AD 72-16-10

72-16-10 BOEING-VERTOL: Amendment 39-1498. Applies to Model 107-II helicopters certificated in all categories.

Compliance required as indicated below:

To prevent failure of the aft transmission collector gear and to prevent separation of the aft transmission planetary carrier retention nut, either of which may cause dephasing of the main rotors, accomplish the following:

a. Within the next 15 hours in service after the effective date of this AD, unless already accomplished, inspect for cracks and flat spline root radii and shot peen internal splines of serial number designated collector gears P/N 107D2066-10 or -12 or -14 and change part number identification in accordance with Accomplishment Instructions Parts I and II of Boeing-Vertol Service Bulletin No. A107-318R-1 dated 19 June 1972 or equivalent methods approved by the Chief, Engineering and Manufacturing Branch, FAA Eastern Region. All other serial numbered collector gears shall be inspected and shot peenedat the next transmission overhaul or within 800 hours, whichever comes first.

b. Within 50 hours time in service after last retorquing of planet carrier retention nut, unless already accomplished, loosen, retorque, and install lock pins in the aft transmission planetary carrier retention nut (P/N 107D1276-7, VS10304-39 or BACN10-GR39) and mark transmission nameplate in accordance with Accomplishment Instructions Parts I and III of Boeing-Vertol Service Bulletin No. A107- 317 dated 12 January 1972 or equivalent methods approved by the Chief, Engineering and Manufacturing Branch, FAA Eastern Region.

This amendment is effective August 11, 1972.