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fes ot jet (pros and cons)



 
 
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  #21  
Old August 7th 19, 01:46 PM posted to rec.aviation.soaring
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Default fes ot jet (pros and cons)

On Wednesday, August 7, 2019 at 5:15:05 AM UTC-4, Paul Ruskin wrote:
At 20:30 06 August 2019, 2G wrote:

I have heard of far too many "failure to start" incidents

with jets to consider them a viable self-retrieve option. Just
consider it a bonus if they do start.

FES is far more reliable, assuming the battery fire

incidents are a thing of the past (there have been design
changes to the battery).

It's a bit more complicated than that.

Personally, I think it's a good idea to consider a start of any
engine a bonus, and to have a safe place to land if it
doesn't.

With the jets, if they are set up right they start very well.
Not all are set up right though, it seems. (It took a few
months to get mine set up correctly - it has been very
reliable ever since). Also, I know more FESs that have
ended up in fields than jets because they haven't had much
range after climbing.

With current battery technology the FESs have other
limitations too. My understanding is that full power is less
likely to be available on an even partially depleted battery.
So you can't perhaps do what you can do in a jet - climb
from low to a sensible height, then turn it off, and if
necessary do it all again a bit later. And again.

What was unexpected to me is that the FES owners I know
are using a higher decision height than I am with a jet. It
is the case that the jet takes ~40 seconds to get to full
power, but you know you have a start after 20 and having
the engine out adds little drag and workload. So in practice
you can start it at low key and go on with flying the rest of
a circuit - which puts my personal lowest start decision
height at about 500 ft AGL. (I've done it lower, but on
reflection think I was reducing my margins too much and
won't do it again). The FES owners seem to be using a lot
more than this due to lack of climb performance.

It's one of those interesting cases where there are several
different technologies to solve a problem - all have pros and
cons, but there's no clear winner. If you could double the
capacity of the batteries, then I think FES would win - but
as has been pointed out elsewhere, battery technology
moves slowly. So at the moment, it's a question of which
factors are important to you.

Paul


My sense, from talking to a number of FES users, is that The major benefit is search for lift, not just climb out at high power for the save. This uses very low power to search around for the thermal that makes the save and conserves battery. Doing at a bit greater height adds margin but also makes the lift found more usable.
Re battery technology. It will remain an evolution, likely not revolution. High volume batteries have a very few common packages. Example- the 18650 cell that is used in everything from lap tops to Teslas. A new battery needs to fit into the user product architecture, as well as the established production system, to get a viable user base. New cells are coming now that add about 10% more capacity while still handling high current loads.
FWIW
UH
  #23  
Old August 7th 19, 05:08 PM posted to rec.aviation.soaring
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Default fes ot jet (pros and cons)

Jet is lighter than FES. And a jet is cool in its own way.
  #24  
Old August 7th 19, 06:03 PM posted to rec.aviation.soaring
Bob Kuykendall
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Default fes ot jet (pros and cons)

On Wednesday, August 7, 2019 at 4:47:45 AM UTC-7, kinsell wrote:

Are you serious about this? You're going down at 1000 fpm and you
really think an FES is going to save you? Wow.


With an old-school motorglider like a DG400, with the motor deployed and windmilling but not running, yes, you're going down at about 1000 FPM.

--Bob K.
  #25  
Old August 7th 19, 08:17 PM posted to rec.aviation.soaring
David Bingham
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Default fes ot jet (pros and cons)

Nor in my Shark FES



18:42 06 August 2019, Dan Marotta wrote:
Not in my Stemme.Â* It *does* have two heat sensors in the

engine bay to
light up a big red light and sound a buzzer, but fire means get

out.Â*
Period.

On 8/5/2019 9:15 PM, JS wrote:
With the well known outcome of a fire, every composite

aircraft with an
engine or motor of some sort has a built-in fire extinguisher.
All the manufacturers have that option.
Jim


--
Dan, 5J


  #26  
Old August 7th 19, 08:56 PM posted to rec.aviation.soaring
Dan Daly[_2_]
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Default fes ot jet (pros and cons)

On Wednesday, August 7, 2019 at 12:08:36 PM UTC-4, wrote:
Jet is lighter than FES. And a jet is cool in its own way.


What is your fuel flow down low? I saw a video with 90 l/hr at max power... https://www.youtube.com/watch?v=B-EycC6OdIo . I think if I had to choose right now it would be FES.
  #27  
Old August 7th 19, 09:13 PM posted to rec.aviation.soaring
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Default fes ot jet (pros and cons)

On Wednesday, August 7, 2019 at 3:56:07 PM UTC-4, Dan Daly wrote:
On Wednesday, August 7, 2019 at 12:08:36 PM UTC-4, wrote:
Jet is lighter than FES. And a jet is cool in its own way.


What is your fuel flow down low? I saw a video with 90 l/hr at max power... https://www.youtube.com/watch?v=B-EycC6OdIo . I think if I had to choose right now it would be FES.


I don't have one. This stuff is way out of my league. Was just spitballing pro jet rationales. Both solutions are very nice.
  #28  
Old August 7th 19, 09:19 PM posted to rec.aviation.soaring
Dave Nadler
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Default fes ot jet (pros and cons)

On Wednesday, August 7, 2019 at 7:47:45 AM UTC-4, kinsell wrote:
On 8/6/19 4:33 PM, Bob Kuykendall wrote:
Apparently the gauge said there was 20% capacity remaining.
We all know how reliable aircraft fuel capacity gauges are...


Actually, on electric systems they're quite good.


That's a rather dangerous misconception.
With these cells, the actual amount of energy stored is not easy to estimate.
Quite unlike older cell technology where its easily estimated based on
cell voltage and monitoring of cell performance.
Now one has to know the exact cycle history...

You do understand the difference between electricity and gasoline?


A bit ;-)

In the CT accident, my understanding is the pilot was showing
a sizeable percentage energy remaining when the motor quit.

My Antares drastically under-estimated remaining power with
the motor running, then the estimate came back to reality
sometime after shutdown. Better that than the alternative!
And of course as the battery discharges, the max power available
decreases. Not important in Antares but critical in FES which
has little excess power to start.

With any motor-glider, its foolhardy to ever get in a situation
where you don't have a safe landing option as PLAN A.
That includes during:
- take-off (no short fields departing over woods)
- in-air start (extra time, altitude, and field length needed vs. pure glider)
- in-air cruise (never where complete failure puts you in the trees)

When the motor fails, its easy to execute PLAN A.
Plan B is when the motor keeps running, cause for happiness if not surprise...

FES failures have included spontaneous shutdown due to electronics failure.
No electric system is even close to 100% reliable.
Of course you don't need to ask me how I know that...

Be safe out there,
Best Regards, Dave
  #29  
Old August 8th 19, 04:36 PM posted to rec.aviation.soaring
AS
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Default fes ot jet (pros and cons)

On Tuesday, August 6, 2019 at 9:38:47 PM UTC-4, wrote:
OK. You need to re read my post. I said technology is changing, and by the time you need to replace your battery, something better MAY be out there. Just because it isn't being widely disseminated NOW does not mean that it isn't coming. Sure KOKAM cells (South Korea) are LiPo and SAFT (France HQ) use Lion cells, but this is not "State of the Art." They are about a generation behind the LiFePO4 technology, but widely available, tested and pretty reliable.

If you want to see what I consider to be "imaginary" power source technology, just pick up a copy of "Gliding International." John Roake will publish any press release about some new fuel cell, unicorn breath, unobtanium or imaginarium battery that is just about to change everything and make us ready to abolish the IGC.


To your point:
https://www.aopa.org/news-and-media/...m-sulfur-power
This was posted in an AOPA newsletter recently.

Uli
'AS'
  #30  
Old August 8th 19, 07:53 PM posted to rec.aviation.soaring
Dave Nadler
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Default fes ot jet (pros and cons)

On Thursday, August 8, 2019 at 11:36:06 AM UTC-4, AS wrote:
On Tuesday, August 6, 2019 at 9:38:47 PM UTC-4, wrote:
If you want to see what I consider to be "imaginary" power source
technology, just pick up a copy of "Gliding International." John Roake will
publish any press release about some new fuel cell, unicorn breath,
unobtanium or imaginarium battery that is just about to change
everything and make us ready to abolish the IGC.


To your point:
https://www.aopa.org/news-and-media/...m-sulfur-power
This was posted in an AOPA newsletter recently.


Very nice. Note only good for 60-100 cycles ;-)
https://45uevg34gwlltnbsf2plyua1-wpe...sheet-v4.2.pdf
 




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