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.