AD 98-22-15

This amendment adopts a new airworthiness directive (AD) that applies to all Slingsby Aviation Limited (Slingsby) Models Dart T.51, Dart T.51/17, and Dart T.51/17R sailplanes that are equipped with aluminum alloy spar booms. This AD requires 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. This AD is the result of mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for the United Kingdom. The actions specified by this 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.

Final rule

98-22-15 SLINGSBY AVIATION LIMITED (Type Certificate No. G5EU formerly held by Slingsby Sailplanes Ltd.): Amendment 39-10863; Docket No. 98-CE-67-AD.

Applicability: Models Dart T.51, Dart T.51/17, and Dart T.51/17R sailplanes, all serial numbers, certificated in any category, that are equipped with aluminum alloy spar booms.

NOTE 1: This AD applies to each sailplane 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 sailplanes 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 in the body of this AD, unless already accomplished.

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, accomplish the following:

(a) Within the next 6 calendar months after the effective date of this AD and thereafter at intervals not to exceed 5 years, inspect the aluminum alloy spar booms and the wing attach fittings for delamination or corrosion damage. Accomplish this inspection in accordance with Slingsby Technical Instruction (TI) No. 109/T51, Issue No. 2, dated October 7, 1997.

NOTE 2: Slingsby TI No. 109/T51, Issue No. 2, dated October 7, 1997, includes guidance to determine whether an affected sailplane is equipped with aluminum alloy spar booms.(b) If any corrosion or delamination damage is found during any inspection required by paragraph (a) of this AD, prior to further flight, accomplish the following:

(1) Obtain a repair scheme from the manufacturer through the FAA, Small Airplane Directorate, at the address specified in paragraph (d) of this AD; and

(2) Incorporate this scheme and continue to repetitively inspect as required by paragraph (a) of this AD, unless specified differently in the instructions to the repair scheme.

(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 sailplane to a location where the requirements of this AD can be accomplished.

(d) 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, Small Airplane Directorate, FAA, 1201 Walnut, suite 900, Kansas City,Missouri 64106. The request shall be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Small Airplane Directorate.

NOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Small Airplane Directorate.

(e) Questions or technical information related to Slingsby TI No. 109/T51, Issue No. 2, dated October 7, 1997, should be directed to Slingsby Aviation Ltd., Kirbymoorside, York Y06 6EZ England; telephone: +44(0)1751 432474; facsimile: +44(0)1751 431173. This service information may be examined at the FAA, Central Region, Office of the Regional Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri 64106.

(f) The inspection required by this AD shall be done in accordance with Slingsby Technical Instruction No. 109/T51, Issue No. 2, dated October 7, 1997. 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 Slingsby Aviation Ltd., Kirbymoorside, York Y06 6EZ England. Copies may be inspected at the FAA, Central Region, Office of the Regional Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri, or at the Office of the Federal Register, 800 North Capitol Street, NW, suite 700, Washington, DC.

NOTE 4: The subject of this AD is addressed in British AD 005-09-97, dated October 3, 1997.

(g) This amendment becomes effective on December 14, 1998.

Events Leading to the Issuance of This AD
A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to all Slingsby Models Dart T.51, Dart T.51/17, and Dart T.51/17R sailplanes that are equipped with aluminum alloy spar booms was published in the Federal Register as a notice of proposed rulemaking (NPRM) on July 15, 1998 (63 FR 38126). The NPRM proposed to 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 action as specified in the NPRM would be in accordance with Slingsby Technical Instruction (TI) No. 109/T51, Issue No. 2, dated October 7, 1997.

The NPRM was the result of mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for the United Kingdom.

Interested persons have been afforded an opportunity to participate in the making of this amendment. No comments were received on the proposed rule or the FAA's determination of the cost to the public.

The FAA's Determination
After careful review of all available information related to the subject presented above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed except for minor editorial corrections. The FAA has determined that these minor corrections will not change the meaning of the AD and will not add any additional burden upon the public than was already proposed.

Compliance Time of this AD
The unsafe condition specified by this AD is caused by corrosion. Corrosion can occur regardless of whether the aircraft is in operation or is in storage. Therefore, to assure that the unsafe condition specified in this AD does not go undetected for a long period of time, the compliance is presented in calendar time instead of hours time-in-service (TIS).Differences Between the British AD, the Technical Instruction, and this AD
Both Slingsby TI No. 109/T51, Issue No. 2, dated October 7, 1997, and British AD 005-09-97, dated October 3, 1997, specify the initial inspection prior to further flight.
The FAA does not have justification through its regulatory process to require the initial inspection prior to further flight. To assure that no affected sailplanes are inadvertently grounded, the FAA is utilizing a compliance time of 6 calendar months for the initial inspection.

Cost Impact
The FAA estimates that 3 sailplanes in the U.S. registry will be affected by this AD, that it will take approximately 40 workhours per sailplane to accomplish the initial inspection, and that the average labor rate is approximately $60 an hour. Based on these figures, the total cost impact of the initial inspection specified in this AD on U.S. operators is estimated to be $7,200, or $2,400 per sailplane.

These figures only take into account the costs of the initial inspection and do not take into account the costs of repetitive inspections and the costs associated with any repair that will be necessary if corrosion or delamination damage is found. The FAA has no way of determining the number of repetitive inspections an owner/operator will incur over the life of the sailplane, or the number of sailplanes that will need repairs.

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 not a "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 copy of the final 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, 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 a new airworthiness directive (AD) to read as follows: