novel or unusual design feature associated with the fly-by-wire flight control system (FBW FCS) in the area of pilot awareness of the control margins remaining while maneuvering the helicopter. 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, Number 109 (Wednesday, June 6, 2018)]
[Proposed Rules]
[Pages 26225-26226]
From the Federal Register Online  [www.thefederalregister.org]
[FR Doc No: 2018-12076]


========================================================================
Proposed Rules
                                                Federal Register
________________________________________________________________________

This section of the FEDERAL REGISTER contains notices to the public of 
the proposed issuance of rules and regulations. The purpose of these 
notices is to give interested persons an opportunity to participate in 
the rule making prior to the adoption of the final rules.

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


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

[[Page 26225]]


=======================================================================
-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 29

[Docket No. FAA-2017-1128; Notice No. 29-045-SC]


Special Conditions: Bell Helicopter Textron, Inc. (BHTI), Model 
525 Helicopters; Control Margin Awareness

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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

SUMMARY: This action proposes special conditions for the BHTI Model 525 
helicopter. This helicopter will have a novel or unusual design feature 
associated with the fly-by-wire flight control system (FBW FCS) in the 
area of pilot awareness of the control margins remaining while 
maneuvering the helicopter. 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-2017-1128] 
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, 
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 current 14 
CFR part 29 regulations do not contain adequate standards for FBW FCS 
with respect to control margin awareness. The airworthiness standards 
for controllability and maneuverability of the rotorcraft are contained 
in Sec.  29.143. These controllability requirements are compatible with 
most FBW systems, while most of the maneuverability requirements are 
not affected by FBW systems, except for the control margins. One of the 
purposes of the rule is to ensure that control margins (at the rotor 
and the anti-torque system level) are sufficient in the defined flight 
envelope to avoid loss of control (that is, the rotorcraft has adequate 
control power for the pilot to exit potentially hazardous flight 
conditions). Implicit in this purpose is that the pilot is provided 
with sufficient awareness of proximity to control limits. Because Sec.  
29.143 was written to address hydro-mechanical flight control systems, 
through which pilot awareness of control margins is provided by cyclic 
and pedal position relative to cockpit control stops, the rule is 
inadequate for certification of a FBW FCS, where there is no mechanical 
link between the inceptor and the receptor. Without a constant 
correlation between cockpit control and main or tail rotor actuator 
positions, the FCS may not provide tactile control margin feedback to 
the pilot through cockpit control position relative to the control 
position physical stop or limit, for all flight conditions. The 
proposed special conditions will require the minimum safety standard to 
ensure awareness of proximity to control limits at the main rotor and 
tail rotor is provided to pilots of the Bell Model 525 helicopter.

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,

[[Page 26226]]

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: A four-axis full authority digital FBW FCS. 
Pilot control inputs, through the mechanically linked cockpit controls 
(cyclic, collective, directional pedals), are transmitted electrically 
to each of the three Flight Control Computers (FCCs). The pilot control 
input signals are then processed and transmitted to the hydraulic 
flight control actuators which affect control of the main and tail 
rotors.

Discussion

    The proposed special condition will require the minimum safety 
standard to ensure awareness of proximity to control limits at the main 
rotor and tail rotor is provided to pilots of the Bell Model 525 
helicopter. The system design must provide the pilot with sufficient 
awareness of proximity to control limits, traditionally achieved 
through conventional flight controls by the pilot's inherent awareness 
of cyclic stick and pedal position relative to control stops.

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:

Control Margin Awareness

    In addition to the existing Sec.  29.143 requirements, the 
following special condition applies: The system design must ensure that 
the flight crew is made suitably aware whenever the means of primary 
flight control approaches the limits of control authority. For the 
context of this special condition, the term ``suitable'' indicates an 
appropriate balance between nuisance and necessary operation.

    Issued in Ft. Worth, Texas, on May 24, 2018.
Jorge Castillo,
Acting Manager, Rotorcraft Standards Branch, Policy and Innovation 
Division, Aircraft Certification Service.
[FR Doc. 2018-12076 Filed 6-5-18; 8:45 am]
BILLING CODE 4910-13-P