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.

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

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

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....

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?

On Sat, 7 Jan 2017 19:54:29 -0800 (PST), 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

The FES system produces 20kw at full power. Most of the gliders
fitted with it will cruise straight and level at about 4-5kw.
Certainly in current versions the system will warm you of a problem
but doesn't shut itself down. I believe the logic is that it is
better to destroy the batteries or motor should the pilot feel that
shutting down will cause a desperate situation. Low voltage or
overheating can generally be cured by reducing the power to cruise
power.

I believe the logic is that it is
better to destroy the batteries or motor should the pilot feel that
shutting down will cause a desperate situation.

Hi Eric,

You're right, a quick read of the manual suggests the FES will step through alerts and warnings but it's ultimately the pilot that decides when to shut down. In the case of battery temperatu
- "Batt. Ext. High 55°C, Stop FES motor!" (red), &
- "Batt. Critical 75°C, Land immediately!" (red)
The latter suggesting a thermal runaway and/or fire is imminent.

CJ

Hi all

The new proposed electric 20m Mini Stemme looks an exiting prospect

http://www.rs-uas.com/products/sk10e-elfin/preface/

Muttley

I believe that any emergency system designed to protect equipment should
have a manual override capability. Think of that Airbus flying happily
into the trees while the pilot struggled unsuccessfully to pull up.

Though I have a highly reliable engine in my Stemme, I never fly outside
of gliding distance of a suitable runway. Of course, this limits my
flying in the great southwest somewhat but, having no trailer, there are
plenty of places I could land safely but would not like to take off from.

On 1/7/2017 8:54 PM, 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

--
Dan, 5J

On Saturday, January 7, 2017 at 7:54:32 PM UTC-8, 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.

[snip]
CJ

CJ, can you give us more detail about this incident? This is the first FES failure I've heard of. You said the FES had to be shut down at "moderately low" altitude, which suggests it didn't run for very long. It's surprising that it could overheat so quickly. How long did the FES run before the shutdown? What was the OAT at the time? What altitude MSL did it fail at? Was the battery damaged? Was there any smoke or burning smell? Has the manufacturer or owner inspected the FES system since the incident?

-Ben