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#31
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FES underpowered for 18m ship?
Dave Walsh wrote on 9/15/2020 2:39 AM:
A real problem is putting the word "KISS" and "FES" is the same sentence or indeed "KISS" and "electric propulsion". There is nothing simple about electric motors powered by LiPo batteries. It should be obvious the "KISS" remark refers to a comparison with other means of propulsion, and not to a sailplane without a motor. Based on my experience with a mast mounted combustion engine and discussions with owners of FES gliders, I believe the FES system is less complex to own and operate. And, as we all know, a motorless glider has it's own complexities, such as getting tow when and where desired, and needing a retrieve if it doesn't get home. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "A Guide to Self-Launching Sailplane Operation" https://sites.google.com/site/motorg...ad-the-guide-1 |
#32
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FES underpowered for 18m ship?
On 9/15/20 6:38 AM, Dave Nadler wrote:
On Monday, September 14, 2020 at 9:32:04 PM UTC-4, kinsell wrote: From the mini-Lak brochure on lak.it: "The FES propulsion system has no known reports of in-flight failures, allowing you to stay confident in areas of no-lift." That's just Nonsense. I know of an instance where the controller failed while FES was under power and the engine quit. I hardly hear about all problems, surely there have been others... Of course it's nonsense, but if you tell people exactly what they want to hear, they gobble it up. Red meat for the base. The Silent 2 that went through the roof in Connecticut made quite a splash, I'd call that an inflight failure. Apparently if a battery explodes on landing roll, that doesn't count as "in flight". People say motors have been around forever, that's true. But inverters that take high-voltage DC, convert it to three-phase power at over 25KW using transistors, and doing it with limited space and cooling, well that's not something you run down to Grainger to pick up. I'm not familiar with the FES accident referenced by the OP, would like more data on that. -Dave |
#33
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FES underpowered for 18m ship?
On Tuesday, September 15, 2020 at 10:02:12 AM UTC-4, Kenn Sebesta wrote:
On Tuesday, September 15, 2020 at 5:45:05 AM UTC-4, Dave Walsh wrote: A real problem is putting the word "KISS" and "FES" is the same sentence or indeed "KISS" and "electric propulsion". There is nothing simple about electric motors powered by LiPo batteries.. I couldn't disagree more. Electric motors are amazingly simple and reliable, and LiPo batteries-- in general-- are extremely safe. The issue arises when you start pushing the technology to its maturity limits. At the power/weight/energy limits we want for the gliders we start making compromises which push into research territory. However, that is a far cry from assuming there is anything complex about the system. We just don't know how to use industrial-grade COTS parts to make the glider's system as light as we desire, so we wind up having to have some bespoke parts. The bespoke parts aren't as well tested because the fleet is small, and this is where problems creep in. The motors themselves have 0 problems and a 20-30kW motor is tiny in the scheme of industrial COTS motors. Given your apparent claimed knowledge could you please list available COT components and sources for such a glider. Motor 25 kw Controller Interface Battery system with BMS and charging system How hard could it be? UH |
#34
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FES underpowered for 18m ship?
Again, this depends on where you fly. I fly out of Truckee usually, and a typical retrieve is from Carson City as I mentioned. It is only 20 miles away, but with a 4000 ft high ridge in between. 100% of the pilots flying cross country out of Truckee will have this problem eventually. It isn't dangerous - a perfectly good airport at Carson - but electric sustainers in their current state of development will not support that retrieve, but an ICE will. There are countless other similar examples in the Great Basin area of a "deep valley with limited exit" - and a good landing site at the bottom. If you don't fly over these, you don't fly in this area. That is not to say the electric isn't useful (and I didn't say that), just that it has limitations in some terrain that the ICE may not (as in the Alps example mentioned above).
On Tuesday, September 15, 2020 at 12:53:30 AM UTC-7, krasw wrote: In order to climb out of deep valley with limited exit is problem that 99% of pilots will never have, and those 1% should reconsider another sport. This is not a problem meant to be solved with tiny engines. |
#35
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FES underpowered for 18m ship?
John, for the Carson relight you are correct if one waits until pattern altitude at Carson. However the strategy should be to relight over spooner the moment you down to your minimum altitude, say 9K. You will need a short run and only 1-2K climb to get to a safe final glide altitude. If you run out of battery before hand you can escape back to Carson.
At least this is what I would do if I have FES. Ramy |
#36
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FES underpowered for 18m ship?
On Tuesday, September 15, 2020 at 4:00:32 AM UTC-4, Matthew Scutter wrote:
...I believe both the PSA jets and the JS jets have approximately the same climb altitude, ~1500m, and range ~110km? Paul Mander figured the utility of the jets in his ASH-25J were about equivalent to electric (heavy load of jet fuel compared to batteries, by total available climb height). Of course jet cruises faster. |
#37
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FES underpowered for 18m ship?
At 08:00 15 September 2020, Matthew Scutter wrote:
On Tuesday, September 15, 2020 at 9:30:06 AM UTC+2, Paul T wrote: Just get a jet turbo far better - wouldn't trust FES for a climb in mountain conditions. How does a jet help? I believe both the PSA jets and the JS jets have approximately the same climb altitude, ~1500m, and range ~110km? See http://js3.at/wp-content/uploads/2018/11/JS- MD_3_Jet_Sustainer_Supplement.pdf Performance seems about the same, the biggest difference as I can tell is trading reliability for cruise speed. A jet will get you out of bad air quicker due to higher cruising speed - minimally more drag than FES and less when stowed.......simples -JS1 has 250 km range I believe .............. - Anything to say a jet is less reliable than FES, where is the data? or just simple speculation from a biased observer? |
#38
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FES underpowered for 18m ship?
On Tuesday, September 15, 2020 at 4:30:06 PM UTC-4, Paul T wrote:
Anything to say a jet is less reliable than FES, where is the data? A bunch of my friends with jet have had problems (and landouts). I believe reliability has been improved, but we'll see. |
#39
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FES underpowered for 18m ship?
On Tuesday, September 15, 2020 at 11:11:26 AM UTC-7, Ramy wrote:
John, for the Carson relight you are correct if one waits until pattern altitude at Carson. However the strategy should be to relight over spooner the moment you down to your minimum altitude, say 9K. You will need a short run and only 1-2K climb to get to a safe final glide altitude. If you run out of battery before hand you can escape back to Carson. At least this is what I would do if I have FES. Ramy Hi Ramy. Is this what happened last month when you had an FES failure and landed on the golf course in incline? Something like: - flies over east lake tahoe - "getting low, here we go!" - goes to turn the FES knob - "dang, did I really leave my FES at the factory?" - wing meets bush Just wondering since I can't think of any other plausible explanation to why someone would go where you went at the altitude you were at without some engine or a will to die. |
#40
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FES underpowered for 18m ship?
Cumungus wrote on 9/15/2020 2:31 PM:
On Tuesday, September 15, 2020 at 11:11:26 AM UTC-7, Ramy wrote: John, for the Carson relight you are correct if one waits until pattern altitude at Carson. However the strategy should be to relight over spooner the moment you down to your minimum altitude, say 9K. You will need a short run and only 1-2K climb to get to a safe final glide altitude. If you run out of battery before hand you can escape back to Carson. At least this is what I would do if I have FES. Ramy Hi Ramy. Is this what happened last month when you had an FES failure and landed on the golf course in incline? Something like: - flies over east lake tahoe - "getting low, here we go!" - goes to turn the FES knob - "dang, did I really leave my FES at the factory?" - wing meets bush Just wondering since I can't think of any other plausible explanation to why someone would go where you went at the altitude you were at without some engine or a will to die. You sound upset. Did Ramy's explanation offend you in some way? I thought he provided a good description of the situation, which is something we rarely get, as the pilot is either dead or unwilling to talk. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "A Guide to Self-Launching Sailplane Operation" https://sites.google.com/site/motorg...ad-the-guide-1 |
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