AD 82-06-51

82-06-51 SIKORSKY: Amendment 39-4387. Applies to Sikorsky Model S-76A series helicopters certificated in all categories equipped with P/N 76351-09000-061 or prior dash-numbered main gearbox assemblies. To prevent possible failure of a main gearbox shaft and spur pinion P/N 76351-09012-103 due to fatigue cracks propagating in the bottom threaded area, accomplish the following:

1. Within the next 50 hours' time in service, unless already accomplished within the last 50 hours' time in service, and thereafter every 100 hours' time in service from the last inspection, inspect all shaft and spur pinions, P/N 76351-09012-103, with 1,500 or more hours' time in service since new on the effective date of this AD, in accordance with Sikorsky Alert Service Bulletin No. 76-66-16A or later FAA approved revision, or FAA approved equivalent.

2. Within the next 100 hours' time in service and thereafter every 100 hours' time in service from the last inspection, inspect all shaft and spur pinions, P/N 76351-09012-103, with 1,100 or more but less than 1,500 hours' time in service since new on the effective date of this AD, in accordance with Sikorsky Alert Service Bulletin No. 76-66-16A or later FAA-approved revision, or FAA approved equivalent.

3. Inspect shaft and spur pinions with less than 1,100 hours' time in service since new on the effective date of this AD before the accumulation of 1,200 hours' time in service, and thereafter every 100 hours' time in service in accordance with Sikorsky Alert Service Bulletin No. 76-66-16A or later FAA-approved revision, or FAA approved equivalent.

4. If a crack is found, replace the shaft and spur pinion with a serviceable part prior to further flight.

5. Replace the shaft and spur pinions, P/N 76351-09012-103, with a serviceable part prior to the accumulation of 1,500 hours' time in service since new or within 200 hours' time in service after the effective date of this AD, whichever occurs later. Thereafter, replace shaft and spur pinions with serviceable parts prior to accumulation of 1,500 hours' time in service.

6. All shaft and spur pinions whose hours' time in service cannot be established are to be inspected in accordance with paragraph 1 and are to be replaced with a serviceable part within 200 hours' time in service from the effective date of this AD.

Equivalent means of compliance may be approved by the Chief, Boston Aircraft Certification Branch, Federal Aviation Administration, New England Region, 12 New England Executive Park, Burlington, Massachusetts 01803.

This amendment becomes effective June 3, 1982, to all persons except those persons to whom it was made immediately effective by telegraphic AD T82-06-51, issued March 5, 1982, which contained this amendment.