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#11
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Time to weigh in with some facts.
First, for those who are skeptical of the jet Silent's self-launch capabilities, I can assure you that I routinely launch from my home airport at 6200' MSL. Ask anyone who saw the demonstration during the 1-26 Nationals this year. Granted, on hot days it does use some runway. I have performed jet-launched aerobatic routines at several airshows this summer, including full aerobatic routines beginning at less than 1000'. Noise has not been a problem. In fact, in the airshow business, where noise equals dollars, the jets are a bit too quiet. At 1000', they are MUCH less noisy than any towplane. In fact, when I'm on a normal downwind, the guys on the ground can't distinguish the jet noise from the noise of the highway about 3 miles from the airport. TBO times are currently low, but an overhaul costs about $300 (typically just inspection and new bearings). These are NOT 'throwaway' engines. The engines can be removed in about 15 minutes, and overnight shipped back to the factory in a breadbox. My overhauls cost less than the shipping for most powerplants. TBO times are getting better as the engines develop. I predict TBO times in the 100-200 hour range within a few years, and over 1000 hours in the not-too-distant future. Fuel burn is high, but for the brief time required for a normal glider launch, tolerable. I carry 10 gallons, good for over 30 minutes of climb, or more than 1 hour at 70 knot cruise. (I climb about 500 ft/minute at sea level) There are other engines 'under development' with better predicted performance numbers than the AMT-USA engines. Some of these are garage-shop projects, some (including one being advertised by a prominent US sailplane dealer) are probably currently nothing more than plans and a mockup. I do not know of any other microjet engine currently available that has the performance, reliability and factory support required for regular service in a manned aircraft. I know of several university projects in which a jet assisted sailplane has been flown. Typically, these have managed to barely sustain level flight under power, and are a far cry from a serviceable aircraft. Jet engines are not a 'perfect' answer. Like the early military jets, there are still issues to be resolved. But, in the next few years, microjets will definitely play an important role in all aspects of sport aviation. Videos of the jet sailplane, Salto sailplane and biplane are available on my website at www.silentwingsairshows.com Bob Carlton At 01:12 30 August 2005, M B wrote: The biggest issue against these engines is the TBO. The AMT 45lbs engines are 25-50 hours for TBO. Not bad in 20 minute spurts, but 160 launches for $4000 just in engine costs ain't chicken feed. $25 per launch? Good, but not fantastic. And for 2 of them maybe a bit more... Still, glider self-launch seems like a much better GA application than many other options... At 21:48 29 August 2005, Titoa wrote: I had a look at the microjet engine. With 65 Lb of thrust, and with 36 cm long, 16 cm diameter, a 400 Kg plane should be able to climb at 1,3 m/s sustained (25 Lb for the aero drag, rest for climbing). Going to 1000 m would take just 12 mins and 11 Kg of fuel. I ignore the cost of fuel, but at 1 $ /kg, that makes for cheap tows to offset the cost of the engine. Next, could the exhaust temperature be solved by embedding the tiny engine behind the pilot and letting the exhaust out throug some openning in the aft taper of the fuselage, and well below the tail planes. This would however need some adjustable intake port in the fuselage. But in all cases it should all be much simpler that folding out a propeller with or without a piston engine.... . Mark J. Boyd |
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I was unaware that overhauls were so very inexpensive.
I assumed the worst case, and am happy this is unneccessary. Thank you Bob for setting the record straight here. Plus, thank you for doing this AT ALL. I think you are definitely raising awareness of this technology, and have completely followed through on FAA issues and have a better handle on this technology as it applies to sailplanes than anyone else I have encountered. My only deep regret is that your airshow performances are not scheduled in Calif. But I am glad many others in the soaring community have had the privilege to see you perform. Your logged hours and experience go a LONG way towards proving the viability of this technology. Thank you! At 03:12 31 August 2005, Bob C wrote: Time to weigh in with some facts. First, for those who are skeptical of the jet Silent's self-launch capabilities, I can assure you that I routinely launch from my home airport at 6200' MSL. Ask anyone who saw the demonstration during the 1-26 Nationals this year. Granted, on hot days it does use some runway. I have performed jet-launched aerobatic routines at several airshows this summer, including full aerobatic routines beginning at less than 1000'. Noise has not been a problem. In fact, in the airshow business, where noise equals dollars, the jets are a bit too quiet. At 1000', they are MUCH less noisy than any towplane. In fact, when I'm on a normal downwind, the guys on the ground can't distinguish the jet noise from the noise of the highway about 3 miles from the airport. TBO times are currently low, but an overhaul costs about $300 (typically just inspection and new bearings). These are NOT 'throwaway' engines. The engines can be removed in about 15 minutes, and overnight shipped back to the factory in a breadbox. My overhauls cost less than the shipping for most powerplants. TBO times are getting better as the engines develop. I predict TBO times in the 100-200 hour range within a few years, and over 1000 hours in the not-too-distant future. Fuel burn is high, but for the brief time required for a normal glider launch, tolerable. I carry 10 gallons, good for over 30 minutes of climb, or more than 1 hour at 70 knot cruise. (I climb about 500 ft/minute at sea level) There are other engines 'under development' with better predicted performance numbers than the AMT-USA engines. Some of these are garage-shop projects, some (including one being advertised by a prominent US sailplane dealer) are probably currently nothing more than plans and a mockup. I do not know of any other microjet engine currently available that has the performance, reliability and factory support required for regular service in a manned aircraft. I know of several university projects in which a jet assisted sailplane has been flown. Typically, these have managed to barely sustain level flight under power, and are a far cry from a serviceable aircraft. Jet engines are not a 'perfect' answer. Like the early military jets, there are still issues to be resolved. But, in the next few years, microjets will definitely play an important role in all aspects of sport aviation. Videos of the jet sailplane, Salto sailplane and biplane are available on my website at www.silentwingsairshows.com Bob Carlton At 01:12 30 August 2005, M B wrote: The biggest issue against these engines is the TBO. The AMT 45lbs engines are 25-50 hours for TBO. Not bad in 20 minute spurts, but 160 launches for $4000 just in engine costs ain't chicken feed. $25 per launch? Good, but not fantastic. And for 2 of them maybe a bit more... Still, glider self-launch seems like a much better GA application than many other options... At 21:48 29 August 2005, Titoa wrote: I had a look at the microjet engine. With 65 Lb of thrust, and with 36 cm long, 16 cm diameter, a 400 Kg plane should be able to climb at 1,3 m/s sustained (25 Lb for the aero drag, rest for climbing). Going to 1000 m would take just 12 mins and 11 Kg of fuel. I ignore the cost of fuel, but at 1 $ /kg, that makes for cheap tows to offset the cost of the engine. Next, could the exhaust temperature be solved by embedding the tiny engine behind the pilot and letting the exhaust out throug some openning in the aft taper of the fuselage, and well below the tail planes. This would however need some adjustable intake port in the fuselage. But in all cases it should all be much simpler that folding out a propeller with or without a piston engine.... . Mark J. Boyd Mark J. Boyd |
#13
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On 31 Aug 2005 03:49:38 GMT, M B
wrote: I was unaware that overhauls were so very inexpensive. I assumed the worst case, and am happy this is unneccessary. Shall we bet that the overhaul is going to become expensive once the engine is certified as a powerplant for certified gliders? Bye Andreas |
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