[Federal Register Volume 61, Number 115 (Thursday, June 13, 1996)]
[Rules and Regulations]
[Pages 29928-29931]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-14761]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 27

[Docket No. 96-ASW-1; Special Condition No. 27-ASW-3]


Special Condition: Agusta Models A109D and A109E, High Intensity 
Radiated Fields

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final special condition; request for comments.

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SUMMARY: This special condition is issued for the Agusta Model A109D 
and A109E helicopters. These helicopters will have a novel or unusual 
design feature associated with electronic systems that perform critical 
functions. The applicable airworthiness regulations do not contain 
adequate or appropriate safety standards for the protection of the 
electronic systems that perform critical functions from the effects of 
external high intensity radiated fields (HIRF). This special condition 
contains the additional safety standards that the Administrator 
considers necessary to establish a level of safety equivalent to that 
established by the applicable airworthiness standards.

DATES: The effective date of this special condition is June 13, 1996. 
Comments must be received on or before August 12, 1996.

ADDRESSES: Comments on this proposal may be mailed in duplicate to the 
Federal Aviation Administration (FAA), Office of the Assistant Chief 
Counsel, Attn: Rules Docket No. 96-ASW-1, Fort Worth, Texas 76193-0007, 
or delivered in duplicate to the Office of the Assistant Chief Counsel, 
2601 Meacham Blvd., Fort Worth, Texas. Comments must be marked Docket 
No. 96-ASW-1. Comments may be inspected in the Rules Docket weekdays, 
except Federal holidays, between 9 a.m. and 3 p.m.

FOR FURTHER INFORMATION CONTACT:
Mr. Carroll Wright, FAA, Rotorcraft Directorate, Regulations Group, 
Fort Worth, Texas 76193-0111; telephone (817) 222-5120.

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 delay delivery of the affected helicopter. These 
notice and comment procedures are also considered unnecessary since the 
public has been previously provided with a substantial number of 
opportunities to comment on substantially identical special conditions, 
and their comments have been fully considered. Therefore, good cause 
exists for making this special condition effective upon issuance.

Comments Invited

    Although this final special condition was not subject to notice and 
opportunity for prior public comment, comments are invited on this 
final special condition. Interested persons are invited to comment on 
this final special condition by submitting such written data, views, or 
arguments as they may desire. Communications should identify the 
regulatory docket number and be submitted in duplicate to the address 
specified under the caption ADDRESSES. All communications received on 
or before the closing date for comments will be considered. This 
special condition may be changed in light of comments received. All 
comments received will be available in the Rules Docket for examination 
by interested persons, both before and after the closing date of 
comments. A report summarizing each substantive public contact with FAA 
personnel concerning this rulemaking will be filed in the docket. 
Persons wishing the FAA to acknowledge receipt of their comments 
submitted in response to this final rule must submit with those 
comments a self-addressed, stamped postcard on which the following 
statement is made: ``Comments to Docket No. 96-ASW-3.'' The postcard 
will be date and time stamped and returned to the commenter.

Background

    Agusta S.p.A., Cascina Costa, Italy, applied for an amendment to 
U.S. Type Certificate H7EU through the Registro Aeronautico Italiano 
(RAI) September 23, 1992, updated July 26, 1993, to include Model A109D 
and A109E helicopters based on previously certified A109C and A109K2 
helicopters. The A109D and A109E helicopters differ from the previously 
certificated model helicopters because they contain the following:
    a. Allison 250-C22(A109D) or Pratt & Whitney PW206C(A109E) FADEC 
controlled engines.
    b. A main landing gear that is held in position by two crossbeams 
that are covered by pods and is retractable into the bottom of the 
helicopter.
    c. A new main rotor titanium hub, composite tension links, 
electomeric bearings, with dampers derived from the Model A129 
helicopter.
    d. Updated fuselage and fuel systems; and
    e. A new cockpit layout with flat panel displays (IDS) for 
powerplant data monitoring.

Type Certification Basis

    The certification basis established for the Agusta Model A109D and 
A109E helicopters includes: 14 Code of Federal Regulations (CFR) 
Sec. 21.29 and 14 CFR part 27 effective February 1, 1965, including 
Amendments 27-1 through 27-8, except as more specifically required by 
the following paragraph amendment levels:

------------------------------------------------------------------------
                          Paragraph                            Amendment
------------------------------------------------------------------------
27.2.........................................................         28
27.21........................................................         21
27.45........................................................         21
27.71........................................................         21
27.79........................................................         21
27.141.......................................................         21
27.143.......................................................         21
27.175.......................................................         21
27.177.......................................................         21
27.401.......................................................         27
27.610.......................................................         21
27.901.......................................................         23
27.903.......................................................         23
27.927.......................................................         23
27.954.......................................................         23
27.1091......................................................         23
27.1093(b)...................................................         23
27.1189......................................................         23
27.1305......................................................         23
27.1309......................................................         21
27.1321......................................................         13

[[Page 29929]]

                                                                        
27.1322......................................................         11
27.1323......................................................         13
27.1325......................................................         13
27.1401......................................................         10
27.1505......................................................         21
27.1519......................................................         21
27.1521......................................................         23
27.1527......................................................         14
27.1529......................................................         18
27.1549......................................................         23
27.1555......................................................         21
27.1557......................................................         11
27.1581......................................................         14
27.1583......................................................         16
27.1585......................................................         21
27.1587......................................................         21
------------------------------------------------------------------------



    Section 29.903(b), effective February 1, 1965, for category ``A'' 
engine isolation, elected by the applicant; Special Conditions No. 27-
54-EU-17 for Agusta Model A109 helicopter, issued on June 26, 1973; 
equivalent safety in lieu of compliance shown for:
     Section 27.1189, regarding shut-off means, and
     Section 27.1305(d), regarding the fuel quantity indicator.
    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 to 
establish a level of safety equivalent to that established in the 
regulations.
    Special conditions, as appropriate, are issued in accordance with 
Sec. 11.49 after public notice, as required by Secs. 11.28 and 
11.29(b), and become part of the type certification basis in accordance 
with Sec. 21.101(b)(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, or should any other model already included on 
the same type certificate be modified to incorporate 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).

Discussion

    The Agusta Model A109D and A109E helicopters, at the time of the 
application for amendment to U.S. Type Certificate H7EU, were 
identified as incorporating one and possibly more electrical, 
electronic, or combination of electrical and electronic (electrical/
electronic) systems that will perform functions critical to the 
continued safe flight and landing of the helicopters. A FADEC is an 
electronic device that performs the critical functions of engine 
control. The control of the engines is critical to the continued safe 
flight and landing of the helicopter during visual flight rules (VFR) 
and instrument flight rules (IFR) operations.
    If it is determined that this helicopter currently or at a future 
date incorporates other electrical/electronic systems performing 
critical functions, those systems also will be required to comply with 
the requirements of this special condition.
    Recent advances in technology have prompted the design of aircraft 
that include advanced electrical and electronic systems that perform 
functions required for continued safe flight and landing. However, 
these advanced systems respond to the transient effects of induced 
electrical current and voltage caused by the HIRF incident on the 
external surface of the helicopters. 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; 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 technological advances in helicopter design 
and the changing environment have resulted in an increased level of 
vulnerability of the electrical and 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 technological developments and a changing environment 
and, in 1986, initiated a high priority program to (1) determine and 
define electromagnetic energy levels; (2) develop 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 a level of HIRF environment that a helicopter could be 
exposed to during IFR operations. While the HIRF requirements are being 
finalized, the FAA is adopting a special condition for the 
certification of aircraft that employ electrical/electronic systems 
that perform critical functions. 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 be protected from 
these energy levels. These external threat levels are believed to 
represent the worst-case exposure for a helicopter operating under IFR.
    The HIRF environment specified in this special condition is based 
on many critical assumptions. With the exception of takeoff and landing 
at an airport, one of these assumptions is the aircraft would be not 
less than 500 feet above ground level (AGL). Helicopters operating 
under visual flight rules (VFR) routinely operate at less than 500 feet 
AGL and perform takeoffs and landings at locations other than 
controlled airports. Therefore, it would be expected that the HIRF 
environment experienced by a helicopter operating VFR may exceed the 
defined environment by 100 percent or more.
    This special condition will require the systems that perform 
critical functions, as installed in the aircraft, to meet certain 
standards based on either a defined HIRF environment or a fixed value 
using laboratory tests.
    The applicant may demonstrate that the operation and operational 
capability of the installed electrical/electronic systems that perform 
critical functions are not adversely affected when the aircraft is 
exposed to the defined HIRF environment. The FAA has determined that 
the environment defined in Table 1 is acceptable for critical functions 
in

[[Page 29930]]

helicopters operating at or above 500 feet AGL. For critical functions 
of helicopters operating at less than 500 feet AGL, additional factors 
must be considered.
    The applicant may also demonstrate by a laboratory test that the 
electrical/electronic systems that perform critical functions 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 v/m and other 
considerations, such as an alternate technology backup that is immune 
to HIRF, are appropriate for critical functions during IFR operations. 
A level of 200 v/m and further considerations, such as an alternate 
technology backup that is immune to HIRF, are more appropriate for 
critical functions during VFR operations.
    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 a failure 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 noncritical 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.
    Compliance with HIRF requirements will be demonstrated by tests, 
analysis, models, similarity with existing systems, or a combination of 
these methods. The two basic options of either testing the rotorcraft 
to the defined environment or laboratory testing may not be combined. 
The laboratory test allows some frequency areas to be under tested and 
requires other areas to have some safety margin when compared to the 
defined environment. The areas required to have some safety margin are 
those that have been, by past testing, shown to exhibit greater 
susceptibility to adverse effects from HIRF; and laboratory tests, in 
general, do not accurately represent the aircraft installation. 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.
    The modulation that represents the signal most likely to disrupt 
the operation of the system under test, based on its design 
characteristics, should be selected. For example, flight control system 
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.
    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.--Field Strength Volts/Meter                  
------------------------------------------------------------------------
                       Frequency                          Peak   Average
------------------------------------------------------------------------
10-100 KHz............................................       50       50
100-500...............................................       60       60
500-2000..............................................       70       70
2-30 MHz..............................................      200      200
30-100................................................       30       30
100-200...............................................      150       33
200-400...............................................       70       70
400-700...............................................     4020      935
700-1000..............................................     1700      170
1-2 GHz...............................................     5000      990
2-4...................................................     6680      840
4-6...................................................     6850      310
6-8...................................................     3600      670
8-12..................................................     3500     1270
12-18.................................................     3500      360
18-40.................................................     2100      750
------------------------------------------------------------------------

    As discussed above, these special conditions are applicable 
initially to the Model A109D and A109E helicopters. Should Agusta 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 conditions would apply to that model as well, under the 
provisions of Sec. 21.101(a)(1).

Conclusion

    This action affects only certain unusual or novel design features 
on two models 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 affected helicopter.
    The substance of this special condition for similar installations 
in a variety of helicopters has been subjected to the notice and 
comment procedure and has been finalized without substantive change. 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 
helicopter, which is imminent, the FAA has determined that prior public 
notice and comment are unnecessary and impractical, and good cause 
exists for adopting this special condition immediately. Therefore, this 
special condition is being made effective upon issuance. The FAA is 
requesting comments to allow interested persons to submit views that 
may not have been submitted in response to prior opportunities for 
comment.

List of Subjects in 14 CFR Parts 21 and 29

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

    The authority citation for this special condition 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 Federal Aviation Administration (FAA) issues the 
following special condition as a part of the type certification basis 
for the Agusta Model A109D and A109E 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 
helicopters are exposed to high intensity radiated fields external to 
the helicopters.


[[Page 29931]]


    Issued in Fort Worth, Texas, on May 31, 1996.
Daniel P. Salvano,
Manager, Rotorcraft Directorate, Aircraft Certification Service.
[FR Doc. 96-14761 Filed 6-12-96; 8:45 am]
BILLING CODE 4910-13-M