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#61
January 12th 04, 12:14 AM
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On Mon, 12 Jan 2004 07:46:52 +1000, Mike Borgelt
wrote: Take a look at the movie clip of the Silent IN with the Jet engines. I ran some numbers on the engines over the weekend and I'm convinced I've seen the future of soaring.  Search for a glider called "Huetter 30 TS"... (look here, for example: http://vintagesailplanes.de/Huetter30TS.htm). First flight was in 1960. It later became the Libelle and Salto... but it failed miserably with the turbine engine although it was a very good glider. Noise, fuel consumption and bad climb rates were the killer factors. Bye Andreas 
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#62
January 12th 04, 12:16 AM
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#63
January 12th 04, 12:58 AM
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Kirk,
Where do you fly from? I am trying to make some plans for travelling with my SparrowHawk over the next few months. I am hoping to show the SparrowHawk to as many people as want to see it, and hopefully convert a few "non-believers". I would be very happy to have the opportunity to show it to you and other people that would be interested in seeing it. For a few qualified individuals there might even be the opportunity to fly it. Until you see it and feel it, I can understand how hard it is for people to grasp just what kind of accomplishment this glider is. 155 pounds!? Ridiculous! That is if you are not familiar with the materials. The carbon pre-preg and the adhesives used to bond the plane together are totally different and more than twice as strong as what is typically used to build sailplanes. We joke about how we could take our rudder and use it to chop up every other glider on the field. This really isn't far from truth. One used as a display sample by the manufacturer of the pre-preg has been through the airlines baggage handling system without the benefit of a box. If anything can survive that....! Is it possible to break it? Of course. One SparrowHawk did suffer some damage to its landing gear while landing out last summer, however the pilot reported that it is one heck of a strong airplane and the tailboom would likely have broken on any of his other sailplanes. Mine has been landed out a couple of times and it has flown off of some fairly rough strips as well as suffering some of my landings. All it has to show for this are some paint scratches. No dents or cracks. Structural testing has been done to the wings, vertical tail, horzontal tail, seat, fuselage and tow hook, as well as the control system. As far as performance goes, like one SparrowHawk owner said, on an average day, flown by average pilots in an average way, it doesn't really give up anything. Some trade-offs were made to make it a very easy glider to fly for less experienced pilots (every CFIG who has flown it has said it would be a good first single seater). Stalls including fully cross controlled with the stick held full aft through a number of cycles are a non-event. Control response and harmony is excellent down to very low speeds making take-off and landing very easy. So what is the trade-off? Up to about 60 knots, there isn't really any. Above that, most of the newer 15M gliders do have a performance advantage. That doesn't mean that the SparrowHawk falls out of the sky though. At 80 knots it is still getting around 20:1 L  . It has flown a 300 km triangle with a 25 knot wind blowing andaveraged 52 mph. I realise that this is all talk until you actually see it, that is why I would like to have the opportunity to show the plane to as many people as possible over the next few months. Anyone who would like to see it, please let me know. Best regards, Doug Taylor ps. I am not an employee of Windward Performance, although I did help out on the construction of tooling and the first few SparrowHawks. I am just trying to help spread the word because I believe this is one fantastic machine! (Kirk Stant) wrote in message No, unfortunately I havn't, so my opinion is worth precisely what you paid for it! I am obviously making an assumption, and I hope I'm proven wrong, by the way, as the Sparrowhawk looks like a nice little glider, but my real concern is triggered by the emphasis on the "ultralight" aspect, which obviously drives the 155lb (!) weight of the glider - I can't help but wonder where the weight has been saved. By the VNE and G limits, it seems to have faily strong wings, so I'm guessing the fuselage is a real eggshell... And I truly hope that an "ultralight" Sparrowhawk (i.e. no N number) never shows up in the hands of an untrained, unlicenced non-pilot, because I think that is a sure way to kill or injure someone, real quick! Has anyone out there actually touched and/or flown a Sparrowhawk? How about an eyewitness report - I havn't eaten any crow in a while... Kirk
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#64
January 12th 04, 04:24 AM
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#65
January 12th 04, 05:15 AM
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In article ,
Mike Borgelt wrote: On 11 Jan 2004 14:39:20 -0700, (Mark James Boyd) wrote: In article , Mike Borgelt wrote: I've come to much the same conclusion as Mike. I'd use a single more powerful turbine (maybe the 1500) instead of 2, but the numbers seem to work for even fairly short fields. The heat on the tail scares me though. Hmmm...how do we get rid of the glider tail?  The guys with the Silent don't seem to have a problem with the heat on the tail - the two AMT 450 turbines seem to be mounted parallel to the centerline. If this still worries you a V tail as on HP gliders or the Salto is the easy answer. I've never seen a turbine airplane design that allows the hot exhaust to reach a control surface of the aircraft. The fact that the Silent flew a few times in this configuration is not convincing to me. If the owner would put it on a stand in a hangar and run it for an hour with his face right in front of the rudder/stab, I'd change my tune. I don't have any hard facts or figures, but my intuition sets off some warning flags here... I first thought of using the AMT1500 but when you do the numbers two AMT450s (and soon the XP versions with about 10% more thrust) are quite adequate for a 400kg glider. The larger engine isn't for more thrust than two engines, but just for the lower complexity of using one engine. Two engines are best used in aircraft with high wing loading that carry passengers through turbulence. Two engines in a light-wing loaded aircraft is just unneccesary, IMHO. Engine failure is a non-issue due to the glide ratio, and the reliability of turbines. The added weight, wiring, two starters, fuel lines, etc. seem silly if a single turbine can be used instead. Great for motorising motorless gliders as the weight in the fuselage is minimal. Convert part of the water tanks/bags for jet fuel.60Kg(75liters) will give you one hour. Figuring out how to manage fuel from two tanks is a minor complexity, and being able to dump fuel should ensure one doesn't fly "chinese style" (won weeng lo). It does seem using the fuel as ballast is an excellent feature, but I'd want to really think hard about fire dangers. Perhaps use less flammable fuel? I guess there is quite a variety of fuel choices available... Now look at a Sparrowhawk One AMT 450 will self launch this adequately. Two smaller engines may still be optimum for slightly increased thrust and engine out capability. More power than adequate = better. One can always throttle back for fuel savings. I suspect the designers used two engines instead of one because the 1500 may not be readily tested/ available rather than due to the need for redundancy. Again, I've flown some twins and they have their uses; a powered glider isn't a good match for two turbine powerplants (just overkill/expense)... Hope the Windward Performance guys have a plan to increase production because if this works they might be swamped by customers. The Sparrowhawk may be ideal for this application, but other light gliders also have comparable potential. And I personally would want to see a competitor which could taxi well. A self-launch glider which has trouble taxiing is less interesting to me personally than something more flexible. Besides, the noise may get one banned from the gliderport and forced to use a gasp towered airport... ;P
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#67
January 12th 04, 02:36 PM
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#68
January 12th 04, 04:41 PM
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Mike Borgelt wrote:
As for complexity of two jet engines compare with a horrible, heavy, noisy vibrating two stroke with reduction drive and propeller, complex and heavy extend /retract mechanism, heat issues if the engine is buried in the fuselage and complex operating procedures with very limited climb speed range. Look at the prices being charged for these contraptions. Compared to a two-stroke, four jet engines is an improvement. But again, IMHO, one jet engine of the same power is better than more engines in light wing-loaded aircraft. The complexity of pilot management, and the extra workload to manage the feeding and maintenance is the downside. And redundancy is, I believe, notional. I'd rather run out of gas and then switch to a full tank than run out of gas on one engine and then, a few seconds later, run out of gas on the other side. I hope we can agree as gentlemen to disagree on this one... I'm strongly in favor of a single turbine engine for this application. I've never seen a turbine airplane design that allows the hot exhaust to reach a control surface of the aircraft. The fact that the Silent flew a few times in this configuration is not convincing to me. If the owner would put it on a stand in a hangar and run it for an hour with his face right in front of the rudder/stab, I'd change my tune. I don't have any hard facts or figures, but my intuition sets off some warning flags here... You can easily then cant then out a little if you want. Problem solved(and a good argument for two engines) I just don't know how large the heat cones are out of these engines, so I can't really agree or disagree...I don't think I can solve this one from an armchair... Given you will have only an electric fuel pump you are going to want two anyway even for one engine. You already have two fuel tanks. You might want two batteries as well to be sure of getting a start when about to land out. Each of two smaller engines is lighter and simpler to swing out than one larger one. This looks one one of those issues where the "obvious" solution isn't so obvious on reflection. The cost of the engines seems to scale roughly with thrust so it is dollars per Newton you pay for. The smaller engines also have thousands of hours operating history which is worth a lot. And I *love* the idea of engine out capability plus with two you really aren't going to fail to get at least one running to avoid an outlanding. Out of gas is out of gas, period. Turbines get more reliable as they get larger, and are lots more reliable than anything with a prop. The reliability card simply has negligible meaning in this context. And again, the cost isn't the acquisition or fuel costs, it's continuing cost... I figured on one tank in each wing anyway and jet fuel is much less flammable than gasoline anyway. The fuel is slightly less flammable but the heat danger is much greater than a pure glider (of course). My point is just that if one has a choice, maybe use the least flammable fuel? You can still fill up with Jet A if needed... And I'm also emphasizing that I think the fire risk is really something to pay attention to and minimize by design... Yes and the redundancy is really nice to have. If the glider was not capable of climbing on one I'd agree with you that one engine is desirable but what is the point of designing around an engine that isn't readily available with lots of operating history? Completely true. If we MUST use two because of marketing/availability/testing reasons then fine. Two in the hand is better than none in the bush. But accepting a sub-optimal design instead of making some extra phone calls means somebody else is gonna compete with you later, at a better price offering reduced maintenance/complexity... The packaging of two is also easier. Boy I gotta strongly disagree with that. Installing, testing, wiring, instrumenting, fueling, operating, shutting down, diagnosing in flight, etc. for two engines is wholly different than one. There's a reason 727s have three crewmembers instead of one, and it isn't because of the complexity of the passengers or so the Captain can take a nap... I've seen and heard the R/C model jets fly. They aren't that noisy at all. Two smaller engines over the wingroots actually shields the people on the ground from much of the noise. My comment about noise meaning you may get banned from the gliderport was tongue in cheek. Here's the that should have been there...Taxiing is still going to be problematical but then very few existing self launchers taxi well(as opposed to Stemme's, Katanas etc and even they would have trouble at our airport. I've got some time in the Jet Caproni about 20 years ago and I wasn't that impressed. When I last flew in it 10 years ago the owner had figured it out and it was good. We are talking the same sort of thrust weight for a 400Kg glider(most 15/18m gliders) with two AMT 450's. Mike Borgelt Yes, I'd very much like to see taxi capability. A short wingspan and light weight like a Sparrowhawk is excellent for this turbine. The extra stuff to make it taxi well would sell it to the biggest market, "power pilots," with the best success. Mark Boyd
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#69
January 12th 04, 04:58 PM
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Mike Borgelt wrote:
As for complexity of two jet engines compare with a horrible, heavy, noisy vibrating two stroke with reduction drive and propeller, complex and heavy extend /retract mechanism, heat issues if the engine is buried in the fuselage and complex operating procedures with very limited climb speed range. Look at the prices being charged for these contraptions. Typical self-launchers are rpm limited to about 70-75 knot cruise, which is painfully slow when flying into a 30-40 knot headwind while trying to reach a wave. As a result, I often don't attempt to fly our best winter waves, since it'd an hour+ to reach them. Being able to cruise at 100+ knots would cut the transit time in half. -- ----- change "netto" to "net" to email me directly Eric Greenwell Washington State USA
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#70
January 12th 04, 05:11 PM
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Kirk Stant wrote:
I just wish the whole "ultralight" aspect would go away - that still scares me. It may be a pretty moot point - I doubt anyone could show up in an unregistered glider and get a tow at any glider operation I know of! Don't they tow ultralights at Turf? You know, on the "other" side of the airport? It doesn't take a 230 hp Pawnee to tow a 400 pound glider, though it tows behind one just fine. One question: how do you buy a factory-built Sparrowhawk and register it if it isn't certified yet? Or did I miss something. Just curious. It was registered in the Experimetal class, just like your LS-6. -- ----- change "netto" to "net" to email me directly Eric Greenwell Washington State USA
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