[FoRK] Where the F&@# is my flying car?

Stephen D. Williams < sdw at lig.net > on > Mon Sep 11 10:09:34 PDT 2006

Eugen Leitl wrote:
> On Mon, Sep 11, 2006 at 08:23:02AM -0400, Stephen D. Williams wrote:
>> There are two levels of "possible": scientifically/engineering possible 
>> and commercially viability.  There are many things that are 
>> scientifically possible that are not yet commercially viable.  The 
>> reason that everyone keeps predicting the flying car is because it has 
>> been perfectly scientifically possible and engineerable for a long 
> Stabilizing a personal VTOL aircraft in a cluttered urban
> environment is a control nightmare. Letting people fly is just
> not an option. Building such an advanced controller in a cheap
> enough package reliable enough to be insured is the reason
> personal aircraft hasn't been happening yet.
Automation will be important, as will dealing with weather.  Weather is 
the real issue with flying.  Everything else is simpler.
> Otoh, UAV environment is principally simpler than a car's, so
> we will see progress there earlier.
>> time.  They have been built, tested, and actually put on the market.  
>> They just aren't commercially viable compared to normal planes and other 
>> forms of transportation.
> What's also a problem is fuel use and range. VTOL takes far larger
> amount of fuel than gliding by aerofoil. Increasing range will require
> heavier aircraft, which will need even more fuel. Of course, 500-600 km
> range might be enough...
The first plane I showed had a range of 900 miles.  Some sport light 
aircraft use 3 gallons per hour at about 100-129 knots, basically the 
same gas mileage as a typical economy vehicle.  A Cessna 172 burns 8 
gallons an hour while cruising at 120, 1 to .5 the economy of an average 
vehicle, except that you can likely take a more conventional route.  
There is even a US standard per diem for mileage for a privately 
operated vehicle (POV) aircraft, $1.07/mile.
>> BTW, Look into "Light Sport Aircraft" and an FAA "Sport Pilot License".  
>> You can get the latter in a week and the former for something like the 
>> cost of a sports car, some with over 700 mile range.  This is a huge 
>> revolution potentially on both sides (although the Sport license has 
>> many practical limits; you really want a Private Pilot with Instrument 
>> Rating).  There are suddenly many manufacturers of Light Sport Aircraft 
>> innovating on cost, performance, and avionics.  Several Czech companies 
>> seem to be very popular right now.  It is entirely possible that a 
>> "flying car" might now evolve from one of these, although it is likely 
>> that the multi-engine barrier would need to be crossed which would 
>> necessitate something like "simplified multi-engine light sport aircraft".
> Two words: takeoff strip. That completely nixes the idea. For 98% 
> of all users, you absolutely, positively need a VTOL. And can you
Really?  50 ft. takeoff and 125 ft. landing with 2200fpm climb (i.e. 
steep) are really that much more burdensome than a helipad?
Most of us live on a block that is 100 yards / 300 ft. long.  It really 
wouldn't take much to accommodate.
Most likely, it would be done similar to flying communities in Florida 
where they put the airstrip in common area between the houses, but even 
traveling a few miles to an airport isn't that bad is it?  It's 
something like going to the train station.

Most likely, greatly increased and managed air traffic would handle 
things like weather by having either commercial alternatives (a 
weather-tough "air bus" typical airliner) or revert to ground 
transportation or just telecommute.
> imagine how compatible flock-guidance and collision radar (TOF UWB) 
> is with conventional human-guided aircraft? With suddenly obsolete 
> concepts like traffic corridors?
Airspace management is doable.  With 3D separation, you can do quite a 
bit.  I've flown a Cessna 172 in and out of Honolulu where they have 
constant simultaneous traffic from commercial airliners, local twin 
commuters, general aviation coming from two directions (over land), and 
a military base that shares the same runways.  They are a little quirky, 
but it works just fine.  It was interesting holding short with a 747 
crossing 4 left ahead of me or hanging crosswind while one landed below 
me.  I have photos somewhere.

> I don't like surveillance UAVs one bit, but it's good that they're
> testing the waters of human/machine airspace interoperability. 
> And they're light enough to not produce major mayhem when crashing.
Light Sport Aircraft are an extension of Ultralight Aircraft, which have 
very relaxed rules exactly because they can't cause much damage.  You 
don't need a license or medical for an Ultralight, which I believe is 
limited to 74 lbs.  A Light Sport is limited to 1320lbs max weight, 
including fuel, passengers, and cargo and 129 knots max speed.  With 
modern technology however, this isn't that difficult to optimize for.  
There must be some disaster analysis that says that this weight is below 
some threshold.  Probably it is not enough to bring down a typical 
airliner by collision in some majority of cases.  It is also becoming 
common to have airbags (finally) and whole-plane parachutes on small planes.

Avionics now going into planes already is doing a kind of peer to peer 
air traffic synthesized radar and avoidance system where planes 
broadcast their GPS location and stats to other nearby planes.  This is 
a big piece of the puzzle and will eventually prevent nearly all collisions.

I don't really see it actually becoming popular or suddenly more 
feasible for typical people anytime soon, but it is well within the 
possible.  We are just at the end of a very long period of aircraft 
stagnation.  Assuming that the airlines and the FAA don't get big usage 
fees enacted against general aviation, it should improve fairly steadily 


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