[Federal Register Volume 65, Number 229 (Tuesday, November 28, 2000)]
[Rules and Regulations]
[Pages 70770-70772]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-30304]


=======================================================================
-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 29

[Docket No. SW008; Special Conditions No. 29-008-SC]


Special Conditions: Sikorsky Aircraft Corporation Model S-92 
Helicopters, High-Intensity Radiated Fields

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special condition; request for comments.

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

SUMMARY: This special condition is issued for Sikorsky Aircraft 
Corporation (Sikorsky) Model S-92 helicopters. These helicopters will 
have novel or unusual design features associated with the installation 
of electronic systems that perform critical functions. 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 November 13, 
2000. Comments must be received on or before January 12, 2001.

ADDRESSES: Comments on this special condition may be mailed in 
duplicate to: Federal Aviation Administration, Office of the Regional 
Counsel, Attention: Rules Docket No. SW008, Fort Worth, Texas 76193-
0007, or delivered in duplicate to the Office of the Regional Counsel 
at 2601 Meacham Blvd., Fort Worth, Texas 76137. Comments must be 
marked: Rules Docket No. SW008. Comments may be inspected in the Rules 
Docket weekdays, except Federal holidays, between 8:30 a.m. and 4 p.m.

FOR FURTHER INFORMATION CONTACT: Jorge Castillo, FAA, Rotorcraft 
Directorate, Rotorcraft Standards, Fort Worth, Texas 76193-0110; 
telephone (817) 222-5127, fax (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 approval 
design and thus delivery of the affected aircraft. In addition, 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. The FAA therefore finds that good cause exists for making 
this special condition effective upon issuance.

Comments Invited

    Interested persons are invited to submit such written data, views, 
or arguments as they may desire. Communications should identify the 
regulatory docket or special condition number and be submitted in 
duplicate to the address specified above. All communications received 
on or before the closing date for comments will be considered. The 
special condition may be changed in light of the comments received. All 
comments received will be available in the Rules Docket for examination 
by interested persons. A report summarizing each substantive public 
contact with FAA personnel concerning this rulemaking will be filed in 
the docket. Commenters wishing the FAA to acknowledge receipt of their 
comments submitted in response to this special condition must include a 
self-addressed, stamped postcard on which the following statement is 
made: ``Comments to Rules Docket No. SW008.'' The postcard will be date 
stamped and returned to the commenter.

Background

    On November 5, 1990, Sikorsky applied for a new type certification 
of Model S-92 helicopters. Since applying for the new type 
certification, Sikorsky has requested two extensions of the type 
certification period. The first extension to August 29, 1999 was 
approved by the FAA on October 7, 1994, and the second extension to May 
31, 2000 was approved on July 21, 1995. Sikorsky Model S-92 helicopters 
are 19-passenger Transport Category helicopters, powered by two General 
Electric Model CT7-8 engines. They will incorporate one auxiliary power 
unit for engine starting and back-up electrical power. The helicopters 
will have a conventional aluminum structure with some composite parts 
and highly integrated digital avionics.

Type Certification Basis

    Under the provisions of 14 CFR 21.17, Sikorsky must show that 
Sikorsky Model S-92 helicopters meet the applicable provisions of the 
regulations as listed below:
     14 CFR Part 29, Amendment 29-1 through Amendment 29-45, 
inclusive;
     14 CFR Part 36, Appendix H, Amendments 36-1 through the 
amendment effective at the time of certification; and
     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, Sikorsky Model S-92 helicopters must comply with the noise 
certification requirements of 14 CFR part 36; and the FAA must issue a 
finding of regulatory adequacy pursuant

[[Page 70771]]

to Sec. 611 of Public Law 92-574, the ``Noise Control Act of 1972.''
    Special conditions, as appropriate, are issued in accordance with 
Sec. 11.49, as required by Secs. 11.28 and 11.29(b), 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(a)(1).

Novel or Unusual Design Features

    Sikorsky Model S-92 helicopters 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 display critical 
information, such as electronic flight instruments, required for 
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 Instrument Flight Rules 
(IFR) operations.

Discussion

    Sikorsky Model S-92 helicopters, at the time of application, were 
identified as incorporating one and possibly more electrical/electronic 
systems, such as electronic flight instruments and FADEC. After the 
design is finalized, Sikorsky 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 given rise 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 a 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 
Sec. 29.1309(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 helicopters. 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 emitters and the expected increase in the future.
    The FAA recognizes the need for aircraft certification standards to 
keep pace with the developments in technology and environment and, in 
1986, initiated a high priority program to (1) determine and define 
electromagnetic energy levels; (2) develop and describe guidance 
material for design, test, and analysis; and (3) prescribe and 
promulgate regulatory standards.
    The FAA participated with industry and airworthiness authorities of 
other countries to develop internationally recognized standards for 
certification.
    The FAA and airworthiness authorities of other countries have 
identified two levels of the HIRF environment that a helicopter could 
be exposed to, one environment for VFR operations and a different 
environment for IFR operations. While the HIRF rulemaking requirements 
are being finalized, the FAA is adopting a special condition for the 
certification of aircraft that employ electrical/electronic systems 
that perform critical control functions or provide critical displays. 
The accepted maximum energy levels that civilian helicopter system 
installations must withstand for safe operation are based on surveys 
and analysis of existing radio frequency emitters. This special 
condition will require the helicopters' electrical/electronic systems 
and associated wiring to be protected from these energy levels. These 
external threat levels are believed to represent the exposure for a 
helicopter operating under VFR or IFR.
    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 the 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. The FAA has 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, using a laboratory test, that 
the electrical/electronic systems that perform critical control 
functions or provide critical displays can withstand 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

[[Page 70772]]

(100 v/m and 150 mA) and Category Y (200 v/m and 300 mA). As stated 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 helicopters. 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.--VFR Rotorcraft (Critical Control Functions)
                       Field strength volts/meter
------------------------------------------------------------------------
                   Frequency                        Peak       Average
------------------------------------------------------------------------
10 kHz-100 kHz................................          130          130
100 kHz-500 kHz...............................          180          140
500 kHz-2 MHz.................................           60           60
2 MHz-30 MHz..................................          320          320
30 MHz-70 MHz.................................           80           80
70 MHz-100 MHz................................           70           70
100 MHz-200 MHz...............................          140          140
200 MHz-400 MHz...............................          140          140
400 MHz-700 MHz...............................          400          400
700 MHz-1 GHz.................................          690          400
1 GHz-2 GHz...................................         2400           80
2 GHz-4 GHz...................................         5120          350
4 GHz-6 GHz...................................        13700          570
6 GHz-8 GHz...................................          130           80
8 GHz-12 GHz..................................         4900          200
12 GHz-18 GHz.................................         1300          560
18 GHz-40 GHz.................................         1300           30
------------------------------------------------------------------------


            TABLE 2.--Rotorcraft (Critical Display Functions)
                       Field strength volts/meter
------------------------------------------------------------------------
                   Frequency                        Peak       Average
------------------------------------------------------------------------
10 kHz-100 kHz................................           30           30
100 kHz-500 kHz...............................           40           30
500 kHz-2 MHz.................................           30           30
2 MHz-30 MHz..................................          190          190
30 MHz-70 MHz.................................           20           20
70 MHz-100 MHz................................           20           20
100 MHz-200 MHz...............................           30           30
200 MHz-400 MHz...............................           30           30
400 MHz-700 MHz...............................           80           80
700 MHz-1 GHz.................................          690          240
1 GHz-2 GHz...................................          970           70
2 GHz-4 GHz...................................         1570          350
4 GHz-6 GHz...................................         7200          300
6 GHz-8 GHz...................................          130           80
8 GHz-12 GHz..................................         2100           80
12 GHz-18 GHz.................................          500          330
18 GHz-40 GHz.................................          780           20
------------------------------------------------------------------------

Applicability

    As previously discussed, this special condition is applicable to 
Sikorsky Model S-92 helicopters. Should Sikorsky 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(a)(1).

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 helicopters.
    The substance of this special condition has been subjected to the 
notice and comment period in several prior instances 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. For this reason and because a 
delay would significantly affect the certification of the helicopters, 
which is imminent, the FAA has determined that prior public notice and 
comment are unnecessary and impracticable, 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 
described above.

List of Subjects in 14 CFR Part 29

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

    Authority: The authority citation for these special conditions 
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 issued as part of the 
type certification basis for Sikorsky Model S-92 helicopters.

Protection for Electrical and Electronic Systems From High-Intensity 
Radiated Fields

    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.

    Issued in Fort Worth, Texas, on November 13, 2000.
Michelle M. Owsley,
Acting Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 00-30304 Filed 11-27-00; 8:45 am]
BILLING CODE 4910-13-P