Aside from the re-engined DC-7D shown previously, Douglas proposed this interesting idea for its DC-8 back in 1946. The unusual aircraft was powered by two engines arranged in tandem turning contra-rotating pusher propellers. The DC-8 airliner enthusiasts have come to love is, of course, a vastly different design. Source: Terry Waddington, Douglas DC-8 (Miami, FL: World Transport Press), 1996, p. 8.