A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Soaring
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Which sustainer system would you chose for your sailplane?



 
 
Thread Tools Display Modes
  #101  
Old February 25th 16, 06:54 PM posted to rec.aviation.soaring
[email protected]
external usenet poster
 
Posts: 155
Default Which sustainer system would you chose for your sailplane?

I agree - FES seems the future.

BUT - now after the SSA Convention..... the 13.5 self launchers are looking so inviting. I origionally thought Sustainer was the way to go on a 15m with 18m tips. But now the 13.5 are claiming 40+:1 glide ratio. next year will be decision time good problem to have!

FES seems to dominate the Convention floor.

WH1
  #102  
Old February 25th 16, 08:48 PM posted to rec.aviation.soaring
son_of_flubber
external usenet poster
 
Posts: 1,550
Default Which sustainer system would you chose for your sailplane?

FES rings all of my bells, but putting aside factors like wingspan, L/D, Vne, what is the additional cost and benefit of Front_Electric_Self_Launch (FESL) compared to FES?

How much does FESL add to the dollar cost of a similar F_Electric_Sustainer sailplane?

What drawbacks does FESL bring with it? The Mini-LAK has a pilot weight limitation for FESL. It has a tall main gear for prop clearance; how does that affect sight picture and stability for landing and takeoff? The tall gear can absorb a lot of landing shock, but would it be less robust and break?

If a towplane were available, I'd take a tow to 1500+ even if I had FESL, so how often would I ever use FESL? (Half the fun of soaring for me is the people on the ground, so I'm not attracted to launching by myself.) I'd take the tow to conserve battery charge for sustained flight, and I like the climb rate behind a Pawnee on a sinky tree lined short field. I know people with gas self-launchers that take aerotows for similar reasons.

FES is a very clean, simple and big payback feature. FESL not so much. I'm tempted to go with FESL because of extra feature of self launch and minimal cost differential between FES and FESL, but it seems a bit crazy to paying any price for a feature that I don't anticipate using, especially if there are additional non-dollar costs/tradeoffs.

  #103  
Old February 25th 16, 09:18 PM posted to rec.aviation.soaring
son_of_flubber
external usenet poster
 
Posts: 1,550
Default Which sustainer system would you chose for your sailplane?

On Thursday, February 25, 2016 at 1:15:33 AM UTC-5, 2G wrote:

I personally won't have a sustainer. I fly a lot in Utah and Nevada, and the sustainer probably won't get me over the mountain ranges I have to cross, or even get me to a landable field that may be 50+ miles away.


But what about the use case where you plan to get home as a pure glider and use the FES to get you the last five miles to home or five miles to a decent landout field when you're a bit too optimistic? What about using FES for a few minutes when you have a PT3 or hit strong sink on final? What about using FES for a few minutes to find the next thermal before you descend below the 'lift band'?

From far off Vermont, there seem to be a lot of uses for FES in the SW that do not involve climbing above mountain ranges or sustaining flight at constant altitude for 50 miles.

On the other hand, I'm under the impression comparing SW and back east soaring, the SW has higher AGL cloudbase and stronger lift, so landouts are easier to avoid, so FES is less of a value proposition. Back east with lower AGL cloudbases and weaker lift, FES has more appeal, especially in areas with poorer landout options.


Questions about FES and Density Altitude:

I understand that High Density Altitude would reduce FES climb rate and that would reduce the value of FES out west (and electric self-launch would be impractical).

But how does Density Altitude affect FES range assuming level sustained flight? Sure, the prop would get less bite on thinner air and therefore the prop rpm would need to be higher to produce the same thrust, but battery charge rundown is proportional to thrust produced over time. I'm thinking that if the motor has the rpm for climbing at low density altitude, it would have the rpm for sustaining at high density altitude. Is the efficiency of FES lower at higher RPM?
  #104  
Old February 25th 16, 10:09 PM posted to rec.aviation.soaring
[email protected]
external usenet poster
 
Posts: 155
Default Which sustainer system would you chose for your sailplane?

I am no expert - but from the info at the convention:

Today there is no FESSL over 13.5m - it is a weight issue. the FES sustainer comes in 15m & 18m . There is one new Polish 13.5 with Electric motor on a boom, also self launching.

the 13.5m seem to have gained glide ratio - going from 37:1 to mid 40's:1 (if you believe the brochure.

I am also inclined to believe most people will opt to aero-tow with more reserve to get home - but having an option to fly on a weekday when no one is around to tow???? inviting, no.

WH1
  #105  
Old February 25th 16, 10:36 PM posted to rec.aviation.soaring
son_of_flubber
external usenet poster
 
Posts: 1,550
Default Which sustainer system would you chose for your sailplane?

On Thursday, February 25, 2016 at 4:09:07 PM UTC-5, wrote:

the 13.5m seem to have gained glide ratio - going from 37:1 to mid 40's:1


As a recreational pilot with small interest in contests, glide ratio seems much less important with FES. If I'm planning to land with the batteries half discharged, the FES will greatly extend my range for the day (and give me the same range as a higher L/D ship). If I'm flying XC with friends with better L/D ships, I can run the FES between thermals, compensate for my inferior polar, and keep up with the higher L/D ships.

If I ever compete it will be in handicapped club class, so 37:1 seems adequate.

  #106  
Old February 26th 16, 03:01 AM posted to rec.aviation.soaring
2G
external usenet poster
 
Posts: 1,439
Default Which sustainer system would you chose for your sailplane?

On Thursday, February 25, 2016 at 2:26:37 AM UTC-8, wrote:
About jet sustainers, it is not true to say that they are not cerified for aircraft use, the M+D (JS1) and PSR (Ventus) jets are EASA certified. As regards the need to be spun to high rpm to start - what is the issue there? Given that the turbines run at 75,000 to 100,000 rpm they have got to get up there somehow. The M+D jet is only spooled up to 8,000 rpm by the electric motor before the fuel system takes over (in two stages). 8000 rpm is nothing remarkable for an electric motor.

Lastly, we can't meaningfully judge the reliability of jets based on the experiences of pre-certification installations during the development stage - which includes all the JS1 installations prior to November 2015. My jet was installed under South African experimental type certificate. I think that the turbine and firmware are at or very close to the certification spec and so far I have had no failed starts out of 44 attempts.

In general I think that failures of all types of sustainer generally arise from ancillary components ( e.g. fuel pump, spark plugs, carburettor diaphragm etc) and electrical issues (e.g. relays, connections etc) and electric glider motors certainly have potential reliabilty vulnerabilities.


Ok, so what you are saying is that jets installed in the last 3 months are reliable. My experience has been that engine installation problems may take years - not months - to reveal themselves. This might be ok if you exercise due caution, primarily having a landable field within easy reach. Jets do have the advantage that they are low vibration, an issue with a reciprocating piston engine (I really like my Wankel for this reason). On the down side, they consume a lot of fuel.

Tom
  #107  
Old February 26th 16, 10:01 AM posted to rec.aviation.soaring
[email protected]
external usenet poster
 
Posts: 374
Default Which sustainer system would you chose for your sailplane?

I am *not* saying that jets installed in the last 3 months are reliable.

I am saying that to judge the reliability of the jets in gliders it is only meaningful consider aircraft with the fully developed specification - just as we would do for any other product.
  #108  
Old February 27th 16, 12:23 AM posted to rec.aviation.soaring
2G
external usenet poster
 
Posts: 1,439
Default Which sustainer system would you chose for your sailplane?

On Friday, February 26, 2016 at 1:01:25 AM UTC-8, wrote:
I am *not* saying that jets installed in the last 3 months are reliable.

I am saying that to judge the reliability of the jets in gliders it is only meaningful consider aircraft with the fully developed specification - just as we would do for any other product.


You did say that "we can't meaningfully judge the reliability of jets based on the experiences of pre-certification installations during the development stage - which includes all the JS1 installations prior to November 2015".. This isn't an endorsement of jet engines installations that are certified, so I stand corrected. I would like to know the differences between uncertified jet and certified jet installations; did they uncover problems and fix them, or is the failure mode still there? You are right: there are a lot of components in any engine installation and it only requires the failure of one of them to prevent a start. The more we share information the better we will understand the strengths and weaknesses of each propulsion system. And don't count on the manufacturers to do this!

Tom
  #109  
Old February 27th 16, 10:05 AM posted to rec.aviation.soaring
[email protected]
external usenet poster
 
Posts: 374
Default Which sustainer system would you chose for your sailplane?

Tom, I am not privvy to the details of the development of the JS1 jet but I have heard about some things along the way:

Change to the tolerances of the tiny gap between the rotor and the casing - corrected surging on starting at at typical South African altitudes.

ECU firmware changes.

Increased fuel pressure and smaller injector nozzles - for better fuel misting and starting.

Electronic component change in the ECU - to correct wrong voltage delivery to the glow plug leading to glow plug failures.

The uncertainties that I have relate to the electronics rather than the turbine - that and making sure the fuel is clean.
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Front Electric Sustainer Dan Marotta Soaring 28 January 31st 13 02:32 AM
would an electric sustainer be practical Brad[_2_] Soaring 7 July 24th 09 06:29 PM
Which Came First, the Santa Monica Airport, Or Those Who Chose To Build Their Homes Adjacent To It? Larry Dighera Piloting 16 May 7th 07 10:34 PM
BAF or CEF? I chose BAF. Paul Tomblin Instrument Flight Rules 0 October 23rd 04 04:33 PM
DG goes the sustainer option. Paul Soaring 25 June 4th 04 12:16 AM


All times are GMT +1. The time now is 09:34 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AviationBanter.
The comments are property of their posters.