20760 Federal Register / Vol. 61, No. 90 / Wednesday, May 8, 1996 / Proposed Rules

Board contends that the proposed

amendment will provide continuity

between fiscal periods and the terms of

office of the chairperson. The Board

indicates that this will allow the Board

to operate more effectively.

A 7-day comment period is deemed

appropriate to permit implementation of

this amendment, if adopted, before the

annual meeting of the Board that is

tentatively scheduled for the beginning

of July 1996.

List of Subjects in 7 CFR Part 1160

Milk, Fluid milk products, Promotion.

For the reasons set forth in the

preamble, it is proposed that 7 CFR part

1160, is amended as follows:

PART 1160—FLUID MILK PROMOTION

ORDER

1. The authority citation for 7 CFR

Part 1160 continues to read as follows:

Authority: 7 U.S.C. 6401–6417.

2. Section 1160.209(a) is revised to

read as follows:

§ 1160.209 Duties of the Board.

The Board shall have the following

duties:

(a) To meet not less than annually,

and to organize and select from among

its members a chairperson, who may

serve for a term of a fiscal period

pursuant to § 1160.113, and not more

than two consecutive terms, and to

select such other officers as may be

necessary;

* * * * *

Dated: May 2, 1996.

Lon Hatamiya,

Administrator.

[FR Doc. 96–11458 Filed 5–7–96; 8:45 am]

BILLING CODE 3410–02–P

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 29

[Docket No. 96–ASW–2; Notice No. SC–96–

2–SW]

Special Condition: Sikorsky Model

S76C, High Intensity Radiated Fields

AGENCY: Federal Aviation

Administration, DOT.

ACTION: Notice of proposed special

condition.

SUMMARY: This notice proposes a special

condition for the Sikorsky Model S76C

helicopter. This helicopter will have a

novel or unusual design feature

associated with the installation of

electronic systems that perform critical

functions. The applicable airworthiness

regulations do not contain adequate or

appropriate safety standards for the

protection of electronic systems that

perform critical functions from the

effects of external high intensity

radiated fields (HIRF). This notice

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: Comments must be received on

or before June 7, 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–2, 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–2.

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. Robert McCallister, FAA, Rotorcraft

Directorate, Regulations Group, Fort

Worth, Texas 76193–0110; telephone

(817) 222–5121.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to

participate in the making of this

proposed 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 above. All communications

received on or before the closing date

for comments will be considered before

taking action on this proposal. The

special condition proposed in this

notice 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 for 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 notice

must submit with those comments a

self-addressed, stamped postcard on

which the following statement is made:

‘‘Comments to Docket No. 96–ASW–2.’’

The postcard will be date and time

stamped and returned to the

commenter.

Background

Sikorsky Aircraft Corporation,

Stratford, Connecticut, applied for an

amendment to the Type Certificate for

Model S76C helicopter on August 15,

1990. The amendment will allow

installation of Turbomeca Arriel Model

2S1 engines with FADEC control and 30

second/2 minute ratings as alternate

engines for the Sikorsky Model S76C

helicopter. This is a 12 (14 including

crew) passenger, twin engine, 11,700

pound transport category helicopter.

Type Certificate Basis

The type certification basis is 14 Code

of Federal Regulations part 29, February

1, 1965, and Amendments 29–1 through

29–11; in addition, portions of

Amendment 29–12, specifically,

§§ 29.67, 29.71, 29.75, 29.141, 29.173,

29.175, 29.931, 29.1189(a)(2),

29.1555(c)(2), 29.1557(c); Amendment

29–13, specifically § 29.965;

Amendment 29–24, specifically

§ 29.1325; Amendment 29–30

specifically § 29.811; Amendment 29–

34, specifically §§ 29.67(a)(1)(i),

29.923(a), (b) (1) & (3), 29.1143(f),

29.1305(a) (24) & (25), 29.1521 (i) & (j)

and 29.1549(e); and Amendment 36–14

of 14 CFR part 36, Appendix H.

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

§ 21.16 to establish a level of safety

equivalent to that established in the

regulations.

Special conditions, as appropriate, are

issued in accordance with Federal

Aviation Administration § 11.49 after

public notice, as required by §§ 11.28

and 11.29(b), and become part of the

type certification basis in accordance

with Federal Aviation Administration

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 § 21.101(a)(1).

Discussion

The Sikorsky Model S76C helicopter,

at the time of the application for

amendment to U.S. Type Certificate
Federal Register / Vol. 61, No. 90 / Wednesday, May 8, 1996 / Proposed Rules 20761

H1NE, was 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 Full

Authority Digital Engine Control

(FADEC) is an example of 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.

Futhermore, the electromagnetic

environment has undergone a

transformation not envisioned by the

current application of § 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 proposed 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

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 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
20762 Federal Register / Vol. 61, No. 90 / Wednesday, May 8, 1996 / Proposed Rules

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 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 500 MHZ and 1 KHZ square

wave with greater than 90 percent depth

of modulation from 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

TABLE 1.—FIELD STRENGTH VOLTS/

METER—Continued

Frequency Peak Average

18–40 2100 750

As discussed above, these special

conditions are applicable initially to the

Sikorsky Model S76C helicopter.

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 conditions would apply to

that model as well, under the provisions

of § 21.101(a)(1).

Conclusion

This action affects only certain

unusual or novel design features on one

model of helicopter. It is not a rule of

general applicability and affects only

the manufacturer who applied to the

FAA for approval of these features on

the affected helicopters.

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 Proposed Special Condition

Accordingly, pursuant to the

authority delegated to me by the

Administrator, the Federal Aviation

Administration (FAA) proposes the

following special condition as a part of

the type certification basis for the

Sikorsky Model S76C helicopter.

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.

Issued in Fort Worth, Texas, on April 26,

1996.

Larry M. Kelly,

Acting Manager, Rotorcraft Directorate,

Aircraft Certification Service.

[FR Doc. 96–11496 Filed 5–7–96; 8:45 am]

BILLING CODE 4910–13–M

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95–NM–241–AD]

RIN 2120–AA64

Airworthiness Directives; Airbus Model

A310 Series Airplanes

AGENCY: Federal Aviation

Administration, DOT.

ACTION: Notice of proposed rulemaking

(NPRM).

SUMMARY: This document proposes the

adoption of a new airworthiness

directive (AD) that is applicable to

certain Airbus Model A310 series

airplanes. This proposal would require

repetitive inspections to detect

discrepancies of the slat universal joint

and steady bearing assemblies, and

replacement of any discrepant assembly

with a new, like assembly. The proposal

also would require replacement of all

slat universal joint and steady bearing

assemblies with improved assemblies,

which would terminate the repetitive

inspections. This proposal is prompted

by reports of broken or missing inner

races on the slat universal joint and

steady bearing assemblies of the slat

transmission system. The actions

specified by the proposed AD are

intended to prevent cracking of the

inner race, which could cause it to break

off and, consequently, allow the slat

universal joint and steady bearing

assemblies to become worn; this

situation could result in failure of the

shaft of the slat transmission system,

and subsequent uncommanded

movement of the associated slat.

DATES: Comments must be received by

June 17, 1996.

ADDRESSES: Submit comments in

triplicate to the Federal Aviation

Administration (FAA), Transport

Airplane Directorate, ANM–103,

Attention: Rules Docket No. 95–NM–

241–AD, 1601 Lind Avenue, SW.,

Renton, Washington 98055–4056.

Comments may be inspected at this

location between 9:00 a.m. and 3:00

p.m., Monday through Friday, except

Federal holidays.

The service information referenced in

the proposed rule may be obtained from

Airbus Industrie, 1 Rond Point Maurice

Bellonte, 31707 Blagnac Cedex, France.

This information may be examined at

the FAA, Transport Airplane

Directorate, 1601 Lind Avenue, SW.,

Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Charles Huber, Aerospace Engineer,

Standardization Branch, ANM–113,

FAA, Transport Airplane Directorate,