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Advice on motor glider wanted - FES - Jet - Engine



 
 
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  #1  
Old January 10th 17, 01:49 AM posted to rec.aviation.soaring
[email protected]
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Default Advice on motor glider wanted - FES - Jet - Engine

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?

Hi Ben,
I wouldn't classify it as a 'failure' as the system worked as advertised. Like any other sustainer (jet, internal combustion, etc) a FES has capacity and operating temperature limitations. These were reached and in accordance with system warnings, the pilot shutdown to prevent damage. To answer your questions (to the best of my knowledge):
- Duration: It had been run previously, hence low capacity and high temp
- Duration immediately before incident: Unknown
- OAT: 86F (approx)
- ALT: Unknown (suspect 2,500AMSL, approx)
- Damage: Nil, it was shutdown in accordance with system warnings. No smoke/smell reported.
- Inspection: Yes. Owner and maintenance provider.

The de-identified summary of the incident is publicly available so I can reproduce it below:

"RUNWAY EXCURSION LAK-19

The pilot was flying cross-country on a weak day and decided to return to the home airfield using the electric sustainer motor. The pilot subsequently flew through lift and decided to continue on task. On return from the turn point the pilot found himself getting low again, so he restarted the electric motor and headed towards some hills in search of lift. Unfortunately, the battery power was low and the motor warning lamp illuminated. The pilot turned off the motor and was immediately faced with an outlanding. While the aircraft was now over hilly terrain with limited landing options, the pilot located a paddock of suitable dimensions with some minor slope. The glider landed at speed and it is suspected that the wheel and starboard wingtip touched the surface simultaneously, resulting in the wing catching in long Lucerne and causing the glider to ground loop. The aircraft was substantially damaged - suffering a bent undercarriage and separation of the starboard wing extension. Pilots of gliders capable of self-retrieving need to fully understand the limitations of their type of motor and must make decisions at sufficient height and with safe landing options available."

Please don't misunderstand the intentions of my post. I'm a fan of the FES in theory and in practice. Personally, I think the next jump in battery technology will push it over the top. It's just that discussions on this topic often include comments on the 'infallibility' of the system. My post was intended to give a real world example of why we still need to apply basic gliding principles to this propulsion type, just like the rest of them.

CJ
  #2  
Old January 10th 17, 02:07 AM posted to rec.aviation.soaring
Tony[_5_]
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Default Advice on motor glider wanted - FES - Jet - Engine

Yea...Running out of "gas" is no good no matter the propulsion type
  #3  
Old January 10th 17, 02:17 AM posted to rec.aviation.soaring
Renny[_2_]
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Default Advice on motor glider wanted - FES - Jet - Engine

On Monday, January 9, 2017 at 7:07:34 PM UTC-7, Tony wrote:
Yea...Running out of "gas" is no good no matter the propulsion type


Indeed...What Tony said!!!
  #4  
Old January 10th 17, 04:29 PM posted to rec.aviation.soaring
Dan Marotta
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Default Advice on motor glider wanted - FES - Jet - Engine

snip It's just that discussions on this topic often include comments
on the 'infallibility' of the system. My post was intended to give a
real world example of why we still need to apply basic gliding
principles to this propulsion type, just like the rest of them.
CJ


Very well put. It is for just the above reason that, though I have a
very reliable engine, I never get out of range of a safe landing field
and, for me, that means an airport.

--
Dan, 5J
  #5  
Old January 11th 17, 01:54 AM posted to rec.aviation.soaring
Dan Marotta
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Default Advice on motor glider wanted - FES - Jet - Engine

It would depend on the airfield. I don't mind landing on grass and I'd
even take off from it. Likewise I'd land on gravel in an emergency but
don't want to take off from it out of concern about damage caused by
rocks thrown up by the tires and damage to the carbon prop. I don't
want to land in an unprepared field due to the possibility of nosing
over and the fact that I wouldn't want to take off from a rough field.

Realistically speaking, it's rare to be out of gliding range of a paved
airport except for the leg between Cedar City and Minden. Very lonely
out there...

On 1/10/2017 11:55 AM, Henry wrote:
Dan Marotta wrote expansively:

though I have a very reliable engine, I never get out of
range of a safe landing field and, for me, that means
an airport.

Won't an airfield do?


--
Dan, 5J
  #6  
Old January 10th 17, 04:50 PM posted to rec.aviation.soaring
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Default Advice on motor glider wanted - FES - Jet - Engine

Thanks for the additional detail, CJ. The fact that the motor was run previously in the flight changes the picture significantly. However, it's still not clear why the pilot had to shut down the motor. In your original post, you said the battery was overheating, but the incident report says "battery power was low", which suggests the battery voltage had reached it's minimum. Which was it, over-temperature, or under-voltage? These are two very different things. If it was low voltage, then most likely the battery power was simply exhausted. If it was overheating, that suggests a failure of some sort. An OAT of 86F is not extreme, so it would be surprising to me if the battery overheated. Does the FES have any known limitations on motor run-time? My assumption was that it could safely be run continuously until the battery was empty.

I am also a fan of FES and am considering purchasing a sailplane equipped with it. I hope it's not true that the battery could overheat under such seemingly normal operating conditions.
  #7  
Old January 11th 17, 03:24 AM posted to rec.aviation.soaring
Bob Kuykendall
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Default Advice on motor glider wanted - FES - Jet - Engine

On Tuesday, January 10, 2017 at 8:50:49 AM UTC-8, wrote:
...Which was it, over-temperature, or under-voltage? These are two very different things.


Not necessarily. I=V/R says that as the battery voltage goes down, the amperage required for specific power level is greater. So when you have a computer-controlled system trying to maintain a commanded power level by regulating current upwards, you can get a situation where low voltage is the direct cause of overheating of specific parts of the system.

Full disclosu I'm not an FES expert, but I am an FES reseller.

--Bob K.
  #8  
Old January 11th 17, 03:33 AM posted to rec.aviation.soaring
Tony[_5_]
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Default Advice on motor glider wanted - FES - Jet - Engine

On Tuesday, January 10, 2017 at 10:50:49 AM UTC-6, wrote:
Thanks for the additional detail, CJ. The fact that the motor was run previously in the flight changes the picture significantly. However, it's still not clear why the pilot had to shut down the motor. In your original post, you said the battery was overheating, but the incident report says "battery power was low", which suggests the battery voltage had reached it's minimum. Which was it, over-temperature, or under-voltage? These are two very different things. If it was low voltage, then most likely the battery power was simply exhausted. If it was overheating, that suggests a failure of some sort. An OAT of 86F is not extreme, so it would be surprising to me if the battery overheated. Does the FES have any known limitations on motor run-time? My assumption was that it could safely be run continuously until the battery was empty.

I am also a fan of FES and am considering purchasing a sailplane equipped with it. I hope it's not true that the battery could overheat under such seemingly normal operating conditions.


My experience self launching the Silent 2 Electro is that Battery temperature has never been an issue. I have once or twice gotten a yellow warning for the motor temp when launching in Uvalde and Kansas on 100ish degF days. Slightly "throttling back" cured that with no issue. Finding a thermal helps a lot too.

The power consumption when cruising level is very low and motor temps have never been a problem at all when i've had to cruise on hot days. One of those days was a fairly long cruise in Lithuania where I ran the motor for about 35 minutes: http://www.onlinecontest.org/olc-2.0...htId=495576510
  #9  
Old January 8th 17, 05:46 AM posted to rec.aviation.soaring
Bruce Hoult
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Default Advice on motor glider wanted - FES - Jet - Engine

On Sunday, January 8, 2017 at 5:58:33 AM UTC+3, 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.


I assumed that "instant starting" implies that you know right away whether it's going to start or not.

You can safely use this to scratch lower, near a landable area, and pull the trigger much later in your landing approach.

Assuming that it *will* always start 100.000% of the time, and using that assumption to fly low over unlandable areas would be foolish. Things do become disconnected sometimes. If you insist on doing this then at least test it for a few seconds in flight before you start the task! That eliminates many of the bigger risks. But personally I'd always try to have an escape route or landing area available.
  #10  
Old January 8th 17, 08:51 AM posted to rec.aviation.soaring
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Default Advice on motor glider wanted - FES - Jet - Engine

Has it ever failed to start? Is this a JS1?

Hi,

It hasn't failed for me yet *touches wood and throws salt over shoulder*. Yes, it's the M&D TJ42 in a JS1.

CJ
 




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