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#21
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Advice on motor glider wanted - FES - Jet - Engine
On Saturday, January 7, 2017 at 3:10:38 PM UTC-5, Dan Marotta wrote:
One problem I've seen is getting low away from a landable area following flight in very cold air, e.g., wave. Whereas my Stemme has very little increase in drag during engine start, and it starts quickly and reliably, there's a requirement not to use much power until the oil temperature reaches a certain level. Even with cowl flaps closed, that can take 5 minutes or more to achieve. Fortunately, with power just above idle, the Stemme has little to no decent. Having flown turbojets in Alaska and turbofans in the lower 48, I don't recall any cautions about oil temperature, though good sense should prevail. There should be enough temperature for oil to circulate. The jets would start and run just fine at -40 deg F. Dan, as far as I know, the small jets we are talking about here or at east the one I looked at seriously in an ASW-20CLJ do not have any oil circuit. The main bearings are lubricated by the jet fuel which is fortified by turbine oil. Uli |
#22
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Advice on motor glider wanted - FES - Jet - Engine
Oh! Learn something new every day. That's a good thing!
On 1/7/2017 4:13 PM, AS wrote: On Saturday, January 7, 2017 at 3:10:38 PM UTC-5, Dan Marotta wrote: One problem I've seen is getting low away from a landable area following flight in very cold air, e.g., wave. Whereas my Stemme has very little increase in drag during engine start, and it starts quickly and reliably, there's a requirement not to use much power until the oil temperature reaches a certain level. Even with cowl flaps closed, that can take 5 minutes or more to achieve. Fortunately, with power just above idle, the Stemme has little to no decent. Having flown turbojets in Alaska and turbofans in the lower 48, I don't recall any cautions about oil temperature, though good sense should prevail. There should be enough temperature for oil to circulate. The jets would start and run just fine at -40 deg F. Dan, as far as I know, the small jets we are talking about here or at east the one I looked at seriously in an ASW-20CLJ do not have any oil circuit. The main bearings are lubricated by the jet fuel which is fortified by turbine oil. Uli -- Dan, 5J |
#23
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Advice on motor glider wanted - FES - Jet - Engine
I side with Bruce. It's pretty obvious to me that FES is the better choice.. I believe Bruce left off the most important advantage of FES...
That being the higher inherent reliability of operation. I can't prove it, but my own feeling is that FES would be an order of magnitude more reliable in starting up. And you'll know much more quickly whether it did or did not. The only real downside to FES is the drag that the folded props will introduce. I'm thinking that the tactical benefit of having a reliable motor escape will prove to be well worth the small added drag over the course of a multi-day event. |
#24
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Advice on motor glider wanted - FES - Jet - Engine
On Saturday, January 7, 2017 at 7:58:33 PM UTC-7, Steve Koerner wrote:
I side with Bruce. It's pretty obvious to me that FES is the better choice. I believe Bruce left off the most important advantage of FES... That being the higher inherent reliability of operation. I can't prove it, but my own feeling is that FES would be an order of magnitude more reliable in starting up. And you'll know much more quickly whether it did or did not. The only real downside to FES is the drag that the folded props will introduce. I'm thinking that the tactical benefit of having a reliable motor escape will prove to be well worth the small added drag over the course of a multi-day event. Steve - Having now flown my LAK-17B FES for 5 years, your "feeling" is dead on. We definitely think alike about the reliability of the FES. After dozens of starts on the ground and in the air, it has never let me down..(knock on wood)! FYI, I am writing an "FES Update" for Soaring magazine, so stay tuned for more info. Thx - Renny |
#25
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Advice on motor glider wanted - FES - Jet - Engine
We had a member place a similar level of faith in his FES to that shown above, using it to climb away from unlandable terrain. The system powered up and climbed away as advertised - initially. During the climb, the battery overheated and the FES shutdown, as it's designed to do, to protect the battery and ultimately, the aircraft. The pilot was now at moderately low altitude and presented with an unexpected outlanding (startle factor) over terrain that hadn't been assessed for such (complacency / over reliance on FES). A successful outlanding was achieved in that the pilot walked away unharmed. The glider was extensively damaged.
My personal opinion is that electric sustainers are the future and in time, will be the hands down winner when it comes to glider propulsion. That day is yet to arrive because of current limitations in battery technology, namely energy density and safety/reliability. I have a jet sustainer in my glider which I love but at the same time don't trust. I climb in the vicinity of my chosen & assessed outlanding field until I feel it's safe move on (terrain dependent but usually 1,800ft or so). A friend, knowing I'd flown over an area with a lot of unlandable terrain, once asked "would you go there in a pure glider?". The answer was yes, because I only ever go to places I wouldn't go in a pure glider, preserving glide out to a landable area. The sustainer is an installation of convenience to me, to get me back to my home airfield instead of sitting in a fly blown paddock in the middle of nowhere. It's not a substitute for basic gliding principles and judgement. CJ |
#26
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Advice on motor glider wanted - FES - Jet - Engine
On Saturday, January 7, 2017 at 8:54:32 PM UTC-7, wrote:
We had a member place a similar level of faith in his FES to that shown above, using it to climb away from unlandable terrain. The system powered up and climbed away as advertised - initially. During the climb, the battery overheated and the FES shutdown, as it's designed to do, to protect the battery and ultimately, the aircraft. The pilot was now at moderately low altitude and presented with an unexpected outlanding (startle factor) over terrain that hadn't been assessed for such (complacency / over reliance on FES). A successful outlanding was achieved in that the pilot walked away unharmed. The glider was extensively damaged. My personal opinion is that electric sustainers are the future and in time, will be the hands down winner when it comes to glider propulsion. That day is yet to arrive because of current limitations in battery technology, namely energy density and safety/reliability. I have a jet sustainer in my glider which I love but at the same time don't trust. I climb in the vicinity of my chosen & assessed outlanding field until I feel it's safe move on (terrain dependent but usually 1,800ft or so). A friend, knowing I'd flown over an area with a lot of unlandable terrain, once asked "would you go there in a pure glider?". The answer was yes, because I only ever go to places I wouldn't go in a pure glider, preserving glide out to a landable area. The sustainer is an installation of convenience to me, to get me back to my home airfield instead of sitting in a fly blown paddock in the middle of nowhere. It's not a substitute for basic gliding principles and judgement. CJ Interesting account and I am sincerely glad your friend walked away. Regardless of the type of sustainer, sound judgement is always critical. Flying over unlandable terrain with the expectation that your sustainer will bail you out, as was seen in this case, was not a wise decision. Whatever system you use, you should always have a "plan B" should it not start. I do believe the time for electric is now here. We all know that no system is perfect, but the FES does an outstanding job when used in conjunction with common sense. Over 100 gliders now have the FES and many of the major glider manufacturers are offering it as an option. It may not be for everyone, but for many folks the FES is a great option to have. Finally, let's not forget the famous expression....“Don't let the perfect be the enemy of the good.” If we all wait for "perfect," we will see very little progress in our sport.... |
#27
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Advice on motor glider wanted - FES - Jet - Engine
On Saturday, January 7, 2017 at 7:54:32 PM UTC-8, wrote:
I have a jet sustainer in my glider which I love but at the same time don't trust. I climb in the vicinity of my chosen & assessed outlanding field until I feel it's safe move on (terrain dependent but usually 1,800ft or so). A friend, knowing I'd flown over an area with a lot of unlandable terrain, once asked "would you go there in a pure glider?". The answer was yes, because I only ever go to places I wouldn't go in a pure glider, preserving glide out to a landable area. The sustainer is an installation of convenience to me, to get me back to my home airfield instead of sitting in a fly blown paddock in the middle of nowhere. It's not a substitute for basic gliding principles and judgement. CJ Has it ever failed to start? Is this a JS1? |
#28
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Advice on motor glider wanted - FES - Jet - Engine
On Sunday, January 8, 2017 at 5:58:33 AM UTC+3, Steve Koerner wrote:
I side with Bruce. It's pretty obvious to me that FES is the better choice. I believe Bruce left off the most important advantage of FES... That being the higher inherent reliability of operation. I can't prove it, but my own feeling is that FES would be an order of magnitude more reliable in starting up. And you'll know much more quickly whether it did or did not. The only real downside to FES is the drag that the folded props will introduce. I'm thinking that the tactical benefit of having a reliable motor escape will prove to be well worth the small added drag over the course of a multi-day event. I assumed that "instant starting" implies that you know right away whether it's going to start or not. You can safely use this to scratch lower, near a landable area, and pull the trigger much later in your landing approach. Assuming that it *will* always start 100.000% of the time, and using that assumption to fly low over unlandable areas would be foolish. Things do become disconnected sometimes. If you insist on doing this then at least test it for a few seconds in flight before you start the task! That eliminates many of the bigger risks. But personally I'd always try to have an escape route or landing area available. |
#29
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Advice on motor glider wanted - FES - Jet - Engine
Has it ever failed to start? Is this a JS1?
Hi, It hasn't failed for me yet *touches wood and throws salt over shoulder*. Yes, it's the M&D TJ42 in a JS1. CJ |
#30
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Advice on motor glider wanted - FES - Jet - Engine
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