On Aug 27, 7:37 am, "Gig 601XL Builder"

Bell 47 rule?

Paraphrased, there is no cheaper/more economical/more efficient way of
achieving vertical takeoff and landing than with a Bell 47 helicopter.
If a proposed rotorcraft or VTOL aircraft is simpler and/or less
expensive than a Bell 47, either the price is unrealistic or the
aircraft will not fly as promised.

Bob K.