What is involved regulation wise adding an electric motor to a glider?

"Condition Inspection" requires only an A&P.

On Tuesday, February 2, 2021 at 1:26:10 PM UTC-8, David Scott wrote:
I DON'T mean to stir up trouble on this forum with this question, especially being new, but have been wondering about this for some time. I am wondering how feasible it would be to do this with either a homebuilt or experimental glider here in the US?

I figure this has been asked but didn't find any threads on it.

Thanks to all for your responses. What I am hearing certainly doesn't scare me away from the idea, which is all it is at the moment but I have been "thinking" about this and possible solutions for years. My biggest take is to talk to those who would be signing it off to find out what they think of it.

On Wednesday, February 3, 2021 at 11:35:51 AM UTC-8, Bob Kuykendall wrote:
On Tuesday, February 2, 2021 at 1:26:10 PM UTC-8, David Scott wrote:

Others have pointed out that this is easier for an Experimental glider. It is easiest for an experimental, amateur-built glider. For E-AB, depending on the operating limitations, you might have to notify the FAA and repeat Phase I testing. But nobody wants to see your engineering validation, and only the person signing off the annual condition inspection needs to review your workmanship. The FAA or DAR only wants to see that the paperwork is correct and that placards and operating limitations are correctly spelled out.. A good DAR will look the airplane over to make sure it doesn't look particularly dangerous, but they aren't required to.

We have FES going into one of our glider kits right now, and are preparing for the installation of electric self-launch systems in future models.

--Bob K.
Since I am new here what kit do you produce? Are you preparing for FES or retractable pylon?
Any idea how much thrust an FES produces? My search came up empty.

Not to hijack the thread, but in response to the reliability issue of two-stroke engines, the primary culprit seems to be the different altitudes at which the engine is supposed to start and operate. The fuel/oil/air mixture has to be within certain parameters for decent running and starting reliability. An increase in altitude (or high density altitude conditions) reduces the amount of available oxygen, which contributes to fouling the spark plugs. I used to ride the Yamaha RD-350 and TZ-250 motorcycles from Albuquerque (elevation ~5,500 ft. MSL) up to Sandia Crest (10,678 ft. MSL) and used to have to stop and adjust the needles in the carburetors four times on the way up and four times on the way down or risk plug fouling or overheating and possibly seizing the engine. About a 1,000 ft. change in altitude was all it took to affect the performance and reliability. Newer two-stroke engines with more sophisticated fuel injection systems seem to be much more reliable in motorgliders.

On Wednesday, February 3, 2021 at 5:31:51 PM UTC-5, David Scott wrote:
On Wednesday, February 3, 2021 at 11:35:51 AM UTC-8, Bob Kuykendall wrote:
On Tuesday, February 2, 2021 at 1:26:10 PM UTC-8, David Scott wrote:

Others have pointed out that this is easier for an Experimental glider. It is easiest for an experimental, amateur-built glider. For E-AB, depending on the operating limitations, you might have to notify the FAA and repeat Phase I testing. But nobody wants to see your engineering validation, and only the person signing off the annual condition inspection needs to review your workmanship. The FAA or DAR only wants to see that the paperwork is correct and that placards and operating limitations are correctly spelled out. A good DAR will look the airplane over to make sure it doesn't look particularly dangerous, but they aren't required to.

We have FES going into one of our glider kits right now, and are preparing for the installation of electric self-launch systems in future models.

--Bob K.
Since I am new here what kit do you produce? Are you preparing for FES or retractable pylon?
Any idea how much thrust an FES produces? My search came up empty.

Look up https://hpaircraftblog.wordpress.com
Lots of interesting info there- especially the old school stuff showing all the work it takes to get set up to produce a kit sailplane.
UH

On Wednesday, February 3, 2021 at 2:24:37 PM UTC-8, David Scott wrote:
On Tuesday, February 2, 2021 at 1:26:10 PM UTC-8, David Scott wrote:
I DON'T mean to stir up trouble on this forum with this question, especially being new, but have been wondering about this for some time. I am wondering how feasible it would be to do this with either a homebuilt or experimental glider here in the US?

I figure this has been asked but didn't find any threads on it.
Thanks to all for your responses. What I am hearing certainly doesn't scare me away from the idea, which is all it is at the moment but I have been "thinking" about this and possible solutions for years. My biggest take is to talk to those who would be signing it off to find out what they think of it.

I have been very involved in high-performance composites for many years, have been machining for 33 years now, and doing product development longer. I have my own CNC machine shop where I mostly make my own products so I am well equipped to do the design and manufacturing. I have done enough projects that took over 2000 hours to get into production that I do understand there is always way more work than expected, but this really isn't that big of a job, comparatively.

I really like the FES idea for modifying a stock glider for its simplicity. The only structural change to the glider would be to cut off the nose but the firewall would certainly reinforce it, depending on how the batteries are stored. The biggest downside is that the propeller has to be too small for efficiency.

You would also have to cut an access port in the fuselage to install & remove the batteries. This will substantially weaken the fuselage, so it will have to be reinforced in an engineered manner.

Tom

David Scott wrote on 2/3/2021 2:24 PM:
On Tuesday, February 2, 2021 at 1:26:10 PM UTC-8, David Scott wrote:
I DON'T mean to stir up trouble on this forum with this question, especially being new, but have been wondering about this for some time. I am wondering how feasible it would be to do this with either a homebuilt or experimental glider here in the US?

I figure this has been asked but didn't find any threads on it.

Thanks to all for your responses. What I am hearing certainly doesn't scare me away from the idea, which is all it is at the moment but I have been "thinking" about this and possible solutions for years. My biggest take is to talk to those who would be signing it off to find out what they think of it.

I have been very involved in high-performance composites for many years, have been machining for 33 years now, and doing product development longer. I have my own CNC machine shop where I mostly make my own products so I am well equipped to do the design and manufacturing. I have done enough projects that took over 2000 hours to get into production that I do understand there is always way more work than expected, but this really isn't that big of a job, comparatively.

I really like the FES idea for modifying a stock glider for its simplicity. The only structural change to the glider would be to cut off the nose but the firewall would certainly reinforce it, depending on how the batteries are stored. The biggest downside is that the propeller has to be too small for efficiency.

Are you familiar with 4 kwh lithium battery packs and BMS units? How about 20-25 kw DC motors
and the electronic controllers for them? The mechanical part of an electric propulsion system
might be harder (perhaps much harder) than the electrical part.

I think you can buy a complete FES system (includes drawings for the installation) for many of
the popular gliders. That would save you an immense mount of design and testing time. Visit the
FES developer's site at

http://www.front-electric-sustainer.com/index.php

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

On Wednesday, February 3, 2021 at 3:52:46 PM UTC-8, Hank Nixon wrote:
On Wednesday, February 3, 2021 at 5:31:51 PM UTC-5, David Scott wrote:
On Wednesday, February 3, 2021 at 11:35:51 AM UTC-8, Bob Kuykendall wrote:
On Tuesday, February 2, 2021 at 1:26:10 PM UTC-8, David Scott wrote:

Others have pointed out that this is easier for an Experimental glider. It is easiest for an experimental, amateur-built glider. For E-AB, depending on the operating limitations, you might have to notify the FAA and repeat Phase I testing. But nobody wants to see your engineering validation, and only the person signing off the annual condition inspection needs to review your workmanship. The FAA or DAR only wants to see that the paperwork is correct and that placards and operating limitations are correctly spelled out. A good DAR will look the airplane over to make sure it doesn't look particularly dangerous, but they aren't required to.

We have FES going into one of our glider kits right now, and are preparing for the installation of electric self-launch systems in future models..

--Bob K.
Since I am new here what kit do you produce? Are you preparing for FES or retractable pylon?
Any idea how much thrust an FES produces? My search came up empty.

Look up https://hpaircraftblog.wordpress.com
Lots of interesting info there- especially the old school stuff showing all the work it takes to get set up to produce a kit sailplane.
UH
I was wondering if that is what he was talking about. I followed that blog for a few years so am somewhat familiar with it.

On Wednesday, February 3, 2021 at 3:54:59 PM UTC-8, 2G wrote:
On Wednesday, February 3, 2021 at 2:24:37 PM UTC-8, David Scott wrote:
On Tuesday, February 2, 2021 at 1:26:10 PM UTC-8, David Scott wrote:
I DON'T mean to stir up trouble on this forum with this question, especially being new, but have been wondering about this for some time. I am wondering how feasible it would be to do this with either a homebuilt or experimental glider here in the US?

I figure this has been asked but didn't find any threads on it.
Thanks to all for your responses. What I am hearing certainly doesn't scare me away from the idea, which is all it is at the moment but I have been "thinking" about this and possible solutions for years. My biggest take is to talk to those who would be signing it off to find out what they think of it.

I have been very involved in high-performance composites for many years, have been machining for 33 years now, and doing product development longer. I have my own CNC machine shop where I mostly make my own products so I am well equipped to do the design and manufacturing. I have done enough projects that took over 2000 hours to get into production that I do understand there is always way more work than expected, but this really isn't that big of a job, comparatively.

I really like the FES idea for modifying a stock glider for its simplicity. The only structural change to the glider would be to cut off the nose but the firewall would certainly reinforce it, depending on how the batteries are stored. The biggest downside is that the propeller has to be too small for efficiency.

You would also have to cut an access port in the fuselage to install & remove the batteries. This will substantially weaken the fuselage, so it will have to be reinforced in an engineered manner.

Tom

That is something I would avoid doing if at all possible. But I do understand that is where the batteries would have to be to maintain CG. If there is no way around it then a pylon mounted motor begins to look much, much better. The fun of design, there is no perfect answer, just the best set of compromises.

On Wednesday, February 3, 2021 at 4:02:37 PM UTC-8, Eric Greenwell wrote:
David Scott wrote on 2/3/2021 2:24 PM:
On Tuesday, February 2, 2021 at 1:26:10 PM UTC-8, David Scott wrote:
I DON'T mean to stir up trouble on this forum with this question, especially being new, but have been wondering about this for some time. I am wondering how feasible it would be to do this with either a homebuilt or experimental glider here in the US?

I figure this has been asked but didn't find any threads on it.

Thanks to all for your responses. What I am hearing certainly doesn't scare me away from the idea, which is all it is at the moment but I have been "thinking" about this and possible solutions for years. My biggest take is to talk to those who would be signing it off to find out what they think of it.

I have been very involved in high-performance composites for many years, have been machining for 33 years now, and doing product development longer. I have my own CNC machine shop where I mostly make my own products so I am well equipped to do the design and manufacturing. I have done enough projects that took over 2000 hours to get into production that I do understand there is always way more work than expected, but this really isn't that big of a job, comparatively.

I really like the FES idea for modifying a stock glider for its simplicity. The only structural change to the glider would be to cut off the nose but the firewall would certainly reinforce it, depending on how the batteries are stored. The biggest downside is that the propeller has to be too small for efficiency.

Are you familiar with 4 kwh lithium battery packs and BMS units? How about 20-25 kw DC motors
and the electronic controllers for them? The mechanical part of an electric propulsion system
might be harder (perhaps much harder) than the electrical part.

I think you can buy a complete FES system (includes drawings for the installation) for many of
the popular gliders. That would save you an immense mount of design and testing time. Visit the
FES developer's site at

http://www.front-electric-sustainer.com/index.php

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

When I checked a year-ish ago you had to go through their distributor in the US and they had to install it. I never checked but figured it would be in the $40k neighborhood. At least their distributor is close by here in Washington. I'm just outside of Hood River.