Extreme STOL/VTOL homebuilt

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by BBerson, Jun 18, 2008.

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  1. Apr 5, 2012 #61

    Head in the clouds

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    Holden replied to this thread 2 days ago.... #45

    How about a Holden amphibious flying car with Joby methode but add a pair of folding prop motors (one would be enough but better to have two for redundancy) on the fin, for better pitch stability in the hover?
     
  2. Apr 5, 2012 #62

    Aircar

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    Somehow overlooked Holden's very recent post ( i read the whole thread through again so probably missed the address box ) --the use of enough power to hover results in an extreme over-powered condition for cruise and in the case of the CGS Hawk is a terrible mismatch . It might not have enough thrust to also lift a pilot and any useful amount of fuel and also might not be able to hover out of ground effect (or have any margin for an actual climb rate --but if it did the result would be enough power to rip the wings off in cruise or be operating all of them at a very low throttle opening and poor SFC . If it was intended for LSA then you would have to incorporate some sort of throttle limitation to stay within the 120 mph? speed limit --is this in fact a permissible way to comply ? (cruise control like in cars --and it could even be linked to the GPS so that groundspeed was limited to 120 --into a headwind you would be allowed more power and downwind less but still have full power for a healthy climb rate ) --who actually certifes that an LSA is max speed compliant ? (if it was tested at max weight and then flown light that speed would be exceeded and changing the prop pitch or 'cleaning up' an otherwise dirty aircraft would add speed .

    What would be the 'offence' for flying 'too fast' in an LSA ?

    For many years in Australia with what amounted to a total prohibition on designing (or flying actually) ANY homebuildable aircraft -by imposing FULL FAR 23 certification on even a hang glider - (and more again in the form of fatigue testing and flutter analysis )
    it made sense to break the law as the lowest cost route to demonstrating a new ,prototype, aircraft . The 'offence' for flying an uncertified aircraft would attaract a fine of maybe several thousand dollars whereas to fully certify an aircraft to FAR 23 would cost MILLIONS of dollars --by being able to demonstrate a new aircraft concept some financing might be obtained and at worst the thing could be sold off or produced overseas . It was a real catch 22

    Kit CARS in Australia are effectively outlawed by the application of emissions compliance to ANY road vehicle even if a one off --ADR s or Australian Design Rules demand that even a change of engine will require a full laboratory test of emissions --regardless of whether the engine used comes from a compliant production car . (this requires an approved test cell with controlled temperature and pressure and the engine must be fed a stoichometric mixture of dry nitrogen and oxygen not just ambient air ) --I became aware of this from a developer of a new car intended to be kitted who was taking his car to the US aftermarket and custom vehicle exposition in Los Angeles to sell it all off since it COULD be sold and operated in "smog central" but not even in outback Australia (but if it was a RACE car then it was OK to emit anything --presumably the barbed wire fence around a race track would keep the pollutants contained) Molt Taylor stated that his problems with selling the Aerocar came from complying with the ROAD rules and not the FAA --thinking ahead to a multiengine VTOL flying car producing enough power to lift itself and climb vertically the emissions hurdle might be a showstopper.
     
  3. Apr 5, 2012 #63

    Aircar

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    Alan--'an amphibious flying Holden (car) along Joby lines etc ' -- one of the problems with amphibious VTOL is the spray created --the convergence of the downwash along the centre line adds to hover lift but lifts a lot of water (or ground debris) into the props and intakes and high disc loading makes it worse than for a helicopter --and helicopters, as you would know, already have the problem of 'brown out' landing on dust and the spray close to water . Blade erosion and junk into the engine intakes aren't desireable either (when the medivac choppers land just after the grass has been cut next to my house they create a real blizzard of flying debris which obscures the chopper from outside looking in but might be less the other way around . I just cannot imagine any sort of VTOL as being remotely acceptable for an aircraft to be used for commutting --if it is within a city the noise and disturbance will rule it out and if in the countryside the throwing up of all sorts of crap on an unimproved surface will be possibbly dangerous but at least pretty messy (even 'flying' the Nova two man hovercraft at Mangalore (Airshow) a few years ago created a bit of friction because of all the dust thrown up that drifted across the campsite and freshly cleaned aircraft etc --the 'side effects' of this sort of thing are bad enough to ground them --last night the TV show "the rise and fall of the Concorde" aired and the sonic boom plus the take off noise --and environmental objectors worried about the ozone depletion etc was enough to kill it stone dead in commercial terms even though it was a magnificent technical achievement.

    I tend to think that the undesirable effects of small aircraft are underestimated in terms of public reaction and this applies in spades to any type of VTOL --if you are consigned to the 'leper colony' way out of town then VTOL is of not so much value (how many helicopters just fly from an airport anyway ? and with STOL --what is gained by landing shorter on a 5000ft runway -- there are no STOLports near to places you might want to go and the overpowered STOL aircraft with complex high lift systems will be slower than one not having enough wing to fly ultra slow (all based on the conventional sort of approach to these things which has resulted in no real sales of STOL or VTOL and only very specialized operations )

    Maybe the case for ATOL and the roadable aircraft can be appreciated only after all the alternatives have been eliminated (apologies to Sherlock Holmes )
     
  4. Apr 5, 2012 #64

    henryk

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  5. Apr 20, 2012 #65

    jokur217

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    Hi Everybody. First time poster here.

    I'm not an engineer. I don't know anything about aerodynamics or fluid mechanics. Nor have I ever built an airplane. BUT couldn't you just use a parasail? Taxi your plane a few feet, parasail fills will air and the plane's thrust makes the sail pull the plane in the air. Get to your cruising height, pull in the chute. (I imagine the rope holding the frame of the chute extends while another chord attached to the center stays the same length, thereby collapsing the chute) and you're on your way. Then for landing, extending the chute and coast on in?

    Problem solved.
     
  6. Apr 20, 2012 #66

    Head in the clouds

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    Welcome to the forum.

    It's a nice bit of lateral thinking. There are a few people here suggesting the need for various forms of morphing to get from the ground state to the air state without too much speed, noise or wash. Sadly I doubt your method will work in it's basic form because the transition from support by chute to support by wing (and back again) might be a bit too exciting for the average citizen due to the considerably different airspeeds required for each.

    You get a gold star from me anyway.
     
  7. Apr 21, 2012 #67

    henryk

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  8. Apr 21, 2012 #68

    Rom

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    maviteccar.jpg As ordered, the Maverick Flying Car. Although it requires the chute for all regiments of flight.
     
  9. Feb 18, 2014 #69

    johanb

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  10. Feb 18, 2014 #70

    henryk

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  11. Feb 18, 2014 #71

    henryk

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  12. Feb 20, 2014 #72
  13. Feb 21, 2014 #73

    johanb

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    Thanks a mil :)
     
  14. Feb 21, 2014 #74

    Xanadrone

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    Valuable information from the eastern inventors (never underestimate them...) - thanks again, henryk!

    I wonder if an electric drive inflating those hover-skirts (only for take-off and landing) would be more compact, reliable and easy to actuate.
    And if a somehow... slender design of the "pontoons" is feasible, making a classic (simple) amphibian-type landing gear obsolete also from the drag point of vue.
     
  15. Feb 21, 2014 #75

    henryk

    henryk

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    -you are right!=electric driven fans\in my case=2\ can be very light...

    -in auer monotracer allphibian at "road" phase they are working as giroscopic stabilizers!
     
  16. Sep 7, 2015 #76

    rtfm

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    Hi guys,
    I see no reason to create yet another thread to discuss the same topic, so I'm resurrecting this one...

    It seems to me that an investigation of the RC world (as far as ideas for VTOL are concerned) is a profitable exercise. Mainly because of the sheer number of RC enthusiasts, and because experimentation in the RC world is completely without danger (and largely, without significant cost).

    And this investigation highlights a number of things:

    For one thing, the power requirements for VTOL are (for them) not an impediment. Electric motors are readily available with huge dollops of power, easily capable of lifting the entire plane vertical at great speeds if required. Secondly - no-one seems to have come up with anything beyond the three basic ideas: Tilt motors, tilt wings, vector thrust. That's it. There isn't anything else. Except, possibly, the few point-heavenward-takeoff designs. A final observation: the control system for these VTOL machines is almost old hat. This is no longer an issue.

    What can we learn from these observations?
    1. Any motor(s) powerful enough to lift an aircraft vertically into the air is WAY too much power for vertical flight. Unless one switches to forward flight power only once airborne.
    2. The "favorite" RC option is huge swiveling props. The second most popular is tilting wings. And the vectored thrust group brings up the rear - popularity wise. This popularity spread is probably relevant to full size aircraft also.
    3. By adopting RC control systems (ie computerised flight radios) it would be a relatively simple thing to control larger engines on full size aircraft.

    As seed-designs, many of the RC VTOL planes would make great full-size designs also. Of the three observations above, I think the first is the most problematic. Extra large props, and a substantial power requirement probably make a home-built VTOL plane unlikely. Unless the plane is very much on the jumbo size. And then it becomes cost-prohibitive. For example, 1000lbs worth of plane would require at least 350hp to lift it off the ground. And that's a lot of engine...

    Just my 2c

    Here's a link to RC VTOL designs...

    And for what it's worth, I just LOVE the Verticopter. In X-Plane it flies like a dream. Now all I have to do is to take enough crazy pills to build one...

    Duncan
     
    Last edited: Sep 7, 2015

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