26422 Federal Register / Vol. 63, No. 92 /Wednesday, May 13, 1998 /Rules and Regulations

the status of a medical emergency

affecting a leave recipient to ensure that

the leave recipient continues to be

affected by the medical emergency. We

encourage agencies to verify the status

of a medical emergency before granting

approval to a leave recipient to use any

and all donated annual leave for the

purpose of establishing initial

retirement eligibility and/or qualifying

for continuance of health benefits.

Final Regulations

After consideration of all comments,

the interim regulations published at 62

FR 10681 are published as final

regulations without further revision.

Regulatory Flexibility Act

I certify that this regulation will not

have a significant economic impact on

a substantial number of small entities

because it only affects Federal

employees.

List of Subjects in Parts 351 and 630

Administrative practice and

procedure, Government employees.

U.S. Office of Personnel Management.

Janice R. Lachance,

Director.

Accordingly, the interim rule

published March 10, 1997 (62 FR 10681)

is adopted as final without change.

[FR Doc. 98–12632 Filed 5–12–98; 8:45 am]

BILLING CODE 6325–01–P

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 21 and 27

[Docket No. SW003; Special Conditions No.

27–003–SC]

Special Conditions: Eurocopter Model

AS–355 E, F, F1, F2, N ‘‘Ecureuil II/

Twinstar’’ Helicopters, Electronic

Flight Instruments

AGENCY: Federal Aviation

Administration (FAA), DOT.

ACTION: Final special condition; request

for comments.

SUMMARY: This special condition is

issued for the Eurocopter Model AS–355

E, F, F1, F2, N ‘‘Ecureuil II/Twinstar’’

helicopters. These helicopters will have

a novel or unusual design feature

associated with the Electronic Flight

Instruments. 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 highintensity 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 April 30, 1998. Comments

must be received on or before July 13,

1998.

ADDRESSES: Comments on this special

condition may be mailed in duplicate

to: Federal Aviation Administration,

Office of the Regional Counsel,

Attention: Rules Docket No. SW003,

Fort Worth, Texas 76193–0007 or

deliver in duplicate to the Office of the

Regional Counsel at 2601 Meacham

Blvd., Fort Worth, Texas 76137.

Comments must be marked: Rules

Docket No. SW003. Comments may be

inspected in the Rules Docket

weekdays, except Federal holidays,

between 8:30 a.m. and 4:00 p.m.

FOR FURTHER INFORMATION CONTACT:

Robert McCallister, FAA, Rotorcraft

Directorate, Regulations Group, Fort

Worth, Texas 76193–0111; telephone

817–222–5121, 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 by the Administrator. 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, 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. 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.

SW003.’’ The postcard will be date

stamped and returned to the

commenter.

Background

On February 25, 1998, American

Eurocopter announced their intent to

amend, under their Designated

Airworthiness Authority (DAS), the

Supplemental Type Certificate (STC)

SH7714AW–D to add electronic flight

instruments, including an Attitude

Display Instrument. This amendment

and the original STC are effective for the

Models AS–355 E, F, F1, F2, N

‘‘Ecureuil II/Twinstar’’ helicopters.

These are normal category fivepassenger helicopters powered by two

Allison 250–C20 engines for the Model

AS–355 E, F, F1, F2 helicopters and by

two Turbomeca Arrius 1A engines for

the Model AS–355 N helicopters.

Type Certification Basis

Under the provisions of 14 CFR

21.101, Eurocopter must show that the

Model AS–355 E, F, F1, F2, N ‘‘Ecureuil

II/Twinstar’’ helicopters meet the

applicable provisions of the regulations

incorporated by reference in Type

Certificate Data Sheet (TCDS) No.

H11EU or the applicable regulations in

effect on the date of notification of

intent to change the Models AS–355 E,

F, F1, F2, N. The regulations

incorporated by reference in the type

certificate are commonly referred to as

the ‘‘original type certification basis.’’

The regulations incorporated by

reference in H11EU are as follows:

§ 21.29 and, for Models AS–355 E, F, F1,

F2, 14 CFR part 27, effective February

1, 1965 plus Amendments 27–1 through

27–16; for Model AS–355 N, part 27,

effective February 1, 1965, plus

Amendments 27–1 through 27–20, and

the following sections of Amendment

27–1: 27.21, 27.45, 27.71, 27.79, 27.143,

27.151, 27.161, 27.173, 27.175, 27.177,

27.672, 27.673, 27.729, 27.735, 27.779,

27.807, 27.1329, 27.1413, 27.1519,

27.1525, 27.1555, 27.1585, and 27.1587.

In addition, the certification basis

includes certain other special

conditions.

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.
Federal Register / Vol. 63, No. 92 /Wednesday, May 13, 1998 /Rules and Regulations 26423

In addition to the applicable

airworthiness regulations and special

conditions, the Models AS–355 E, F, F1,

F2, N must comply with the noise

certification requirements of 14 CFR

part 36; and the FAA must issue a

finding of regulatory adequacy pursuant

to section 611 of Public Law 92–574, the

‘‘Noise Control Act of 1972.’’

Special conditions, as appropriate, are

issued in accordance with § 11.49, as

required by §§ 11.28 and 11.29(b), and

become part of the type certification

basis in accordance with § 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).

Novel or Unusual Design Features

The Eurocopter Model AS–355 E, F,

F1, F2, N ‘‘Ecureuil II/Twinstar’’

helicopters will incorporate the

following novel or unusual design

features: Electrical, electronic, or

combination of electrical electronic

(electrical/electronic) systems, such as

electronic flight instruments, that will

be providing displays critical to the

continued safe flight and landing of the

helicopter. Electronic flight instruments

provide information critical for

operation in instrument meteorological

conditions.

Discussion

The Eurocopter Model AS–355 E, F,

F1, F2, N ‘‘Ecureuil II/Twinstar’’

helicopters, at the time of application,

were identified as having modifications

that incorporate one and possibly more

electrical/electronic systems, such as

electronic flight instruments. After the

design is finalized, Eurocopter will

provide the FAA with a preliminary

hazard analysis that will identify any

other critical functions, required for safe

flight and landing, 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 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 § 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

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 Visual

Flight Rules (VFR) operations and a

different environment for Instrument

Flight Rules (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 provides 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

systems that perform critical control

functions, or provide critical displays,

as installed in the aircraft, 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

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
26424 Federal Register / Vol. 63, No. 92 /Wednesday, May 13, 1998 /Rules and Regulations

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

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, 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, FIELD

STRENGTH VOLTS/METER

Frequency Peak Average

10–100 KHz ............... 150 150

100–500 .................... 200 200

500–2000 .................. 200 200

2–30 MHz .................. 200 200

30–100 ...................... 200 200

100–200 .................... 200 200

200–400 .................... 200 200

400–700 .................... 730 200

700–1000 .................. 1400 240

1–2 GHz .................... 5000 250

2–4 ............................ 6000 490

4–6 ............................ 7200 400

6–8 ............................ 1100 170

8–12 .......................... 5000 330

12–18 ........................ 2000 330

18–40 ........................ 1000 420

TABLE 2.—IFR ROTORCRAFT FIELD

STRENGTH VOLTS/METER

Frequency Peak Average

10–100 KHz ............... 50 50

100–500 .................... 50 50

500–2000 .................. 50 50

2–30 MHz .................. 100 100

30–70 ........................ 50 50

70–100 ...................... 50 50

100–200 .................... 100 100

200–400 .................... 100 100

400–700 .................... 700 50

700–1000 .................. 700 100

1–2 GHz .................... 2000 200

2–4 ............................ 3000 200

4–6 ............................ 3000 200

6–8 ............................ 1000 200

8–12 .......................... 3000 300

12–18 ........................ 2000 200

18–40 ........................ 600 200

Applicability

As previously discussed, this special

condition is applicable to the Model

AS–355 E, F, F1, F2, N helicopters.

Should American Eurocopter 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 § 21.101(a)(1).

Conclusion

This action affects only certain novel

or unusual design features on one model

series 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

helicopter.

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 helicopter,

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 Parts 21 and

27

Aircraft, Air transportation, Aviation

safety, Rotorcraft, Safety.

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 Eurocopter Models

AS 355 E, F, F1, F2, N ‘‘Ecureuil II/

Twinstar’’ 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 April 30,

1998.

Eric Bries,

Acting Manager, Rotorcraft Directorate

Aircraft Certification Service, ASW–100.

[FR Doc. 98–12710 Filed 5–12–98; 8:45 am]

BILLING CODE 4910–13–U