Federal Register / Vol. 63, No. 135 /Wednesday, July 15, 1998 / Proposed Rules 38123

action is necessary for products of this

type design that are certificated for

operation in the United States.

Explanation of Requirements of

Proposed Rule

Since an unsafe condition has been

identified that is likely to exist or

develop on other airplanes of the same

type design registered in the United

States, the proposed AD would require

accomplishment of the actions specified

in the service bulletin described

previously, except as discussed below.

Differences Between Proposed Rule and

Service Bulletin

Operators should note that, although

the service bulletin specifies that the

manufacturer may be contacted for

disposition of certain repair conditions,

this proposal would require the repair of

those conditions to be accomplished in

accordance with a method approved by

either the FAA or the Direction Ge ́ne ́rale

de l’Aviation Civile (or its delegated

agent).

Cost Impact

The FAA estimates that 9 airplanes of

U.S. registry would be affected by this

proposed AD, that it would take

approximately 6 work hours per

airplane to accomplish the proposed

actions, and that the average labor rate

is $60 per work hour. Required parts

would cost approximately $390 per

airplane. Based on these figures, the cost

impact of the proposed AD on U.S.

operators is estimated to be $6,750, or

$750 per airplane.

The 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.

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 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. 106(g), 40113, 44701.

§ 39.13 [Amended]

2. Section 39.13 is amended by

adding the following new airworthiness

directive:

Airbus Industrie: Docket 97–NM–159–AD.

Applicability: Model A320–111, –211,

and –231 series airplanes, on which

Airbus Modification 20903 has not been

installed; certificated in any category.

Note 1: This AD applies to each airplane

identified in the preceding applicability

provision, regardless of whether it has been

otherwise 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 (b) 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, unless

accomplished previously.

To prevent fatigue cracking of certain

fastener holes on the outer frames of the

fuselage, which could result in reduced

structural integrity of the airplane,

accomplish the following:

(a) Prior to the accumulation of 20,000 total

flight cycles, or within 4,000 flight cycles

after the effective date of this AD, whichever

occurs later, remove the existing fasteners

located at fuselage frame 35 between the leftand right-hand stringers 30 and 31, and

perform a rotating probe inspection to detect

fatigue cracking of the fastener holes, in

accordance with Airbus Service Bulletin

A320–53–1137, dated June 24, 1997.

(1) If no cracking is detected, prior to

further flight, modify the fastener holes and

install new, improved fasteners, in

accordance with the service bulletin.

(2) If any cracking is detected, prior to

further flight, repair in accordance with a

method approved by the Manager,

International Branch, ANM–116, FAA,

Transport Airplane Directorate; or the

Direction Ge ́ne ́rale de l’Aviation Civile (or its

delegated agent).

(b) 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,

International Branch, ANM–116. Operators

shall submit their requests through an

appropriate FAA Principal Maintenance

Inspector, who may add comments and then

send it to the Manager, International Branch,

ANM–116.

Note 2: Information concerning the

existence of approved alternative methods of

compliance with this AD, if any, may be

obtained from the International Branch,

ANM–116.

(c) 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.

Note 3: The subject of this AD is addressed

in French airworthiness directive 98–154–

113(B), dated April 8, 1998.

Issued in Renton, Washington, on July 8,

1998.

S.R. Miller,

Acting Manager, Transport Airplane

Directorate, Aircraft Certification Service.

[FR Doc. 98–18776 Filed 7–14–98; 8:45 am]

BILLING CODE 4910–13–P

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97–NM–227–AD]

RIN 2120–AA64

Airworthiness Directives; Boeing

Model 727–200 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 all

Boeing Model 727–200 series airplanes.

This proposal would require repetitive

inspections to detect cracks in certain

areas between the upper and lower sills

of the number 1 cargo door, and repair,
38124 Federal Register / Vol. 63, No. 135 /Wednesday, July 15, 1998 / Proposed Rules

if necessary. This proposal is prompted

by reports indicating that fatigue cracks

were found in certain structures

adjacent to the number 1 cargo door

cutout at the forward and aft doorway

frames. The actions specified by the

proposed AD are intended to detect and

correct such fatigue cracking, which

could result in rapid decompression of

the fuselage and consequent reduced

structural integrity of the airplane.

DATES: Comments must be received by

August 31, 1998.

ADDRESSES: Submit comments in

triplicate to the Federal Aviation

Administration (FAA), Transport

Airplane Directorate, ANM–114,

Attention: Rules Docket No.97–NM–

227–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

Boeing Commercial Airplane Group,

P.O. Box 3707, Seattle, Washington

98124–2207. This information may be

examined at the FAA, Transport

Airplane Directorate, 1601 Lind

Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT:

Walter Sippel, Aerospace Engineer,

Airframe Branch, ANM–120S, FAA,

Transport Airplane Directorate, Seattle

Aircraft Certification Office, 1601 Lind

Avenue, SW., Renton, Washington

98055–4056; telephone (425) 227–2774;

fax (425) 227–1181.

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 97–NM–227–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–114, Attention: Rules Docket No.

97–NM–227–AD, 1601 Lind Avenue,

SW., Renton, Washington 98055–4056.

Discussion

The FAA has received reports

indicating that cracks were found in the

structure adjacent to the number 1 cargo

door cutout at the doorway frames at

body station (BS) 560 and BS 620 on

Boeing Model 727–200 series airplanes.

In one of these incidents, the aft frame

web and frame inner chord of the

number 1 cargo door cutout, which was

previously repaired because of cracking,

was found completely severed. In

another incident, a crack was found in

the aft doorway structure of the number

1 cargo door during pressure cycling of

the fuselage of a Model 727–200 series

airplane. The frame web and the frame

inner and outer chords were severed

and cracks were found in the bear strap

and skin, which prevented

pressurization of the airplane. The

cracking has been attributed to fatigue,

caused by pressurization cycles of the

fuselage structure. Such fatigue

cracking, if not corrected, could result

in rapid decompression of the fuselage

and consequent reduced structural

integrity of the airplane.

Explanation of Relevant Service

Information

The FAA has reviewed and approved

Boeing Alert Service Bulletin 727–

53A0219, Revision 1, dated May 8,

1997, which describes the following

procedures:

• Performing repetitive close visual

inspections to detect cracks in the

forward and aft frames, bear strap, and

fuselage skin between the upper and

lower sills of the number 1 cargo door

at BS 560 and BS 620;

• Performing repetitive high

frequency eddy current inspections to

detect cracks in the forward and aft

frames, and bear strap between the

upper and lower sills of the number 1

cargo door at BS 560 and BS 620; and

• Repairing any cracked forward or

aft frame, bear strap, or fuselage skin.

Explanation of Requirements of

Proposed Rule

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 accomplishment of the actions

specified in the alert service bulletin

described previously, except as

discussed below.

Differences Between Proposed Rule and

Relevant Alert Service Bulletin

Operators should note that, although

the referenced alert service bulletin

specifies that the manufacturer may be

contacted for disposition of certain

conditions, this proposal would require

the repair of those conditions to be

accomplished in accordance with a

method approved by the FAA. Likewise,

operators also should note that,

although the alert service bulletin

defines the inspection intervals and

methods for inspecting repairs that have

been accomplished after contacting the

manufacturer for repair information,

this proposal would require the

inspection methods and intervals to be

accomplished in accordance with

methods and intervals approved by the

FAA.

Interim Action

This is considered to be interim

action until final action is identified, at

which time the FAA may consider

further rulemaking.

Other Relevant Rulemaking

The FAA has previously issued AD

98–11–03, amendment 39–10530 (63 FR

27455, May 19, 1998), which addresses,

in part, cracking of the number 1 cargo

door cutout structure on certain Model

727 series airplanes. That AD requires

that the FAA-approved maintenance or

inspection program be revised to

include inspections of Structural

Significant Items, and repair of cracked

structure. These actions are conducted

as part of the Supplemental Structural

Inspection Program. (Components of the

number 1 cargo door cutout structure

are identified as structural significant

items.) This proposed AD would not

affect the current requirements of AD

98–11–03.

Cost Impact

There are approximately 1,100

airplanes of the affected design in the

worldwide fleet. The FAA estimates that

770 airplanes of U.S. registry would be

affected by this proposed AD, that it

would take approximately 60 work
Federal Register / Vol. 63, No. 135 /Wednesday, July 15, 1998 / Proposed Rules 38125

hours per airplane to accomplish the

proposed inspections, and that the

average labor rate is $60 per work hour.

Based on these figures, the cost impact

of the inspections proposed by this AD

on U.S. operators is estimated to be

$2,772,000, or $3,600 per airplane, per

inspection cycle.

The 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.

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 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. 106(g), 40113, 44701.

§ 39.13 [Amended]

2. Section 39.13 is amended by

adding the following new airworthiness

directive:

Boeing: Docket 97–NM–227–AD.

Applicability: All Model 727–200 series

airplanes, 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 (d) 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, unless

accomplished previously.

To detect and correct fatigue cracking

between the upper and lower sills of the

number 1 cargo door, which could result in

rapid decompression of the fuselage and

consequent reduced structural integrity of the

airplane, accomplish the following:

(a) Perform a close visual inspection or a

high frequency eddy current (HFEC)

inspection (as applicable) to detect cracks in

the forward and aft frames (web, inner chord,

and outer chord), bear strap, and fuselage

skin between the upper and lower sills of the

number 1 cargo door at BS 560 and BS 620;

in accordance with Boeing Alert Service

Bulletin 727–53A0219, Revision 1, dated

May 8, 1997; at the time specified in

paragraph (a)(1), (a)(2), or (a)(3) of this AD,

as applicable.

(1) For airplanes on which the repair to the

forward or aft frame (web, inner chord, or

outer chord), bear strap, or fuselage skin

specified in the alert service bulletin has not

been accomplished: Inspect prior to the

accumulation of 30,000 total flight cycles, or

within 3,000 flight cycles after the effective

date of this AD, whichever occurs later.

(2) For airplanes on which the repair to the

forward or aft frame (web, inner chord, or

outer chord) specified in the alert service

bulletin has been accomplished: Inspect

within 3,000 flight cycles after the effective

date of this AD.

(3) For airplanes on which the repair to the

bear strap, fuselage skin, or a combination of

the frame web and chord (inner or outer) on

either the forward or aft frame specified in

the alert service bulletin has been

accomplished: Inspect within 3,000 flight

cycles after the effective date of this AD, in

accordance with a method approved by the

Manager, Seattle Aircraft Certification Office

(ACO), FAA, Transport Airplane Directorate.

Note 2: Where there are differences

between this AD and the referenced alert

service bulletin, the AD prevails.

Note 3: The inspections specified in

paragraph (a)(3) of this AD are not defined in

the alert service bulletin.

(b) If no crack is detected during any

inspection required by paragraph (a) of this

AD, accomplish paragraph (b)(1) or (b)(2) of

this AD, as applicable.

(1) For airplanes identified in paragraphs

(a)(1) and (a)(2) of this AD: Repeat the close

visual and HFEC inspection required by

paragraph (a) of this AD thereafter at the

times specified in paragraphs (b)(1)(i) and

(b)(1)(ii) of this AD.

(i) Repeat the close visual inspection of the

frame web at intervals not to exceed 3,000

flight cycles.

(ii) Repeat the close visual and HFEC

inspections (as applicable) of the frame web,

frame inner and outer chords, bear strap, and

fuselage skin thereafter at intervals not to

exceed 15,000 flight cycles.

(2) For airplanes identified in paragraph

(a)(3) of this AD: Repeat the inspections of

the repaired bear strap, fuselage skin, or

combination of a repaired frame web and

chord (inner or outer) thereafter at intervals

not to exceed those approved by the

Manager, Seattle ACO.

(c) If any crack is detected during any

inspection required by paragraph (a) of this

AD, prior to further flight, accomplish

paragraph (c)(1) or (c)(2) of this AD, as

applicable.

(1) For any crack detected in the frame

web, inner chord, or outer chord: Repair in

accordance with Boeing Alert Service

Bulletin 727–53A0219, Revision 1, dated

May 8, 1997. Prior to the accumulation of

3,000 flight cycles after accomplishment of

the repair, accomplish the close visual and

HFEC inspections specified in paragraph (a)

of this AD. Repeat the close visual inspection

of the frame web thereafter at intervals not

to exceed 3,000 flight cycles. Repeat the close

visual and HFEC inspections (as applicable)

of the frame web, inner chord, and outer

chord thereafter at intervals not to exceed

15,000 flight cycles.

(2) For any crack detected in the fuselage

skin, bear strap, or a combination of the

frame web and chord (inner or outer): Repair

and perform repetitive inspections in

accordance with both a method and

repetitive inspection interval approved by

the Manager, Seattle ACO.

Note 4: The repairs and inspections

specified in paragraph (c)(2) of this AD are

not defined in the alert service bulletin.

(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, Seattle

ACO. Operators shall submit their requests

through an appropriate FAA Principal

Maintenance Inspector, who may add

comments and then send it to the Manager,

Seattle ACO.

Note 5: Information concerning the

existence of approved alternative methods of

compliance with this AD, if any, may be

obtained from the Seattle 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.
38126 Federal Register / Vol. 63, No. 135 /Wednesday, July 15, 1998 / Proposed Rules

Issued in Renton, Washington, on July 8,

1998.

S. R. Miller,

Acting Manager, Transport Airplane

Directorate, Aircraft Certification Service.

[FR Doc. 98–18775 Filed 7–14–98; 8:45 am]

BILLING CODE 4910–13–P

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98–CE–67–AD]

RIN 2120–AA64

Airworthiness Directives; Slingsby

Sailplanes Ltd., Models Dart T.51, Dart

T.51/17, and Dart T.51/17R Sailplanes

AGENCY: Federal Aviation

Administration, DOT.

ACTION: Notice of proposed rulemaking

(NPRM).

SUMMARY: This document proposes to

adopt a new airworthiness directive

(AD) that would apply to all Slingsby

Sailplanes Ltd. (Slingsby) Models Dart

T.51, Dart T.51/17, and Dart T.51/17R

sailplanes that are equipped with

aluminum alloy spar booms. The

proposed AD would require repetitively

inspecting the aluminum alloy spar

booms and the wing attach fittings for

delamination or corrosion damage, and

repairing any delamination or corrosion

damage found. The proposed AD is the

result of mandatory continuing

airworthiness information (MCAI)

issued by the airworthiness authority for

the United Kingdom. The actions

specified by the proposed AD are

intended to prevent failure of the spar

assembly and adjoining structure caused

by delamination or corrosion damage to

the aluminum alloy spar booms or the

wing attach fittings, which could result

in reduced controllability or loss of

control of the sailplane.

DATES: Comments must be received on

or before August 14, 1998.

ADDRESSES: Submit comments in

triplicate to the Federal Aviation

Administration (FAA), Central Region,

Office of the Regional Counsel,

Attention: Rules Docket No. 98–CE–67–

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

Slingsby Aviation Ltd., Kirbymoorside,

York Y06 6EZ England; telephone:

+44(0)1751 432474; facsimile:

+44(0)1751 431173. This information

also may be examined at the Rules

Docket at the address above.

FOR FURTHER INFORMATION CONTACT: Mr.

Mike Kiesov, Aerospace Engineer, Small

Airplane Directorate, Aircraft

Certification Service, FAA, 1201

Walnut, suite 900, Kansas City, Missouri

64106; telephone: (816) 426–6934;

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. 98–CE–67–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

Regional Counsel, Attention: Rules

Docket No. 98–CE–67–AD, Room 1558,

601 E. 12th Street, Kansas City, Missouri

64106.

Discussion

The Civil Aviation Authority (CAA),

which is the airworthiness authority for

the United Kingdom, notified the FAA

that an unsafe condition may exist on

Slingsby Models Dart T.51, Dart T.51/

17, and Dart T.51/17R sailplanes that

are equipped with aluminum alloy spar

booms. The CAA reports an incident of

glue joint failure on a starboard wing

caused by water entering the area of the

airbrake box. Investigation of this

incident revealed delamination and

corrosion in the area of the aluminum

alloy spar booms and the wing attach

fittings.

These conditions, if not detected and

corrected, could result in failure of the

spar assembly and adjoining structure

with possible reduced controllability or

loss of control of the sailplane.

Relevant Service Information

Slingsby has issued Technical

Instruction (TI) No. 109/T51, Issue No.

2, dated October 7, 1997, which

specifies procedures for inspecting the

aluminum alloy spar booms and the

wing attach fittings for delamination or

corrosion damage.

The CAA classified this service

bulletin as mandatory and issued British

AD 005–09–97, dated October 3, 1997,

in order to assure the continued

airworthiness of these sailplanes in the

United Kingdom.

The FAA’s Determination

These sailplane models are

manufactured in the United Kingdom

and are type certificated for operation in

the United States under the provisions

of section 21.29 of the Federal Aviation

Regulations (14 CFR 21.29) and the

applicable bilateral airworthiness

agreement. Pursuant to this bilateral

airworthiness agreement, the CAA has

kept the FAA informed of the situation

described above.

The FAA has examined the findings

of the CAA; reviewed all available

information, including the service

information referenced above; and

determined that AD action is necessary

for products of this type design that are

certificated for operation in the United

States.

Explanation of the Provisions of the

Proposed AD

Since an unsafe condition has been

identified that is likely to exist or

develop in other Slingsby Models Dart

T.51, Dart T.51/17, and Dart T.51/17R

sailplanes equipped with aluminum

alloy spar booms of the same type

design registered in the United States,

the FAA is proposing AD action. The

proposed AD would require repetitively

inspecting the aluminum alloy spar

booms and the wing attach fittings for

delamination or corrosion damage, and

repairing any delamination or corrosion

damage found. Accomplishment of the

proposed inspection would be in

accordance with Slingsby TI No. 109/

T51, Issue No. 2, dated October 7, 1997.