Special Conditions: Bell Helicopter Textron Canada Limited, Model Bell 505, Visual Flight Rules Autopilot and Stability Augmentation System (AP/SAS System)
| Published date | 21 November 2019 |
| Citation | 84 FR 64233 |
| Record Number | 2019-25291 |
| Section | Proposed rules |
| Court | Federal Aviation Administration |
Federal Register, Volume 84 Issue 225 (Thursday, November 21, 2019)
[Federal Register Volume 84, Number 225 (Thursday, November 21, 2019)]
[Proposed Rules]
[Pages 64233-64234]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-25291]
[[Page 64233]]
=======================================================================
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 27
[Docket No. FAA-2019-0546; Notice No. 27-048-SC]
Special Conditions: Bell Helicopter Textron Canada Limited, Model
Bell 505, Visual Flight Rules Autopilot and Stability Augmentation
System (AP/SAS System)
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed special conditions.
-----------------------------------------------------------------------
SUMMARY: These special conditions are proposed for the Bell Helicopter
Textron Canada Limited (BHTCL) Bell Model 505 helicopter. This
helicopter as modified by S-TEC will have a novel or unusual design
feature associated with installation of the autopilot and stability
augmentation system (AP/SAS system). 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: Send your comments on or before December 23, 2019.
ADDRESSES: Send comments identified by docket number [FAA-2019-0546]
using any of the following methods:
[squ] Federal eRegulations Portal: Go to http://www.regulations.gov
and follow the online instructions for sending your comments
electronically.
[squ] 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.
[squ] 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.
[squ] 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: Andy Shaw, Aerospace Engineer, FAA,
Rotorcraft Standards Branch, Policy and Innovation Division, 10101
Hillwood Pkwy., Fort Worth, TX 76177; telephone (817) 222-5384; email
[email protected].
SUPPLEMENTARY INFORMATION:
Comments Invited
The FAA invites 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.
The FAA will consider all comments received by the closing date for
comments. The FAA will consider comments filed late if it is possible
to do so without incurring expense or delay. The FAA may change these
special conditions based on the comments received.
Background
On January 21, 2019, S-TEC applied for a supplemental type
certificate (STC) to install an AP/SAS system on the Bell Model 505
helicopter. The Bell Model 505 helicopter is a 14 CFR part 27 normal
category, single turbine engine, conventional helicopter designed for
civil operation. This helicopter model is capable of carrying up to
four passengers with one pilot and has a maximum gross weight of up to
4,475 pounds, depending on the model configuration. The major design
features include a 2-blade main rotor, an anti-torque tail rotor
system, a skid landing gear, and a visual flight rule basic avionics
configuration. S-TEC proposes to modify this model helicopter by
installing an AP/SAS system.
The AP/SAS system provides attitude stabilization in two or three
axes (pitch and roll with optional yaw) as well as higher-level
autopilot functions such as altitude hold, heading command and
navigation tracking. However, the possible failure conditions for this
system, and their effect on the continued safe flight and landing of
the helicopter, are more severe than those envisioned by the present
rules.
The effect on safety is not adequately covered under 14 CFR 27.1309
for the application of new technology and new application of standard
technology. Specifically, the present provisions of Sec. 27.1309(c) do
not adequately address the safety requirements for systems whose
failures could result in catastrophic or hazardous/severe-major failure
conditions, or for complex systems whose failures could result in major
failure conditions. The current regulations are inadequate because when
Sec. 27.1309(c) was promulgated, it was not envisioned that a normal
category rotorcraft would use systems that are complex or whose failure
could result in ``catastrophic'' or ``hazardous/severe-major'' effects
on the rotorcraft. This is particularly true with the application of
new technology, new application of standard technology, or other
applications not envisioned by the rule that affect safety. Possible
failure modes exhibited by the S-TEC AP/SAS system could result in a
catastrophic event.
Type Certification Basis
Under 14 CFR 21.101, S-TEC must show that the Bell Model 505
helicopter, as modified by the installed AP/SAS, continues to meet the
applicable regulations incorporated by reference in the Type
Certificate Number R00008RD. The regulations incorporated by reference
in the type certificate are commonly referred to as the ``original type
certification basis.'' The regulations incorporated by reference in
Type Certificate Number R00008RD are as follows:
14 CFR part 27, dated October 2, 1964, amendment 27-1 through 27-47
14 CFR part 36, amendment 36-1 through 36-30
In addition, the certification basis includes certain equivalent
level of safety findings that are not relevant to these special
conditions.
The Administrator has determined the applicable airworthiness
regulations (that is, 14 CFR part 27), as they pertain to this STC, do
not contain adequate or appropriate safety standards for the Bell Model
505 helicopter because of a novel or unusual design feature. Therefore,
special conditions are prescribed under Sec. 21.16.
Special conditions are initially applicable to the model for which
they
[[Page 64234]]
are issued. Should S-TEC apply for an STC to modify any other model
included on the same type certificate to incorporate the same novel or
unusual design feature, the special conditions would also apply to the
other model.
The FAA issues special conditions, as defined in Sec. 11.19, in
accordance with Sec. 11.38 and they become part of the type
certification basis under Sec. 21.101(d).
Novel or Unusual Design Features
The Bell Model 505 helicopter will incorporate the following novel
or unusual design features: AP/SAS. An autopilot (AP) is a system used
to control the trajectory of an aircraft without constant input from
the pilot. This allows the pilot to focus on other aspects of
operations such as weather and systems. A stability augmentation system
(SAS) is another type of automatic flight control system; however,
instead of maintaining the aircraft on a predetermined attitude or
flight path, the SAS will reduce pilot workload by dampening aircraft
buffeting regardless of the attitude or flight path.
Discussion
To comply with the provisions of the special conditions, the FAA
proposes to require that S-TEC provide the FAA with a systems safety
assessment (SSA) for the final AP/SAS installation configuration that
will adequately address the safety objectives established by a
functional hazard assessment (FHA). This process will ensure that all
failure conditions and their resulting effects are adequately addressed
for the installed AP/SAS. The SSA process is part of the overall safety
assessment process discussed in FAA Advisory Circular 27-1B,
Certification of Normal Category Rotorcraft, and Society of Automotive
Engineers document Aerospace Recommended Practice 4761, Guidelines and
Methods for Conducting the Safety Assessment Process on Civil Airborne
Systems and Equipment.
These proposed special conditions would require that the AP/SAS
installed on a Bell Model 505 helicopter meet the requirements to
adequately address the failure effects identified by the FHA, and
subsequently verified by the SSA, within the defined design integrity
requirements.
Failure conditions are classified according to the severity of
their effects on the rotorcraft. Radio Technical Commission for
Aeronautics, Inc. (RTCA) Document DO-178C, Software Considerations in
Airborne Systems and Equipment Certification, provides software design
assurance levels most commonly used for the major, hazardous/severe-
major, and catastrophic failure condition categories. The AP/SAS system
equipment must be qualified for the expected installation environment.
The test procedures prescribed in RTCA Document DO-160G, Environmental
Conditions and Test Procedures for Airborne Equipment, are recognized
by the FAA as acceptable methodologies for finding compliance with the
environmental requirements. Equivalent environment test standards may
also be acceptable. Environmental qualification provides data to show
that the AP/SAS system can perform its intended function under the
expected operating condition. Some of the main considerations for
environmental concerns are installation locations and the resulting
exposure to environmental conditions for the AP/SAS system equipment,
including considerations for other equipment that may also be affected
environmentally by the AP/SAS equipment installation. The level of
environmental qualification must be related to the severity of the
considered failure conditions and effects on the rotorcraft.
Applicability
These special conditions are applicable to the S-TEC AP/SAS
installed as an STC approval in Bell Model 505 helicopters, Type
Certificate Number R00008RD.
Conclusion
This action affects only certain novel or unusual design features
for an S-TEC AP/SAS STC installed on one model helicopter. It is not a
rule of general applicability and affects only the applicant who
applied to the FAA for approval of these features.
List of Subjects in 14 CFR Part 27
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, pursuant to the authority delegated to me by the
Administrator, the following special conditions are proposed as part of
the S-TEC supplemental type certification basis for installation of an
autopilot/stabilization augmentation system (AP/SAS) system on Bell
Model 505 helicopters.
Instead of the requirements of 14 CFR 27.1309(b) and (c), the
following must be met for certification of the AP/SAS system installed
on Bell Model 505 helicopters:
a. The equipment and systems must be designed and installed so that
any equipment and systems do not adversely affect the safety of the
rotorcraft or its occupants.
b. The rotorcraft systems and associated components considered
separately and in relation to others systems, must be designed and
installed so that:
(1) The occurrence of any catastrophic failure condition is
extremely improbable;
(2) The occurrence of any hazardous failure condition is extremely
remote; and
(3) The occurrence of any major failure condition is remote.
c. Information concerning an unsafe system operating condition must
be provided in a timely manner to the crew to enable them to take
appropriate corrective action. An appropriate alert must be provided if
immediate pilot awareness and immediate or subsequent corrective action
is required. Systems and controls, including indications and
annunciations, must be designed to minimize crew errors which could
create additional hazards.
Issued in Fort Worth, Texas, on November 13, 2019.
Jorge Castillo,
Manager, Rotorcraft Standards Branch, Policy and Innovation Division,
Aircraft Certification Service.
[FR Doc. 2019-25291 Filed 11-20-19; 8:45 am]
BILLING CODE 4910-13-P
