88-20-06: Vertical Stabilizer Front Spar Fitting

88-20-06 MITSUBISHI HEAVY INDUSTRIES, LTD. (formerly Nihon Aeroplane Manufacturing Company (NAMC): Amendment 39-6023. Applies to all Model YS-11/-11A series airplanes, certificated in any category. Compliance required as indicated, unless previously accomplished. To prevent failure of the vertical stabilizer front spar-to-fuselage fittings, accomplish the following: A. Within 600 hours time-in-service after the effective date of this AD or within 4 months after the effective date of this AD, whichever occurs first, visually inspect the vertical stabilizer front spar fuselage side fittings, Part Number (P/N) 01-38101-11/-12, for cracked lugs, in accordance with Paragraph 2., "Instructions," of NAMC YS-11 Alert Service Bulletin (SB) A53-71, dated May 23, 1986. Repeat this inspection at intervals not to exceed 1,000 hours time-in-service. B. If any crack is found in fitting P/N 01-38101-11/-12 during the inspections required by paragraph A., above: Prior to further flight, remove that fitting from the airplane and accomplish the inspections, corrosion treatment, and replacement of parts, as necessary, in accordance with Paragraph 2., "Instructions," of NAMC YS-11 Service Bulletin 53-70, dated May 23, 1986. Once this has been accomplished, the required repetitive inspections may be discontinued. C. If no cracking is found in fitting P/N 01-38101-11/-12 during the inspections required by paragraph A., above: Within 6,000 hours time-in-service after the effective date of this AD, or by January 1, 1990, whichever occurs first, accomplish the inspections, corrosion treatment, and replacement of parts, as necessary, in accordance with paragraph 2., "Instructions," of NAMC YS-11 Service Bulletin 53-70, dated May 23, 1986. Once this has been accomplished, the required repetitive inspections may be discontinued. D. The repetitive inspections required by paragraph A., above, may be terminated if the vertical stabilizer front spar fuselageside fitting P/N 01-38101-11/-12 had been given corrosion prevent treatment after September 1, 1985, or once it has been replaced by fitting P/N 01-38101-21/-22. E. An alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Los Angeles Aircraft Certification Office, FAA, Northwest Mountain Region. NOTE: The request should be forwarded through an FAA Principal Maintenance Inspector (PMI), who may add any comments and then send it to the Manager, Los Angeles Aircraft Certification Office. F. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to ferry aircraft to a maintenance base in order to comply with the requirements of this AD. All persons affected by this directive who have not already received the appropriate service documents from the manufacturer may obtain copies upon request to the Mitsubishi Heavy Industries, Ltd., Nagoya AircraftWorks, YS-11 Technical Publications, Service Department, 10, Oye-Cho, Minato-ku, Nagoya, Japan. These documents may be examined at the FAA, Northwest Mountain Region, 17900 Pacific Highway South, Seattle, Washington, or the Los Angeles Aircraft Certification Office, 3229 E. Spring Street, Long Beach, California. This amendment, 39-6023, supersedes AD 86-03-05, Amendment 39-5233. This amendment, 39-6023, becomes effective November 1, 1988.