Rob Beschizza at 6:00 pm Sun, Jan 16, 2011
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Years ago, I went to Warren Dunes State Park on Lake Michigan’s east shore on a windy November day. It turned out to be a perfect day for hang gliding, with the dunes providing plenty of ridge lift.
Aside from the hang gliders, I also saw a couple of hawks taking advantage of the ridge lift as well.
I was technical-climbing in the Gunks, many years ago — on the second pitch of a three-pitch climb — when an ultralight flew by just about level with me. I looked at him, he looked at me, and I’m sure we were both thinking “Looks like fun, and it’s probably less dangerous than it appears, but I still think he’s crazy.”
This beastie impresses me because it’s so much more serious a glider than the early parawing-based hang gliders. It’s essentially a serious glider which can be launched without a tow plane. Way cool. And probably a lot safer than the older beasts.
The plane takes off because the engine (propellor or jet) pushes against the air, not the ground; so the treadmill becomes irrelevant.
If that’s what they said, they’re full of bunk. I don’t care if they are mythbusters.
Newton, people! NEWTON!
Its not taking off at zero speed. The launch site is a classic bowl. There are lots of places like that in the UK and they were very popular during the hang glider craze of the mid 1970s. Aircraft like this were popping up towards the end of the ’70s and into the 80s.
The bowl shape of the hills focuses the wind on the launch site. The hill pushes the air upwards giving the glider free lift.
The short cord gives the glider quite a bit of instability in pitch. Yaw is controlled by the drag brakes on the wing tips, but they will cause upward pitch when activated. The low wing design makes it hard to triangulate the wings with cables. Because of this the aircraft needs a strong wing spar to add strength to the wings. It doesn’t look like the kind of thing which could pull a lot of gees.
>It doesn’t look like the kind of thing which could pull a lot of gees.
The Swift was designed to meet the existing FAA structural criteria for sailplanes, which was (is?) 6 gees, both positive and negative.
the physics of this is very easy… if you could see the wind here it is blowing upwards at about a 45degree angle… I’ve done this many times, it’s rather dangerous because if you dip a wing down too near the ground you could be lifted and cartwheel backwards! the rush is worth it :)
there is a hill just like this in San Luis Obispo CA, called “foothill” flown there many times :)
Excellent! He moves forward, directly against the wind, and upwards, with no power input but wind directly in his face.
The people who refuse to believe that you can sail downwind faster than the wind just had their heads explode!
Of course, logically, and physically, it’s no problem. Energy’s there, you harvest it with a machine, and the only limitations on how you can spend that energy are your creativity, mechanical capabilities, and the efficiency of the machines you build.
Treadmills don’t make airplanes fly. Wheels on airplanes don’t make airplanes fly. The movement of air over a wing producing lift makes an airplane fly. If the speed of the airplane through the air around it (“air speed”) is above the wing’s stall speed, the airplane will fly.
But doing this depends so very much on weather and geography.
Growing up on a bluff overlooking Lake Michigan, we would sometimes have long periods of strong, steady winds coming off the lake – and then hitting the bluff and creating an updraft.
I recall hang-gliders going by the house a few times in the late 1970s. At eye-level.
One of the YouTube comments suggests the location could be Devil’s Dyke, but rolling hills like that are the normal kind of hill for England — although not usually so steep.
We have a “normal kind” of hill in England?
Hills made of soft rock get worn smooth. Hills made of hard rock stay jagged. More details available on teh interwebs filed under: “geology” or, more generally “science”.
Devil’s Dyke (a reasonable candidate for this shot) is on the South Downs, which are made primarily of chalk (with Wealden clay in the dips, if you’re interested). That the English call a range of hills (no; at least two ranges of hills: the North and the South Downs) “Downs” when they plainly should be “Ups” is another matter.
I didn’t think it was Devils Dyke because that hill is fairly isolated while in the video you can see the surrounding hills.
In the year 2000, that’s how we will all be commuting to work. Want.
Man, I can’t wait for the future.
In my late teens I wanted to build myself one of those. Dad simply had to ask, “don’t you remember what happened to Lilienthal?”, and since of course I did, that was the end of it. Interestingly, Wikipedia has very little on dear old Otto, and even less on how this kind of craft were all over the place in Nazi Germany when, by treaty, they were not officially supposed to be training airplane pilots – no rule about home made, hobby gliders, thus the HJ and such had a blast going down slopes and pulling ropes…
@frankieboy, you right, alas…
@yamaplos: “Kleine Opfer mÃ¼ssen gebracht werden!” – Lilienthal
I assume they landed at some point. I’d like to see that too, before I decline to try it out.
Well, that certainly looks safe.
Maybe surprisingly though, aircraft like this are perfectly legal to operate (in the U.S., anyway) with no pilot’s license or registration. At least during the daytime away from populated areas.
You know if you are going to do something like this, get some nicer pants. Hit up some American Apparel and get some shiny leggings and sneakers with wings on them.
That’s quite a head wind.
Nature’s wind tunnel!
Does this video disprove the airplane-treadmill problem? In that thought exercise the plane was exhibiting a high groundspeed but no airspeed, and supposedly the plane would take off (but I insist it wouldn’t). In this instance there’s a high airspeed thanks to the wind but zero groundspeed, and the plane takes off anyway.
Also, you are incorrect on there being 0 ground speed. There is just VERY LITTLE ground speed. If you take a look at the video, he does a little jump and moves forward a foot or two, then stays off the ground. Still ground speed.
It was disproved on Mythbusters due to the separation of airplane wheels and airplane propulsion.
I don’t think there would be controversy regarding airplanes and treadmills if the problem were described properly and consistently in all cases.
Airplanes work 100% because of air speed and not ground speed. I think almost everyone understands this, so variations in peoples assumptions as to the configuration of the treadmill, the plane, and the air account for most of the controversy regarding this problem.
The airplane-treadmill problem was a stupid one. Put a hundred thousand pounds of thrust out the back of a plane, it’s *not* going to stay stationary short of physical restraints.
OK, I’ll bite (procrastinating work!). The plane takes off in that problem (to the extent that it is a meaningful question e.g. if you are just looking at airspeed vs groundspeed), you can understand it as follows:
To start, imagine the plane is hovering over the treadmill at zero airspeed / groundspeed (let’s say maglev or something for the moment). Then imagine you fire up the engines – the plane accelerates and gains enough airspeed to fly and takes off. The presence and speed of the treadmill is irrelevant*.
Now take this plane, and stick some Newtonian physics-problem wheels under it (e.g. frictionless and subject to only Newtonian mechanics). They behave the same as the maglev support, and off it goes as well*.
*In practise, if you could build a treadmill able to accelerate at an arbitrary rate capable of infinite speed bearing friction, the effects of friction in the bearings become relevant, as does the entrainment of air over the treadmill, and eventually relativistic effects of the treadmill moving with superluminal velocity. But that screws up the maglev example as well and renders the question meaningless except as an example of pedantry.
MythBusters has already busted that myth:
No, because your characterization of the airplane treadmill problem is incorrect – there is in fact normal airspeed and extra high groundspeed, the latter being irrelevant.
The gentleman in this video is, if anything, demonstrating the same thing: airspeed matters, groundspeed doesn’t.
It looks like a kite. Otherwise it would go backwards. The string is too fine to see in the video.
That’s a mighty conveniently-shaped piece of land there. Did they make that just for zero-speed takeoffs?
That’s actually a naturally occurring geological formation commonly referred to by non-specialists as a ‘hill’.
While I’m an internet user, and have therefore never been outdoors, I’ve heard that these ‘hills’ are actually quite common.
In this video you can also observe the effects of ‘wind’, which I’m told is like air conditioning, but for everywhere.
You’re my hero.
You’re very helpful.
It looks to me like a highly manicured mountain pass or saddle, not like a natural land formation. But I live in the southwest USA, so the hills I’m used to are big jumbles of huge rocks that require lots of dynamite and earthmovers to render smooth and flat. Hence, my wonder.
Perhaps there are naturally occurring smooth, flat mountain saddles where you live, so you think nothing of it. Huh, I’ll bet your hills don’t even have cactus on them!
Called a Swift, you can learn to hang glide. The US Hang Gliding Association is at http://www.ushpa.org
That’s pretty much the same way that I fly in dreams, without the hardware. A slow lack of gravity, bouncing up a bit, then floating up and out.
I’ve seen seagulls take off like this in steady winds on SF Bay.
It is called a Swift, designed in the US back in the 90′s. Hang gliding instruction information can be found at US Hang Gliding Association http://www.ushpa.org PS the designer Steve Morris was involved in the Direct Downwind Faster than the Wind project. http://www.fasterthanthewind.org/
Montey Python sketches have really gotten more elaborate.
Looking at the link, I think part of the confusion with the treadmill problem was down to the framing:
“The conveyer belt is designed to exactly match the speed of the wheels”
Given I can easily imagine the engines pushing the plane forward no matter what the wheels are doing, I think the belt physically can’t behave in that manner (unless the wheels skid).
When I lived in San Francisco, I would frequent Fort Funston, where hang gliders would launch from the cliffs. If the winds were just right, which was frequently, the hang gliders could simple stand at the cliff, angle their gliders and lift into the air. IT was amazing.
I presume this was followed quickly by an unanticipated vertical “landing”.
Not at all strange for hang glider pilots flying in ridge lift. When wind speed is at or above the crafts minimum airspeed, the pilot ground handling his craft has to take care to keep the nose down and wings level or Very Bad Things will happen. To fly, one just has to increase the angle of attack (raise the nose). Flying close to the ground is dangerous, so the pilot then lowers his nose to get some ground speed and flys away, increasing AGL (altitude above ground level) as he goes because the ground is not level.
Sorry for any incorrect technical terms, it’s been 10 years since flight school.
I don’t know why the title says “Somewhat cool”, its totally cool. But I don’t think you can really call it a vertical takeoff, if the craft requires a 20 to 30 knot headwind. :)
I think this is the coolest example of human flight I’ve ever seen. And to the dork suggesting it’s a kite, consider this: birds have been taking off (and hovering) into headwinds like this for millions of years. Pretty sure birds don’t use strings. Go look up “flight” on wikipedia and learn how wings work.
Nice find on the video (even if it’s stale–a veritable oldie).
Had this track playing in the background when I was watching this:
Oddly fitting, IMHO.
Now that’s what I call a “jump jet.”
Amazing what you can do with a bit of flubber and a radiation source.
Seriously though I so badly want an ultralight.
I think he is finding the razors edge where oncoming wind creates an updraft at the peak and he can jump into it for the great VTOL effect.
more guts than sense, from where I’m sitting!
David Attenborough’s “The Life of Birds” has a clip of a bird doing a similar maneuver, gliding “forward” through air that is moving “backward” at the same speed and thus appearing to effortlessly hover over the same spot of ground. No kite string required.
I need a holiday and this would certainly save on the flights! ;)