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

FES underpowered for 18m ship?



 
 
Thread Tools Display Modes
  #1  
Old September 14th 20, 07:58 PM posted to rec.aviation.soaring
Mana
external usenet poster
 
Posts: 9
Default FES underpowered for 18m ship?

I just had a chat with a fellow pilot whose friend sold his LAK 17b FES because he was disappointed by the ability of the FES to gain altitude. The problem being that when applying sufficient power to gain altitude, the battery would get warm to the point where the controller shuts the motor down. I read recently an accident report tied to the same issue, in that case pilot too low and not in reach of a landing spot (pilot mistake) who counted on FES to regain altitude, but as the battery was too hot it wouldn’t power the motor and the pilot crashed. On the other hand FES works reliably to maintain level flight at a lower power ratio.

Does any LAK 17 or Shark 304 FES (or other glider of similar weight) pilot have any feedback on this? In real life, how much altitude are you able to gain, with fresh and semi full batteries? Is it a matter of being patient and accepting a low rate of climb?

It would be disappointing if when you fly “by the rules” and remain above a landing / outlanding spot until you turn power on, that the FES doesn’t allow to regain altitude, but only to maintain level flight. It changes the flight planning strategy altogether.

I find this surprising and I’ll try to get in touch with the pilot who sold his LAK, but thought I would ask the question in the forum in the meantime.
Ads
  #2  
Old September 14th 20, 08:31 PM posted to rec.aviation.soaring
Dave Nadler
external usenet poster
 
Posts: 1,544
Default FES underpowered for 18m ship?

On Monday, September 14, 2020 at 2:58:08 PM UTC-4, Mana wrote:
It would be disappointing if when you fly “by the rules” and remain above
a landing / outlanding spot until you turn power on, that the FES doesn’t
allow to regain altitude, but only to maintain level flight.
It changes the flight planning strategy altogether.


And it will be dangerous and fool-hardy if you DO NOT always:
- keep a landing spot in easy reach, and
- never engage power until the landing is planned in you're in position.

To quote a recent email I received from LBA/EASA:

....please let us point out that the pilot of a powered glider
shall always have in mind, that it might be necessary to operate
his aircraft as a pure glider. The engine of a powered glider,
predefined by airworthiness requirements JAR/CS-22, does not
meet the same safety standards as a "Part-E" engine of a motorplane.

The flight training for powered gliders shall take into account, that
loss of engine power may occur anytime, and result in a scenario, which is
comparable to a cable break during a winch launch or an aerotow.
This deviation to the operation of a motorplane is reflected in several
paragraphs of the airworthiness requirements JAR/CS-22, applicable for a
powered glider. Examples are the specifications for engines, used for
powered gliders (JAR/CS-22 Subpart H) that are less stringent than those
for powered aircraft (CS-23). Moreover, requirements for software are
not mentioned in the JAR/CS-22 at all - contrary to the specification
for large aeroplanes (CS-25).
  #3  
Old September 14th 20, 08:38 PM posted to rec.aviation.soaring
Matthew Scutter
external usenet poster
 
Posts: 14
Default FES underpowered for 18m ship?

I think something has been lost in translation, but I'm pretty sure you will not shut down from battery heat - my batteries barely change temperature regardless of use, and neither controller nor motor have temperature problems even running through most of the capacity at full power.
What does happen is the voltage quickly drops as used capacity goes up, such that while I can get ~20kW (5kt climb) of power at full charge, at 30% charge remaining I can only get 8kW (1-2kt climb). I haven't discharged below that yet but I understand you reach the point where the voltage doesn't sustain level flight at approximately the same time you reach 0% charge.

The FES is most efficient at low power so it's much better to climb to lowest safe altitude, then go sideways at level flight power. I need about 3.5kW for level flight at 350kg (Diana 2-FES), which with the 5.3kWh batteries seems to get me about 150km. I haven't measured the full climb height at high power, but extrapolating my shorter climbs I think I should get 5000ft before I can only go sideways.
Range/altitude seems to scale linearly with weight if you're at 450kg or 500kg like some of those 18m ships with a heavy pilot, you can calculate the fractions accordingly.

I think you can plan on smaller margins with the FES since the engine-not-running drag is much lower with the FES than a stuck-out pylon. You'll have to make your own decisions of course.

On Monday, September 14, 2020 at 8:58:08 PM UTC+2, Mana wrote:
I just had a chat with a fellow pilot whose friend sold his LAK 17b FES because he was disappointed by the ability of the FES to gain altitude. The problem being that when applying sufficient power to gain altitude, the battery would get warm to the point where the controller shuts the motor down. I read recently an accident report tied to the same issue, in that case pilot too low and not in reach of a landing spot (pilot mistake) who counted on FES to regain altitude, but as the battery was too hot it wouldn’t power the motor and the pilot crashed. On the other hand FES works reliably to maintain level flight at a lower power ratio.

Does any LAK 17 or Shark 304 FES (or other glider of similar weight) pilot have any feedback on this? In real life, how much altitude are you able to gain, with fresh and semi full batteries? Is it a matter of being patient and accepting a low rate of climb?

It would be disappointing if when you fly “by the rules” and remain above a landing / outlanding spot until you turn power on, that the FES doesn’t allow to regain altitude, but only to maintain level flight. It changes the flight planning strategy altogether.

I find this surprising and I’ll try to get in touch with the pilot who sold his LAK, but thought I would ask the question in the forum in the meantime.

  #4  
Old September 14th 20, 08:52 PM posted to rec.aviation.soaring
Mana
external usenet poster
 
Posts: 9
Default FES underpowered for 18m ship?

Thank you Matthew, this is very interesting data, exactly what I was looking for. :-)

BTW battery low = lower voltage, so for same output power to the motor you need more amps, hence the battery warms faster (P=U*I = R*I*I).

On Monday, September 14, 2020 at 9:31:25 PM UTC+2, wrote:
And it will be dangerous and fool-hardy if you DO NOT always:
- keep a landing spot in easy reach, and
- never engage power until the landing is planned in you're in position.


Agreed, of course! But the whole point of a "turbo" is to be able to regain altitude :-) If FES only allowed level flight, then it may expand the area where you'll find the thermal you need, but since you need to keep a landing spot in reach for the exact reasons you pointed out, level flight only would be very limiting.

It could be that the pilot in question used FES regularly during his flights and found himself with battery low towards the end (vs. only using FES once with a fresh battery in case of trouble)? I asked for his contact data to get real facts vs. speculation and I'll report if I'm able to reach him.
  #5  
Old September 14th 20, 09:06 PM posted to rec.aviation.soaring
Mana
external usenet poster
 
Posts: 9
Default FES underpowered for 18m ship?

I think you can plan on smaller margins with the FES since the engine-not-running drag is much lower with the FES than a stuck-out pylon. You'll have to make your own decisions of course.
That's what I find so cool about FES. The JS3 RES has a pylon with motor in front, whereas the GP15 Jeta has the motor in the back, which at least allows to fold the prop and minimize drag in case it gets stuck. I'm not sure if the Antares prop folds if the pylon is stuck?

FES is a great illustration of KISS: keep it simple, then fewer things can go wrong - and the 1 point L/D penalty is OK by me. I'm on the market for a FES glider and currently debating between LAK 17 and Shark 304.
  #6  
Old September 14th 20, 09:07 PM posted to rec.aviation.soaring
Dave Nadler
external usenet poster
 
Posts: 1,544
Default FES underpowered for 18m ship?

On Monday, September 14, 2020 at 3:52:25 PM UTC-4, Mana wrote:
...the whole point of a "turbo" is to be able to regain altitude :-)


Right, but many have extremely slow climb, especially in high/hot locales.
There electric of course doesn't loose much efficiency,
but batteries/motor may suffer.

Antares at Uvalde required low power settings and could only launch
to low altitude before battery temp hit max.

It could be that the pilot in question used FES regularly
during his flights and found himself with battery low towards the end...
I'll report if I'm able to reach him.


That would be most helpful, Thanks!

PS: Does FES motor ever overheat (again especially in hot locales)??
  #7  
Old September 14th 20, 09:27 PM posted to rec.aviation.soaring
Dave Nadler
external usenet poster
 
Posts: 1,544
Default FES underpowered for 18m ship?

On Monday, September 14, 2020 at 4:06:32 PM UTC-4, Mana wrote:
I'm not sure if the Antares prop folds if the pylon is stuck?


Nope. But drag isn't too bad (engine bay doors closed, no radiator).

  #8  
Old September 14th 20, 09:32 PM posted to rec.aviation.soaring
Kevin Neave[_2_]
external usenet poster
 
Posts: 68
Default FES underpowered for 18m ship?

Definitely not underpowered for 18m D2c (400 kg)

I can climb quickly from 200m to 400m (500 - 1200ft) then have
enough left for 75km in stillish air. Low power is more efficient so
if you recognise the day is dying earlier you don’t need to invest
the charge in climbing so range is much better. It will never
match the range of a conventional turbo but will always get you
away from a farmer’s field to an airfield near home.

Once the FES is running you’re still “soaring” to maximise range.
Still playing the same game, making the same decisions, just
have way better L/D.

I have access to both and first choice is the FES every time.



At 19:52 14 September 2020, Mana wrote:
Thank you Matthew, this is very interesting data, exactly what I

was
lookin=
g for. :-)

BTW battery low =3D lower voltage, so for same output power

to the motor
yo=
u need more amps, hence the battery warms faster (P=3DU*I

=3D R*I*I).=20

On Monday, September 14, 2020 at 9:31:25 PM UTC+2,

wrote:
And it will be dangerous and fool-hardy if you DO NOT

always:=20
- keep a landing spot in easy reach, and=20
- never engage power until the landing is planned in you're in

position.=
=20
=20
Agreed, of course! But the whole point of a "turbo" is to be able

to
regain=
altitude :-) If FES only allowed level flight, then it may expand

the
area=
where you'll find the thermal you need, but since you need to

keep a
landi=
ng spot in reach for the exact reasons you pointed out, level

flight only
w=
ould be very limiting.=20
=20
It could be that the pilot in question used FES regularly during

his
flight=
s and found himself with battery low towards the end (vs. only

using FES
on=
ce with a fresh battery in case of trouble)? I asked for his

contact data
t=
o get real facts vs. speculation and I'll report if I'm able to reach

him.


  #9  
Old September 14th 20, 09:38 PM posted to rec.aviation.soaring
Matthew Scutter
external usenet poster
 
Posts: 14
Default FES underpowered for 18m ship?

On Monday, September 14, 2020 at 10:07:18 PM UTC+2, wrote:
On Monday, September 14, 2020 at 3:52:25 PM UTC-4, Mana wrote:
...the whole point of a "turbo" is to be able to regain altitude :-)


Right, but many have extremely slow climb, especially in high/hot locales..
There electric of course doesn't loose much efficiency,
but batteries/motor may suffer.

Antares at Uvalde required low power settings and could only launch
to low altitude before battery temp hit max.
It could be that the pilot in question used FES regularly
during his flights and found himself with battery low towards the end....
I'll report if I'm able to reach him.

That would be most helpful, Thanks!

PS: Does FES motor ever overheat (again especially in hot locales)??


BTW battery low = lower voltage, so for same output power to the motor you need more amps, hence the battery warms faster (P=U*I = R*I*I).

Right, but output power is continually coming down as the voltage comes down as it seems amps stay more or less constant or decrease.
I only have a tenuous understanding of electronics and battery chemistry, but I'm told because the FES uses pouch cells rather than cylindrical cells the internal resistance is much lower, which would explain why the battery doesn't seem to meaningfully heat. I have not seen my batteries get above 25c.

I'll be flying it in Australia later this year so I'll return with my experience on motor temperatures. So far in Europe it seems to plateau around 55c at high power. When I asked Luka about Australia, he seemed to think it wouldn't be an issue and told me there was a very large margin of safety on both the motor and controller temperature. Theoretically if you did manage to overheat it though, you could demagnetize the permanent magnets.
  #10  
Old September 14th 20, 11:02 PM posted to rec.aviation.soaring
jfitch
external usenet poster
 
Posts: 1,076
Default FES underpowered for 18m ship?

Depends a bit on where you fly. In the western US (absent pyrocumulus to soar, which has been reliable of late....) the nearest airport may be 150 km away, and it you waited until 500 ft you might have to climb 4000 ft over a ridge to get there. There are a few reasons why ICE turbos still outsell electric by something like 4:1. I like the idea of electrics, but for my use it needs about 3x the energy storage currently available. Even the shortest simple retrieve where I fly (let's say Carson City to Truckee) will require a 4000 ft climb. More practical in the flatlands of the east or Europe where airports are close and ridges are lower.

On Monday, September 14, 2020 at 1:45:06 PM UTC-7, Kevin Neave wrote:
Definitely not underpowered for 18m D2c (400 kg)

I can climb quickly from 200m to 400m (500 - 1200ft) then have
enough left for 75km in stillish air. Low power is more efficient so
if you recognise the day is dying earlier you don’t need to invest
the charge in climbing so range is much better. It will never
match the range of a conventional turbo but will always get you
away from a farmer’s field to an airfield near home.

Once the FES is running you’re still “soaring” to maximise range.
Still playing the same game, making the same decisions, just
have way better L/D.

I have access to both and first choice is the FES every time.
At 19:52 14 September 2020, Mana wrote:
Thank you Matthew, this is very interesting data, exactly what I

was
lookin=
g for. :-)

BTW battery low =3D lower voltage, so for same output power

to the motor
yo=
u need more amps, hence the battery warms faster (P=3DU*I

=3D R*I*I).=20

On Monday, September 14, 2020 at 9:31:25 PM UTC+2,

wrote:
And it will be dangerous and fool-hardy if you DO NOT

always:=20
- keep a landing spot in easy reach, and=20
- never engage power until the landing is planned in you're in

position.=
=20
=20
Agreed, of course! But the whole point of a "turbo" is to be able

to
regain=
altitude :-) If FES only allowed level flight, then it may expand

the
area=
where you'll find the thermal you need, but since you need to

keep a
landi=
ng spot in reach for the exact reasons you pointed out, level

flight only
w=
ould be very limiting.=20
=20
It could be that the pilot in question used FES regularly during

his
flight=
s and found himself with battery low towards the end (vs. only

using FES
on=
ce with a fresh battery in case of trouble)? I asked for his

contact data
t=
o get real facts vs. speculation and I'll report if I'm able to reach

him.

 




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
Thunderbird 4-ship departure - Thunderbirds 4 ship departure sun n fun 2010 (Custom).jpg Glen in Orlando Aviation Photos 0 April 22nd 10 09:10 PM
F-104 Three Ship Glen in Orlando Aviation Photos 0 October 9th 09 07:00 PM
T6 Formation flight with Ship to Ship and ATC COMS - Video [email protected] Piloting 5 September 10th 09 06:09 PM
OT T6 Formation flight with Ship to Ship and ATC COMS - Video A Lieberma[_2_] Owning 0 September 10th 09 12:47 AM
OT - T6 Formation flight with Ship to Ship and ATC COMS - Video [email protected] Instrument Flight Rules 0 September 10th 09 12:47 AM


All times are GMT +1. The time now is 04:51 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Copyright 2004-2020 AviationBanter.
The comments are property of their posters.