Propeller description systems (From War Production Board Report). Hamilton Standard Hydraulic e.g. 12B20
1 First revision
2 Number of blades
B Blade shank size
20 Engine shaft size
Hamilton Standard 2-B-20, controllable, 2 blade, dural, already in production before 1940, phased out in 1944/5, used on AT-8, 9, 10, 19, UC-78
As of 16 March 1942, 2-B-20 with blade design 6135A-15, 7 feet 9 inches, on AT-8 and AT-10, same combination but 7 feet 7 inches on AT-17 (Wood?), 2-B-20 with blade design 6135A-6, 8 feet 6 inches on AT-17