DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39 [63 FR 38126 No. 135, 7/15/98] [R5Y]

[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.

Compliance Time of the Proposed AD

	The unsafe condition specified by the proposed 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 the proposed 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 Proposed 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 proposing a compliance time of 6 calendar months for the initial inspection.

Cost Impact

	The FAA estimates that 3 sailplanes in the U.S. registry would be affected by the proposed AD, that it would take approximately 40 workhours per sailplane to accomplish the proposed 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 proposed 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 proposed initial inspection and do not take into account the costs of repetitive inspections and the costs associated with any repair that would 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 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 U.S.C. 106(g), 40113, 44701.

Sec. 39.13  [Amended]

	2. Section 39.13 is amended by adding a new airworthiness directive (AD) to read as follows:

Slingsby Sailplanes Ltd.: 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 Small Airplane Directorate.

	(e) Questions or technical information related to Slingsby Technical Instruction 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.

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

	Issued in Kansas City, Missouri, on July 8, 1998.

Michael Gallagher, Manager, Small Airplane Directorate, Aircraft Certification Service.

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.