[Federal Register Volume 72, Number 248 (Friday, December 28, 2007)]
[Rules and Regulations]
[Pages 73579-73582]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-25143]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 21 and 27

[Docket No. SW017; Special Condition No. 27-017-SC]


Special Condition: Bell Helicopter Textron Canada Limited Model 
429 Helicopters, High Intensity Radiated Fields

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special condition; request for comments.

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SUMMARY: This special condition is issued for the Bell Helicopter Model 
429 helicopters. These helicopters will have novel or unusual design 
features associated with installing electrical and electronic systems 
that perform critical functions, including an Electronic Flight 
Instrument System (EFIS) and a Full Authority Digital Engine Control 
(FADEC). The applicable airworthiness regulations do not contain 
adequate or appropriate safety standards to protect systems that 
perform critical control functions, or provide critical displays, from 
the effects of high-intensity radiated fields (HIRF). This special 
condition contains the additional safety standards that the 
Administrator considers necessary to ensure that critical functions of 
systems will be maintained when exposed to HIRF.

DATES: The effective date of this special condition is December 11, 
2007. Comments must be received on or before February 11, 2008.

ADDRESSES: Send comments on this special condition in duplicate to: 
Federal Aviation Administration, Rotorcraft Directorate, Attention: 
Rules Docket (ASW-111) Docket No. SW017, Fort Worth, Texas 76193-0111, 
or deliver them in duplicate to the Rotorcraft Directorate at 2601 
Meacham Blvd., Fort Worth, Texas 76137. Comments must be marked: Docket 
No. SW017. 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: Carroll Wright, Electrical Flight 
Systems

[[Page 73580]]

Engineer, FAA, Rotorcraft Directorate, Rotorcraft Standards, 2601 
Meacham Blvd., Fort Worth, Texas 76193-0110; telephone (817) 222-5120, 
FAX (817) 222-5961.

SUPPLEMENTARY INFORMATION: We have determined that notice and 
opportunity for prior public comment are unnecessary since the 
substance of this special condition has been subject to the public 
comment process in several prior instances with no substantive comments 
received. Therefore, we determined that good cause exists for making 
this special condition effective upon issuance.

Comments Invited

    You are invited to submit written data, views, or arguments. Your 
communications should include the regulatory 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 summarizing each substantive public contact with FAA personnel 
concerning this special condition in the docket. 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. SW017.'' We will date stamp the postcard and 
mail it to you.

Background

    On September 13, 2004, Bell Helicopter submitted an application for 
a Type Certificate for the Model 429 helicopter. The Model 429 
helicopter is a new design based on the existing drive train of the 
Bell Model 427 helicopter and a new fuselage. The Model 429 is a twin-
engine, 4-bladed main and tail rotor helicopter with a maximum gross 
weight of 7,000 pounds, capable of carrying up to nine passengers plus 
a pilot. The helicopter will be designed for dual and single pilot 
instrument flight rules (IFR) and Category A operations.

Type Certification Basis

    Under the provisions of 14 CFR 21.17, Bell Helicopter must show 
that the Model 429 helicopter meets the applicable provisions of the 
regulations as listed below:
    14 CFR part 27, Amendment 27-0 through Amendment 27-40 dated May 9, 
2001.
    Sections of 14 CFR part 29, Amendment 29-14 dated September 1, 
1977, as listed in 14 CFR part 27 Appendix B for instrument flight 
rules (IFR).
    Sections of 14 CFR part 29 Amendment 29-0 through Amendment 29-47 
dated May 9, 2001, as listed in 14 CFR part 27 Appendix C for Category 
A.
    14 CFR part 36 Appendix H, Amendment 36-25, including FAA stage 3 
noise limits for helicopters.
    Any special conditions, exemptions, and equivalent safety findings 
deemed necessary.
    In addition, the certification basis includes certain special 
conditions and equivalent safety findings that are not relevant to this 
special condition.
    If the Administrator finds that the applicable airworthiness 
regulations do not contain adequate or appropriate safety standards for 
these helicopters because of a novel or unusual design feature, special 
conditions are prescribed under the provisions of Sec.  21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, Bell Helicopter Model 429 helicopters must comply with the 
noise certification requirements of 14 CFR part 36; and the FAA must 
issue a finding of regulatory adequacy pursuant to Sec.  611 of Public 
Law 92-574, the ``Noise Control Act of 1972.''
    Special conditions, as appropriate, are defined in Sec.  11.19, and 
issued by following the procedures in Sec.  11.38, and become part of 
the type certification basis in accordance with Sec.  21.17(a)(2).
    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 novel or 
unusual design feature, the special conditions would also apply to the 
other model under the provisions of Sec.  21.101.

Novel or Unusual Design Features

    The Bell Helicopter Model 429 helicopter will incorporate the 
following novel or unusual design features: Electrical, electronic, or 
combination of electrical electronic (electrical/electronic) systems 
that perform critical control functions or provide critical displays, 
such as electronic flight instruments that will be providing displays 
critical to the continued safe flight and landing of the helicopter 
during operation in Instrument Meteorological Conditions (IMC), and 
Full Authority Digital Engine Control (FADEC) that will be performing 
engine control functions that are critical to the continued safe flight 
and landing of the helicopter during visual flight rules (VFR) and IFR 
operations.

Discussion

    The Bell Helicopter Model 429 helicopter, at the time of 
application, was identified as incorporating one and possibly more 
electrical/electronic systems, such as electronic flight instruments 
and FADEC. After the design is finalized, Bell Helicopter will provide 
the FAA with a preliminary hazard analysis that will identify any other 
critical functions, required for safe flight and landing, that are 
performed by the electrical/electronic systems.
    Recent advances in technology have led to the application in 
aircraft designs of advanced electrical/electronic systems that perform 
critical control functions or provide critical displays. These advanced 
systems respond to the transient effects of induced electrical current 
and voltage caused by HIRF incident on the external surface of the 
helicopter. These induced transient currents and voltages can degrade 
the performance of the electrical/electronic systems by damaging the 
components or by upsetting the systems' functions.
    Furthermore, the electromagnetic environment has undergone a 
transformation not envisioned by the current application of 14 CFR 
27.1309(a). Higher energy levels radiate from operational transmitters 
currently used for radar, radio, and television. Also, the number of 
transmitters has increased significantly.
    Existing aircraft certification requirements are inappropriate in 
view of these technological advances. In addition, the FAA has received 
reports of some significant safety incidents and accidents involving 
military aircraft equipped with advanced electrical/electronic systems 
when they were exposed to electromagnetic radiation.
    The combined effects of the technological advances in helicopter 
design and the changing environment have resulted in an increased level 
of vulnerability of the electrical/electronic systems required for the 
continued safe flight and landing of the helicopter. Effective measures 
to protect these helicopters against the adverse effects of exposure to 
HIRF will be provided by the design and installation of these systems. 
The following primary factors contributed to the current conditions: 
(1) Increased use of sensitive electronics that perform critical 
functions; (2) reduced electromagnetic shielding afforded helicopter 
systems by advanced technology airframe materials; (3) adverse service 
experience of military aircraft using these technologies; and (4) an 
increase in the number and power of radio frequency

[[Page 73581]]

emitters and the expected increase in the future.
    On July 30, 2007, we issued a final HIRL rule (72 FR 44016, August 
6, 2007). This rule provides standards to protect aircraft electrical 
and electronic systems from HIRFs. It was effective September 5, 2007. 
However, that rule included provisions that provide relief from the new 
testing requirements for equipment previously certificated under HIRF 
special conditions issued in accordance with 14 CFR 21.16. To obtain 
this relief the applicant must be able to show that--
    (1) The system has previously been shown to comply with special 
conditions for HIRF, prescribed under Sec.  21.16, issued before 
December 1, 2007;
    (2) The HIRF immunity characteristics of the system have not 
changed since compliance with the special conditions was demonstrated; 
and
    (3) The data used to demonstrate compliance with the HIRF special 
conditions is provided.
    The Bell 429 installations are eligible for this relief provided in 
14 CFR 29.1317(d) of the final HIRF rule. However, to meet their HIRF 
requirements they must comply with this Special Condition, which is 
based on similar, historical HIRF protections requirements.
    Compliance with HIRF requirements will be demonstrated by tests, 
analysis, models' similarity with existing systems, or a combination of 
these methods. Service experience alone will not be acceptable since 
such experience in normal flight operations may not include an exposure 
to HIRF. Reliance on a system with similar design features for 
redundancy as a means of protection against the effects of external 
HIRF is generally insufficient because all elements of a redundant 
system are likely to be concurrently exposed to the radiated fields.
    This special condition will require aircraft installed systems that 
perform critical control functions or provide critical displays to meet 
certain standards based on either a defined HIRF environment or a fixed 
value using laboratory tests. Control system failures and malfunctions 
can more directly and abruptly contribute to a catastrophic event than 
display system failures and malfunctions. Therefore, it is considered 
appropriate to require more rigorous HIRF verification methods for 
critical control systems than for critical display systems.
    The applicant may demonstrate that the operation and operational 
capabilities of the installed electrical/electronic systems that 
perform critical functions are not adversely affected when the aircraft 
is exposed to the defined HIRF test environment. We have determined 
that the test environment defined in Table 1 is acceptable for critical 
control functions in helicopters. The test environment defined in Table 
2 is acceptable for critical display systems in helicopters.
    The applicant may also demonstrate, by a laboratory test, that the 
electrical/electronic systems that perform critical control functions 
or provide critical displays can withstand a peak electromagnetic field 
strength in a frequency range of 10 kHz to 18 GHz. If a laboratory test 
is used to show compliance with the defined HIRF environment, no credit 
will be given for signal attenuation due to installation. A level of 
100 volts per meter (v/m) is appropriate for critical display systems. 
A level of 200 v/m is appropriate for critical control functions. 
Laboratory test levels are defined according to RTCA/DO-160D Section 20 
Category W (100 v/m and 150 mA) and Category Y (200 v/m and 300 mA). As 
defined in DO-160D Section 20, the test levels are defined as the peak 
of the root means squared (rms) envelope. As a minimum, the modulations 
required for RTCA/DO-160D Section 20 Categories W and Y will be used. 
Other modulations should be selected as the signal most likely to 
disrupt the operation of the system under test, based on its design 
characteristics. For example, flight control systems may be susceptible 
to 3 Hz square wave modulation while the video signals for electronic 
display systems may be susceptible to 400 Hz sinusoidal modulation. If 
the worst-case modulation is unknown or cannot be determined, default 
modulations may be used. Suggested default values are a 1 kHz sine wave 
with 80 percent depth of modulation in the frequency range from 10 kHz 
to 400 MHz, and 1 kHz square wave with greater than 90 percent depth of 
modulation from 400 MHz to 18 GHz. For frequencies where the 
unmodulated signal would cause deviations from normal operation, 
several different modulating signals with various waveforms and 
frequencies should be applied.
    Applicants must perform a preliminary hazard analysis to identify 
electrical/electronic systems that perform critical functions. The term 
``critical'' means those functions whose failure would contribute to or 
cause an unsafe condition that would prevent the continued safe flight 
and landing of the helicopter. The systems identified by the hazard 
analysis as performing critical functions are required to have HIRF 
protection. A system may perform both critical and non-critical 
functions. Primary electronic flight display systems and their 
associated components perform critical functions such as attitude, 
altitude, and airspeed indications. HIRF requirements would apply only 
to the systems that perform critical functions, including control and 
display.
    Acceptable system performance would be attained by demonstrating 
that the critical function components of the system under consideration 
continue to perform their intended function during and after exposure 
to required electromagnetic fields. Deviations from system 
specifications may be acceptable, but must be independently assessed by 
the FAA on a case-by-case basis.

  Table 1.--Rotorcraft Critical Control Functions Field Strength Volts/
                                  Meter
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                   Frequency                        Peak       Average
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10 kHz-100 kHz................................          150          150
100 kHz-500 kHz...............................          200          200
500 kHz-2 MHz.................................          200          200
2 MHz-30 MHz..................................          200          200
30 MHz-70 MHz.................................          200          200
70 MHz-100 MHz................................          200          200
100 MHz-200 MHz...............................          200          200
200 MHz-400 MHz...............................          200          200
400 MHz-700 MHz...............................          730          200
700 MHz-1 GHz.................................         1400          240
1 GHz-2 GHz...................................         5000          250
2 GHz-4 GHz...................................         6000          490
4 GHz-6 GHz...................................         7200          400
6 GHz-8 GHz...................................         1100          170
8 GHz-12 GHz..................................         5000          330
12 GHz-18 GHz.................................         2000          330
18 GHz-40 GHz.................................         1000          420
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  Table 2.--Rotorcraft Critical Display Functions Field Strength Volts/
                                  Meter
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                   Frequency                        Peak       Average
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10 kHz-100 kHz................................           50           50
100 kHz-500 kHz...............................           50           50
500 kHz-2 MHz.................................           50           50
2 MHz-30 MHz..................................          100          100
30 MHz-70 MHz.................................           50           50
70 MHz-100 MHz................................           50           50
100 MHz-200 MHz...............................          100          100
200 MHz-400 MHz...............................          100          100
400 MHz-700 MHz...............................          700           50
700 MHz-1 GHz.................................          700          100
1 GHz-2 GHz...................................         2000          200
2 GHz-4 GHz...................................         3000          200

[[Page 73582]]

 
4 GHz-6 GHz...................................         3000          200
6 GHz-8 GHz...................................         1000          200
8 GHz-12 GHz..................................         3000          300
12 GHz-18 GHz.................................         2000          200
18 GHz-40 GHz.................................          600          200
------------------------------------------------------------------------

Applicability

    As previously discussed, this special condition is applicable to 
the Bell Helicopter Model 429 helicopter. Should Bell Helicopter 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 condition would apply to that model as well under the 
provisions of Sec.  21.101.

Conclusion

    This action affects only certain novel or unusual design features 
on one model series of helicopters. 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 this special condition has been subjected to the 
notice and comment period previously and is written without substantive 
change from those previously issued. It is unlikely that prior public 
comment would result in a significant change from the substance 
contained in this special condition. For this reason, we have 
determined that prior public notice and comment are unnecessary, and 
good cause exists for adopting this special condition 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 Parts 21 and 27

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


0
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 Condition

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special condition is issued as part of the 
type certification basis for Bell Helicopter Model 429 helicopters.

Protection for Electrical and Electronic Systems from High Intensity 
Radiated Fields

    1. Each system that performs critical functions must be designed 
and installed to ensure that the operation and operational capabilities 
of these critical functions are not adversely affected when the 
helicopter is exposed to high intensity radiated fields external to the 
helicopter.
    2. For the purpose of this special condition, critical functions 
are defined as those functions, whose failure would contribute to, or 
cause, an unsafe condition that would prevent the continued safe flight 
and landing of the aircraft.

    Issued in Fort Worth, Texas, on December 11, 2007.
Mark R. Schilling,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
 [FR Doc. E7-25143 Filed 12-27-07; 8:45 am]
BILLING CODE 4910-13-P