95-06-07: Flexplate

95-06-07 ROBINSON HELICOPTER COMPANY: Amendment 39-9177. Docket Number 94-SW-22-AD. Supersedes Priority Letter AD 94-11-01, issued May 18, 1994. Applicability: Model R22 helicopters, with forward flexplate (flexplate), part number (P/N) A947-1 with bonded washers, or P/N A193-1 without bonded washers, installed, certificated in any category. Flexplate, P/N A947-1E and subsequent FAA-approved revisions to P/N A947-1, is exempt from the requirements of this AD. Compliance: Required as indicated, unless accomplished previously. To prevent failure of the flexplate, failure of the main rotor drive, and subsequent loss of control of the helicopter, accomplish the following: (a) Within the next 25 hours time-in-service (TIS) after the effective date of this airworthiness directive (AD), accomplish the following: (1) With the clutch disengaged, support the forward end of the clutch shaft, P/N A166-1, remove the flexplate, and record the shim locations for useduring reinstallation. (i) Replace any flexplate that does not have eight bonded washers (two per arm) with an airworthy flexplate, P/N A947-1E or a subsequent FAA-approved revision to P/N A947-1. (ii) For those flexplates that have eight bonded washers (two per arm), comply with the following: (2) Remove all coating down to bare metal from the outer edges of the flexplate to approximately 0.125 inches inward, but in no case within 0.50 inches of the bonded washers, using Scotch Brite or 600 grit sand paper. Do not use a chemical paint stripper since it may adversely affect the adhesive that bonds the washers to the flexplate. (3) Inspect the outer edges of the flexplate for cracks, avoiding the bonded washers, using a dye penetrant inspection method in accordance with Appendix I of this AD. If the dye penetrant contacts the bonded washers, remove the solution from the bonded washers within 1 minute since longer exposure may adversely affect the adhesive.(i) If a crack is found, replace the flexplate with an airworthy flexplate, P/N A947-1E or a subsequent FAA-approved revision to P/N A947-1. (ii) If no crack is found, paint the bare edge area of the flexplate with an even coat of zinc-chromate or epoxy primer. Do not paint the bare metal surface of the bonded washers. (4) Reinstall the flexplate and ensure sheave and clutch shaft angle are properly aligned in accordance with the applicable maintenance manual. (b) For those helicopters with flexplates that have less than 2 years or 450 hours TIS, accomplish the following prior to or upon reaching 2 years or 500 hours TIS, and thereafter at intervals not to exceed 50 hours TIS from the last inspection; for those helicopters with flexplates that have 2 years or more or 450 hours or more TIS, accomplish the following at intervals not to exceed 50 hours TIS from the last inspection. (If the flexplate TIS cannot be determined through a review of the maintenance records, then use the helicopter TIS as the TIS of the flexplate). (1) Remove the flexplate in accordance with the applicable maintenance manual. (2) Clean the flexplate using a solvent (e.g., methyl-ethyl ketone or naphtha). (3) Inspect the flexplate for nicks, cracks, or corrosion using a 10-power or higher magnifying glass, paying close attention to the edges of the flexplate. (i) If a crack is found, replace the flexplate with an airworthy flexplate, P/N A947-1E or a subsequent FAA-approved revision to P/N A947-1, in accordance with the applicable maintenance manual. (ii) If a nick or corrosion is found, repair the flexplate in accordance with the applicable maintenance manual. (iii) Paint any bare edges of the flexplate with an even coat of zinc-chromate or epoxy primer. Do not paint the bare metal surface of the bonded washers. (iv) If any nick or corrosion cannot be repaired within the rework limits specified in the applicable maintenance manual, replace the flexplate with an airworthy flexplate, P/N A947-1E or a subsequent FAA-approved revision to P/N A947-1, in accordance with the applicable maintenance manual. (4) Reinstall the flexplate and ensure sheave and clutch shaft are properly aligned in accordance with the applicable maintenance manual. NOTE 1: Robinson Helicopter Company R22 Maintenance Manual, Change 14, dated March 14, 1994, pertains to this AD. (c) If a crack, nick, or corrosion is found on the flexplate as a result of the inspections required by this AD, report a description of the crack, nick, or corrosion, the total TIS, and the operating conditions to the Manager, Propulsion Branch, Los Angeles Aircraft Certification Office, FAA. Reporting requirements have been approved by the Office of Management and Budget and assigned control number 2120-0056. (d) Installation of a flexplate, P/N A947-1E or a subsequent FAA-approved revision to P/N A947-1, constitutes terminating actionfor the requirements of this AD. (e) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used when approved by the Manager, Los Angeles Aircraft Certification Office, FAA. Operators shall submit their requests through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Los Angeles Aircraft Certification Office. NOTE 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Los Angeles Aircraft Certification Office. (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 helicopter to a location where the requirements of this AD can be accomplished. (g) This amendment becomes effective on April 4, 1995. APPENDIX I DYE PENETRANTS Several dye penetrant typeinspection kits are now available that will reveal the presence of surface cracks or defects and subsurface flaws that extend to the surface of the part being inspected. These penetrant type inspection methods are considered acceptable, provided the part being inspected has been thoroughly cleaned, all areas are readily accessible for viewing, and the manufacturer's recommendations as to the method of application are closely followed. a. Cleaning. An inspection is initiated by first cleaning the surface to be inspected of dirt, loose scale, oil, and grease. Precleaning may usually be accomplished by vapor degreasing or with volatile cleaners. Use a volatile cleaner as it will evaporate from the defects before applying the penetrant dye. Sand blasting is not as desirable a cleaning method, since surface indications may be obscured. It is not necessary to remove anodic films from parts to be inspected, since the dye readily penetrates such films. Special procedures for removing the excess dye should be followed. b. Application of Penetrant. The penetrant is applied by brushing, spraying, or by dipping and allowing to stand for a minimum of 2 minutes. Dwell time may be extended up to 15 minutes, depending upon the temperature of the part and fineness of the defect or surface condition. Parts being inspected should be dry and heated to at least 70* F, but not over 130* F. Very small indications require increased penetration periods. c. Removal of Dye Penetrant. Surplus penetrant is usually removed by application of a special cleaner or remover, or by washing with plain water and allowing the part to dry. Water rinse may also be used in conjunction with the remover, subject to the manufacturer's recommendations. d. Application of Developer. A light and even coat of developer is applied by spraying, brushing, or dipping. When dipping, avoid excess accumulation. Penetrant that has penetrated into cracks or other openings in the surface of the material will be drawn out by the developer resulting in a bright red indication. Some idea of the size of the defect may be obtained after experience by watching the size and rate of growth of the indication.