Use of UNAV ALT-3 and RTL on a glider, first flights complete.

[Disciple4123]

Well I have the 2m glider set up with UNAV alt-3 and RTL. Just finished trimming the aircraft for normal flight and began to use the ALT-3, At 1/3 setting on the pot, it would nosedive and I had to cancel it, basically the unit was giving too much control too late. I took the setting to 2/3 on the pot, then it did a couple of up/down cycles, but clearly not in control. Perhaps my glider is too low-speed of an aircraft, something a little faster may give more controlled elevator responses? My CG is 1/2" forward of the reccomended settings, still feels light. Does anyone, perhaps KD7OST, have advise on this? I am building a Tower trainer 40 to try, with the ail and rudder joined under the RTL. Perhaps that airframe with it's longer tail, less lift, and faster cruise speed will allow the ALT-3 to work better.

[icebear]

Hi,

Try an even lower gain on the Alt3 pot - note direction on the gain also - I believe the Alt 3 is reversed, i e full clockwise setting of the pot is minimum gain.

It sounds as if you still have too much gain - it is a very sensitive unit so elevator throw should not be too much mechanically either.

I don't think it is a matter of the unit controlling to late, rather that your mechanical throw and gain is too high. It shouldn't be a problem for the Alt3 to control your glider in my opinion. Just play some more with the gain and/or throw.

Good luck!

Icebear

[Disciple4123]

OK, thanks Icebear, the pot turns normally on mine, I have set both the RTL and ALT-3 to the lowest setting for testing. The glider flies great in 5mph or lower winds, but even though it is 62 oz, it gets blown over when sitting on the ground prior to takeoff if the wind is 7mph or higher. Today winds are at 20-40mph, so testing be in a few days. I am building the Tower 40 trainer to try that as well, I'll use the glider for a few more flights to gain experience, as I am a heli guy and new to the airplanes.

Thanks,

[clolson]

Today winds are at 20-40mph

Small dog warning!

[Disciple4123]

Very funny Clolson, I am putting this boat anchor out right now...

http://www.aerialphotographyservices.com/pictures/P1012260.JPG

[icebear]

Ha ha - isn't that a horse!? :) (nice looking animal anyhow!)

Disciple - just make sure to check that the gain pot is working the way you describe...

I heard from someone here recently that the ALT3 gain is reduced when pot is turned clockwise. It is easy to check as you can see from servo movements that sensitivity is increased at the max setting by looking at the elevator when the unit is enabled.

/Icebear

[d_wheel]

Well I have the 2m glider set up with UNAV alt-3 and RTL. Just finished trimming the aircraft for normal flight and began to use the ALT-3, At 1/3 setting on the pot, it would nosedive and I had to cancel it, basically the unit was giving too much control too late. I took the setting to 2/3 on the pot, then it did a couple of up/down cycles, but clearly not in control. Perhaps my glider is too low-speed of an aircraft, something a little faster may give more controlled elevator responses? My CG is 1/2" forward of the reccomended settings, still feels light. Does anyone, perhaps KD7OST, have advise on this? I am building a Tower trainer 40 to try, with the ail and rudder joined under the RTL. Perhaps that airframe with it's longer tail, less lift, and faster cruise speed will allow the ALT-3 to work better.

Is this a powered glider? If not, I can't see how any kind of altitude hold would work.

On my Alt-E board, the gain adjustment pot is reversed. In other words, I have to turn it clockwise to reduce the gain. Fully counter clockwise would be full sensitivity.

What is the voltage going into the Alt-3 board. With my board, if it is not 6 volts I get erratic results. On the bench it SEEMS to work at 5 volts, but is very erratic in the air. With 6 volts and it solid in both cases.

Later;

D.W.

[Disciple4123]

Thanks, it is a Great Dane, 1 year old, trained in Spanish only. It's a "Me no speak english," dog :)

I just rechecked mine, counterclockwise=gentle elevator pulses / clockwise=stronger pulses. I guess mine's build diferent than yours, mine is an ALT-elevator as well.


Both devices are set to minimum gain right now, we shall see how that works.

I made it a powered glider, A123 cells 4s1p, 2826/12 motor 13x8 prop.

Thanks,

[d_wheel]

Thanks, it is a Great Dane, 1 year old, trained in Spanish only. It's a "Me no speak english," dog :)

I just rechecked mine, counterclockwise=gentle elevator pulses / clockwise=stronger pulses. I guess mine's build diferent than yours, mine is an ALT-elevator as well.


Both devices are set to minimum gain right now, we shall see how that works.

I made it a powered glider, A123 cells 4s1p, 2826/12 motor 13x8 prop.

Thanks,

Bye the way, you are REALLY going to like the RTL unit. I have one on a 2 meter glider that has been specked out a couple of times in thermals. Around here, there is always wind blowing, so the thermal and glider drift downwind. Sometimes quite a ways! All I have to do is flip the switch that turns on the RTL unit and it heads back home. I just lay back in a lawn chair with my transmitter on my stomach and watch it head back, and then circle overhead, until I am ready to look for another thermal. My winter project is a 4 meter sailplane. I hope to be doing the same thing with it and the RTL next spring/summer.

Later;

D.W.

[Disciple4123]

Glad to hear it works well, there is little info on the forums on the UNAV stuff. I am nearly completed with the 40 sized trainer build, hopefully it will allow better wind performance, I don't know about your 2m glider, but mine will just tip over on takeoff or just sitting on the ground if there is breazy weather. I plan on joining the ailerons and rudder for RTL, and having a heading hold gyro on the same circuit to manage straight and level flight when RTL is not engaged. The goal is to have a longer range reconnaisance aircraft than the heli can provide, and pretty well ensure it's ability to return to base.

6 volts: I use a homemade regulator to put out 6v from the main battery, the directions warn about 4.8 volts being too low.

4 meter sailplane, that sounds large. How far and high do sailplane folks like yourself go? Does the FAA get on your case?

[d_wheel]

Glad to hear it works well, there is little info on the forums on the UNAV stuff. I am nearly completed with the 40 sized trainer build, hopefully it will allow better wind performance, I don't know about your 2m glider, but mine will just tip over on takeoff or just sitting on the ground if there is breazy weather. I plan on joining the ailerons and rudder for RTL, and having a heading hold gyro on the same circuit to manage straight and level flight when RTL is not engaged. The goal is to have a longer range reconnaisance aircraft than the heli can provide, and pretty well ensure it's ability to return to base.

In this part of the country, the wind is almost always blowing. We just learn to deal with it. My glider is hand launch so I just toss it into the wind. The 4 meter will be a little different. I am working on a cradle to use for piggy-back launching off of a large power plane so wind should not be much of a factor.

6 volts: I use a homemade regulator to put out 6v from the main battery, the directions warn about 4.8 volts being too low.

Good. You have that part nailed down then.


4 meter sailplane, that sounds large. How far and high do sailplane folks like yourself go? Does the FAA get on your case?

The FAA recommends that no one fly above 400 feet when near an airport. We are not near any airports and are not in controlled airspace so we just keep an eye out for full size aircraft in the area. I have an altitude recorder and the highest so far is 1800 feet. The 4 meter should be able to go higher before specking out.

Later;

D.W.

[dmgoedde]

I got my Miss2 to 2466 feet AGL (derived from GPS alt, recorded by AttoPilot while flying in RC mode). Then I saw a Cessna and helicopter lower than my plane, I figured it was time to stop and bring her down. Besides that, it was no fun flying a plane so high that it is a mere dot.

[Disciple4123]

It is fun flying at altitude allright, but I think if you are seeing the fullscale crowd below there may be issues. We have some piston fullscale heli's that perform low level flight sometimes around the area, wife spotted one land behind our field one day, probably autorotation training I guess, either way I get a little concerned that they may take issue with me if spotted.

OK, well some flights were completed today with the Glider. Bear in mind that the glider was crashed early on and has cotton medical tape, epoxy, and packing tape holding the wing and parts of the fuselage together :eek: There was no wind and it flew well, was able to use ALT-3 and RTL. The ALT-3 was operating at minimum gain, and mechanically set up for slightly less travel (as gain reduction alone was insufficient) At times it held level perfectly, at times it bobed up and down enough to be a nuisance on the video, but still under control. The RTL was engaged several times 1/4 to 1/2 mile away. At minimum gain it banked right 40 degrees, then leveled out acceptably until reaching base. Electrical consumption is less than expected, 10 minute flights were hardly draining the A123's running at about 35% throttle.

I observed something with the ALT-3 that perhaps others can chime in on: When I have throttle set to a smooth cruise (about 35%) and the ALT-3 begins to induce bobbing, the prop slows down on the upward pass, and speeds up a lot when it bobs down. It bobs about one cycle per every 4 seconds. The prop speeding up seems to generate inertia and propel it into the upward bob. This is with a fixed 13x8 prop. I have a 12x8.5 folder that I plan to use as well. Will the folding prop not speed up with minor bobbing as much, perhaps it will fold up or the pitch difference will not engage the air as much? That is the only detail left in the autopilot system that I feel needs fine-tuning.

The 40 trainer is complete, within a week or so I may transfer the goodies over to it, no cottony medical tape on that one yet :cool: .

[walkermsg]

Removing the red jumper reverses the servo movement which sounds like the trouble you are having. Also air blowing on or near the little tube affects the flight up and down. It needs to be inside the plane where it can sense altitiude but not wind. You may need to make the small metal tube pickup unit they describe. Mine is max at CW like a volume control and min at ccw.
If you put it where the wind blows on it it will really act crazy. Try holding the plane and blowing on the small tube sticking up from the ALT 3 and see what I mean. Hope this helps.
Lee : :D

[Paul_BB]

Bye the way, you are REALLY going to like the RTL unit. I have one on a 2 meter glider that has been specked out a couple of times in thermals. Around here, there is always wind blowing, so the thermal and glider drift downwind. Sometimes quite a ways! All I have to do is flip the switch that turns on the RTL unit and it heads back home. I just lay back in a lawn chair with my transmitter on my stomach and watch it head back, and then circle overhead, until I am ready to look for another thermal. My winter project is a 4 meter sailplane. I hope to be doing the same thing with it and the RTL next spring/summer.

Later;

D.W.

This is what I have been doing these last weeks. It is really cool to feel secure with RTL. Today my glider disappeared inside a cloud for a short time, I wonder how high she was. I could barely see her, switched over to RTL and added some down trim (I don't have airbrakes).
I wonder why a small and cheap PNP auto-pilot for gliders is not yet available on the market ? Something like less than 200$. Plug it and forget it.

[Disciple4123]

An old thread brought back...

Well in the two years since this thread came to be, I have gone fully autonomous with the heli, and as a result, have parted out the plane. The RTL is available for $220, if anyone is interested

[dmgoedde]

I wonder why a small and cheap PNP auto-pilot for gliders is not yet available on the market ? Something like less than 200$. Plug it and forget it.By "the market" you mean a commercial item, and not just open source DIY type, right? The only way to sell something like this for < $200 is if the maker doesn't care about making any profit whatsoever, which will never happen with a company. On the other hand, Chris Anderson and Jordi, by nature of what they are trying to achieve with the Ardupilot, simply don't care about profit and in fact Chris is (I think) losing money overall. If you add up the total cost of getting an Ardupilot together, the costs is not far off $200 (GPS, Ardu itself, FMA parts). So < $200 is really scraping bottom.

[Paul_BB]

By "the market" you mean a commercial item, and not just open source DIY type, right? The only way to sell something like this for < $200 is if the maker doesn't care about making any profit whatsoever, which will never happen with a company. On the other hand, Chris Anderson and Jordi, by nature of what they are trying to achieve with the Ardupilot, simply don't care about profit and in fact Chris is (I think) losing money overall. If you add up the total cost of getting an Ardupilot together, the costs is not far off $200 (GPS, Ardu itself, FMA parts). So < $200 is really scraping bottom.

I was thinking about B. Premerlani and his UAV DevBoard. He is not interested by a PnP product but his board is worth 150$. With a plastic case, a "simple" user-freindly USB-PC program to change a very limited number of parameters and some development costs, would 250$ be a realistic price ?

Functions:
- Manual
- Stabilized (commanded bank angle and commanded pitch)
- RTL

With DCM or Atto's IMU firmware.

I was talking to a RC enthusiast working in my company at lunch today and he said that a "lot" of glider pilots would be interested by a robust PnP product that could save their gliders. Maybe some advertising is needed on RC Groups among glider pilots ?
I am so happy with my RTL, I cannot imagine anyone else unhappy with this feature. If only they could try it.