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Thread: Extreme STOL/VTOL homebuilt

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    Registered User BBerson's Avatar
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    Extreme STOL/VTOL homebuilt

    I have been considering the idea of an extreme STOL homebuilt. This is my plan:
    Start with a conventional light or ultralight airplane and add one or more lift fans to provide direct powered lift. This powered lift system would only be needed briefly for takeoff and landing just a few feet above the ground.

    Start with a small amount of lift, then gradually add more lift fans for extreme STOL. Then with enough lift eventually VTOL might be possible but start with STOL first.

    Any ideas for powered lift fans that could be used for brief thrust of a few seconds?
    Stored energy was suggested in a previous thread. JATO works, but is not practical for a civilian, I think.
    Any other thoughts appreciated.
    BB

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    Registered User Tom Nalevanko's Avatar
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    Re: Extreme STOL/VTOL homebuilt

    So if you use the fans to get off the ground, now what? You still have all that aircraft mass to accelerate to a speed where the wings provide enough lift. Rubber tires on the ground might get you there faster if you could get a lot more lift out of the wings at a slower speed. On landing you have the reverse problem.

    But there are examples of your idea. See the pix I took at the Camarillo Air Show a year or maybe two ago...
    Attached Thumbnails Attached Thumbnails Extreme STOL/VTOL homebuilt-img_0645.jpg   Extreme STOL/VTOL homebuilt-img_0647.jpg   Extreme STOL/VTOL homebuilt-img_0646.jpg  


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    Registered User BBerson's Avatar
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    Re: Extreme STOL/VTOL homebuilt

    You are correct, I left out part of the explanation...
    The lift fans need to be on a swivel similar to your photos. The fans would be tilted up and forward for takeoff or up and rearward for landing. The pilot could choose the angle depending on weight and altitude.

    So for instance, an ultralight that normally lands at 28mph might be able to land at 20mph with 50% additional lift from some light fans. But the big advantage at landing is the reverse thrust component used to slow the landing even before ground contact and before the brakes are usable. This is how birds land on a branch. I don't want to come to a complete hover because that requires much more control devices. And I think this STOL type assisted landing would be almost as useful as a helicopter but safer and simpler.
    Same thing for takeoff but with more forward thrust and lift the takeoff would be short but not vertical. Maybe a future version could be vertical, but that is too much to bite off for now.
    BB

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    Registered User Tom Nalevanko's Avatar
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    Re: Extreme STOL/VTOL homebuilt

    Why not give Robert Parker a call about his plane and possibly report back to the group? He might sell it to you for a really good price... Good luck in your design.

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    Registered User Tom Nalevanko's Avatar
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    Re: Extreme STOL/VTOL homebuilt

    Ooops it is Roger Parker and no, I have never met him although he lives fairly close to me. He is not in our local EAA Chapter. A lone wolf going vertical...

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    Re: Extreme STOL/VTOL homebuilt

    BBerson,

    You put the prop in front. Make the prop 8-10 ft in diameter, make it 8-10 inches in chord, variable, turn it at 1000 (cruise power)-2000 (short term power) rpm and at best L/D. Make the wing a double delta shape with LONG chord, with flaps, with square wings outboard that are freewing with coupled elevators that control AOA.

    This makes the flaps a thrust vector device keeping the cockpit flat to max 30 degrees AOA and in cruise the prop runs quiet and slow and at max L/D. The freewing makes it stall proof (roll control) and easy to fly into high AOA with power on giving dynamic air to the wing. Blow the delta and freewings with stored compressed air from the spar for touchdown to get cls in the range of 4 with dynamic air, yielding touchdowns in the <15 mph. That is the solution I am doing in part.

    The delta shape is critical (I have wind tunnel data I did on a model, so I have some experience with it). The airplane will be high and low speed capable by 10+ times low speed, whereas the typical flower flap stuff get you no more than 3 times stall to cruise speed ratio. This is critical for a smooth ride in turbulence making it useful in any condition.

    Under all this, and most important, is a high energy landing gear. A flare is NOT wanted at this point to avoid high wind loss of control.

    There you have it...

  7. #7
    Registered User Tom Nalevanko's Avatar
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    Re: Extreme STOL/VTOL homebuilt

    Sounds like an interesting idea. Not sure what a double delta is though... Like the Draaken?

    While the high to low speed ratio is important, the absolute speeds cannot be neglected. I would argue that for general STOL work a 6 to 1 with stall at 40 knots and cruise at 240 knots would be much more desirable than one at 15 mph to 150 mph. The era of the bushplane is over! Most all STOL landing spots are within several hundred miles of an improved strip with road access or services like fuel. So if you can do 240 knots and have 4 hours autonomy; you can go out and back 500 nautical miles. That pretty much covers the world. I hope to show this on Google Earth sometime later this year. There are other considerations which favor a high top speed like time in the air, both for pilots but also for passengers who may be sick or become sick.
    Attached Thumbnails Attached Thumbnails Extreme STOL/VTOL homebuilt-draken_kicsi.jpg  

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    Re: Extreme STOL/VTOL homebuilt

    Tom,

    So, make it "stall" at 45 and go 450! Am I missing something here? That 15 mph could also top out at 250 kts just as well with the right power and provide a smooth ride. Double delta with freewing IS the smoothest ride out there.

    I think that flight "progress" will be in local micro/neighborhood airports built into parks or subdivsions, or even on the side of the road. We have interstate freeways with "airport" spots at each exit if you follow my train of thought. I can beat your 250 kt machine with a 125 kt machine any day "door to door" when I don't need the airport, inspection time, etc. , support car and all that junk.

    Airports are obsolete and must become obsolete before flying is affordable and useful. Speed cost money.

    500 miles is useless in the daily life of a person. I am talking about using it as a primary vehicle, not a "for the rich guy with a limo weighting with a driver crowd who is off to a glowball meeting with VIPs." I am suggesting doing it at less than 2 cents/mile.

    Your vision is old, well tried and useless for 99% of the world, and with fuel at $5/gallon, it seems outdated in a world that wants the USA standard of living. Natural Gas is 6.5/deca therm or $0.78/gallon equivalent of gasoline. We have 20,000 years of NG in the Gulf of Mexico alone. The planet produces it yearly many times more than what we could ever use.

    A Boeing airliner gets 60 mpg per passenger. My airplane will be around 50-70 mpg and with two people, or six for that matter, it will make the big guys obsolete. This is the future, not bigger and faster. Seldom do I ever need to go 500 miles.

    We have not learned to fly until it parks in your home garage and it can land just about anywhere, especially at Wal-Mart. The reason Boeing does not do what I am talking about it is because it is HARDER to do than big. I was offered a Level three engineering job on the Dreamliner and I turned it down...why? Buses are outdated, Socialistic in nature, and have little respect for a person's time. My schedule MUST be flexible and a bus schedule it so much a joke to a "freeman" or American at that.

    I think most of the problem in aerospace is a problem of vision, which is not wanted in corporate America, not smarts. They are all trying to build the latest Titanic (Airbus 380, 747) and forget about the individual who needs to get around. What about an airplane you can ware on your back and stow under your desk at work (when you need to show up once a week). That is the future, not this junk the mainstream focuses on.

    Real estate is about location, transportation to the location, transportation, transportation. The best place to live is on the top of a mountain...if you can commute there... I have zero uses for buses, airports and the like, anymore than taking a train.

    later,

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    Registered User WileEZ's Avatar
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    Re: Extreme STOL/VTOL homebuilt

    Sounds like a gyrocopter will fit the bill nicely.
    WileEZ
    "All of my ideas are suspect until proven otherwise!"


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    Re: Extreme STOL/VTOL homebuilt

    Wilez,

    Great comment.

    No, one will NOT work. The large swinging blade is very offensive in tight areas and the drag is many times more per load ability, not to mention speed limited.

    Groen brothers from SLC have tried it without success. Carter copter has also made a combination system, and have not had success.

    The skill level is much to high for the average person. Rotor speed management and such is just so much to go wrong. Most have the rotor too high for a garage.

    The rotor is a poor way to generate lift at hight speeds and the maintenance is very high. Clearly nobody has been successful with them for the last 50 years.

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    Site Developer Jman's Avatar
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    Re: Extreme STOL/VTOL homebuilt

    Call me a pie in the sky kind of person but I do believe the next big leap of engineering will come from the garage, not the corporate boardroom. Money and power seems to stifle creative thought in many cases. Design by democracy I think I heard someone else say. That being said, it's easy to get jaded by the continuous onslaught of promised breakthroughs of homebrewed unlimited power that never go anywhere. I'm still hopeful though...

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    Re: Extreme STOL/VTOL homebuilt

    The era of the bushplane is over! Most all STOL landing spots are within several hundred miles of an improved strip with road access or services like fuel
    Have you ever been to Australia? You can fly for a lot of hours and not come close to a bitumen strip in a lot of areas.. That, and STOL aircraft are regularly needed to get in and out of areas that are completely inaccessable by road in emergency situations. They are needed DAILY. Not just every once in a while...

    Your vision is old, well tried and useless for 99% of the world
    Holden, I'm all for progress, don't get me wrong... I'm watching with great interest the development of diesel technology in aircraft. I agree, it is too little too late, but it IS progress, and ANY progress is good progress. What you're saying in this and other posts is that we should abandon ALL aircraft development of ANY kind and start developing hover cars (an interpretation). What you appear to be looking for is an "engineering dictatorship" of sorts.

    You have a great dream, and hopefully a goal on where you want to go in aviation, and I hope you can keep the vision alive and maybe someday achieve it, but in the meantime, don't declare every other idea and design as "useless", "outdated" and "a waste of time". The world is not going to stop turning just because you have a dream. Saying tried and proven designs are useless to 99% of the population may be true to some extent... 99% of the population are probably not the least bit interested in aviation. Did you know though, that 74.6% of all statistics are made up on the spot?

    As a 1%er (to use an old outlaw biker term) I'm going to thoroughly enjoy designing, building and flying my "cub clone". Just like the majority of other homebuilders out there.

    - Dave Roberts.

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    Re: Extreme STOL/VTOL homebuilt

    Oh yeah, to get back on topic... I think starting with an existing ultralight is probably not the easiest way of doing this. It will mean that you will be building a lot of compromise into it. As I'm sure Orion would say, it would be better to start fresh, and design it specifically for the purpose. Take compromise out of the equation right from the word go..

    As a practical example, I used to buil hotrods for a living. I found that in the vast majority of projects I was involved in, any "little" modification, usually intruded on some other component and required a LOT more thinking than previously anticipated. There was one car that truly stood out from all the others as NOT having this problem, and that was a GT40 kitcar that I did some work on. AFAIK, the kits are very similar in construction to the original cars that ford produced in the 60's.

    The requirements of the car right from the beginning was that it was to win races. This meant it needed to be powerful, with good suspension and brakes, well balanced and LIGHT WEIGHT. I'm sure they had some class rules to comply to as well, and these probably would have determined the engine used. And this is where the design began. They started with a flippin big V8. Then designed a race car around it. No extra bits like wind up windows and power steering or even carpeted interior for that matter. Just pure race car. Converting road cars to be race cars is a bit of an uphill battle, because everything is built on a compromise. Everything I touched on that GT40 kitcar just "fitted". Have I illustrated my point sufficiently? I feel like I've just added confusion to the issue.

    I guess what I'm trying to say is, if you were to retrofit lift fans to an existing design, where would you put them? And what structure (ie: spars, etc) will they intrude on? And what extra structure will be required to support these fans, as well as substitute structure that was in the way of them? All of this = extra weight that COULD be designed out if you start with a clean slate.

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    Registered User rtfm's Avatar
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    Re: Extreme STOL/VTOL homebuilt

    Well done, Dave. Excellent post.

    What we need both on this forum and in aviation generally, is a healthy mix of brash innovation and wise conservatism. And no, I don't think the two are antithetic. They are on opposite ends of the spectrum, but it is the same spectrum.

    Part of me thrills at the sometimes abrasive expostulations of guys like Holden. Good on you, mate. We all need to confront our comfortablenesses. But another part of me is quietly satisfied with the conservatism and world-wisdom of some of the other posters here. Could we be more adventurous in our thinking, design-wise? Of course. Should we eschew things simply because they are tried and un-new? Of course not.

    Real advances are seldom if ever the result of radical departures from history. More often than not, the first glimpse of a new landscape is had by standing on the shoulders of those who have gone before.

    Having said this, I think that decrying the best efforts of honest and talented people because we disagree with them is mean-spirited. You can do better Holden. My suggestion would be to design something wonderful first, and then rail against the rest of us. That at least would give your words some weight.

    So c'mon mate - blaze the trail. If you build it, they will come...

    Regards,
    Duncan

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    Re: Extreme STOL/VTOL homebuilt

    Oh, and one more thing... Take careful consideration in regards to your powerplant(s). There would be nothing worse than having the noise stop when you are in alpha configuration 50 - 500 feet off the deck. There would not be many (if any) options available to you in this situation besides "stick your head between your legs and kiss your a$$ goodbye".

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