Boeing—B-52 Stratofortress: USAF Variants and Serials GB-52G: Surplus B-52Gs have begun to join Air Training Command as ground instructional airframes, including three with the Sheppard TTC (82nd Training Wing). · 57-6469; 58-0200; 59-2578 B-52H: The most distinguishable feature to differentiate the B-52H from its predecessors is the fitment of TF33 turbofan engines in place of the J57 turbojets, and a six-barreled 20-mm rotary cannon instead of the four 0.5-in guns. One hundred and two B-52Hs were obtained during 1960 and 1961 with all, except a handful lost in accidents, remaining operational. · 60-0001 to 60-0062; 61-0001 to 61-0040