DM>Bell 47's w/ Lycomings are the "MASH" helo's with the steel tube tail struct
DM>Hiller 12's look similar but have an aluminum monocoque tail and have
DM>Franklin Engines.
DM>both engines are 6 cyl vertical opposed.  flat/opposed engines are the norm
DM>in general aviation aircraft.

Actually later Bells had covered frame tail struts as well giving a
monocoque appearance, this was the first chopper to really make
it due largely to the war as anything, and was in production for a
good long time, as aircraft go.

John