84-18-04: Main Rotor Gearbox

84-18-04 ROBINSON HELICOPTER COMPANY: Amendment 39-4948. Applies to Model R-22 series helicopters certificated in all categories having main rotor gearbox Part Number A006-1, Revision A through V, installed. Compliance required as indicated unless already accomplished. To prevent main rotor gearbox failure, accomplish the following: (a) Within the next 15 hours time in service after the effective date of this AD, unless already accomplished within the last 35 hours time in service, and thereafter at intervals not to exceed 50 hours time in service from the last inspection: (1) Remove the oil level sight glass from the main rotor gearbox. NOTE: To prevent oil loss the right skid may be elevated. (2) Manually rotate the drive system and visually inspect all 12 bolt heads located on underside of ring gear using suitable illumination. (3) If any bolt failure is observed (including head separation), replace the gearbox with a serviceable gearboxbefore further flight. (4) If no indication of bolt failure is observed, reinstall sight glass in accordance with normal maintenance instructions. (b) If the main rotor gearbox oil chip detector illuminates during ground or flight operation, in addition to normal maintenance procedures, comply with paragraph (a) before further flight. (c) Within the next 200 hours time in service after the effective date of this AD, modify the main rotor gearbox to include Robinson Kit No. KI-37 in accordance with Instructions No. KI-37 dated August 24, 1984. When this modification has been accomplished, the inspections required by Paragraph (a) may be discontinued. NOTE: Robinson Service Bulletin No. 43, dated August 24, 1984, pertains to this subject. (d) The helicopter may be flown under the provisions of FAR Sections 21.197 and 21.199 to a base where the inspections and modification of paragraphs (a) and (c) may be accomplished, provided the gearbox oil chip detector has not illuminated. (e) Alternative means of compliance providing an equivalent level of safety with this AD may be used when approved by the Manager, Western Aircraft Certification Office, FAA, Northwest Mountain Region. This amendment becomes effective November 8, 1984, as to all persons except those persons to whom it was made immediately effective by priority letter AD 84-18-04 issued September 6, 1984, which contained this amendment.