AD 69-08-08

69-08-08 FAIRCHILD HILLER: Amdt. 39-753. Applies to UH-12D, UH-12E, UH- 12E-L, UH-12L and UH-12L4 type helicopters certified in all categories, with P/N 55046 and P/N 55046-5 tail rotor yokes.

Compliance required as indicated.

To prevent fatigue failures of the tail rotor yoke, P/N 55046 and P/N 55046-5 accomplish the following:

(a) Within the next 10 hours time in service after the effective date of this AD, unless already accomplished, conduct a magnetic-particle inspection and a measurement of the tail rotor yoke fillet radius as shown in Figure 1 in Fairchild Hiller Service Letters SL-UH-12L- 55-1 and SL-UH-12D thru G-55-1 dated March 20, 1969.

(1) If a crack is found, or if the measured fillet radius is less than 0.030 inches, remove the tail rotor yoke from service prior to further flight.

(2) If the measured fillet radius is 0.030 inches or larger but less than 0.050 inches, the yoke may continue in service provided that magnetic-particle inspections are conducted after the inspection required in paragraph (a) at intervals not to exceed 50 hours time in service from the last inspection. Remove cracked yokes from service prior to further flight. Remove from service tail rotor yokes having a fillet radius 0.030 inches or larger but less than 0.050 inches within 250 hours time in service from the effective date of this AD. The service life limit of 2500 hours for the tail rotor yokes of UH-12E-L, UH-12L and UH-12L4 helicopters must not be exceeded.

(b) Replacement parts must be tail rotor yokes having a fillet radius of at least 0.050 inches.

This amendment is effective April 23, 1969.