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Thread: slowest airplane

  1. #1
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    slowest airplane

    Does anyone know the slowest flying airplane designed? Seen the takeoff and landing figures for some planes like the storch, but it seems they focus on takeoff and landing.
    Sitting outback and watching the hawks and kites hunt mice in the alfalfa and wodering if there are any airplanes that fly like this? 5, 10 or 15 mph and 10 or 20 feet above the ground in calm still air. I guess similar to a hang glider but without relying on the thermals or wind on the face of a cliff. Not interested in a heli or gyro but a small self powered extremely light and slow aircraft.

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    Moderator addaon's Avatar
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    Re: slowest airplane

    Sounds like you want a powered paraglider. Even there, the comfortable cruise speed is much closer to 20 mph than 10 mph; 15 mph is the bottom range of normal operations.

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    Re: slowest airplane

    Probably be something like the Gossamer Condor. Problem is, such low stall speeds (and the flimsy structure they imply) severely limit the wind speeds you can safely fly in.

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    Re: slowest airplane

    The only way you're going to fly that slow without beating the air to death is with something that looks like a human powered airplane.

    Hmmm... come to think of it, if you had a fair amount of power you could probably use a lower aspect ratio, even more area, and a decent motor. This would be sturdier in the air, too, though I doubt if it would be much less vulnerable to being blown away.

    Here's one that ought to be able to get down close to 20mph:
    Parker P1 High Altitude Airplane
    And also go t0 35k feet!!! If you took the big motor out and put in a little, light one with maybe 5-10hp, you might be able to go a little slower.
    (the chart goes down to 40mph at 35k feet, same Cl would give 22mph at sea level)

    Alternatively, you could do 500 lbs gross, 6:1 aspect ratio, 580 square feet, 59 foot span, Cl of 1.5, drag maybe only around 75 lbs or so. (Induced 60 to 70 lbs). Power required would be prop efficiency times 3hp or so. Prop efficiency would depend on how absurd your redrive was.

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    Re: slowest airplane

    The human powered answer would be it.

    Lowest power and lowest stall speed for a man carrying aircraft. I remember when it was thought to probably be impossible and foolish to try. McCready looked at it from a fresh vantage point and came up with very light construction which would make possible the very low wing loading to fly with minimum power at the very low speeds possible with human power, maybe 1/2 h.p. maximum, or whatever a trained human cyclist can produce.

    The first Volmer Jensen powered hang-glider in the early 70's would be a more durable second option. His wing loading was low enough that he could simply start flying at walking speed when heading into a slight headwind. The foot launching requirement also ends up requireing a very low stall speed.

    The human powered boat events are (were) also fascinating. I've attended a few of those. Back in the 80's they were using human powered hydrofoils to set those records and claim those prizes.

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    Re: slowest airplane

    A very large paraglider would also fly very slowly without excessive structural weight (though there's lots of drag from the lines). However, such a slow PG is very susceptible to collapses since the low speed means less internal pressurization.

    For that matter, a standard paraglider trimmed to fly at Clmax rather than best L/D (PG's pretty much operate at a fixed AOA) would also be able to fly very slowly.

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    Re: slowest airplane

    Every time I hear "walking speed" about an aircraft, I get very skeptical. I've heard it about many, but the only ones I've ever seen that slow were models weighing perhaps 3 grams or less.

    Human powered hydrofoils are kind of interesting. I was fortunate enough to see some of the trial runs of "Decavitator", around 1991 or so.

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    Re: slowest airplane

    Hey Dana, did you read the part of my post where I described the wind speeds for this kind of flying? Calm and still, lazy afternoon roaming around a mile or two from the house maybe, just like these raptors are doing. Had a really good suggestion on the Yahoo groups about a pressurized fabric wing inflated with Helium. Kind of like a more maneuverable and smaller derigible. Derive some of the lift from the airfoil and some from the gas. Aquiring some of the lift from an airfoil would help with not having to fly it down and having a way of catching or anchoring it. Seen some promising fabric but don't have a clue how to work with the stuff and shape it.

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    Re: slowest airplane

    If you're willing to go with an inflatable wing, why not a paraglider?

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    Re: slowest airplane

    I used to fly a 100cc 15hp weight-shift Eipper Quicksilver back in the 80's a lot. I loved that thing! In smooth evening air I would cross my feet off to one side of the nose wheel, clasp my hands behind my back and slow fly around at a minimum of 18mph. If I had my feet in the right spot, the trim would be prefect for no hands flying : )

    Martt

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    Re: slowest airplane

    To get any real useable amount of lift your wing would have the volume of a blimp....so it would be a blimp. Arup had the same idea as an "extra" for his plane probably because the wing seemed so voluminous. It wouldn't have enough volume to have any real lifting effect though. To get the most "lift" that way he'd also have to use hydrogen....and the wing couldn't leak hydrogen....and it's explosive....but the volume factor is what really controls.

    For flying in light weather.....the wind speed changes all the time. A certain amount of turbulence and gusting should be designed for in any case.

    It might be different for butterflies. They manage to migrate down to Mexico (as long as their places there remain) while getting blown all over the place by what would be proportionally gale force winds. Kudos to the butterfly.

    Quote Originally Posted by kurtjfred View Post
    Hey Dana, did you read the part of my post where I described the wind speeds for this kind of flying? Calm and still, lazy afternoon roaming around a mile or two from the house maybe, just like these raptors are doing. Had a really good suggestion on the Yahoo groups about a pressurized fabric wing inflated with Helium. Kind of like a more maneuverable and smaller derigible. Derive some of the lift from the airfoil and some from the gas. Aquiring some of the lift from an airfoil would help with not having to fly it down and having a way of catching or anchoring it. Seen some promising fabric but don't have a clue how to work with the stuff and shape it.

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    Re: slowest airplane

    Howdy addaon, just looking for something slower and quieter.

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    Re: slowest airplane

    Looking at the difference in lift between helium and hydrogen, 7 percent seems negligble, I think it would be damned foolish to use hydrogen.

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    Re: slowest airplane

    You're not going to find anything much slower than a paraglider... wing loading is king. Sure, a really fancy, fowler-flapped design can probably get a CL twice as high as a paraglider... but it's going to be at a lot more than twice the 1 lb/ft^2 wing loading.

    In terms of quiet, if you're unpowered your right, paragliders aren't great (lines produce easily audible noise). But if you're powered, engine/prop noise is going to be the main contribution, especially in anything small. You can go electric, if you don't care about range, but other than that, see other threads on noise.

    Unless we're talking about large aircraft, the volume of anything with a conventional wing is just going to be too small to overcome even the weight difference of using a coated surface that's slightly less permeable to helium. (Back when I was in physics land, we'd run helium into vacuum chambers to check for leaks, with a mass spec on the outside to light up when helium concentrations rose. But even on a great vacuum jar, you only had about an hour to check for leaks, since enough helium to trigger the detector would diffuse straight through the glass by then...)

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    Re: slowest airplane

    Buoyancy will be on the order of 1 oz. per cubic foot. I think for an Arup something like 15 lbs, plus or minus quite a bit.

    Human powered and similar probably won't do well even on a calm afternoon.

    You could probably make electric work, though the weight and therefore the speed will be up a little if you want to stay up more than a few minutes. Perhaps you could get around that with solar cells, though I suppose they would raise the weight too. But there have been solar powered planes that flew ok. Probably a little faster than what you have in mind, but maybe not much faster.

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