Flying Car More Economical Than SUV

fusion812 writes "The M400 needs 35 clear feet to take off but thanks to its 770 hp engine can whiz to 365 mph - cruise control kicks in at 326 mph - and climb at 6,400 feet per minute. You may hear it before you see it: it emits a rather noisy 65 dba at 500 feet. Interestingly, with a fuel consumption of 20 miles to the gallon on the road, it's rather more economical than a Sports Utility Vehicle (SUV) and looks positively eco-friendly compared to a Hummer."

Comments

video link

[mm0mm]

details of M400 here.

the site has video/media page as well, in which you can see noisy hover test.

I don't mean to be cynic, but I couldn't help wondering what practical use this vehicle may have. with two passengers maximum, this looks to me like fancy miata of aircraft. maybe this can become California governor's commuter vehicle, but I don't want to see dozens of these flying around above my neighborhood.

MOD PARENT DOWN

[localroger]

The author of the parent comment knows just enough about gyrocopters to tell a lot of shit-stirring lies.

First and foremost, gyrocopters can't stall. At all. That's why they were invented. Juan de la Cierva was obsessed with the dangers of stalling in fixed-wing aircraft, which is why he devoted his life to promoting the autogyro. (Ironically enough, he actually died when the fixed-wing aircraft he was riding in stalled and crashed.)

Autogyros aren't used commercially because helicopters are better at VTOL, slow-speed and hover flight, and fixed-wing aircraft are more fuel efficient and faster for distance and heavy lifting.

You can get a personal Experimental class autogyro for under $20,000 (about the same as the less expensive fixed-wing EA class kits) and they're much safer than either fixed-wing craft or (especially) helicopters for novice flyers.

Re:MOD PARENT DOWN

[The Evil Couch]

yes and no. they're safer in some respects and more dangerous in others.

here, text from the wikipedia

Flight characteristics

Autogyros are often regarded by fixed-wing aircraft pilots as "dangerously unstable", which is certainly true if one tries to fly a autogyro using fixed-wing principles. Piloted properly, a autogyro is slightly safer than a fixed-wing aircraft because it cannot stall. A "stall" does not mean an engine-out event, it means a fixed wing aircraft is travelling too slowly for the wings to produce lift. Since the rotor of a autogyro is always spinning, it cannot stall. If forward airspeed becomes zero, the autogyro will slowly drift to the ground, rotor still spinning. A vertical landing in this manner will not critically damage most autogyros.

One weakness in the autogyro is pitch instability (pitch is the tilting up or down of the craft as viewed from the front or the back). Pitch instability is a problem because autogyros cannot handle negative-gee forces (positive-gee forces push people into their seats; negative-gee forces make people float out of them, such as driving down a steep hill at high speed in an automobile). Negative-gee forces "unload the rotor". A flying autogyro hangs from the rotor much like an object hung from a string. As long as the plane is hanging from the rotor, stability is maintained. The instant zero or negative-gees are introduced, rotor speed begins to decay and the gyroscopic forces stabilizing the plane are lost.

Negative-gees are usually caused by Pilot-Induced Oscillation, or PIO. PIO happens when a pilot adjusts his pitch too much too quickly, then makes a countering control input to bring the pitch back. The countering input often overcompensates, and the autogyro begins to buck like a bronco. This is most likely at high engine throttle settings. If the pilot continues to fight the plane, the rotor (which is flexible) usually flops down and strikes the spinning propeller, which destroys both and sends the autogyro into an uncontrolled fall. The way to avoid this during an incipient PIO is to apply gentle backpressure on the stick (to raise pitch) and cut engine power. Note that this is the exact opposite of what fixed-wing pilots are trained to do when in trouble, which has lead to some unfortunate accidents and the autogyro's undeserved reputation for being "dangerous".

Another danger is "bunting over" or a Power Push-Over (PPO). A autogyro's vertical airspeed (climb or sink rate) is directly coupled to airspeed. Increase forward airspeed, increase rate of climb. In order to maintain level flight at high engine throttle settings, the pilot must tilt the rotor forward to translate some of his lift into forward motion. Too much tilt, and the autogyro's overall pitch will aim down towards the ground. When this happens, negative-gees occur, rotor speed drops too low to provide lift, and the autogyro tumbles end-over-end in a sommersault. It is impossible to regain control after a PPO.

Two factors lead to pitch instability: no or too small horizontal stabilizers (h-stabs) and high thrustline engine placement. A large h-stab, ideally in the prop wash (where the propeller blows on it) will reduce the tendency of a autogyro to over-pitch as a result of improper control input.

If the engine thrustline in a pusher-type autogyro is high -- meaning the axis of propeller power is above the center of gravity for the aircraft -- the autogyro tends to pitch forward under sudden power application (see PPOs above, as for why this is Bad). (Unfortunately, Benson-type autogyros have a notably high thrustline.) If the thrustline is low, the autogyro tends to pitch up under sudden power application, which is harmless. It's difficult to have a low thrustline without a really tall autogyro (such as a "Dominator" style) however, so most autogyro designs simply try to get the thrustline as low as possible though still being slightly abo

Re:WTF?

[Reverberant]

It's 65dBa at 500 feet. Since loudness decreases/increases quadratically

Warrax_666 makes a good point. (and to answer your question, sound usually decays at a rate of 10*log10(D/Dref) for line-sources and 20*log10(D/Dref) for point sources, although ground absorption and atmospheric absorption can cause more rapid attenuation in certain circumstances).

65 dBA at 500 feet translates to 85 dBA at 50 ft (assuming point source propagation, which is probably reasonable).

For comparison:

• Locomotive idling @ 50 ft: 80 dBA
• Bus idling @ 50 ft: 75 dBA
• Automobile @ 50 ft, 50 mph: 70 dBA
• Diesel locomotive @ 50 ft, 50 mph: 92 dBA
• Transit train (electric) @ 50 ft, 50 mph: 86 dBA
• Train horn @ 50 ft: 105 dBA

So in short, it's louder than cars traveling at 50 mph, but not as bad as a train horn. Also keep in mind that if the flying car is, well, flying, there won't be anything to shield the noise from the vehicle, and that may make it louder than normal cars in practice.