The Double Wasp by Pratt & Whitney

All variants of the B-26 were powered by Pratt & Whitney R-2800s, either the "A" or "B" series. These engines were boosted by single-stage, two-speed superchargers. It was critical the adequate electrical power be supplied to the propellors and consequently an APU (auxiliary power unit) was provided for. This was a 28-volt generator powered by a small two stroke engine. Prior to starting the R-2800s, The APU was removed from the waist compartmen were it was stored and connected to an electrical outlet in the left nacelle.