AD 99-21-22

This amendment adopts a new airworthiness directive (AD), applicable to all Short Brothers Model SD3-30, SD3-60, SD3 SHERPA, and SD3-60 SHERPA series airplanes, that requires a visual 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 amendment is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by this 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.

Final rule

99-21-22 SHORT BROTHERS PLC: Amendment 39-11367. Docket 98-NM-137-AD. Issued October 4, 1999.
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, accomplish all actions, including a visual inspection using a borescope, specified in 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), 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 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.

NOTE 3: For Model SD3-60 SHERPA series airplanes, accomplishment of the actions required by paragraph (a) of this AD in accordance with Shorts Service Bulletin SD360-53-43, dated November 4, 1997, or Revision 1, dated November 27, 1998, is acceptable for compliance with the requirements of that paragraph.

(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 4: 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.

Incorporation by Reference
(g) The actions shall be done in accordance with Shorts Service Bulletin SD330-53-68, dated November 27, 1998, Shorts Service Bulletin SD360-53-43, Revision 1, dated November 27, 1998, Shorts Service Bulletin SD3 Sherpa-53-4, dated November 27, 1998, or Shorts Service Bulletin SD360-Sherpa-53-4, dated November 27, 1998; as applicable. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Short Brothers, Airworthiness & Engineering Quality, P.O. Box 241, Airport Road, Belfast BT3 9DZ, Northern Ireland. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

NOTE 5: The subject ofthis AD is addressed in British airworthiness directives 006-11-97, 006-11-98, 007-11-98, and 008-11-98.

(h) This amendment becomes effective on November 17, 1999.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to all Short Brothers Model SD3-30, SD3-60, SD3 SHERPA, and SD3-60 SHERPA series airplanes was published in the Federal Register on June 23, 1999 (64 FR 33439). That action proposed to 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.

Comments Received
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

Request to Revise Inspection Method
One commenter suggests that the proposed AD be revised to include instructions to remove the main landing gear (MLG) forward pintle pin (which requires removal of the wheel lever assemblies)and to steam clean the areas identified by the referenced service bulletin. The commenter also suggests that all reference to use of a borescope be deleted to prevent misinterpretation. The commenter states that the proposed AD dictates a different inspection method than the referenced manufacturer's service bulletin, since it does not reference removing the MLG or steam cleaning the area, and requires a borescope inspection. Such a method may actually degrade safety, since without removal of the MLG forward pintle pins, thorough cleaning and subsequent inspection of the area cannot be accomplished. The commenter states that most technicians would interpret the requirement to use a borescope to mean that removal of the MLG is not required, since the purpose of a borescope is to enable inspection without disassembly.

The FAA has determined that clarification of the AD is necessary. The intent of the AD is to require the same inspection methods specified in the referenced service bulletins. The actions required by paragraph (a) of the AD are specifically required to be accomplished in accordance with Part A of the Accomplishment Instructions of the applicable service bulletin. Part A includes instructions for removal of the port and starboard MLG, and steam cleaning of the affected area, prior to inspection. Part A, paragraph 7., also specifies to "visually inspect inner surfaces and interfaces between ribs for corrosion using a borescope." The FAA does not specify in an AD each action described in the referenced service information, since such restatement would be unnecessarily duplicative and could result in misunderstanding of the requirements. However, to avoid any confusion as to the actions required by this AD, the FAA has revised paragraph (a) of the AD to require that all actions in Part A of the service bulletin be accomplished. The FAA has also restated the borescope inspection requirement to specify a "visual inspection using a borescope."Request to Allow Use of Alternate Service Information
One commenter requests that the proposed AD be revised to allow accomplishment of the required inspections on Short Brothers Model SD3-60 SHERPA airplanes having serial numbers SH3420 through SH3428 in accordance with Shorts Service Bulletin SD360-53-43, Revision 1, dated November 27, 1998. This service bulletin was specified in the proposed AD as the appropriate source of service information for Model SD3-60 airplanes, and SD360-Sherpa-53-4, dated November 27, 1998, was specified as appropriate for Model SD3-60 SHERPA airplanes. The commenter provides documentation showing that the airplane manufacturer has previously accomplished service bulletin SD360-53-43 on certain Model SD3-60 SHERPA airplanes, and requests that the FAA consider such action to be adequate for compliance with the inspection required by this AD.

The FAA concurs. The actions described in Shorts Service Bulletins SD360-53-43, Revision 1, and SD360-Sherpa-53-4 are substantially equivalent. The FAA has determined that for Model SD3-60 SHERPA series airplanes, inspections accomplished in accordance with SD360-53-43, dated November 4, 1997, or Revision 1, dated November 27, 1998, are acceptable for compliance with the initial inspection required by paragraph (a) of this AD. A "NOTE" has been added to the final rule to provide such credit.

Conclusion
After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes described previously. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

Cost Impact
The FAA estimates that 112 airplanes of U.S. registry will be affected by this AD, that it will take approximately 100 work hours per airplane to accomplish the required inspection, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the 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 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 adopted herein will 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 final rule does 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 nota "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39 Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 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: