99-21-33: Inspect Installation Of Countersunk Screws

99-21-33 FOKKER SERVICES B.V.: Amendment 39-11379. Docket 99-NM-225-AD. Applicability: Model F.27 Mark 050 series airplanes, serial numbers 20103 through 20263 inclusive; 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 (c) 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, unlessaccomplished previously. To detect and correct improper installation of countersunk screws in the attachment of access panels of the bottom skin of the center wing, which could result in fatigue cracking of the bottom skin of the center wing and consequent reduced structural integrity of the airplane, accomplish the following: Initial Inspection (a) Prior to the accumulation of 24,000 total flight cycles, perform a one-time detailed visual inspection to detect improper installation (excessive gap) of the countersunk screws used to attach the access panels to the bottom skin of the center wing, in accordance with the Accomplishment Instructions of Fokker Service Bulletin SBF50-57-015, dated February 28, 1996. NOTE 2: For the purposes of this AD, a detailed visual inspection is defined as: "An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required." Inspection and Corrective Action (b) If any improper installation (excessive gap) is found during the inspection required by paragraph (a) of this AD: Prior to the accumulation of 24,000 total flight cycles, ream the fastener holes in the rabbet of the bottom skin of the center wing and perform an eddy current inspection for cracking of the fastener holes in accordance with the Accomplishment Instructions of Fokker Service Bulletin SBF50-57-018, dated February 28, 1996. Repair (1) For any fastener hole for which no crack is found during the eddy current inspection: Prior to further flight; accomplish corrective actions for the fastener hole, in accordance with Step C. of Repair Scheme No. 1 of Fokker Service Bulletin SBF50-57-018, dated February 28, 1996. (2) For any fastener hole for which a crack is found during the eddy current inspection: Prior to further flight; repair and re-inspect the fastener hole, in accordance with Steps A. and B. of Repair Scheme No. 1 of Fokker Service Bulletin SBF50-57-018, dated February 28, 1996. For any crack that is outside the limits specified in the service bulletin, 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 Rijksluchtvaartdienst (RLD) (or its delegated agent). For a repair method to be approved by the Manager, International Branch, ANM-116, as required by this paragraph, the Manager's approval letter must specifically reference this AD. Alternative Methods of Compliance (c) 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, FAA, Transport Airplane Directorate. 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 (d) 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 (e) Except as provided by paragraph (b)(2) of this AD, the actions shall be done in accordance with Fokker Service Bulletin SBF50-57-015, dated February 28, 1996, and Fokker Service Bulletin SBF50-57-018, dated February 28, 1996. 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 Fokker Services B.V., P.O. Box 231, 2150 AE Nieuw-Vennep, The Netherlands. 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 4: The subject of this AD is addressed in Dutch airworthiness directive 1996-042 (A), dated April 29, 1996. (f) This amendment becomes effective on November 4, 1999.