Air Force Solidifies Options for B-52 Engine Replacement. The Air Force has laid out three potential plans for replacing the B-52’s engines, a key step for keeping its oldest bomber in service into the 2050s. For almost two decades, the Air Force has studied whether and how to replace the B-52’s Pratt & Whitney TF33-PW-103 engines, eight of which have powered each Stratofortress since the 1960s. Now the clock is counting down for the Air Force to make a decision, as age, obsolescence and diminishing sources for spare parts could make current engines unsustainable as early as 2030, according to slides presented at a Dec. 12 industry day. The service appears to have settled on broad requirements for the engines.