This section of the FEDERAL REGISTER

contains notices to the public of the proposed

issuance of rules and regulations. The

purpose of these notices is to give interested

persons an opportunity to participate in the

rule making prior to the adoption of the final

rules.

Proposed Rules Federal Register

26003

Vol. 60, No. 94

Tuesday, May 16, 1995

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95–NM–25–AD]

Airworthiness Directives; Learjet

Model 35, 35A, 36, 36A, 55, 55B, and

55C 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 Learjet Model 35, 35A, 36, 36A,

55, 55B, and 55C airplanes. This

proposal would require installation of a

placard on the instrument panel in the

cockpit to advise the flightcrew that the

Omega navigation system may be

inoperative at certain engine speeds.

This proposal is prompted by reports of

loss of certain navigation signals during

extended over water operation. The

actions specified by the proposed AD

are intended to prevent excessive

deviation from the intended flight path

due to loss of navigation signals, which

could result in a potentially low-fuel

condition or a traffic conflict.

DATES: Comments must be received by

June 26, 1995.

ADDRESSES: Submit comments in

triplicate to the Federal Aviation

Administration (FAA), Transport

Airplane Directorate, ANM–103,

Attention: Rules Docket No. 95–NM–

25–AD, 1601 Lind Avenue, SW.,

Renton, Washington 98055–4056.

Comments may be inspected at this

location between 9 a.m. and 3 p.m.,

Monday through Friday, except Federal

holidays.

The service information referenced in

the proposed rule may be obtained from

Gates Learjet, Mid-Continent Airport,

P.O. Box 7707, Wichita, Kansas 67277.

This information may be examined at

the FAA, Transport Airplane

Directorate, 1601 Lind Avenue, SW.,

Renton, Washington.

FOR FURTHER INFORMATION CONTACT: C.

Dale Bleakney, Aerospace Engineer,

ACE–130W, Systems and Equipment

Branch, FAA, Wichita Aircraft

Certification Office, Small Airplane

Directorate, 1801 Airport Road, Room

100, Mid-Continent Airport, Wichita,

Kansas 67209; telephone (316) 946–

4135; fax (316) 946–4407.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to

participate in the making of the

proposed rule by submitting such

written data, views, or arguments as

they may desire. Communications shall

identify the Rules Docket number and

be submitted in triplicate to the address

specified above. All communications

received on or before the closing date

for comments, specified above, will be

considered before taking action on the

proposed rule. The proposals contained

in this notice may be changed in light

of the comments received.

Comments are specifically invited on

the overall regulatory, economic,

environmental, and energy aspects of

the proposed rule. All comments

submitted will be available, both before

and after the closing date for comments,

in the Rules Docket for examination by

interested persons. A report

summarizing each FAA-public contact

concerned with the substance of this

proposal will be filed in the Rules

Docket.

Commenters wishing the FAA to

acknowledge receipt of their comments

submitted in response to this notice

must submit a self-addressed, stamped

postcard on which the following

statement is made: ‘‘Comments to

Docket Number 95–NM–25–AD.’’ The

postcard will be date stamped and

returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this

NPRM by submitting a request to the

FAA, Transport Airplane Directorate,

ANM–103, Attention: Rules Docket No.

95–NM–25–AD, 1601 Lind Avenue,

SW., Renton, Washington 98055–4056.

Discussion

The FAA has received reports of loss

of the Omega navigation signal from

certain global navigation systems (GNS)

manufactured by Flight Management

Systems and installed on various Learjet

airplane models. These systems, GNS–

500, GNS–1000, and GNS–X, have been

shown to be susceptible to generator

noise at approximately 92.5% N2. This

generator noise has the potential to

render the Omega navigation signal

inoperative. GNS–500, GNS–1000, and

GNS–X systems all rely on a single

Omega frequency of 13.6 KHz. This is

the same frequency as the noise created

by the Bendix generator used on Model

35, 36, and 55 airplanes when operated

near 92.5% N2. If alternate suitable

navigation signals such as VOR, VOR/

DME, GPS, and VLF, are deselected and

the GNS–500, –1000, or –X system is

used exclusively, the aircraft may enter

a ‘‘dead reckoning’’ mode until a

suitable navigation signal is obtained.

Use of the GNS–500, –1000, or –X

navigation system exclusively during

extended overwater operation with the

Omega signal rendered inoperative due

to generator noise, could result in

excessive deviation from the intended

flight path, and may lead to a potential

low-fuel condition or a traffic conflict.

Since an unsafe condition has been

identified that is likely to exist or

develop on other products of this same

type design, the proposed AD would

require installation of a placard on the

instrument panel in the cockpit to

advise the flightcrew that the Omega

navigation system may be inoperative

when engine speed reaches 92.5% N2.

Additionally, the FAA has reviewed

and approved Gates Learjet Airplane

Accessory Kit Model 55 AAK 55–85–2

(for Model 55 airplanes) dated January

14, 1986, as revised by Airplane

Accessory Kit Change Notice AAK No.

AAK55–85–2, Change 1 (undated). The

FAA has also reviewed and approved

Gates Learjet Airplane Accessory Kit

Model AAK 85–1, dated January 14,

1986 (for the Model 35 and 36

airplanes), as revised by Airplane

Accessory Kit Change Notice AAK–85–

1, Change 1 (undated).

These kits describe procedures for

installation of a generator band reject

filter on certain Model 35, 36, and 55

series airplanes. This noise filter will

prevent generator noise from reaching

the 13.6 KHz frequency.

This proposed AD also would provide

operators with the option of installing

the applicable modification as
26004 Federal Register / Vol. 60, No. 94 / Tuesday, May 16, 1995 / Proposed Rules

terminating action for the required

placard.

As a result of recent communications

with the Air Transport Association

(ATA) of America, the FAA has learned

that, in general, some operators may

misunderstand the legal effect of AD’s

on airplanes that are identified in the

applicability provision of the AD, but

that have been altered or repaired in the

area addressed by the AD. The FAA

points out that all airplanes identified in

the applicability provision of an AD are

legally subject to the AD. If an airplane

has been altered or repaired in the

affected area in such a way as to affect

compliance with the AD, the owner or

operator is required to obtain FAA

approval for an alternative method of

compliance with the AD, in accordance

with the paragraph of each AD that

provides for such approvals. A note has

been included in this notice to clarify

this long-standing requirement.

There are approximately 710 Learjet

Model 35, 35A, 36, 36A, 55, 55B, and

55C airplanes of the affected design in

the worldwide fleet. The FAA estimates

that 177 airplanes of U.S. registry would

be affected by this proposed AD, that it

would take approximately 1 work hour

per airplane to accomplish the proposed

actions, and that the average labor rate

is $60 per work hour. The cost of

required parts (local manufacture of a

placard) is negligible. Based on these

figures, the total cost impact of the

proposed AD on U.S. operators is

estimated to be $10,620, or $60 per

airplane.

Should an operator elect to

accomplish the optional terminating

action that would be provided by this

AD action, it would take approximately

14 work hours to accomplish it, at an

average labor rate of $60 per work hour.

The cost of required parts would be

approximately $3,050 per airplane.

Based on these figures, the total cost

impact of the optional terminating

action would be $3,890 per airplane.

The total cost impact figure discussed

above is based on assumptions that no

operator has yet accomplished any of

the proposed requirements of this AD

action, and that no operator would

accomplish those actions in the future if

this AD were not adopted.

The regulations proposed herein

would not have substantial direct effects

on the States, on the relationship

between the national government and

the States, or on the distribution of

power and responsibilities among the

various levels of government. Therefore,

in accordance with Executive Order

12612, it is determined that this

proposal would not have sufficient

federalism implications to warrant the

preparation of a Federalism Assessment.

For the reasons discussed above, I

certify that this proposed regulation (1)

Is not a ‘‘significant regulatory action’’

under Executive Order 12866; (2) is not

a ‘‘significant rule’’ under the DOT

Regulatory Policies and Procedures (44

FR 11034, February 26, 1979); and (3) if

promulgated, will not have a significant

economic impact, positive or negative,

on a substantial number of small entities

under the criteria of the Regulatory

Flexibility Act. A copy of the draft

regulatory evaluation prepared for this

action is contained in the Rules Docket.

A copy of it may be obtained by

contacting the Rules Docket at the

location provided under the caption

ADDRESSES.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation

safety, Safety.

The Proposed Amendment

Accordingly, pursuant to the

authority delegated to me by the

Administrator, the Federal Aviation

Administration proposes to amend part

39 of the Federal Aviation Regulations

(14 CFR part 39) as follows:

PART 39—AIRWORTHINESS

DIRECTIVES

1. The authority citation for part 39

continues to read as follows:

Authority: 49 U.S.C. App. 1354(a), 1421

and 1423; 49 U.S.C. 106(g); and 14 CFR

11.89.

§ 39.13 [Amended]

2. Section 39.13 is amended by

adding the following new airworthiness

directive:

Learjet: Docket 95–NM–25–AD.

Applicability: Model 35, 35A, 36, 36A, 55,

55B, and 55C airplanes; equipped with

Global Wulfsburg GNS 500, GNS–1000, and

GNS-X Flight Management Systems;

certificated in any category.

Note 1: This AD applies to each airplane

identified in the preceding applicability

provision, regardless of whether it has been

modified, altered, or repaired in the area

subject to the requirements of this AD. For

airplanes that have been modified, altered, or

repaired so that the performance of the

requirements of this AD is affected, the

owner/operator must use the authority

provided in paragraph (d) to request approval

from the FAA. This approval may address

either no action, if the current configuration

eliminates the unsafe condition; or different

actions necessary to address the unsafe

condition described in this AD. Such a

request should include an assessment of the

effect of the changed configuration on the

unsafe condition addressed by this AD. In no

case does the presence of any modification,

alteration, or repair remove any airplane from

the applicability of this AD.

Compliance: Required as indicated, unless

accomplished previously.

To prevent excessive deviation from the

intended flight path which, if the aircraft is

on an extended overwater operation, may

lead to a potential low-fuel condition or a

traffic conflict operation, accomplish the

following:

(a) Within 60 days after the effective date

of this AD, install a placard in a prominent

location on the instrument panel that states:

‘‘VLF/OMEGA MAY BE INOPERATIVE AT

92.5% N2’’

(b) For Model 35 airplanes, serial numbers

35–001 through 35–603 inclusive; and Model

36, serial numbers 36–001 through 36–053

inclusive: Installation of a GNS 500/1000

generator band reject filter in accordance

with Gates Learjet Airplane Accessory Kit

Model AAK 85–1, dated January 14, 1986, as

revised by Airplane Accessory Kit Change

Notice AAK–85–1, Change 1 (undated),

constitutes terminating action for the placard

requirement of paragraph (a) of this AD.

Following installation of the filter, the

placard required by paragraph (a) of this AD

may be removed.

(c) For Model 55 airplanes, serial numbers

55–003 through 55–124 inclusive:

Installation of a GNS 500/1000 generator

band reject filter in accordance with Gates

Learjet Airplane Accessory Kit Model 55

AAK 55–85–2, dated January 14, 1986, as

revised by Airplane Accessory Kit Change

Notice AAK No. AAK55–85–2, Change 1

(undated), constitutes terminating action for

the placard requirement of paragraph (a) of

this AD. Following installation of the filter,

the placard required by paragraph (a) of this

AD may be removed.

(d) An alternative method of compliance or

adjustment of the compliance time that

provides an acceptable level of safety may be

used if approved by the Manager, Wichita

Aircraft Certification Office (ACO), FAA,

Small Airplane Directorate. Operators shall

submit their requests through an appropriate

FAA Principal Maintenance Inspector, who

may add comments and then send it to the

Manager, Wichita ACO.

Note 2: Information concerning the

existence of approved alternative methods of

compliance with this AD, if any, may be

obtained from the Wichita ACO.

(e) Special flight permits may be issued in

accordance with sections 21.197 and 21.199

of the Federal Aviation Regulations (14 CFR

21.197 and 21.199) to operate the airplane to

a location where the requirements of this AD

can be accomplished.

Issued in Renton, Washington, on May 10,

1995.

Darrell M. Pederson,

Acting Manager, Transport Airplane

Directorate, Aircraft Certification Service.

[FR Doc. 95–11975 Filed 5–15–95; 8:45 am]

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