Shown below are the Second Stage Planetary Gears in the Forward Transmission that are partly responsible for the August 1999 worldwide grounding of the Chinook fleet. During a transmission overhaul, a 145DS010-8 second stage planetary gear/bearing assembly in a British Royal Air Force HC-II (CH-47) was found to contain a crack in the spherical raceway of the gear. Subsequent metallurgical investigation determined the crack to be from a grinding process during the original manufacturing stages which had not been detected during final inspection of the product. Further inspection of other new first and second stage planet gear/bearing assemblies found additional second stage planetary gear/bearing assemblies with similar cracks. The Planetary Gears are the six smaller gears (first photograph) located around the larger Sun Gear (second photograph) in the center of the transmission
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