Williamknowsbest wrote:

The one shown in the illustration appears to be a Hiller Hornet, a
two-seat mini-helicopter that was powered by a ramjet on either rotor
tip. These were extremely noisy in operation, and the rotor span of the
aircraft was 30 feet.
Range was 31 miles Besides the inability to take the kids along with
you on a parent's trip to the mall (which better be pretty close with a
range limitation like that), imagine the size of the parking lot at the
mall if every helicopter there needs a minimum 30 foot diameter landing
circle for each arriving helicopter. Just for safety's sake you'd want
to make each landing circle 40 feet in diameter, and at a major mall
that today has a 500-1,000 car capacity parking lot you'd have to hike
from your helicopter to the mall entrance.
To get up to something that's equivalent to a family car in capacity,
you are going to need something along the line of a McDonnell-Douglas
MD-520N, and you may want to have a peek at the per-hour operating cost
of one of those - which was around $345.73 before the gas price crisis
got going full tilt:
http://www.mdhelicopters.com/helicopters/pdf/MD520NTechSpecs/520operatingcosts4....

Assuming you could drop that figure to even 1/4, and you still are
talking a lot of money for that simple trip to the mall.
Any technology that would drop the operating cost of the helicopter (say
you replace the gas turbine with some sort of super battery) would also
be applicable to cars, so the advantage of it disappears. It's simply
more energy efficient to roll things across the ground than fly them
through the air. And although getting stuck in a traffic jam is very
annoying, imagine hovering over the mall parking landing field due to a
crash, and watching your fuel/energy gauge slowly working itself towards
zero. When your car runs out of gas, you generally don't fall several
hundred or thousand feet.

Again, that's a two-seater like the Hornet. It would be fun from a
recreational point of view, like a aerial sports car, but it's not
what's needed to replace the family car - that has to carry at least
four people, and some cargo (i.e. groceries) as well.

That was another two-seater from back in 1992.

Not the size of the "garage" which is more like a "hangar".
Now extrapolate that out to the two or three helicopter family, where
the garage is now larger than the house they live in.

Yup, a Hughes model 269 or 300... another two-or-three seater. Hughes
developed it back in 1955, and although they kept improving it over the
years, it's uses were limited to police, agriculture, and light military
duties, such as helicopter training.
Not only is there not one in my neighbor's garage, I've seen three total
in my whole life, and I worked at a airport for twelve years.
Schweizer now makes it...since this is at least getting into the
ballpark of the abilities needed by a private helicopter car
replacement, let's look at its specs:
http://www.sacusa.com/products/pdfs/300C_datasheet.pdf
Cruise speed - 86 knots, so that's acceptable.
...with 32 gallons of fuel aboard it can fly for 3.7 hours, so 3.7 x 86
= 318.2 nautical miles on one tank of gas, or almost exactly 10 nautical
miles per gallon, or 11.5 mpg as far as statute miles go.
This isn't very good; even a Toyota Tundra giant pick-up (I have a
friend with one of these...you almost need a ladder to get into it.)
gets around 15 mpg on average, and could easily carry this helicopter
around in its truckbed as far as weight goes.
It could also tow around 5 of them around in a fully fueled and crewed
state, as it can tow over 10,000 pounds, and they come in at 1,100
pounds empty or 2,050 pounds at max load.
Then there's initial cost to look at; a Tundra will set you back around
$23,000 to $40,000 for a fully tricked-out one.
A three-seater 300C will set you back over $300,000:
http://www.bush-planes.com/HummingbirdHelicopterPrice.html
...and then will come the insurance costs. :-)

Pat