what autopilot?

[sansolo]

Hi, (my english is very poor, i said VERY)

I'm starting to project an eletric plane(probably an wing) to climb 12000ft. I know nothing about autopilots because here in brasil its something very strange, so tell me what autopilot fits this specs.:
> i insert the route, altitude, climb rate and speed at specific places.
> i need to have the real time data(altitude, speed,...) in a laptop.
> what adicional equipment i need to view the cam image also in real time. remind that i need a very good range of the transmitter!
> if possible, and don't be so expensive, changing some waypoints during the flight would be nice.

thanks,
Ricardo. :D

[Dan_Jones]

Maybe somebody else can answer your question about which autopilot to use.

I just got done flying my airplane at 7000 ft. It didn't fly half as well as it did at sea level. I crashed it into a tree because it couldn't climb. So when flying at altitudes higher than 2000ft than what you are used to, please be careful. We brought some electric helicopters and the throttle curves had to be bumped up 25% to equal the flying characteristics at sea level. I was amazed at the difference altitude makes to a model airplane. 12000ft is quite a height. Good luck and keep us posted!

[clolson]

Different airframes can have a huge variety of performance characteristics, but climbing up to 12,000' from let's say 1000' at 500 fpm is going to take 22 minutes out of your battery and at a relatively high throttle setting.

If you have to carry a decent payload and can't live with small/light parkflyer airframes, then electric power system for larger aircraft (with enough power and duration to get up to such high altitudes and be able to do something for a while up there) are going to be really expensive.

I'm getting about 25 minutes of flight time off an 8000mAh 5cell lipo battery pack on an 8' telemaster. And that does somewhere between 500-1000 fpm climb at sea level. But I get easily double those flight times and unlimited vertical performance on my 49" Rascal park flyer with an outrunner motor and an 1800 mAh 3 cell battery pack ... but that's not carrying any payload.

Curt.

[danstah]

How high is legal to fly in the US?

[Dan_Jones]

As I understand it, in the US we can fly up to 400ft above ground level. Anything above that is reserved for full sized aircraft. Its funny, but kites are also limited to this height too.

[clolson]

My understanding is that this is sort of a "gentleman's agreement" between the AMA and the FAA, but not necessarily defined in any sort of law. I'm pretty sure that your AMA insurance expires above 400' AGL, that's the motivation to stay < 400 AGL, but this is really not very high. I've flown my UAV locked in at 500' AGL so I have a good sense of what that altitude looks like, and that doesn't seem very high either. I would guess that at my club this 400' limit is busted on just about every flight.

[Unterhausen]

My club had a guy flying a plane at 400' AGL next to a model airplane, and it's pretty far up there, but as people have said, it's a limit that is observed in the breech more than anything.

Turns out the parallax error from the ground is horrible, the model airplane looked like it was above the full scale airplane, but it was actually below it.

[clolson]

I was flying an 8' wing span bird when I observed that 400' AGL didn't seem very high up. :-) I've had our 110" wing span Rascal up to about 1200' AGL with a spotter, but perhaps I shouldn't be posting that? At 1200' AGL it does look like it is pretty high up there, but still very easy to see since it's so big.

Curt.

[d_wheel]

It's in the AMA safety code:

5. I will not fly my model aircraft higher than approximately 400 feet above ground level, when within three (3) miles of an airport without notifying the airport operator. I will yield the right-of-way and avoid flying in the proximity of full-scale aircraft, utilizing a spotter when appropriate.

[macboffin]

Had to do some demos for Indian Army with a small hand-launched UAV with live video, this was a flying wing weighing about four pounds, fifty inch span.
Power was O.S.32 running on 5 per cent nitro. Just toss in the air, away it goes.
They wanted to see what it would be like at altitude,(ground level 12k feet in the Himalayas near Kashmir border) so took us up there. We had to go to 50 per cent nitro, run like hell, and launch like a javelin to get it into the air.Once up it did pretty well, although inclined to tip stall in a tight turn, plus it was flying noticeably faster than at lower altitudes ; we were putting down on snow, and it was sliding a fair way!
Apart from the power necessary at high altitude, one possible problem with electric might be due to battery temperature, they don't deliver as well when cold, and up there it is COLD!

[clolson]

I live in MN and for whatever it's worth, last winter I set my airframe outside so I could get gps signal. My flight computer/sensors was running off 3.7v lipoly batteries that normally power the system for 1+ hours at room temperature. I was able to get about 5 minutes of run time at the most at +10 degrees F. When I brought the batteries back in and warmed them up to room temp and tried to charge them, they still had almost a full charge, they just couldn't deliver it at those cold temps.

I switched to some NiMH receiver packs I had laying around and found I got surprisingly good results out of them. There was some diminished capacity, but maybe on the order of 10-20% not 99% like with the lipoly batteries I was using.

I'm not a big battery expert so maybe my lipoly batteries were atypical, but kind of scared me how quickly their voltage dropped below usable levels in the cold temps.

Curt.

[macboffin]

I live in MN and for whatever it's worth, last winter I set my airframe outside so I could get gps signal. My flight computer/sensors was running off 3.7v lipoly batteries that normally power the system for 1+ hours at room temperature. I was able to get about 5 minutes of run time at the most at +10 degrees F. When I brought the batteries back in and warmed them up to room temp and tried to charge them, they still had almost a full charge, they just couldn't deliver it at those cold temps.

I switched to some NiMH receiver packs I had laying around and found I got surprisingly good results out of them. There was some diminished capacity, but maybe on the order of 10-20% not 99% like with the lipoly batteries I was using.

I'm not a big battery expert so maybe my lipoly batteries were atypical, but kind of scared me how quickly their voltage dropped below usable levels in the cold temps.

Curt. Goes along with my experience, Nicads lose a bit, but lipolys need warmth to deliver.I can see problems ahead for people who launch as usual on a colder day and rapidly run out of power.

[DACeller]

Hold on,, I have had no trouble at all flying with my Electric Power LiPos from XUS hobby. These are 12C rated 1800 mah and my motor sucks 16 AMPs. I believe that's enough to keep them warm and they give me all that I expect down to -14F. I chose the lightest pack possible to share with my Scooter, Glider, and Miss 2-which I hope to make UAV now this winter.
I used to do the same thing with NiMH and they too would perform fine at cold temperatures provided they started out warm and usage kept them as such; If I let them get cold, I couldn't even get the glider off the ground.

[sansolo]

Hi,
this project is for december, but I have already same ideas, lets do the good part:

Lift = 1/2 . S . Cl . V² . density in SI(meter, newton, kg,...)
7,84 = 1/2 . S . 1,26 . 69,4 . 0,85 => S = 0,211m²
gravity 9,8
V stall 8,3
Cl at 12000ft

this is a reasonable result considering that my shock flyer with rimfire 22M 1000kv, 10x4,7(yes, I kill the engine), same wing area and 1000mah battery can fly for 15 minutes.
My preliminary idea: equivalent engine with better eficience, associate batteries in parallel to diminish the resistance, make a rectangular wing to build with CNC machine.
PS.: somebody can help me with the autopilot? :)
about Bocci-Dowty Roto from Aerunautical Research what you think?

[Unterhausen]

I think lipos are ok in cold as long as they start out warm and have a reasonable current draw which will keep the battery warm. At least that is what people have reported here. I believe Curt's experience has to do with them becoming too cold due to inadequate current draw.

[sansolo]

can someone help me with the auto pilots?
i was looking the u-nav picopilot but i understood that speed and altitude cant be programmed, you just climb there turn the AP on and it will hold the plane in the same altitude.

[macboffin]

I think lipos are ok in cold as long as they start out warm and have a reasonable current draw which will keep the battery warm. At least that is what people have reported here. I believe Curt's experience has to do with them becoming too cold due to inadequate current draw. Agreed. Mac