[Federal Register Volume 70, Number 109 (Wednesday, June 8, 2005)]
[Proposed Rules]
[Pages 33399-33401]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 05-11412]


 ========================================================================
 Proposed Rules
                                                 Federal Register
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 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.
 
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 

  Federal Register / Vol. 70, No. 109 / Wednesday, June 8, 2005 / 
Proposed Rules  

[[Page 33399]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 27

[Docket No. SW013; Special Condition No. 27-013-SC]


Special Condition: Robinson R44 Helicopters, Section 27.1309, 
Installation of an Autopilot (AP) Stabilization Augmentation System 
(SAS) That Has Potential Failure Modes With Criticality Categories 
Higher Than Those Envisioned by the Applicable Airworthiness 
Regulations

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special condition.

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SUMMARY: This proposed special condition is issued for the modification 
of the Robinson Model R44 helicopter. This modification will have novel 
or unusual design features associated with installing a complex 
Autopilot/ Stabilization Augmentation System (AP/SAS) that has 
potential failure modes with more severe adverse consequences than 
those envisioned by the existing applicable airworthiness regulations. 
This proposal contains the additional safety standards that the 
Administrator considers necessary to ensure that the failures and their 
effects are sufficiently analyzed and contained.

DATES: Comments must be received on or before July 8, 2005.

ADDRESSES: Send comments on this special condition in duplicate to: 
Federal Aviation Administration (FAA), Rotorcraft Standards Staff, 
Attention: Docket No. SW013, Fort Worth, Texas 76193-0110, or deliver 
them in duplicate to the Rotorcraft Standards Staff at 2601 Meacham 
Blvd., Fort Worth, Texas 76137. Comments must be marked: Docket No. 
SW013. You may inspect comments in the Docket that is maintained in 
Room 448 in the Rotorcraft Directorate offices at 2601 Meacham Blvd., 
Fort Worth, Texas, on weekdays, except Federal holidays, between 8:30 
a.m. and 4 p.m.

FOR FURTHER INFORMATION CONTACT: Robert McCallister, Aviation Safety 
Engineer, FAA, Rotorcraft Directorate, Rotorcraft Standards Staff, 2601 
Meacham Blvd., Fort Worth, Texas 76193-0110; telephone (817) 222-5121, 
FAX (817) 222-5961.

SUPPLEMENTARY INFORMATION:

Comments Invited

    You are invited to submit written data, views, or arguments. Your 
communications should include the docket or special condition number 
and be sent in duplicate to the address stated above. We will consider 
all communications received on or before the closing date and may 
change the special condition in light of the comments received. 
Interested persons may examine the Docket. We will file a report in the 
docket summarizing each substantive public contact with FAA personnel 
concerning this special condition. If you wish us to acknowledge 
receipt of your comments, you must include a self-addressed, stamped 
postcard on which the following statement is made: ``Comments to Docket 
No. SW013.'' We will date stamp the postcard and mail it to you.

Background

    On January 18, 2000, Hoh Aeronautics, Inc. submitted an application 
for Supplemental Type Certification (STC) for the installation of an 
Autopilot Stability/Augmentation System (AP/SAS) on a Robinson Model 
R44 helicopter through the FAA's Los Angeles Aircraft Certification 
Office (LA ACO). The Robinson Model R44 helicopter is a part 27 Normal 
category, single reciprocating engine, conventional helicopter designed 
for civil operation. The helicopter is capable of carrying three 
passengers with one pilot, and has a maximum gross weight of 
approximately 2,400 pounds. The major design features include a 2-
blade, fully articulated main rotor, a 2-blade anti-torque tail rotor, 
a skid landing gear, and a visual flight rule (VFR) basic avionics 
configuration. Hoh Aeronautics, Inc. proposes to install a three-axis 
AP/SAS.

Type Certification Basis

    Under the provisions of 14 CFR 21.115, Hoh Aeronautics, Inc. must 
show that the Robinson Model R44 helicopter, as modified by the 
installed AP/SAS, meets 14 CFR 21.101. The baseline of the 
certification basis for the unmodified R44 is listed in Type 
Certification Data Sheet Number H11NM, Revision 3. Additionally, 
compliance must be shown to any special conditions prescribed by the 
Administrator.
    If the Administrator finds that the applicable airworthiness 
regulations, as they pertain to this STC, do not contain adequate or 
appropriate safety standards because of a novel or unusual design 
feature, special conditions are prescribed under the provisions of 
Sec.  21.101(d). Special conditions, as appropriate, are defined in 
Sec.  11.19, and issued by following the procedures in Sec.  11.38.
    In addition to the applicable airworthiness regulations and special 
conditions, Hoh Aeronautics, Inc. must show compliance of the AP/SAS 
STC-altered Robinson Model R44 helicopter with the noise certification 
requirements of 14 CFR part 36; and the FAA must issue a finding of 
regulatory adequacy pursuant to 49 U.S.C. 44715 (formerly section 611 
of the Federal Aviation Act of 1958 as amended by section 7 of Pub. L. 
92-574, the ``Noise Control Act of 1972.'').

Novel or Unusual Design Features

    The Hoh Aeronautics, Inc. AP/SAS system incorporates novel or 
unusual design features, for installation in a Robinson Model R44 
helicopter, Type Certification Data Sheet Number H11NM. This AP/SAS 
system performs non-critical control functions, since this model 
helicopter has been certificated to meet the applicable requirements 
independent of this system. However, the possible failure modes for 
this system, and their effect on the helicopter's ability to continue 
safe flight and landing, are more severe than those envisioned by the 
present rules when they were first promulgated.

Discussion

    Definitions: Definitions of Failure Condition Categories--Failure 
Conditions are classified, according to the severity of their effects 
on the

[[Page 33400]]

aircraft, into one of the following categories:
    1. No Effect--Failure Conditions that would have no effect on 
safety; for example, Failure Conditions that would not affect the 
operational capability of the rotorcraft or increase crew workload; 
however, could result in an inconvenience to the occupants, excluding 
the flight crew.
    2. Minor--Failure conditions which would not significantly reduce 
rotorcraft safety, and which would involve crew actions that are well 
within their capabilities. Minor failure conditions may include, for 
example, a slight reduction in safety margins or functional 
capabilities, a slight increase in crew workload, such as routine 
flight plan changes, or some physical discomfort to occupants.
    3. Major--Failure conditions which would reduce the capability of 
the rotorcraft or the ability of the crew to cope with adverse 
operating conditions to the extent that there would be, for example, a 
significant reduction in safety margins or functional capabilities, a 
significant increase in crew workload or in conditions impairing crew 
efficiency, physical distress to occupants, possibly including 
injuries, or physical discomfort to the flight crew.
    4. Hazardous/Severe-Major--Failure conditions which would reduce 
the capability of the rotorcraft or the ability of the crew to cope 
with adverse operating conditions to the extent that there would be:
     A large reduction in safety margins or functional 
capabilities;
     Physical distress or excessive workload that would impair 
the flight crew's ability to the extent that they could not be relied 
on to perform their tasks accurately or completely; or,
     Possible serious or fatal injury to a passenger or a cabin 
crewmember, excluding the flight crew.

    Note: ``Hazardous/Severe-Major'' failure conditions can include 
events that are manageable by the crew by use of proper procedures, 
which, if not implemented correctly or in a timely manner, may 
result in a Catastrophic Event.


    5. Catastrophic--Failure Conditions which would result in multiple 
fatalities to occupants, fatalities or incapacitation to the flight 
crew, or result in loss of the rotorcraft.
    The present Sec. Sec.  27.1309(b) and (c) regulations 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. Sec.  27.1309(b) and (c) were promulgated, it was not 
envisioned that this type of 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.
    We propose to require that Hoh Aeronautics, Inc. 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 the Functional Hazard Assessment (FHA) and 
the Preliminary System Safety Assessment (PSSA), including the Fault 
Tree Analysis (FTA). This will ensure that all failure modes and their 
resulting effects are adequately addressed for the installed AP/SAS. 
The SSA process, FHA, PSSA, and FTA are all parts of the overall Safety 
Assessment (SA) process discussed in FAA Advisory Circular (AC) 27-1B 
(Certification of Normal Category Rotorcraft) and SAE document ARP 4761 
(Guidelines and Methods for Conducting the Safety Assessment Process on 
civil airborne Systems and Equipment).

Requirements

    We propose to require that the applicant comply with the existing 
requirements of Sec.  27.1309 for all applicable design and operational 
aspects of the AP/SAS that are associated with the failure condition 
categories of ``No Effect,'' and ``Minor,'' and for non-complex systems 
whose failure condition category is classified as ``Major.'' We propose 
to require that the applicant comply with the requirements of this 
special condition for all applicable design and operational aspects of 
the AP/SAS that are associated with the failure condition categories of 
``Catastrophic'' and ``Hazardous Severe/Major,'' and for complex 
systems whose failure condition category is classified as ``Major.''

    Note: A complex system is a system whose operations, failure 
modes, or failure effects are difficult to comprehend without the 
aid of analytical methods (e.g., Fault Tree Analysis, Failure Modes 
and Effect Analysis, Functional Hazard Assessment, etc.).


    Design Integrity Requirements: Each of the failure condition 
categories defined in this special condition relate to corresponding 
aircraft systems integrity requirements. The systems design integrity 
requirements, for the Hoh Aeronautics, Inc. AP/SAS, as they relate to 
the allowed probability of occurrence for each failure condition 
category, along with the proposed software design assurance level, are 
as follows:
     ``Major''--Failures resulting in Major effects must be 
shown to be improbable, or on the order of 1 x 10-\5\ 
failures/hour, and associated software must be developed to the RTCA/
DO-178B (Software Considerations in Airborne Systems And Equipment 
Certification) Level C software design assurance level.
     ``Hazardous/Severe-Major''--Failures resulting in 
Hazardous/Severe-Major effects must be shown to be extremely remote, or 
on the order of 1 x 10-\7\ failures/hour, and associated 
software must be developed to the RTCA/DO-178B (Software Considerations 
in Airborne Systems And Equipment Certification) Level B software 
assurance level.
     ``Catastrophic''--Failures resulting in Catastrophic 
effects must be shown to be extremely improbable, or on the order of 1 
x 10-\9\ failures/hour, and associated software must be 
developed to the RTCA/DO-178B (Software Considerations in Airborne 
Systems And Equipment Certification) Level A design assurance level.
    Design Environmental Requirements: We propose to require that the 
AP/SAS system equipment be qualified to the appropriate environmental 
level in the RTCA document DO-160D (Environmental Conditions and Test 
Procedures for Airborne Equipment), for all relevant aspects. This is 
to ensure that the AP/SAS system performs its intended function under 
any foreseeable operating condition, which includes the expected 
environment in which the AP/SAS is intended to operate. 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 be affected environmentally by the AP/SAS equipment 
installation. The level of environmental qualification must be related 
to the severity of the considered failure effects on the aircraft.
    Test & Analysis Requirements: Compliance with the requirements 
contained in this special condition may be shown by a variety of 
methods, which typically consist of analysis, flight tests, ground 
tests, and simulation, as a minimum. Compliance methodology is partly 
related to the

[[Page 33401]]

associated failure condition category. If the AP/SAS is considered to 
be a complex system, compliance with the requirements contained in this 
document for aspects of the AP/SAS that can result in failure 
conditions classified as ``Major'' may be shown by analysis, in 
combination with appropriate testing to validate the analysis. 
Compliance with the requirements contained in this special condition 
for aspects of the AP/SAS that can result in failure conditions 
classified as ``Hazardous/Severe-Major'' may be shown by flight-testing 
in combination with analysis and simulation, and the appropriate 
testing to validate the analysis. Flight tests may be limited for this 
classification of failures due to safety considerations. Compliance 
with the requirements contained in this special condition for aspects 
of the AP/SAS that can result in failure conditions classified as 
``Catastrophic'' may be shown by analysis, and appropriate testing in 
combination with simulation to validate the analysis. Very limited 
flight tests in combination with simulation are typically used as a 
part of a showing of compliance for failures in this classification. 
Flight tests are performed only in circumstances that use operational 
variations, or extrapolations from other flight performance aspects to 
address flight safety.
    This proposed special condition would require that the AP/SAS 
system installed on a Robinson Model R44 helicopter, Type Certification 
Data Sheet Number H11NM, Revision 3, meet these requirements to 
adequately address the failure effects identified by the FHA, and 
subsequently verified by the SSA, within the defined design integrity 
requirements.

Applicability

    This special condition would be applicable to the Hoh Aeronautics, 
Inc. AP/SAS installed as an STC approval, in a Robinson Model R44 
helicopter, Type Certification Data Sheet Number H11NM, Revision 3.

Conclusion

    This action would affect only certain novel or unusual design 
features for a Hoh Aeronautics, Inc. AP/SAS STC installed on one model 
series of helicopter. It is not a rule of general applicability and 
affects only the applicant who applied to the FAA for approval of these 
features on the helicopter. The FAA is requesting comments to allow 
interested persons to submit views.

List of Subjects in 14 CFR Part 27

    Aircraft, Air transportation, Aviation safety, Rotorcraft, Safety.

    The authority citation for this special condition is as follows: 42 
U.S.C. 7572, 49 U.S.C. 106(g), 40105, 40113, 44701-44702, 44704, 44709, 
44711, 44713, 44715, 45303.

The Special Condition

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special condition is proposed as part of 
the Hoh Aeronautics, Inc. supplemental type certificate basis for an 
Autopilot/Stability Augmentation System to be installed on a Robinson 
Model R44 helicopter, Type Certification Data Sheet Number H11NM, 
Revision 3.
    The Autopilot/Stability Augmentation System must be designed and 
installed so that the failure conditions identified in the Functional 
Hazard Assessment and verified by the System Safety Assessment, after 
design completion, are adequately addressed in accordance with the 
``Definitions'' and ``Requirements'' sections (including the integrity, 
environmental, and test and analysis requirements) of this special 
condition.

    Issued in Fort Worth, Texas, on May 26, 2005.
S. Frances Cox,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 05-11412 Filed 6-7-05; 8:45 am]
BILLING CODE 4910-13-P