[Federal Register Volume 76, Number 38 (Friday, February 25, 2011)]
[Rules and Regulations]
[Pages 10489-10492]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-4229]


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

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 27

[Docket No. SW025; Special Conditions No. 27-025-SC]


Special Conditions: Bell Helicopter Textron Canada Limited Model 
407 Helicopter, Installation of a Hoh Aeronautics, Inc. Autopilot/
Stabilization Augmentation System (AP/SAS)

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

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

SUMMARY: These special conditions are issued for the modification of 
the Bell Helicopter Textron Canada Limited (Bell) model 407 helicopter. 
This model helicopter will have novel or unusual design features when 
modified by installing the Hoh Aeronautics, Inc. (Hoh) complex 
Autopilot/Stabilization Augmentation System (AP/SAS) that has potential 
failure conditions with more severe adverse consequences than those 
envisioned by the existing applicable airworthiness regulations. These 
special conditions contain the added safety standards the Administrator 
considers necessary to ensure the failures and their effects are 
sufficiently analyzed and contained.

DATES: The effective date of these special conditions is February 14, 
2011. We must receive your comments by April 26, 2011.

ADDRESSES: You must mail your comments to: Federal Aviation 
Administration, Rotorcraft Directorate, Attn: Rules Docket (ASW-111), 
Docket No. SW025, 2601 Meacham Blvd., Fort Worth, Texas 76137. You may 
deliver your comments to the Rotorcraft Directorate at the indicated 
address. You must mark your comments: Docket No. SW025. You can inspect 
comments in the Rules Docket weekdays, except Federal holidays, between 
8:30 a.m. and 4 p.m., in the Rotorcraft Directorate.

FOR FURTHER INFORMATION CONTACT: Mark Wiley, Aviation Safety Engineer, 
FAA, Rotorcraft Directorate, Regulations and Policy Group (ASW-111), 
2601 Meacham Blvd., Fort Worth, Texas 76137; telephone (817) 222-5134; 
facsimile (817) 222-5961.

SUPPLEMENTARY INFORMATION: 
    The FAA has determined that notice and opportunity for prior public 
comment hereon are impracticable because these procedures would 
significantly delay issuance of the design approval and thus delivery 
of the affected aircraft. In addition, the substance of these special 
conditions has been subject to the public comment process previously 
with no substantive comments received. The FAA therefore finds that 
good cause exists for making these special conditions effective on 
issuance.

Comments Invited

    While we did not precede this with a notice of proposed special 
conditions, we invite interested people to take part in this action by 
sending written comments, data, or views. The most helpful comments 
reference a specific portion of the special conditions, explain the 
reason for any

[[Page 10490]]

recommended change, and include supporting data.
    We will file in the special conditions docket all comments we 
receive, as well as a report summarizing each substantive public 
contact with FAA personnel about these special conditions. You can 
inspect the docket before and after the comment closing date. If you 
wish to review the docket in person, go to the address in the ADDRESSES 
section of this document between 8:30 a.m. and 4 p.m., Monday through 
Friday, except Federal holidays.
    We will consider all comments we receive by 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.
    If you want us to let you know we received your mailed comments on 
these special conditions, send us a pre-addressed, stamped postcard on 
which the docket number appears. We will stamp the date on the postcard 
and mail it back to you.

Background

    On July 16, 2009, Hoh submitted an application to the FAA's Los 
Angeles Aircraft Certification Office (LA ACO) for a supplemental type 
certification (STC) to install an AP/SAS on a Bell model 407 
helicopter. The Bell model 407 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 six 
passengers with one pilot, and has a maximum gross weight of 
approximately 5,250 pounds, depending on the configuration. The major 
design features include a 4-blade, soft-in-plane main rotor, a 2-blade 
anti-torque tail rotor, a skid landing gear, and a visual flight rule 
(VFR) basic avionics configuration. Hoh proposes to modify a model 407 
Bell helicopter by installing a two-axis AP/SAS.

Type Certification Basis

    Under 14 CFR 21.115, Hoh must show that the Bell model 407 
helicopter, as modified by the installed AP/SAS, continues to meet the 
14 CFR 21.101 standards. The baseline of the certification basis for 
the unmodified Bell model 407 helicopter is listed in Type Certificate 
Number H2SW. Additionally, compliance must be shown to any applicable 
equivalent level of safety findings, exemptions, and special 
conditions, prescribed by the Administrator as part of the 
certification basis.
    If the Administrator finds 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 407 
helicopter because of a novel or unusual design feature, special 
conditions are prescribed under Sec.  21.101(d).
    In addition to the applicable airworthiness regulations and special 
conditions, Hoh must show compliance of the AP/SAS STC-altered Bell 
model 407 helicopter with the noise certification requirements of 14 
CFR part 36.
    The FAA issues special conditions, as defined in Sec.  11.19, under 
Sec.  11.38 and they become part of the type certification basis under 
Sec.  21.101.

Novel or Unusual Design Features

    The Hoh AP/SAS incorporates novel or unusual design features, for 
installation in a Bell model 407 helicopter, Type Certificate Number 
H2SW. This AP/SAS 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 
conditions for this system, and their effect on continued safe flight 
and landing of the helicopter, are more severe than those envisioned by 
the present rules.

Discussion

    The effect on safety is not adequately covered under Sec.  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.
    To comply with the provisions of the special conditions, we require 
that Hoh 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 must ensure that all failure 
conditions 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 
Society of Automotive Engineers (SAE) document Aerospace Recommended 
Practice (ARP) 4761 (Guidelines and Methods for Conducting the Safety 
Assessment Process on Civil Airborne Systems and Equipment).
    These special conditions require that the AP/SAS installed on a 
Bell model 407 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.

Applicability

    These special conditions are applicable to the Hoh AP/SAS installed 
as an STC approval, in Bell model 407 helicopter, Type Certificate 
Number H2SW.

Conclusion

    This action affects only certain novel or unusual design features 
for a Hoh 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 on the helicopter.
    The substance of these special conditions has been subjected to the 
notice and comment period previously and has been derived without 
substantive change from those previously issued. It is unlikely that 
prior public comment would result in a significant change from the 
substance contained herein. Therefore, because a delay would 
significantly affect the certification of the helicopter, which is 
imminent, the FAA has determined that prior public notice and comment 
are unnecessary and impracticable, and good cause exists for adopting 
these special conditions upon issuance. The FAA is requesting comments 
to allow interested persons to submit views that may not have been 
submitted in response to the prior opportunities for comment.

List of Subjects in 14 CFR Part 27

    Aircraft, Aviation safety.

    The authority citation for these special conditions is as follows:

    Authority: 42 U.S.C. 7572, 49 U.S.C. 106(g), 40105, 40113, 
44701-44702, 44704, 44709, 44711, 44713, 44715, 45303.

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the Hoh Aeronautics, Inc. (Hoh) supplemental type certificate basis for 
the installation of an autopilot/stability augmentation system (AP/SAS) 
on the Bell Helicopter Textron Canada Limited (Bell) model

[[Page 10491]]

407 helicopter, Type Certificate Number H2SW.
    The AP/SAS 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 ``failure condition 
categories'' and ``requirements'' sections (including the system design 
integrity, design environmental, and test and analysis requirements) of 
these special conditions.
    Failure Condition Categories Failure conditions are classified, 
according to the severity of their effects on the rotorcraft, 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 would 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 result in 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 result in impairing crew 
efficiency, physical distress to occupants, 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 1: ``Hazardous/severe-major'' failure conditions can 
include events that are manageable by the crew by the 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.
    Hoh must 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 show that all 
failure conditions and their resulting effects are adequately addressed 
for the installed AP/SAS.

    Note 2: 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 Society of Automotive Engineers (SAE) document Aerospace 
Recommended Practice (ARP) 4761 (Guidelines and Methods for 
Conducting the Safety Assessment Process on Civil Airborne Systems 
and Equipment).

Requirements

    Hoh must comply with the existing requirements of Sec.  27.1309 for 
all applicable design and operational aspects of the AP/SAS with the 
failure condition categories of ``no effect,'' and ``minor,'' and for 
non-complex systems whose failure condition category is classified as 
``major.'' Hoh must comply with the requirements of these special 
conditions for all applicable design and operational aspects of the AP/
SAS with the failure condition categories of ``catastrophic'' and 
``hazardous severe/major,'' and for complex systems whose failure 
condition category is classified as ``major.''
    A complex system is a system whose operations, failure conditions, 
or failure effects are difficult to comprehend without the aid of 
analytical methods (for example, FTA, Failure Modes and Effect 
Analysis, FHA).

System Design Integrity Requirements

    Each of the failure condition categories defined in these special 
conditions relate to the corresponding aircraft system integrity 
requirements. The system design integrity requirements, for the Hoh AP/
SAS, as they relate to the allowed probability of occurrence for each 
failure condition category, and the proposed software design assurance 
level, are as follows:
     ``Major''--For systems with ``major'' failure conditions, 
failures resulting in these major effects must be shown to be remote, a 
probability of occurrence on the order of between 1 x 10 -5 
to 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 C software design assurance 
level.
     ``Hazardous/Severe-Major''--For systems with ``hazardous/
severe-major'' failure conditions, failures resulting in these 
hazardous/severe-major effects must be shown to be extremely remote, a 
probability of occurrence on the order of between 1 x 10 -7 
to 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 B software assurance level.
     ``Catastrophic''--For systems with ``catastrophic'' 
failure conditions, failures resulting in these catastrophic effects 
must be shown to be extremely improbable, a probability of occurrence 
on the order of 1 x 10 -9 failures/hour or less, and 
associated software must be developed to the RTCA/DO-178B (Software 
Considerations in Airborne Systems and Equipment Certification) Level A 
design assurance level.

System Design Environmental Requirements

    The AP/SAS system equipment must be qualified to the appropriate 
environmental level per RTCA document DO-160F (Environmental Conditions 
and Test Procedures for Airborne Equipment), for all relevant aspects. 
This is to show that the AP/SAS system performs its intended function 
under any foreseeable operating condition, which includes the expected 
environment in which the AP/

[[Page 10492]]

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 conditions and effects on the rotorcraft.

Test & Analysis Requirements

    Compliance with the requirements of these special conditions 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 related to the associated failure condition category. If 
the AP/SAS is a complex system, compliance with the requirements for 
failure conditions classified as ``major'' may be shown by analysis, in 
combination with appropriate testing to validate the analysis. 
Compliance with the requirements for 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 ``hazardous/
severe-major'' failure conditions and effects due to safety 
considerations. Compliance with the requirements for 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 
used as a part of a showing of compliance for ``catastrophic'' failure 
conditions. Flight tests are performed only in circumstances that use 
operational variations, or extrapolations from other flight performance 
aspects to address flight safety.
    These special conditions require that the Hoh AP/SAS system 
installed on a Bell model 407 helicopter, Type Certificate Number H2SW, 
meet these requirements to adequately address the failure effects 
identified by the FHA, and subsequently verified by the SSA, within the 
defined system design integrity requirements.

    Issued in Fort Worth, Texas, on February 14, 2011.
Kimberly K. Smith,
Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 2011-4229 Filed 2-24-11; 8:45 am]
BILLING CODE 4910-13-P