83 FR 51624 - Special Conditions: Bell Helicopter Textron, Inc. (BHTI), Model 525 Helicopters; Control Margin Awareness

DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration

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

Page Range		51624-51625
FR Document		2018-22265

These special conditions are issued 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 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 51624-51625]
From the Federal Register Online  [www.thefederalregister.org]
[FR Doc No: 2018-22265]


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

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: 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 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 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 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 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

[[Page 51625]]

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 incorporates 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

    These special conditions 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.

Discussion of Comments

    Notice of proposed special conditions No. 29-045-SC for the BHTI 
Model 525 helicopter was published in the Federal Register on June 6, 
2018 (83 FR 26225). 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.

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:

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 October 3, 2018.
Jorge Castillo,
Acting Manager, Rotorcraft Standards Branch, Policy and Innovation 
Division, Aircraft Certification Service.
[FR Doc. 2018-22265 Filed 10-11-18; 8:45 am]
BILLING CODE 4910-13-P

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 10:07:42
Document Modified: 2018-10-13 10:07:42

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 51624
CFR Associated		Aircraft; Aviation Safety and Reporting and Recordkeeping Requirements

83 FR 51624 - Special Conditions: Bell Helicopter Textron, Inc. (BHTI), Model 525 Helicopters; Control Margin Awareness

DEPARTMENT OF TRANSPORTATIONFederal Aviation Administration

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

DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration