fes ot jet (pros and cons)

On Tuesday, August 6, 2019 at 4:22:16 AM UTC+3, wrote:
Steve brings up a good point on the replacement cost of batteries, but one thing that needs to be considered is the rapid advance in battery technology.

FES has used same Kokam cell for 10 years. Lange has used same SAFT cells for 20 years. There has been absolutely zero advance in electric glider battery technology. Just a reminder.

FES has used same Kokam cell for 10 years. Lange has used same SAFT cells for 20 years. There has been absolutely zero advance in electric glider battery technology. Just a reminder.

Just because they are still using 10 and 20 year old cells doesn't mean the technology hasn't improved. It just means they aren't using it.

On Tuesday, August 6, 2019 at 7:10:26 AM UTC-5, wrote:
FES has used same Kokam cell for 10 years. Lange has used same SAFT cells for 20 years. There has been absolutely zero advance in electric glider battery technology. Just a reminder.

Just because they are still using 10 and 20 year old cells doesn't mean the technology hasn't improved. It just means they aren't using it.

Mark, it's an often repeated myth that battery technology has improved. In reality, all the e-vehicles from bikes to light trucks and FES or Pipistrel still use LiPo or LiFe chemistry, so do the solar storage systems. Yes, there are new chemistries that compete for future applications but none has even shown up in cutting edge systems such e-remote controlled planes - and those guys don't mind the occasional fiery crash. Please show me one commercially USED battery type that is substantially beyond the current 200 WH/kg..

Another thing to remember about possible "new" battery
technology is whether the glider manufacturers will have any
financial interest in updating their current systems. New &
better batteries may well appear but you can bet the glider
manufacturers will be fitting them in their latest creations. So
for anyone wanting to fly electric in the near future, or now,
your are back with Li-Ion etc.
Despite their many drawbacks it seems some of these (old) Li-
Ion cells (e.g. the SAFT cells used by Lange) will last ~20
years.
While the cost of an electric launch looks economic compared
to a tug the real costs are much higher......I seriously doubt
that overall the costs are lower; you pay for autonomy!
For FES/Jet sustainer systems (the original post) I'd say the
critical factor is start reliability; sitting in a field with an engine
that did not start must rank as bl**dy frustrating.

On 8/6/19 3:14 PM, Dave Walsh wrote:


For FES/Jet sustainer systems (the original post) I'd say the
critical factor is start reliability; sitting in a field with an engine
that did not start must rank as bl**dy frustrating.


Not nearly as bad as ending up crashing into an attic and making
international news. Still haven't seen an NTSB prelim for the guy from
Connecticut.

Tried to start his electric low over a high-density urban area, got
nothing but grinding sounds. Too low even to fire the ballistic chute.

Very poor flying technique, and I'm sure we'll see lots more of it as
FES becomes more prevalent. The OP's obsession with startup time is a
good indication of that.

On Tuesday, August 6, 2019 at 2:28:30 PM UTC-7, kinsell wrote:

Tried to start his electric low over a high-density urban area, got
nothing but grinding sounds. Too low even to fire the ballistic chute.

Better check your facts on that. As I understand it, it was absolutely not a case of FES not starting. Rather, he'd been running the FES motor for some time before it quit, likely because he ran out of juice.

Apparently the gauge said there was 20% capacity remaining. We all know how reliable aircraft fuel capacity gauges are...


But, yeah, beyond that the whole thing reflects very poorly on the pilot's planning and execution.

Startup interval is an important metric because it determines how soon you know which contingencies remain available. If it takes half a minute to deploy the engine and see if it's going to produce power, and you're coming down at 1000 fpm, your options are dwindling about as rapidly as your pulse rate is excalating. When you can flick one switch and twist a knob and know within a couple seconds that you can drive away from the hole you dug, it's a pretty strong motivator.


--Bob K.

On 8/6/19 4:33 PM, Bob Kuykendall wrote:
On Tuesday, August 6, 2019 at 2:28:30 PM UTC-7, kinsell wrote:

Tried to start his electric low over a high-density urban area, got
nothing but grinding sounds. Too low even to fire the ballistic chute.

Better check your facts on that. As I understand it, it was absolutely not a case of FES not starting. Rather, he'd been running the FES motor for some time before it quit, likely because he ran out of juice.

From the original discussion on this, the pilot who had been flying
with him that day said he had run his motor previously, but tried to
restart with the computer showing 18 minutes left. He got nothing but
grinding sounds. So maybe "as you understand it" isn't correct.




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. You do understand the
difference between electricity and gasoline?




But, yeah, beyond that the whole thing reflects very poorly on the pilot's planning and execution.

Startup interval is an important metric because it determines how soon you know which contingencies remain available. If it takes half a minute to deploy the engine and see if it's going to produce power, and you're coming down at 1000 fpm, your options are dwindling about as rapidly as your pulse rate is excalating. When you can flick one switch and twist a knob and know within a couple seconds that you can drive away from the hole you dug, it's a pretty strong motivator.


--Bob K.


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

On Tuesday, August 6, 2019 at 2:15:06 PM UTC-7, Dave Walsh wrote:
Another thing to remember about possible "new" battery
technology is whether the glider manufacturers will have any
financial interest in updating their current systems. New &
better batteries may well appear but you can bet the glider
manufacturers will be fitting them in their latest creations. So
for anyone wanting to fly electric in the near future, or now,
your are back with Li-Ion etc.
Despite their many drawbacks it seems some of these (old) Li-
Ion cells (e.g. the SAFT cells used by Lange) will last ~20
years.
While the cost of an electric launch looks economic compared
to a tug the real costs are much higher......I seriously doubt
that overall the costs are lower; you pay for autonomy!
For FES/Jet sustainer systems (the original post) I'd say the
critical factor is start reliability; sitting in a field with an engine
that did not start must rank as bl**dy frustrating.

I have never heard a fellow MG owner say that they bought the thing to save money on anything, let alone tows. That said, the more you can fly, the lower the flying costs, and motors allow you to fly more. Nothing worse than a great soaring day and no tow pilots; been there, done that.

Tom

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.

On Tue, 06 Aug 2019 18:38:45 -0700, markmocho53 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.

I know exactly what you mean.

A year or three ago "New Scientist" would give 1/4 - 1/2 page to any test-
tube scale, proof-of-concept experiment for a new battery technology that
was going to change the world. Without exception these were never
mentioned again.

Thankfully, they've stopped doing that, and for good reason: the
theoretical capacity of say, Lithium-based batteries, was determined
decades ago and once cells were designed with capacities that were
reasonably close to the theoretical maximum, subsequent development has
been concerned with maximising charge/discharge rates, battery life,
operating safety, cost and weight. In short: we already know what energy
storage capacity is achievable with any practical cell chemistry and
further research isn't going to produce new, currently unknown super
capacity batteries.


--
Martin | martin at
Gregorie | gregorie dot org