84-11-03 SIKORSKY AIRCRAFT DIVISION: Amendment 39-4866. Applies to all Sikorsky Model S-61 L/N/A series helicopters, certificated in all categories and authorized for flight with gross weights in excess of 19,500 pounds, when equipped with the following tail rotor drive system components:
a. Flange Part Number (P/N) S6135-66228-0 installed at the input and output couplings of the intermediate gearbox.
b. Flange P/N S6135-64013-0 installed at either end of the pylon drive shaft and at the aft end of the section IV tail drive shaft (shaft immediately forward of the intermediate gearbox).
c. Flange P/N S6135-66657-0 installed at the input coupling of the tail gearbox.
Compliance is required as indicated (unless already accomplished).
To intercept impending failure of the flanges identified above, accomplish the following:
d. For flanges with more than 800 hours time in service since new, inspect the flange for cracks utilizing a 5-power or greater magnifying glass in the area surrounding the bolt attachments within the next 15 hours time in service after the effective date of this AD, unless already accomplished, and thereafter at intervals no to exceed 15 hours time in service from the last inspection.
e. If cracks are found, replace the flange and assure proper alignment of intermediate gearbox, tail gearbox, and pylon drive shaft before further flight.
f. Upon request, with substantiating data submitted through an FAA maintenance inspector, equivalent methods of compliance or adjustment in the inspection intervals or compliance time may be approved by the Manager, Boston Aircraft Certification Branch, FAA, New England Region.
This amendment becomes effective June 6, 1984.