Stuck_in_an_ATR:
With all the advantages of the AC power, why some aircraft (mostly turboprops, like eg. ATR or the Q400) use 28V DC as their primary power source?
Some systems are going to require 28 Vdc so that they may also be powered by a battery (usually at 24 Vdc) as a backup. For smaller aircraft, the power requirements are low enough to be adequately supplied by a lower voltage DC system. The weight penalty of generating 115 Vac and transforming in down to 28 Vdc is not warranted.
