80-07-04 HILLER HELICOPTERS: Amendment 39-3722. Applies to Hiller Model UH-12D, UH-12E and UH-12 (4 place) helicopters including military models UH-23D, OH-23G, H-23F and turbine-powered models, equipped with main rotor blade assembly, Parsons P/N 2253-1101-03 or 2253-1101-04 certificated in all categories.
Compliance is required as indicated, unless already accomplished.
To prevent fatigue failure of the main rotor blade anti-node bars accomplish the following:
a. Before the accumulation of 2500 hours' time in service, or within 10 additional hours' time in service on main rotor blades with 2500 or more hours' time in service on the effective date of this AD, whichever occurs sooner, inspect the threaded ends of the anti-node bar per instructions specified in Part II accomplishment instructions of Hiller Aviation Service Bulletin No. 51-5 dated January 22, 1980, to determine whether the threads are rolled or cut.
b. If the anti-node bar thread inspection ofparagraph (a) of this AD reveals that the bar has cut threads, remove the anti-node bar from service and replace with like serviceable part in accordance with paragraph 4.55 of the UH-12E Structural Repair Manual.
c. If the inspection of paragraph (a) of this AD does not provide satisfactory evidence that the threads are either cut or rolled, remove the rod from service and replace with a like serviceable part.
d. If the inspection of paragraph (a) of this AD reveals that the bar has rolled threads and the total time on the bar is less than 6670 hours, reinstall the bar in accordance with the instructions of paragraph 4.55 of the UH-12E Structural Repair Manual.
Note: Caution; Use extreme care in reinstalling the anti-node bar assembly to ensure that the screws attaching the anchor nut to the anti-node bar are not sheared during insertion. Hand pressure is the maximum force allowed in installing the anti-node bar.
e. Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate rotorcraft to a base for the accomplishment of inspections required by this AD.
f. Alternative inspections, modifications or other actions which provide an equivalent level of safety may be used when approved by the Chief, Aircraft Engineering Division, FAA Western Region.
This amendment becomes effective March 31, 1980.