88-26-01 R2 ROBINSON HELICOPTER COMPANY: Amendment 39-6646. Final Copy of, and Revision to, Priority Letter AD 88-26-01 R1. Docket No. 88-ASW-58-AD. \n\n\tApplicability: Model R22 series helicopters, all serial numbers containing A158-1 main rotor spindle and A106 journals, certificated in any category. \n\n\tCompliance: Required prior to further flight for all helicopters with spindles having over 500 hours time in service, and for all helicopters regardless of total time in service that have experienced an unexplained increase in main rotor vibration level, unless already accomplished. For those helicopters with spindles having less than 500 hours total time in service, compliance is required prior to attaining 500 hours total time in service, unless already accomplished. Thereafter, conduct repetitive inspections of the original design spindles and journals as specified in paragraph (f) of this AD at intervals not to exceed 50 hours time in service since the last inspection, or conduct repetitive inspections of spindles and journals which have been reworked and replaced as specified in paragraphs (b) and (c) of the AD at intervals not to exceed 500 hours time in service from the last inspection. \n\n\tTo prevent main rotor spindle failure, which could result in subsequent loss of the helicopter, accomplish the following: \n\n\t(a)\tRemove both main rotor blades (ref. Section 9.111 of the R22 Maintenance Manual). Clean and dye penetrant inspect both boltholes and adjacent surfaces on the A158-1 spindles. If a crack indication is found replace the spindle with an airworthy part which has been reworked in accordance with the following: \n\n\t\t(1)\tRemove both main rotor blades. Clean, visually inspect with a 10X magnifying glass, and dye penetrant inspect both bolthole surfaces. If any crack indication is found, immediately remove from service. Visually inspect surfaces for nicks, scratches, pits, or excessive fretting. If surface defects greater than 0.0005inch deep are found, the spindle must be replaced with an airworthy part. \n\n\t\t(2)\tPolish bolthole surfaces with 220, 320, and 400 grit abrasive paper to remove surface defects and all indications of fretting. Inspect with a 10X magnifying glass to insure that no fretting indications remain. The abrasive paper must be mounted on a flat block so the polished surface will remain perfectly flat. \n\n\t\t(3)\tWithout removing the spindle from the blade, shot peen both surfaces (ref. AMS2430) to 98 percent minimum coverage, intensity 0.010A to 0.013A, with 0.019/0.033 diameter steel shot. Mask with duct tape all areas and blade parts not to be peened. Overspray in the 0.625 diameter bolthole can be prevented by installing a 0.625 inch diameter dowel or discarded bolt shank. \n\n\t\t(4)\tPolish peened surfaces using 220, 320, and 400 grit paper mounted on a flat block to keep surfaces perfectly flat. Do not remove all indications of shot peening. Polish only until 95 to 98 percent of the surface appears polished and flat with only a few tiny pock marks from the shot peening still barely visible. Remove all shot peen balls between the spindle and the boot. Vibro-etch the letter "P" on the spindle, as shown below. \n\n\n\n\nAD 88-26-01 R2 \n\n\n\t(b)\tIf no defects are found when accomplishing the inspection required by paragraph (a), unless previously accomplished, rework the A158-1 spindle by shot peening the surfaces which mate with the A106 journals as required by paragraph a(1) through (4) of this AD. This rework may be performed by an FAA-approved repair station authorized to perform this process. \n\n\t(c)\tRemove and replace all A106 journals in the coning and teeter hinges (a total of six per aircraft) with new A106 Revision 0 or subsequent journals. These redesigned journals may be identified by a yellow primed bore of the bolthole. \n\n\t(d)\tManually rock the A158-1 spindle back and forth to check for roughness in the A159-1 pitch bearing set and, if roughness isdetected, return the pitch bearing set to an approved RHC overhaul facility for inspection and/or repair (ref. Section 2.540, R22 Maintenance Manual, Robinson Technical Report 60). \n\n\t(e)\tAfter performing the A158-1 spindle rework specified in paragraph (b) and the A106 journal replacement specified in paragraph (c) of this AD, reinstall the main rotor blades (ref. Section 9.112, R22 Maintenance Manual). Make certain the journal and spindle surfaces are clean and dry before assembling. Also, exercise caution to insure that the bolts are stretched to the new limits specified in paragraph (a)(7). Track and balance the rotor (ref. Section 10.200, R-22 Maintenance Manual). \n\n\t(f)\tSpindles (without rework) and original design journals may be used in accordance with the following procedures: \n\n\t\t(1)\tConduct the following inspections and rework at intervals not to exceed 50 hours time in service: \n\t\t\t(i)\tRemove both main rotor blades (ref. Section 9.111, R22 Maintenance Manual).(ii)\tClean and dye penetrant inspect both the boltholes and the adjacent surfaces on the A158-1 spindles. \n\n\t\t\t(iii)\tIf any spindle is found to contain a crack, replace with an airworthy part before further flight. \n\n\t\t\t(iv)\tIf spindle surface defects exceed 0.0005 inches in depth, the spindle must be replaced with an airworthy part before further flight. Superficial fretting may be removed by lightly polishing with 400 or finer abrasive paper. \n\n\t\t\t(v)\tVisually inspect the A106 journals. If cracked, replace with an airworthy part before further flight. \n\n\t\t\t(vi)\tCheck pitch bearing set for roughness, and comply with paragraph (d) of this AD. \n\n\t\t\t(vii)\tReinstall main rotor blades (ref. Section 9.112, R22 Maintenance Manual). Make certain the journal and spindle surfaces are clean and dry before assembling. \n\n\t\t(2)\tReplace the NAS 630-80 bolts and A189-10 nuts with new parts after each fifth inspection which requires disassembly and reassembly of the main rotor system.(3)\tThis alternate means of compliance terminates March 31, 1989, after which compliance with the requirements of paragraphs (a) though (e) of this AD is required. \n\n\t(g)\tIn accordance with FAR Section 21.197 and 21.199, the helicopter may be flown to a base where the inspection required by this AD may be accomplished. \n\n\t(h)\tAn alternate method of compliance with this AD, which provides an equivalent level of safety, may be used if approved by the Manager, Los Angeles Aircraft Certification Office, FAA, 3229 E. Spring Street, Long Beach, California 90806-2425. \n\n\tThis amendment (39-6646, AD 88-26-01 R2) becomes effective on August 7, 1990, as to all persons except those persons to whom it was made immediately effective by Priority Letter AD 88-26-01, issued December 15, 1988, as amended by AD 88-26-01 R1 issued February 8, 1989, which contained this amendment.