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Why battery-powered aircraft will never have significant range

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pictsidhe

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Why are we wasting our time on this nonsense? We should just ignore him until he builds his impossible airplane. I am too easily sucked into trying to teach the unteachable.
Unfortunately, not everyone has him on ignore. So somebody will always bite.

Anyone remember that other Finnish nutjob who kept spamming threads about his pedal powered airliners?
 

Speedboat100

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Unfortunately, not everyone has him on ignore. So somebody will always bite.

Anyone remember that other Finnish nutjob who kept spamming threads about his pedal powered airliners?

That was a good one Pitchside. Dan knows this will blow everyone's mind.
 

Speedboat100

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It is ready...the initial lay out !

Name is ROADRUNNER !

After the legendary finnish rock band Hurriganes:


ROADRUNNER.jpg
 

Motorgliderpilot

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Unfortunately, not everyone has him on ignore. So somebody will always bite.

Anyone remember that other Finnish nutjob who kept spamming threads about his pedal powered airliners?
Topspeed and Speedboat are the very same guy, as you can see from his signature link
 

John.Roo

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It is ready...the initial lay out !

Name is ROADRUNNER !

After the legendary finnish rock band Hurriganes:


View attachment 105014
This interesting post from blane.c can help you :)

Perhaps you will be amused.
For figuring stall speed of part 103 ultra light aircraft, scroll down "Just past" pg16 and you will find appendix (1) and 3pg below that is appendix (2) which is, Determining power-off stall speed of ultralights.

 

Speedboat100

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This interesting post from blane.c can help you :)

Perhaps you will be amused.
For figuring stall speed of part 103 ultra light aircraft, scroll down "Just past" pg16 and you will find appendix (1) and 3pg below that is appendix (2) which is, Determining power-off stall speed of ultralights.


I have gone through the Part 103 requirements.

My plane at the lowest weight with just 8 -10 kg batteries will have very slow stall speed and cannot fly very fast if the motors are small enough. Increasing the batteries onboard and having bigger engines will considerably speed up the machine....becoming an experimental.
 

John.Roo

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8-10 kg of batteries?
It means capacity of +-2 kWh.
For TakeOff power 14 kW you have discharge rate of 7C.

It is your project just...
I really recommend you to make several ground tests with max. power and power necessary for level flight with detailed measurement of temp. of battery cells and motors. It will give you some impression how long you can use max. and cont. power.
 

Speedboat100

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8-10 kg of batteries?
It means capacity of +-2 kWh.
For TakeOff power 14 kW you have discharge rate of 7C.

It is your project just...
I really recommend you to make several ground tests with max. power and power necessary for level flight with detailed measurement of temp. of battery cells and motors. It will give you some impression how long you can use max. and cont. power.
Part 103 plane needs only 8-12 KW for take off. Plane works as a plat form for several FAI records...with more batteries and 14 KW of max power.

----

There are several aims with this:

1. Finnish 70 kg motorglider...that is first intented...with 8-10 kg of batteries.
2. Part 103...that can have flaps and more batteries as it is 115 kg limit ( 5 gallons worth ? ).
3. Certified ultra under 300 kg.

Plane has very low stall speed at 70 kg weight...so it fits PART 103 as such.

I hope this clear the subject.
 
Last edited:

John.Roo

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I don´t see problem with propulsion power.
Few weeks ago I was personally flight testing light plane with MTOM arround 300 kg with 15 kW propulsion system and battery had capacity of 6 kWh. Nice experience :)

So 12 kW is OK. I just prefer higher capacity of batteries.
Ideally 1 C of less for level flight and 2-3 C for TakeOff.
 

Geraldc

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On the negative side the accident report is out from a Glider fire and crash in New Zealand.

1607629872705.png
 

John.Roo

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On the negative side the accident report is out from a Glider fire and crash in New Zealand.

View attachment 105103
Thanks! Really interesting report.
Good reason to keep batteries away from cockpit (in the wings or in the front of firewall).

And this is also interesting reading:

The glider manufacturer’s Flight manual and Maintenance manual provides direction on battery charging. This includes two cautions:

CAUTION! DURING THE PERIODS OF NOT USING THE AIRCRAFT, IT IS REQUIRED TO PERFORM A KEEP-ALIVE (STORAGE) CHARGE ONCE EVERY 30 DAYS. TO DO SO, CONNECT THE CHARGER AND SELECT ‘REST CHARGE’ MODE, THAN WAIT UNTIL COMPLETED. THIS WILL REFRESH THE BATTERIES AND KEEP THE SYSTEM IN A HEALTHY STATE. ALSO, AFTER A PERIOD OF NO-FLYING ACTIVITY, PERFORM A FILLUP CHARGE 24 HOURS BEFORE THE ACTUAL FLIGHT.

CAUTION! AFTER PERFORMING A FULL CHARGE, DO NOT KEEP THE BATTERY AT A VOLTAGE OVER 260 VOLTS FOR MORE THAN 5 DAYS. EITHER PERFORM A FLIGHT OR RUN THE MOTOR TO DISCHARGE THE BATTERY TO THE RECOMMENDED 240-260 VOLTS FOR STORAGE.
 

Speedboat100

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That was informative.

Smoke in the cockpit could have been more of an issue than the actual fire. Compromised breathing and eyesight could acerbate an already difficult problem leading to poor judgement.

I agree. I decided to keep the batteries outside. I even discussed with my structural engineer about possibility to jettison the batteries in case of an emergency. It would be rather easy to do in my design.
 

John.Roo

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I agree. I decided to keep the batteries outside. I even discussed with my structural engineer about possibility to jettison the batteries in case of an emergency. It would be rather easy to do in my design.
I don´t know if CAA/LAA/FAA... would allow to jettison batteries + unless you have bateries exactly in airplane CG you should consider CG change after "drop out".
 
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