Product Improvement Test of UH-1B Tail-Boom Fitting
ARMY AVIATION BOARD FORT RUCKER AL
Pagination or Media Count:
Numerous cracking failures of the original production UH-1B upper- left-hand tail-boom attaching fittings occurred in the field when the helicopters were operated at high gross weights. The fittings cracked approximately 18 inches aft of the tail boom bulkhead. To correct this problem, a stronger fitting was designed and incorporated MWO 55-1520-21128 in the UH- 1B fleet. In September 1964, one of the modified fittings cracked after 553 hours of operation at high takeoff gross weights reference d. The crack was two inches aft of the tail-boom bulkhead and extended through the first rivet hole. Subsequently, several similar failures were reported to have occurred in the Republic of Vietnam in UH-1B Helicopters after approximately 500 hours of operation.