Could it be similar to the Mayo One helicopter?
http://www.mayo.edu/mmt/mayoone_indepth.htm The one I saw refueling at FRM
last Sunday was a twin tail jet helicopter. Once it took off, it got about
1/4 mile away and then couldn't be heard...

"John Ross" wrote in message
. 3.6...
Several times over the last few months, I have heard what sounded like a
small bizz jet overhead, and gone outside only to find that it is some
kind
of a helicopter. I can hear almost no rotor sounds, just the light roar
of
a jet engine. The only distinguishing feature (to my eye) is that it has
two parallel vertical tail structures, kind of like on an A-10 Warthog,
but
very much smaller.

It looks like a normal commercial 'copter, other than that. Does anyone
know what kind it might be?