Federal Register / Vol. 62, No. 44 / Thursday, March 6, 1997 / Proposed Rules 10233

elevator trim tab actuators with actuators that

have P/N 159SCC100–11, in accordance with

Gulfstream Aircraft Service Change No.191,

dated August 18, 1972. This installation

constitutes terminating action for the

inspections required by this AD.

(e)(1) 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, Atlanta

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, Atlanta ACO.

(2) Alternative methods of compliance,

approved previously in accordance with AD

72–24–02, amendment 39–1559, are

approved as alternative methods of

compliance with this AD.

Note 2: Information concerning the

existence of approved alternative methods of

compliance with this AD, if any, may be

obtained from the Atlanta ACO.

(f) 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 February

27, 1997.

Darrell M. Pederson,

Acting Manager, Transport Airplane

Directorate, Aircraft Certification Service.

[FR Doc. 97–5460 Filed 3–5–97; 8:45 am]

BILLING CODE 4910–13–U

14 CFR Part 39

[Docket No. 96–CE–25–AD]

RIN 2120–AA64

Airworthiness Directives; Pilatus

Britten-Norman Ltd. (formerly BrittenNorman) BN–2A, BN–2B, and BN–2T

Series Airplanes

AGENCY: Federal Aviation

Administration, DOT.

ACTION: Notice of proposed rulemaking

(NPRM).

SUMMARY: This document proposes to

adopt a new airworthiness directive that

would apply to Pilatus Britten-Norman

Ltd. (Pilatus Britten-Norman) BN–2A,

BN–2B, and BN–2T series airplanes.

The proposed AD would require

repetitively inspecting the junction of

the torque link lug and upper case of the

main landing gear (MLG) torque link

assemblies for cracks, and replacing any

MLG torque link assembly with a

Modification A39 MLG torque link

assembly, either immediately when

cracks are found or after a certain period

of time if cracks are not found.

Replacing all MLG torque link

assemblies with Modification A39 MLG

torque link assemblies would eliminate

the need for the repetitive inspections.

These proposed repetitive inspections

are currently required by AD 86–07–02

for the BN–2A, BN–2B, and BN–2T

series airplanes, as well as the BN2A

MK. 111 series airplanes. There are no

improved design parts for the BN2A

MK. 111 series airplanes. The Federal

Aviation Administration (FAA) is

issuing in a separate action a proposed

revision to AD 86–07–02 to retain the

repetitive inspection and replacement

(if cracked) requirements for the BN2A

MK. 111 series airplanes. The actions

specified in the proposed AD are

intended to prevent failure of the main

landing gear caused by cracks in the

torque link area, which could lead to

loss of control of the airplane during

landing operations.

DATES: Comments must be received on

or before May 12, 1997.

ADDRESSES: Submit comments on the

proposal in triplicate to the FAA,

Central Region, Office of the Assistant

Chief Counsel, Attention: Rules Docket

No. 96–CE–25–AD, Room 1558, 601 E.

12th Street, Kansas City, Missouri

64106. Comments may be inspected at

this location between 8 a.m. and 4 p.m.,

Monday through Friday, holidays

excepted.

Service information that applies to the

proposed AD may be obtained from

Pilatus Britten-Norman Limited,

Bembridge, Isle of Wight, United

Kingdom PO35 5PR; telephone 44–1983

872511; facsimile 44–1983 873246. This

information also may be examined at

the Rules Docket at the address above.

FOR FURTHER INFORMATION CONTACT: Mr.

Tom Rodriguez, Program Officer,

Brussels Aircraft Certification Division,

FAA, Europe, Africa, and Middle East

Office, c/o American Embassy, B–1000

Brussels, Belgium; telephone (32 2)

508.2717; facsimile (32 2) 230.6899; or

Mr. S.M. Nagarajan, Project Officer,

Small Airplane Directorate, Airplane

Certification Service, FAA, 1201

Walnut, Suite 900, Kansas City,

Missouri 64106; telephone (816) 426–

6932; facsimile (816) 426–2169.

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

should 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 that

summarizes 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 No. 96–CE–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, Central Region, Office of the

Assistant Chief Counsel, Attention:

Rules Docket No. 96–CE–25–AD, Room

1558, 601 E. 12th Street, Kansas City,

Missouri 64106.

Discussion

The FAA has determined that reliance

on critical repetitive inspections on

aging commuter-class airplanes carries

an unnecessary safety risk when a

design change exists that could

eliminate or, in certain instances,

reduce the number of those critical

inspections. In determining what

inspections are critical, the FAA

considers (1) the safety consequences if

the known problem is not detected

during the inspection; (2) the

probability of the problem not being

detected during the inspection; (3)

whether the inspection area is difficult

to access; and (4) the possibility of

damage to an adjacent structure as a

result of the problem.

These factors have led the FAA to

establish an aging commuter-class

aircraft policy that requires

incorporating a known design change

when it could replace a critical

repetitive inspection. With this policy

in mind, the FAA conducted a review

of existing AD’s that apply to Pilatus

Britten-Norman BN–2A, BN–2B, BN–2T,

and BN2A MK. 111 series airplanes.

Assisting the FAA in this review were

(1) Pilatus Britten-Norman; (2) the

Regional Airlines Association (RAA); (3)

the Civil Aviation Authority of the
10234 Federal Register / Vol. 62, No. 44 / Thursday, March 6, 1997 / Proposed Rules

United Kingdom; and (4) several

operators of the affected airplanes.

From this review, the FAA has

identified AD 86–07–02, Amendment

39–5382, as one which falls under the

FAA’s aging aircraft policy. AD 86–07–

02 currently requires repetitively

inspecting the junction of the torque

link lug and upper case of the main

landing gear (MLG) torque link

assemblies for cracks on Pilatus BrittenNorman BN–2A, BN–2B, BN–2T, and

BN2A MK. 111 series airplanes, and

replacing any cracked part.

Pilatus Britten-Norman has developed

a modification that, when incorporated,

would eliminate the need for the

repetitive inspection requirement of AD

86–07–02 for the Pilatus Britten-Norman

BN–2A, BN–2B, and BN–2T series

airplanes. The requirements of AD 86–

07–02 should still apply for the Pilatus

Britten-Norman BN2A MK. 111 series

airplanes.

Applicable Service Information

Fairey Hydraulics Limited has issued

Service Bulletin (SB) 32–4, Issue 4,

dated January 30, 1990, which applies

to the Pilatus Britten-Norman BN–2A,

BN–2B, and BN–2T series airplanes.

This SB includes procedures for

inspecting the junction of the torque

link lug and upper case of the MLG

torque link assemblies, and installing

new Modification A39 MLG torque link

assemblies. Pilatus Britten-Norman SB

BN–2/SB.170, Issue 4, dated November

16, 1990, references Fairey Hydraulic

Limited SB32–4, Issue 4, dated January

30, 1990.

The FAA’s Determination

The FAA has examined all available

information related to this subject

matter and has determined that:

• AD action should be taken for the

Pilatus Britten-Norman BN–2A, BN–2B,

and BN–2T series airplanes to require

the installation of Modification A39

MLG torque link assemblies. The

repetitive inspections of the junction of

the torque link lug and upper case of the

MLG torque link assemblies would still

be required until the improved parts are

installed; and

• AD 86–07–02 should be revised to

remove the BN–2A BN–2B, and BN–2T

series airplanes from the applicability of

that AD, but retain the actions for the

BN2A MK. 111 series airplanes (this is

being proposed in a separate action).

Explanation of the Provisions of the

Proposed AD

Since an unsafe condition has been

identified that is likely to exist or

develop in other Pilatus Britten-Norman

BN–2A, BN–2B, and BN–2T series

airplanes of the same type design, the

proposed AD would require repetitively

inspecting the junction of the torque

link lug and upper case of the MLG

torque link assemblies for cracks, and

replacing any MLG torque link assembly

with a Modification A39 MLG torque

link assembly, either immediately when

cracks are found or at a certain period

of time if cracks are not found.

Installation of the improved part would

eliminate the need for the repetitive

inspections. Accomplishment of the

proposed inspections and installation

would be in accordance with Fairey

Hydraulics Limited SB 32–4, Issue 4,

dated January 30, 1990.

Cost Impact

The FAA estimates that 112 airplanes

in the U.S. registry would be affected by

the proposed AD, that it would take

approximately 13 workhours per

airplane to accomplish the proposed

action (1 workhour per inspection and

12 workhours for the installation), and

that the average labor rate is

approximately $60 an hour. Parts cost

approximately $6,200 per airplane.

Based on these figures, the total cost

impact of the proposed AD on U.S.

operators is estimated to be $781,760 or

$6,980 per airplane.

The proposed inspections are

currently required on the 112 affected

airplanes by AD 86–07–02. The

proposed AD would not require any

additional inspection requirements over

that already required by AD 86–07–02.

In addition, the cost figures referenced

above are based on the presumption that

no affected airplane operator has

incorporated the proposed inspectionterminating installation. Pilatus BrittenNorman does not know the number of

parts distributed to the affected airplane

owners/operators. Numerous sets of

parts were sent out to the owners/

operators of the affected airplanes, but

over the years Pilatus Britten-Norman

has not retained these records.

The FAA’s Aging Commuter Aircraft

Policy

The intent of the FAA’s aging

commuter airplane program is to ensure

safe operation of commuter-class

airplanes that are in commercial service

without adversely impacting private

operators. Of the approximately 112

airplanes in the U.S. registry that would

be affected by the proposed AD, the

FAA has determined that approximately

25 percent are operated in scheduled

passenger service by 11 different

operators. A significant number of the

remaining 75 percent are operated in

other forms of air transportation such as

air cargo and air taxi.

The proposed action would allow at

least 1,000 hours TIS after the effective

date of the AD before mandatory

accomplishment of the design

modification (upon the accumulation of

5,000 hours TIS or within the next 1,000

hours TIS after the effective date of the

AD, whichever is later). The average

utilization of the fleet for those

airplanes in commercial commuter

service is approximately 25 to 50 hours

TIS per week. Based on these figures,

operators of commuter airplanes

involved in commercial operation

would have to accomplish the proposed

modification within 5 to 10 calendar

months (at the least) after the proposed

AD would become effective. For private

owners, who typically operate between

100 to 200 hours TIS per year, this

would allow 5 to 10 years (at the least)

before the proposed modification would

be mandatory. The time it would take

those in air cargo/air taxi operations

before the proposed action would be

mandatory is unknown because of the

wide variation between each airplane

used in this service. The exact numbers

would fall somewhere between the

average for commuter operators and

private operators.

Regulatory Flexibility Determination

and Analysis

The Regulatory Flexibility Act of 1980

(RFA) was enacted by Congress to

ensure that small entities are not

unnecessarily or disproportionally

burdened by government regulations.

The RFA requires government agencies

to determine whether rules would have

a ‘‘significant economic impact on a

substantial number of small entities,’’

and, in cases where they would,

conduct a Regulatory Flexibility

Analysis in which alternatives to the

rule are considered. FAA Order

2100.14A, Regulatory Flexibility Criteria

and Guidance, outlines FAA procedures

and criteria for complying with the

RFA. Small entities are defined as small

businesses and small not-for-profit

organizations that are independently

owned and operated or airports

operated by small governmental

jurisdictions. A ‘‘substantial number’’ is

defined as a number that is not less than

11 and that is more than one-third of the

small entities subject to a proposed rule,

or any number of small entities judged

to be substantial by the rulemaking

official. A ‘‘significant economic

impact’’ is defined by an annualized net

compliance cost, adjusted for inflation,

which is greater than a threshold cost

level for defined entity types.

The entities that would be affected by

this AD are mostly in the portion of

Standard Industrial Classification (SIC)
Federal Register / Vol. 62, No. 44 / Thursday, March 6, 1997 / Proposed Rules 10235

4512, Operators of Aircraft for Hire,

classified as ‘‘unscheduled.’’ FAA Order

2100.14A sets the size threshold for

small entities operating aircraft in this

category at nine or fewer aircraft owned

and the annualized cost thresholds of at

least $4,975 (1996 dollars) for

unscheduled operators. A four-year life

for the torque link assembly and capital

cost of 15-percent would establish an

annualized cost of $2,445 (1996 dollars).

This is less than 50-percent of the

threshold cost of $4,975 per year. In

order to incur costs of at least $4,975,

an entity would have to operate three or

more of the airplanes referenced in the

proposed AD. FAA data shows that only

five small entities operate three or more

of these airplanes. In addition, this data

shows that approximately 60 entities

operate the airplanes referenced in the

proposed AD, but that only 15 of these

entities (one-fourth) operate two or more

of these airplanes.

Based on this information, less than

one-third of the entities would incur

significant operating costs under FAA

Order 2100.14A. Therefore, the

proposed AD would not significantly

affect a number of small entities.

A copy of the full Cost Analysis and

Regulatory Flexibility Determination for

the proposed action may be examined at

the FAA, Central Region, Office of the

Assistant Chief Counsel, Attention:

Rules Docket No. 96–CE–25–AD, Room

1558, 601 E. 12th Street, Kansas City,

Missouri.

Regulatory Impact

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 action (1) is not a

‘‘significant regulatory action’’ under

Executive Order 12866; (2) is not a

‘‘significant rule’’ under 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 has been placed 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 USC 106(g), 40113, 44701.

§ 39.13 [Amended]

2. Section 39.13 is amended by

adding a new airworthiness directive

(AD) to read as follows:

Pilatus Britten-Norman: Docket No. 96–CE–

25–AD.

Applicability: Models BN–2, BN–2A, BN–

2A–3, BN–2A–6, BN–2A–8, BN–2A–2, BN–

2A–9, BN–2A–20, BN–2A–21, BN–2A–26,

BN–2A–27, BN–2B–20, BN–2B–21, BN–2B–

26, BN–2B–27, and BN–2T airplanes (all

serial numbers), 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 request approval for an

alternative method of compliance in

accordance with paragraph (f) of this AD. The

request should include an assessment of the

effect of the modification, alteration, or repair

on the unsafe condition addressed by this

AD; and, if the unsafe condition has not been

eliminated, the request should include

specific proposed actions to address it.

Compliance: Required as indicated after

the effective date of this AD, unless already

accomplished.

To prevent failure of the main landing gear

caused by cracks in the torque link assembly

area, which could lead to loss of control of

the airplane during landing operations,

accomplish the following:

(a) Prior to further flight after the effective

date of this AD or within the next 100 hours

time-in-service (TIS) after the last inspection

required by AD 86–07–02, whichever occurs

later, and thereafter at intervals not to exceed

100 hours TIS until the installations required

by paragraph (c) of this AD are accomplished,

inspect the junction of the torque link lug

and upper case of all main landing gear

(MLG) torque link assemblies for cracks

(using a 10-power magnifying glass or by dye

penetrant methods). Accomplish these

inspections in accordance with the

ACCOMPLISHMENT INSTRUCTIONS

section of Fairey Hydraulics Limited Service

Bulletin (SB) 32–4, Issue 4, dated January 30,

1990. Pilatus Britten-Norman SB BN–2/

SB.170, Issue 4, November 16, 1990,

references this service bulletin.

Note 2: These inspections were initially a

part of AD 86–07–02, which applied to the

BN2A MK. 111 series airplanes as well as the

airplanes affected by this AD. The ‘‘prior to

further flight after the effective date of this

AD’’ compliance time was the original initial

compliance time of AD 86–07–02, and is

being retained to provide credit and

continuity for already-accomplished and

future inspections.

(b) If any cracks are found during any of

the inspections required by this AD, prior to

further flight, replace the MLG torque link

assembly with a Modification A39 MLG

torque link assembly in accordance with the

ACCOMPLISHMENT INSTRUCTIONS

section of Fairey Hydraulics Limited SB No.

32–4, Issue 4, dated January 30, 1990.

(1) Repetitive inspections are no longer

required when all MLG torque assemblies are

replaced with Modification A39 MLG torque

link assemblies.

(2) Repetitive inspections may no longer be

required on one MLG torque assembly, but

still be required on another if all haven’t been

replaced with a Modification A39 MLG

torque link assembly.

(c) Upon the accumulation of 5,000 hours

TIS or within the next 1,000 hours TIS after

the effective date of this AD, whichever

occurs later, unless already accomplished as

specified in paragraph (b) of this AD, replace

each MLG torque link assembly with a

Modification A39 MLG torque link assembly

in accordance with of the

ACCOMPLISHMENT INSTRUCTIONS

section of Fairey Hydraulics Limited SB No.

32–4, Issue 4, dated January 30, 1990.

(d) The intervals between the repetitive

inspections required by this AD may be

adjusted up to 10 percent of the specified

interval to allow accomplishing these actions

along with other scheduled maintenance on

the airplane.

(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 inspection requirements

of this AD can be accomplished.

(f) An alternative method of compliance or

adjustment of the initial or repetitive

compliance times that provides an equivalent

level of safety may be approved by the

Manager, Brussels Aircraft Certification

Division, Europe, Africa, Middle East office,

FAA, c/o American Embassy, 1000 Brussels,

Belgium. The request should be forwarded

through an appropriate FAA Maintenance

Inspector, who may add comments and then

send it to the Manager, Brussels Aircraft

Certification Division.

Note 3: Information concerning the

existence of approved alternative methods of

compliance with this AD, if any, may be

obtained from the Brussels Aircraft

Certification Division.

(g) All persons affected by this directive

may obtain copies of the documents referred

to herein upon request to Fairey Hydraulics
10236 Federal Register / Vol. 62, No. 44 / Thursday, March 6, 1997 / Proposed Rules

Limited, Claverham, Bristol, England; or

Pilatus Britten-Norman Limited, Bembridge,

Isle of Wight, United Kingdom PO35 5PR, as

applicable; or may examine these documents

at the FAA, Central Region, Office of the

Assistant Chief Counsel, Room 1558, 601 E.

12th Street, Kansas City, Missouri 64106.

Issued in Kansas City, Missouri, on

February 24, 1997.

Michael Gallagher,

Manager, Small Airplane Directorate, Aircraft

Certification Service.

[FR Doc. 97–5471 Filed 3–5–97; 8:45 am]

BILLING CODE 4910–13–U

14 CFR Part 39

[Docket No. 96–CE–23–AD]

RIN 2120–AA64

Airworthiness Directives; Aviat

Aircraft, Inc. Models S–1S, S–1T, S–2,

S–2A, S–2S, and S–2B Airplanes

(formerly known as Pitts Models S–1S,

S–1T, S–2, S–2A, S–2S, and S–2B

Airplanes)

AGENCY: Federal Aviation

Administration, DOT.

ACTION: Notice of proposed rulemaking

(NPRM).

SUMMARY: This document proposes to

revise AD 96–12–03, which applies to

Aviat Aircraft, Inc. (Aviat) Models S–1S,

S–1T, S–2, S–2A, S–2S, and S–2B

airplanes that are equipped with aft

lower fuselage wing attach fittings

incorporating either part number (P/N)

76090, 2–2107–1, or 1–210–102. That

AD currently requires repetitively

inspecting the aft lower fuselage wing

attach fitting on both wings for cracks,

and modifying any cracked aft lower

fuselage wing attach fitting. Modifying

both aft lower fuselage wing attach

fittings eliminates the repetitive

inspection requirement of AD 96–12–03.

Aviat recently started incorporating

modified aft lower fuselage wing attach

fittings on newly manufactured

airplanes. The proposed AD would

retain the requirements of AD 96–12–03,

but would exempt airplanes that had the

modified aft lower fuselage wing attach

fittings incorporated at manufacture.

The actions specified by the proposed

AD are intended to prevent possible inflight separation of the wing from the

airplane caused by a cracked fuselage

wing attach fitting.

DATES: Comments must be received on

or before June 4, 1997.

ADDRESSES: Submit comments in

triplicate to the Federal Aviation

Administration (FAA), Central Region,

Office of the Assistant Chief Counsel,

Attention: Rules Docket No. 96–CE–23–

AD, Room 1558, 601 E. 12th Street,

Kansas City, Missouri 64106. Comments

may be inspected at this location

between 8 a.m. and 4 p.m., Monday

through Friday, holidays excepted.

Service information that applies to the

proposed AD may be obtained from

Aviat Aircraft, Inc., P.O. Box 1240

(postal service delivery), 672 South

Washington Street (express mail), Afton,

Wyoming 83110. This information also

may be examined at the Rules Docket at

the address above.

FOR FURTHER INFORMATION CONTACT: Mr.

Roger Caldwell, Aerospace Engineer,

FAA, Denver Aircraft Certification

Office, 26805 E. 68th Avenue, Room

214, Denver, Colorado 80249; telephone

(303) 342–1086; facsimile (303) 342–

1088.

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

should 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 that

summarizes 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 No. 96–CE–23–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, Central Region, Office of the

Assistant Chief Counsel, Attention:

Rules Docket No. 96–CE–23–AD, Room

1558, 601 E. 12th Street, Kansas City,

Missouri 64106.

Events Leading to the Proposed AD

AD 96–12–03, Amendment 39–9645

(61 FR 28730, June 6, 1996), applies to

Aviat Models S–1S, S–1T, S–2, S–2A,

S–2S, and S–2B airplanes that are

equipped with aft lower fuselage wing

attach fittings incorporating either part

number (P/N) 76090, 2–2107–1, or 1–

210–102. The AD currently requires

repetitively inspecting the aft lower

fuselage wing attach fitting on both

wings for cracks, and modifying any

cracked aft lower fuselage wing attach

fitting. Modifying both aft lower

fuselage wing attach fittings eliminates

the repetitive inspection requirement of

AD 96–12–03. Accomplishment of the

actions required by AD 96–12–03 is in

accordance with Aviat Service Bulletin

(SB) No. 25, dated April 3, 1996.

Aviat recently started incorporating

modified aft lower fuselage wing attach

fittings on newly manufactured Models

S–1S, S–1T, S–2, S–2A, S–2S, and S–2B

airplanes. In addition, Aviat revised SB

No. 25 (Revised November 12, 1996) to

include this airplane serial number

effectivity change.

The FAA’s Determination

After examining the circumstances

and reviewing all available information

related to the incidents described above,

the FAA has determined that (1) those

airplanes with modified aft lower

fuselage wing attach fittings

incorporated at manufacture should be

exempt from AD 96–12–03; and (2) AD

action should be taken to prevent

possible in-flight separation of the wing

from the airplane caused by a cracked

fuselage wing attach fitting.

Explanation of the Provisions of the

Proposed AD

Since an unsafe condition has been

identified that is likely to exist or

develop in other Aviat Models S–1S, S–

1T, S–2, S–2A, S–2S, and S–2B

airplanes of the same type design that

are equipped with aft lower fuselage

wing attach fittings incorporating either

P/N 76090, 2–2107–1, or 1–210–102, the

FAA is proposing to revise AD 96–12–

03. The proposed AD would retain the

requirements of AD 96–12–03, but

would exempt airplanes that had the

modified aft lower fuselage wing attach

fittings incorporated at manufacture.

Accomplishment of the proposed AD

would be in accordance with Aviat SB

No. 25, dated April 3, 1996, Revised

November 12, 1996.

Cost Impact

The FAA estimates that 500 airplanes

in the U.S. registry would be affected by

the proposed AD, that it would take

approximately 2 workhours per airplane