I'd probably put it into one of these: http://www.moller.com/skycar/m400/.

I don't want to rain on anybody's parade here, but just like that 78 million dollar personal submarine discussed in another thread, there are a lot of numbers that don't add up here.

1) Gross weight 2400 pounds; 900 miles @ 15 MPG = 60 gallons of fuel at 6.6 lbs per gallon = about 400 lbs for fuel. Four passengers at 185 lbs each = 740 lbs. Add another 60 lbs for oil, coolant, etc., and you are up to 1200 lbs useful load, leaving 1200 lbs for the empty aircraft. OK, no arguments there, just laying the groundwork.

2) Eight 120 horsepower engines in a vehicle that weighs (empty) 1200 pounds. Even assuming that the airframe were made of exotic unobtainium alloys and weighed only 800 pounds (impossible for a four-passenger vehicle) that leaves 50 pounds for each 120 HP engine, which is about 1/3 the weight per horsepower of any internal combustion engine I am aware of.

3) 960 horsepower... it would probably need that to generate the thrust to keep it in the air. Since the aiframe lacks wings or other lifting surfaces, the lift/drag ratio is going to be ridiculous. I don't believe that 960 HP would be enough to both provide lift and provide propulsion to a maximum speed of 390 MPH.

4) A general rule of thumb for fuel consumption in an internal combustion engine lightweight enough to be used in an aircraft is one-half pound of fuel per horsepower hour. Figure 75% of max power at the claimed cruise speed of 350 MPH, that would be 720 HP, which would require 360 lbs of fuel per hour or 54 gallons of fuel per hour, which works out to something less than 6.5 miles per gallon, about 40% of the mileage they are claiming. Their FAQ page strongly implies that the engines are Wankel-type rotary engines. These engines have never been known for fuel economy.

5) Operating ceiling of 30,000 feet. By the time they reach that altitude, they might have 400 horsepower left (internal combustion engines don't work well at Mt. Everest altitudes) and remember, there are no lifting surfaces on this little jewel, so it's all thrust. Some really good mountain rescue helicopters (priced in the multi-million dollar range) with big honkin' twin turbojet engines putting out several thousand shaft horsepower at sea level (and without as large a power penalty at altitude as an internal combustion engine) can make it up to about 23,000 feet, and that's with several hundred square feet of lifting surface (rotors) spinning at 1,000 RPM or so.

6) Noise level: 65 decibels at 500 feet. Yeah, right. With eight engines cranking out 960 horsepower and four eight-bladed ducted fans screaming for all they're worth... 65 decibels is the noise level you would expect to hear in a good luxury car at 60 miles per hour. You wouldn't even need to crank your empeg into overdrive to overcome that much noise.

7) Maximum rate of climb 7800 feet per minute. That's the equivalent of 90 miles per hour straight up. A good twin-engine turboprop aircraft with double the power plus the considerable advantage of generating lift by means of wings (far more efficient than brute thrust) might be able to attain a third of that rate per climb.

8) 900 mile range. I don't see how. With no aerodynamic lift, the fuel efficiency (i.e., miles per gallon) could only improve as speed went up (at hover, you are getting zero miles per gallon) but somewhere along the line the fuel consumption curve will butt heads with the wind drag curve and that's likely to be in the neighborhood of 100 MPH. (just guessing here, but to push any 4-passenger vehicle beyond 100 MPH starts requiring pretty serious power) So you need 9 hours of fuel. 60 gallon capacity, you could burn no more than 6.6 gallons per hour. Well, you can make about 90 horsepower with 6.6 gallons of fuel per hour. That thing is not going to be airborne on 90 horsepower (remember -- no lifting surfaces) much less fly 900 miles.

9) Enough. You get my point? I have seen a lot of these "miracle aircraft" come and go over the decades, and the main thing they have in common is for one reason or another they never quite come into existance.

So, I've heartlessly trashed submarines and aircars... what's next? How about ornithopters, or maybe lighter-than-air vehicles?

tanstaafl.


"There Ain't No Such Thing As A Free Lunch"