53-09-03 HILLER: Applies to All UH-12, UH-12A, UH-12B, HTE-1, HTE-2, H-23A and H-23B Model Helicopters.
Compliance required as soon as possible but no later than the next 25-hour inspection and as indicated in part C below.
The following has been found necessary to prevent fatigue failure of the clevis head on the outboard tension torsion bar pins, P/N 51414-1:
A. Inspect P/N 51414-1 pins to determine the fillet radius under the clevis head. If radius is less than 0.030 inch the pin must be scrapped and replaced with a pin having at least 0.030-inch radius before further flight.
B. If radius is 0.030 or greater and the pin has less than 500 hours total time it may be reinstalled. If a featheredge is found at the base of the clevis it should be carefully removed.
C. All 51414-1 pins must be replaced when they have accumulated a total of 500 hours of flight time.
(Hiller Service Bulletin No. 36 covers this procedure.)