Airworthiness Directives; Short Brothers Model SD3-30, SD3-60, SD3 SHERPA, and SD3-60 SHERPA Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-137-AD]

RIN 2120-AA64

Airworthiness Directives; Short Brothers Model SD3-30, SD3-60,

SD3 SHERPA, and SD3-60 SHERPA Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness

directive (AD) that is applicable to all Short Brothers Model SD3-30,

SD3-60, SD3 SHERPA, and SD3-60 SHERPA series airplanes. This proposal

would require a one-time borescope inspection to detect corrosion of

the shear decks and ribs of the left and right stub wings, follow-on

corrective actions, if necessary; and drilling of new drain holes in

the lower shear decks. This proposal is prompted by issuance of

mandatory continuing airworthiness information by a foreign civil

airworthiness authority. The actions specified by the proposed AD are

intended to prevent corrosion of the stub wing shear decks and ribs,

which could result in cracking or failure of the stub wing structure.

DATES: Comments must be received by July 23, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Transport Airplane Directorate, ANM-114,

Attention: Rules Docket No. 98-NM-137-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 Short Brothers, Airworthiness & Engineering Quality, P.O.

Box 241, Airport Road, Belfast BT3 9DZ, Northern Ireland. This

information may be examined at the FAA, Transport Airplane Directorate,

1601 Lind Avenue, SW., Renton, Washington.

FOR FURTHER INFORMATION CONTACT: Norman B. Martenson, Manager,

International Branch, ANM-116, FAA, Transport Airplane Directorate,

1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425)

227-2110; fax (425) 227-1149.

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.

[[Page 33440]]

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 98-NM-137-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. 98-NM-137-AD, 1601 Lind Avenue, SW., Renton, Washington

98055-4056.

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 all Short Brothers Model SD3-30, SD3-60, SD3

SHERPA, and SD3-60 SHERPA series airplanes. The CAA advises that

corrosion has been found in the area of the upper and lower shear

decks, and on the outer and inner ribs of the left and right stub

wings. The corrosion is believed to have been caused by the ingress of

water and debris into the area from the main landing gear wheels, and

lack of follow-on maintenance in ensuring that the area is dry and

clean. Corrosion of the stub wing shear decks and ribs, if not

corrected, could result in cracking or failure of the stub wing

structure.

Explanation of Relevant Service Information

Shorts has issued the following service bulletins, all dated

November 27, 1998:

SD330-53-68 (for Model SD3-30 series airplanes);

SD360-53-43, Revision 1 (for Model SD3-60 series

airplanes);

SD3 Sherpa-53-4 (for Model SD3 SHERPA series airplanes);

and

SD360-Sherpa-53-4 (for Model SD3-60 SHERPA series

airplanes).

These service bulletins describe procedures for a one-time

borescope inspection to detect corrosion of the shear decks and ribs of

the left and right stub wings, in the areas of the inner and outer

ribs, front and rear web plates, strut support bracket, and upper and

lower shear decks; and corrective actions, if necessary. The corrective

actions include additional inspections for corrosion in other areas;

removal of corrosion within acceptable limits; replacement of certain

components with new components; and, follow-on repetitive inspections

if corrosion is found. The service bulletins also describe procedures

for drilling of new drain holes in the lower shear decks. Additionally,

the service bulletins specify that operators are to report the results

of the initial inspection to the manufacturer.

Accomplishment of the actions specified in these service bulletins

is intended to adequately address the identified unsafe condition. The

CAA classified these service bulletins as mandatory and issued British

airworthiness directives 006-11-97, 006-11-98, 007-11-98, and 008-11-98

in order to assure the continued airworthiness of these airplanes in

the United Kingdom.

FAA's Conclusions

These airplane 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, and determined

that AD 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 bulletins described previously,

except as discussed below.

Differences Between Proposed Rule and Service Bulletins

Operators should note that, although the service bulletins specify

that the manufacturer may be contacted for disposition of certain

corrosion 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 CAA (or its delegated agent). In light of the

type of repair that would be required to address the identified unsafe

condition, and in consonance with existing bilateral airworthiness

agreements, the FAA has determined that, for this proposed AD, a repair

approved by either the FAA or the CAA would be acceptable for

compliance with this proposed AD.

Cost Impact

The FAA estimates that 112 airplanes of U.S. registry would be

affected by this proposed AD, that it would take approximately 100 work

hours per airplane to accomplish the proposed inspection, and that the

average labor rate is $60 per work hour.

Based on these figures, the cost impact of the proposed AD on U.S.

operators is estimated to be $672,000, or $6,000 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.

[[Page 33441]]

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.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

Short Brothers PLC: Docket 98-NM-137-AD.

Applicability: All Model SD3-30, SD3-60, SD3 SHERPA, and SD3-60

SHERPA 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 (e) 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 corrosion of the stub wing shear decks and ribs,

which could result in cracking or failure of the stub wing

structure, accomplish the following:

Inspection and Corrective Actions

(a) Within 6 months after the effective date of this AD, perform

a borescope inspection in the areas of the stub wing shear decks and

ribs to detect corrosion, and drill new drain holes in the lower

shear decks, in accordance with Part A of the Accomplishment

Instructions of the applicable Shorts Service Bulletin specified

below, all dated November 27, 1998 (hereinafter referred to as the

applicable service bulletin):

SD330-53-68 (for Model SD3-30 series airplanes);

SD360-53-43, Revision 1 (for Model SD3-60 series

airplanes);

SD3 Sherpa-53-4 (for Model SD3 SHERPA series

airplanes); and

SD360-Sherpa-53-4 (for Model SD3-60 SHERPA series

airplanes).

Note 2: In the case where no corrosion is detected during the

inspection described in Part A of the Accomplishment Instructions of

the applicable service bulletin, the service bulletin specifies

accomplishment of follow-on repetitive inspections of this area as

specified in Short Brothers Aircraft Maintenance Programme, Chapter

5-26-57.

(b) Except as provided by paragraph (c) of this AD: If any

corrosion is detected during the inspection required by paragraph

(a) of this AD, prior to further flight, accomplish corrective

actions (i.e., additional inspections, removal of corrosion,

replacement of components), as applicable, in accordance with Part B

of the Accomplishment Instructions of the applicable service

bulletin. Thereafter, repeat the inspection required by paragraph

(a) of this AD at intervals not to exceed 12 months.

(c) If any corrosion condition is found for which the applicable

service bulletin specifies that Short Brothers is to be contacted

for an appropriate repair action: Prior to further flight, repair in

accordance with a method approved by either the Manager,

International Branch, ANM-116, FAA, Transport Airplane Directorate,

or the Civil Aviation Authority (CAA) of the United Kingdom (or its

delegated agent).

Reporting Requirement

(d) Within 10 days after accomplishment of the initial

inspection required by paragraph (a) of this AD, or within 30 days

after the effective date of this AD, whichever occurs later, submit

a report of the inspection findings (positive or negative) to: Team

Leader, Service Engineering-Aerospace Customer Support Short

Brothers plc, Belfast, N. Ireland. Information collection

requirements contained in this regulation have been approved by the

Office of Management and Budget (OMB) under the provisions of the

Paperwork Reduction Act of 1980 (44 U.S.C. 3501 et seq.) and have

been assigned OMB Control Number 2120-0056.

Alternative Methods of Compliance

(e) 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 3: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the International Branch, ANM-116.

Special Flight Permits

(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.

Note 4: The subject of this AD is addressed in British

airworthiness directives 006-11-97, 006-11-98, 007-11-98, and 008-

11-98.

Issued in Renton, Washington, on June 17, 1999.

Vi L. Lipski,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 99-15930 Filed 6-22-99; 8:45 am]

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