51-29-01 BELL: Applies to All Models 47B, 47B3, 47D, 47D1 Helicopters.
Compliance required as indicated.
1. Replace the tail rotor gearbox shaft, P/N 47-645-028-1 or 47-645-051-1, when it has accumulated 900 hours of operation.
2. Any shaft having already accumulated 900 hours of operation must be replaced by February 1, 1952. In the interim, conduct the following inspection after every 25 hours of operation: Remove tail rotor and inspect attachment bolt hole for cracks. Replace the shaft if a crack is found, or the hole is elongated over 0.010 inch.
(Bell Service Bulletin No. 83 covers this same subject.)