AD 80-21-09 R1

80-21-09 R1 BELL: Amendment 39-3942 as amended by amendment 39-3976. Applies to all Model 47 series helicopters and military Model H-13, OH-13, and TH-13T series helicopters, including modified versions, certificated in all categories, that are equipped with the 47-641-170 series tail rotor hub and blade assemblies (Airworthiness Docket No. 80-ASW-29).

Compliance required within 100 hours' time in service after November 17, 1980.

To prevent loss of directional control as a result of possible tail rotor pitch link failure, accomplish the following, unless already accomplished in accordance with Bell Helicopter Textron Alert Service Bulletin No. 47-80-5, Rev. A, dated April 29, 1980.

(a) Remove the tail rotor pitch link from each blade pitch horn.

(b) Inspect the pitch link bearings for axial and radial play. Remove bearings having .015 inch or more of play or looseness, and install serviceable bearings.

(c) Install bolts P/N NAS1304-32D or 20-057-4-32D (used with pitch horn, P/N 47-641-187-1, -3, or -5), or P/N NAS1304-30D, or 20-057-4-30D (used with pitch horn, P/N 47-641-187-7) as appropriate, with washer, P/N 47-641-189-1 or -3 under the bolt head or nut, and washer P/N 47-641-189-3 between the link bearing and pitch horn with bevel towards the bearing. Torque nuts 80 to 100 inch-pounds and install cotter pins.

(d) Determine that no binding or interference occurs in the blade controls when the tail rotor controls are full left and right, and the tail rotor hub is flapped to each stop. Track the tail rotor blades in accordance with the appropriate Model 47 maintenance manual if a rod end bearing or a link is replaced in accordance with paragraph (b) of this AD.

(e) Equivalent means of compliance with this AD may be approved by the Chief, Engineering and Manufacturing Branch, Flight Standards Division, FAA, Southwest Region.

(Bell Helicopter Textron Operations Safety Notice OSN 47-79-1 dated October 19, 1979, also pertains to this subject.)

Amendment 39-3942 became effective November 17, 1980. This amendment 39-3976 becomes effective November 24, 1980.