What do you think about "e-soaring"?

Help Support Homebuilt Aircraft & Kit Plane Forum:

John.Roo

Well-Known Member
=iff compare AEROPRAKT A-22 /A-32 systems=my Fellow prefer to fly A-22 yoke mode
(A-32 have better parameters!)...=probably long cardriver practice ?

-I personally like motorcykle like system=

(at the end=two halves of "bike" controllbar )

-or simpler, "SILENTGLIDER" (one rotating bar).

Why not? For sure they are some pilots prefering unusual control systems.

But young pilot really needs to build flight experience and knowleadge on airplane with standard control lines. It makes no sense to let young pilot to fly with not standard controls. After building flight experience he must have opportunity to fluently continue on competition gliders or on airplanes in higher categories to obtain PPL, CPL or ATPL pilot license.

Experienced ultralight pilot flying with ultralight (LSA) airplanes is able to make easily PPL license.
Pilot trained on gliders like L-13 Blanik must be able to fly simple e-glider with minimal time for conversion. Every difference in control lines will make conversion difficult or impossible and also CAA (FAA, LAA...) inspectors will not like it.

John.Roo

Well-Known Member
That's pretty close to my project goals for Echo:

MTOW = 220 kg
Vne = 185 kph
Price? Well it's a home-built structure
(no price estimate yet, but really its just materials, molds and fixtures, (contract out canopy?) plus smaller electric pod maybe $30K-$35K?)
Conventional, auto hook up controls, stores in trailer.
L/D (current estimate with fixed wheel and pod is 32:1 )
Pilot view is just in front of and above LE
aft folding prop (passive)
+6/-3 g plus factor of safety of 2 on all composites (1.5 on metal components)

I think where we deviate is that I don't plan to carry more than 20 to 30 minutes of battery. And I need to use more carbon to meet my weight and stiffness goals.

But as you can see I think we have pretty similar ideas on taking the current state of the art and applying it to electric flight in a realistic manner.
As opposed drawing up a vertical take off super-cruiser and planning for next gen batteries.
Perfect

Strength requirements....
Standard requirements are +4 / -2 g.
For gliders is often used +5,3 / -2,65 g.
With safety factor 1,875 (typical minimum for composites) you have to test it for +10 g and -5 g.
In my opinion is good to have strength reserve, but not too high reserve. Higher reserve = higher airframe weight and in our case is low weight of airframe really important

Battery size...
Well, we discussed this before however I keep on mind max. discharge rate of 3C.
For safe Take Off from not perfectly maintained grass RWY I estimate 15 kW power.
3C discharge rate = 5 kWh battery = 30 kg. If would be chance to use bigger battery it would be ony better. Larger capacity means lower temperatures and possibility to keep always some reserve energy in battery = longer battery life (= lower costs per hour).

Sraight'nlevel

Well-Known Member
Well in my opinion is necessary to compare "comparable" configurations.
Heron is using Rotax 914 so should be compared with Velis with Rotax 912 or 914.
Also would be interesting to know fuel tanks volume of Heron and Empty Weight.
Heron has 1 150 kg MTOM and Velis only 600 kg.
If EW is the same and fuel consumption will be similar (same type of engine) that is also efficiency similar and only difference are huge fuel tanks of Heron

By the way....
15 lit / hour = 780 lit of fuel per 52 hours = approx. 600 kg of weight.
MTOM difference is 550 kg....
In my opinion is efficiency (if measured by fuel consuption at comparable airspeed) very similar.

If Heron was electrified..how much range would you estimate on her ?

I say 2,5 hrs ?

peter hudson

Well-Known Member
Perfect

Strength requirements....
For gliders is often used +5,3 / -2,65 g.
With safety factor 1,875 (typical minimum for composites) you have to test it for +10 g and -5 g.

With my light wing loading the gust loads become a factor in my envelope (5.7g per the basic glider criteria)
Bumping up just a little to 6gs allows for potential weight over-run for the one off "prototype" . It also allows for future battery weight increases if my marginal pack allows you to say "I told you so!"

And with "uncharacterized" composite processes and relying on "similar materials databases" I don't feel comfortable with less than F.S. = 2 (Which is also what the FAA wants when using the AGATE database for materials properties).
I do plan some component tests to failure and then I'll want a proof load test of 1.1 x limit on the primary structures.

John.Roo

Well-Known Member
With my light wing loading the gust loads become a factor in my envelope (5.7g per the basic glider criteria)
Bumping up just a little to 6gs allows for potential weight over-run for the one off "prototype" . It also allows for future battery weight increases if my marginal pack allows you to say "I told you so!"

And with "uncharacterized" composite processes and relying on "similar materials databases" I don't feel comfortable with less than F.S. = 2 (Which is also what the FAA wants when using the AGATE database for materials properties).
I do plan some component tests to failure and then I'll want a proof load test of 1.1 x limit on the primary structures.
OK - that is right way
Even here we prefer safety factor 2-2,25 if company (builder) has not large previous experience with composite airplnes production For strength test requested before first test flight is also good to increase load a a little bit so safety factor 1,1 is reasonable.

Last edited:

John.Roo

Well-Known Member
If Heron was electrified..how much range would you estimate on her ?

I say 2,5 hrs ?
Well... lets assume +-similar fuel consumption of Heron and Velis (not exact because at MTOM Heron will have higher energy requirments but for our estimation is OK).
Velis is based on Virus and Virus has 100 lit fuel tanks with MTOM 600 kg.
Heron has MTOM 1 150 kg - already mentioned difference is 550 kg.
I would say that would be possible to install battery with weight of 600-650 kg.
That is 120-130 kWh.
Main problem for me is air speed.
Heron has max. speed 207 kmph.
Cruise speed will be not far from Vne. It means 180-190 kmph. That requires a lot of power and that is decreasng endurance dramatically.
Positive is that wing span 16 m makes Heron interesting "motorglider" so for horizontal flight at 130-140 kmph could be possible to use only... 35-40 kW?
In that case 2,5-3 hours seems to be realistic expectation.
However another poblem is operating altitude.
2,5-3 hours endurance means endurance at 40 kW power settings.
Climbing to high altitude = high power requirements and this can dramatically decrease cruise time....

Last edited:

John.Roo

Well-Known Member
If Heron was electrified..how much range would you estimate on her ?

I say 2,5 hrs ?
If there would be interest to operate UAV with electric propulsion in size of Heron than is in my point of view 600-650 kg battery nonsence... Army have access to DARPA projects and I am sure that there are existing prototypes of nice small generators - possible range extenders.
Actually makes use of Rotax 914 (or new 915) sense.
Price of ICE propulsion is lower (in compare with price of battery and electric motor etc.) and fuel is standard MOGAS - available everywhere.

I mentioned this before... so far makes perfect sense only one electric vehicle - electric bicycle
Affordable, simple to use and with small power requirements using standard components available everywhere....
....and idea of basic e-glider is based on same principle

Sraight'nlevel

Well-Known Member
If there would be interest to operate UAV with electric propulsion in size of Heron than is in my point of view 600-650 kg battery nonsence... Army have access to DARPA projects and I am sure that there are existing prototypes of nice small generators - possible range extenders.
Actually makes use of Rotax 914 (or new 915) sense.
Price of ICE propulsion is lower (in compare with price of battery and electric motor etc.) and fuel is standard MOGAS - available everywhere.

I mentioned this before... so far makes perfect sense only one electric vehicle - electric bicycle
Affordable, simple to use and with small power requirements using standard components available everywhere....
....and idea of basic e-glider is based on same principle
Yes I mostly agree.

OTOH..when still much more streamlined ( as the electrical can ) the Heron and other could be much more aerodynamic. As for now they are just platforms for huge amount of SATCOMs...hard points, antenna and optical devices etc etc.

Adding also cells as range extenders I figure we could have 5-6 hrs capable all electric UAV:s too.

PiperCruisin

Well-Known Member
And with "uncharacterized" composite processes and relying on "similar materials databases" I don't feel comfortable with less than F.S. = 2 (Which is also what the FAA wants when using the AGATE database for materials properties).
I do plan some component tests to failure and then I'll want a proof load test of 1.1 x limit on the primary structures.

Also depends on what you are starting with. For material properties maybe start with A or B bases then maybe downgrade for hot/wet conditions then add you factor of safety. I think 2 on top of all of that might be a bit much.

EzyBuildWing

Well-Known Member
A pity Pistrel doesn't have a longer span eTrainer/soarer with 30:1 glide and tricycle-gear and 1 hr 100.mph range (with 30 minutes reserve) and 200kg payload...I guess it all depends on battery-tech "break-throughs" . Longer span pic photo-shopped looks good:

John.Roo

Well-Known Member
Yes I mostly agree.

OTOH..when still much more streamlined ( as the electrical can ) the Heron and other could be much more aerodynamic. As for now they are just platforms for huge amount of SATCOMs...hard points, antenna and optical devices etc etc.

Adding also cells as range extenders I figure we could have 5-6 hrs capable all electric UAV:s too.
You are right - all the antennas and sensors are really not improving aerodynamic characteristics....
On F-22 Raptor you can see that they now how to hide all sensors, but question is if makes sense to do that on UAV. Fuel price is minor cost comparing with prices of all sensors, weapons etc. Seems to me that nobody care about a bit higher drag.

I found this info....
"Three Heron UAVs and one ground control station costs $140 million." Price of new Duo Discus glider is 250 000 USD. So for three Heron UAV you theoretically could have 560 new Duo Discus gliders..... And if very simple e-glider could cost around 50 000 USD (+-45 000 EUR) than you could give to gliding clubs 2 800 toys to play.... Just playing with numbers Really difficult to imagine prices of "army toys". Sraight'nlevel Well-Known Member You are right - all the antennas and sensors are really not improving aerodynamic characteristics.... On F-22 Raptor you can see that they now how to hide all sensors, but question is if makes sense to do that on UAV. Fuel price is minor cost comparing with prices of all sensors, weapons etc. Seems to me that nobody care about a bit higher drag. I found this info.... "Three Heron UAVs and one ground control station costs$140 million."
Price of new Duo Discus glider is 250 000 USD.
So for three Heron UAV you theoretically could have 560 new Duo Discus gliders.....
And if very simple e-glider could cost around 50 000 USD (+-45 000 EUR) than you could give to gliding clubs 2 800 toys to play.... Just playing with numbers
Really difficult to imagine prices of "army toys".
Yes the airframe there is just a necessary evil....it is full of electronics, optics, radars, sensors and whatever.

EzyBuildWing

Well-Known Member
eGenius hybrid 2-seater soarer looking good......above 300m start the "Mercedes Smart" diesel gen-set Range-extender..... ie; environmentally-quiet footprint at low level. And 500km range possible.

John.Roo

Well-Known Member
e-Genius is great students project
Team of boys from Stuttgart shown how is possible to make hybrid TMG.
At the beginning they tried generator based on wankel engine installed in the pod under the wing...

In the end they had to use a Mercedes engine and the entire generator prototype installation weighs over 100 kg. After optimization, it would be possible to reduce the weight, but the important thing is that the installation of the generator (range extender) is not as simple as it seems.

The current version is a great example of what can be produced in the category of "adult" motor gliders - TMG with MTOM 850 kg. The same installation in the UL / LSA category (MTOM 600 kg) would require a large weight reduction of range extender installation.

In one category of light electric one-seater is installaton of range extender based on ICE engine practically impossible.... Even hybrid version needs battery. I cannot imagine extremelly light intallation of combination of ICE system plus electric propulsion system in airplane with MTOM arround 300 kg and usefull load 100-110 kg. Even if in 100-110 kg range is calculated +-10 lit of fuel = pilot weight range would be reduced to +-90-100 kg).

Lets see if also Elfin team will show some progress...

Last edited:

blane.c

Well-Known Member
I know we are pilots and our dream machines are flying, but lets stay "on the ground" with used technology.
"Oscilating plates", "flaping wings".... it can be interesting project for students.

I would personally really prefer conservative way.... simple small glider like Axel or eBirdie.
Material - glass fibre with carbon reinforcements (maybe carbon main spare).
Control lines - automatic or very simple connections to make dismantling easy and fast.
Standard control system - no combination of trike and airplane. Controlled should be elevator, rudder, ailerons and airbrakes. Flaps are nice option, but if plane stall speedfits into UL category than lets keep it simple without flaps.
Simple propulsion system - no contra-rotation, no multimotor config (ok ok, lets say that two motors should be maximum) Ideally only folding prop(s). Of course feathering / in flight adjustable prop could be interesting option for flight testing.
No special cells used in main battery - lets take standard Li-Ion 18650 or 21700.
No need of super high Vne and cruise speed.

Main requirements:
- MTOM +-300 kg
- Vne 180-200 kmph
- as low as possible airframe and propulsion price
- nice handling
- safe flight characteristics
- L/D 30:1 or better
- comfortable cocpit with simple instrument panel layup
- perfectly vissible upper hemisphere
- min. safety factor for airframe 1,875

Why glass? Why not all carbon?

Controls, what are best proven disconnects?

I know you said before difference in motors is a "lunch" but maybe take a new look at motors? Is having some mass in the motor a good thing for heat dissipation? Are there motors with less friction or that somehow give more hp out from a given wattage? Weight aside a motor that is more electrically efficient would be interesting?

The mechanism for propeller pitch control could be small diameter considering hp involved so folding gizmo for prop could be past cowling diameter but might it be better if having controllable pitch to just go all the way and make it full feathering?

Why are a whole bunch of dinky batteries soldered together better than a few prismatic batteries? -- https://www.geebattery.com/battery/3-7v-50ah-prismatic-lithium-ion-battery-supplier -- Another lunch perhaps?

I know it never be speedster but lets make it as fast as possible?

I need to diet but there are limits, what is greatest MTOM conceivable or legal?

Is 200kmph a legal limit if not maybe make it legal limit?

As low as possible price is dangling a carrot in front of the safety Mule?

What means "nice handling", I mean there must be some parameters that help to insure "nice handling"? Surely it isn't a "dark art".

By "safe flight characteristics" you mean it stalls clean? And recovers from stall easily? Also no overt tendency to aileron stall and wing over in steep slow turn? Spin recovery is "normal"? Perhaps you could explain safe flight characteristics more succinctly? As it is crucial?

LD 30:1 minimum so really trying for 35:1 or better but willing to accept failure if other aspects work out?

"comfortable cockpit" maybe to some extent "customizable cockpit"? Or possibly if kit maybe a "fat boy" cockpit option? Maybe a couple bulges, blisters, or just more "blimpy" than standard cockpit?

Simple instrument panel is somehow not very informative?

Yes on visibility I want to see like a bird otherwise what is point?

Minimum safety factor for airframe 1.875 seems arbitrary?

Could it be painted nice bright color like beautiful balloon? White is so passé. Maybe use pre-preg fabric and an easy bake oven?

EzyBuildWing

Well-Known Member
Than Elfin "RangeExtender 1000" looks interesting.....could be retrofitted to any eAircraft.
Pipistrel Taurus G4 with the eGenius diesel range-extender would have been awesome......

henryk

Well-Known Member
I need to diet but there are limits,

=I propose fasten feve days=cirka minus 1 kg/day... (NO more as 90 days !!!)

-in my case (COVID19) =87/82 kg in one weak, only water!.

Attachments

• 20190804_102812_529960177947657(1).mp4
19.5 MB

blane.c

Well-Known Member
=I propose fasten feve days=cirka minus 1 kg/day... (NO more as 90 days !!!)

-in my case (COVID19) =87/82 kg in one weak, only water!.

Funny, ha ha.

John.Roo

Well-Known Member
Ok, lets explain my point of view....

Why glass? Why not all carbon?
Glass used on wings is helping to achiveve wings flexibility = better comfort.
Fuselage should be probably produced from carbon.
In any case... less carbon = lower price.

Controls, what are best proven disconnects?
They are many ways how to make safe quick connection control lines system. I would use system already well tested on gliders. Exact type will depend on available space.

Exactly. Weight and complexity.

I know you said before difference in motors is a "lunch" but maybe take a new look at motors? Is having some mass in the motor a good thing for heat dissipation? Are there motors with less friction or that somehow give more hp out from a given wattage? Weight aside a motor that is more electrically efficient would be interesting?
Of course is good to keep eye on new motors and controllers etc. I still hope

The mechanism for propeller pitch control could be small diameter considering hp involved so folding gizmo for prop could be past cowling diameter but might it be better if having controllable pitch to just go all the way and make it full feathering?
I also personally prefer to have in flight adjustable prop. At least for first testing prototype to see real benefit of this solution (or to see that is cheaper and better to use folding prop)

Why are a whole bunch of dinky batteries soldered together better than a few prismatic batteries? -- https://www.geebattery.com/battery/3-7v-50ah-prismatic-lithium-ion-battery-supplier -- Another lunch perhaps?
Good idea with the prismatic cells Thanks to remind me.

I know it never be speedster but lets make it as fast as possible?
Accoring to requirements (SSDR, LAA UL-2, Class 120 etc.) we have to keep Vne max. 180 kmph.

I need to diet but there are limits, what is greatest MTOM conceivable or legal?
If we want to precede expensive certification proces and pass thru "simplier" requirements we have to keep MTOM 300 kg. Note - simplier requirement doesn´t mean less safe requirement.

Is 200kmph a legal limit if not maybe make it legal limit?
200 kmph is flutter test limit. But 200 kpmh is Vd so we have to stay 10% below....

As low as possible price is dangling a carrot in front of the safety Mule?
No, request for high safety is far above price requirments. But price must be kept on mind as well since beginning.

What means "nice handling", I mean there must be some parameters that help to insure "nice handling"? Surely it isn't a "dark art".
Nice handling.... I like when control are precise and harmonized. It is subjective feeling, I know. Well lets say that should be like handling good glider (for example Discus).

By "safe flight characteristics" you mean it stalls clean? And recovers from stall easily? Also no overt tendency to aileron stall and wing over in steep slow turn? Spin recovery is "normal"? Perhaps you could explain safe flight characteristics more succinctly? As it is crucial?
Yes, I mean predictible stall characteristics, stall warning, standard spin recovey procedure etc.. Like nice handling characteristcs it is a bit subjective so in short - flight characteristics similar to school gliders.

LD 30:1 minimum so really trying for 35:1 or better but willing to accept failure if other aspects work out?
L/D 30:1 should be reasonale minimum in this e-glider category.
Here we are entering into circle of compromises (weight vs complexity of airframe vs strength requirements vs price....). So higher L/D would be nice, however I expect reality in range between 35:1 to 30:1...

"comfortable cockpit" maybe to some extent "customizable cockpit"? Or possibly if kit maybe a "fat boy" cockpit option? Maybe a couple bulges, blisters, or just more "blimpy" than standard cockpit?
Well... is practically impossible to make cocpit comfortable for every pilot size. Some "customization" would be good (adjustable pedals, different back seat or adjustable seat back position....) but I don´t think that somebody will make two cockpit sizes in this category. If I remember well - Schempp Hirth Discus has been offered with two different cockpit sizes - however Schempp Hirth is large producer of certified gliders.

Simple instrument panel is somehow not very informative?
I am still thinking about this concept. They are existing combined flight instruments however question is if you can read easily important numbers. What pilot really need?

Yes on visibility I want to see like a bird otherwise what is point?
Point is that airframe design must allow to watch perfectly upper hemisphere. So wing cannot be above cockpit (like for example Pipistrel Sinus).
Birds are usually looking down, forward and to the sides. We need to have clear view up, forward and to the sides (to area where are you turning).

Minimum safety factor for airframe 1.875 seems arbitrary?
1,875 is minimum acceptable safety factor if airframe is produced by experienced workers.
Prototype is typically tested with safety factor 1 (operating load) before first flight. Airframe must survive this load without any permanent deformations etc. Of course we usually use a bit higher load (5-10%) but rules are very exact.

Could it be painted nice bright color like beautiful balloon? White is so passé. Maybe use pre-preg fabric and an easy bake oven?
Bright colors? Why not But I personally prefer to to avoid use of prepreg.

blane.c

Well-Known Member
Why don't you like pre-preg? It seems a preferred way to get proper plastic to fiber ratio? It also will tolerate higher temperatures before melting so better for painting bright colors?