Need help understanding RC with ArduCopter

My Arducopter is built and flying, but I'm crashing on most my flights. Here are the issues:

1. When I slowly increase the throttle to take off, the front and back props spin, but the side props usually don't. If I move the stick left/right, I can sort of trick the sides props into spinning, and then once they're spinning, I keep moving the throttle up with increased power to get them all spinning. Sometimes while trying to do this, I'll get the sides spinning, but front and back will stop spinning. Eventually, after playing around with it enough, and giving it quite a bit of throttle, I can get them all spinning. I then have the confidence to increase throttle and take off. Is this normal?   (It could be that I just need to push the throttle hard with confidence and take off, but I don't like seeing propellers that aren't spinning).

2. Once I'm airborne, the unit is stable, flat, and responsive, but actually far too responsive. The slightest movement of the throttle stick makes it go up or down very fast, which makes hovering and flying very difficult. When trying to hover or land, I usually crash.

3. In a previous forum topic, "jasonshort" said, "You can tell it's in Acro mode because the motors only spin at low throttle while the model is moving. In stable, they spin continuously." I'm not sure If I understand the full context of what he was talking about. I'm also not sure if he's talking about the "Acro" (airplaine) mode on the Futaba Transmitter or "Acrobatic" mode in the ArduCopter software. I assume I'm in "Stable" mode. When I arm the motors, the green light blinks slowly, not fast, so I assume it's in "Stable" mode. However, if it's not, that would certainly explain it's hypersensitivity. Is it possible I'm in Acrobatic mode even though my green light is blinking slowly?

4. When trying to land, or if I make a half-hearted attempt at launching (because I'm worried about the fact that not all the propellers are spinning), the Arducopter usually flips very fast and crashes.

5. In my last outing, I was hovering around pretty nicely about 10' off the ground, but then the Arducopter suddenly shot straight up into the air really fast to about 200'. I brought the throttle down to reverse its upward climb, and I was trying to be careful not to over-react and slam the throttle down. I was able to reverse the climb, it started coming down, then it rocketed toward the ground very fast, did an instantaneous perfect flip about four feet off the ground, and slammed top down into the ground. (Replacement arms and propellers are now on order).

So, my theories are...

1. I'm new to flying RC aircraft. Maybe I just need more practice on using the transmitter, and in particular the throttle. I'm trying to be very, very careful, but it's not working.
2. Perhaps the Futaba transmitter isn't setup properly and is sending the wrong instructions to the Arudcoputer.
3. Perhaps the ArduCopter software has a problem (This seems very unlikely, since others are flying without these problems).

Although I'm sure #1 is part of it, I'm thinking it's probably more #2. In a previous forum topic "jasonshort" mentioned that he uses H1 Heli mode with his Futaba rather than using Airplane mode, and that he adjusted the throttle curve so that it's not so sensitive, so perhaps that's an option.

I would really appreciate any advice people could give me on what I can do to resolve my problem(s). Although I'm having fun, my poor Arducopter is taking a serious beating while I try to figure this out.

In case any of these details matter, here is my configuration:

RC: Futaba T10CHG Tx (in airplane mode) & 8-channel Rx.
Software:  Arducopter_alpha_1.0
ESCs: Turnigy Basic 18A 
Motors: KDA20-22L
Front/Back Props:  APC 10x4.7 Pushers, lettering facing up
Side Props: APC 10x4.7-P Pullers, lettering facing up
Frame Arms:  aluminum arms from beta kit
Frame center:  several thin sheets of perforated aluminum, same size as beta kit
Battery: zippy 2200 3 cell lipo
Total Weight:  967 grams

I've used the Configurator as indicated in the Arducopter manual, and I've also done the pre-flight test, all of which checks out fine as far as I can tell. Please note that I can fly the arducopter, and it flies quite nicely and flat, it's just very hard to control the altitude (and then there's the sudden flipping issue).

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  • I was getting good flights and now I am seeing some issues in configuration that might be related, the Z axis acceleration bar hovers around the top of the scale at 430 instead of going to center or 0. It drops toward 0 when I rapidly lower the arducopter and returns to the top of the scale when at rest. When I arm the throttle the motor indicators all jump from 1040 to 1100 and the motors start turning when they are armed. Lowering the trim doesn't affect it. Recalibration doesn't help either.

    Thanks, Ed
  • In an effort to solve my problem, I have now done the following:

    1. Changed from Airplane mode to Helicopter H-1 Mode on my Transmitter.
    2. Re-calibrated the ESCs to the throttle on the transmitter. This time I made sure I did this step very carefully (on the first go around, I'm not totally positive that I did it properly).
    3. Removed the GPS and xBee, which broke off in the crash, and aren't needed in this version of the software anyway.
    4. Commented out the GPS, Magnetometer, and xBee lines in the Arducopter software, and re-uploaded it to the APM.
    5. Removed the cables that went from the APM into RC channels 5-8, which I don't need right now because I just want to fly in stable mode. I assume the software defaults to stable mode and doesn't need those signals.
    6. Hooked up the arducopter to the configurator, where I double-checked the sensors, re-calibrated the transmitter, and re-did the pre-flight test. Everything checked out OK there.

    Once I repair the arm that was broken in the crash, then I'll try another test flight with the above changes.
    If its seems to be OK, but the throttle is still too sensitive, then I'll adjust the throttle curve in the RC transmitter (it's currently set to the default for H-1, which is 0, 25, 37.5, 50.0, 62.5, 75.0, 100.0.)

    Any other suggestions would be welcome.
  • You need to add some Expo in your radio that will help thatst if you all ready have not done that hope this helps Tom
  • Try a two cell lipo, it will reduce the over compensation and hover will be more relaxed. When your reactions are better you can use the three cell lipo, it also gives you time to learn to trim things out. The small car lipos work great for me, they come in the 2000 range, the lower voltage to the motors will reduce the reaction time of the motors. All you need is enough flying time to know that it works.

    Ed
  • throttle is always very snesitive on quadrotors
    doe the throttle stick reutrn to mid position? if yes, you should remove a spring inside your transmitter, to make it stay where you let it go

    altitude hold would be a nice thing for you (it's not implemented yet...)
  • Developer
    The arducopter has two flight modes right now. One is Stable, which will fight to keep you level. To see if you're in Stable, with the throttle low, rotate the model 45°, at least one motor will stay on to correct the pitch or roll.

    Acro mode is all about rate change. If you rotate the model, it will fight the acceleration. but then the motors should stop spinning.

    The flip may have been caused by low voltage in your battery.
  • Did you calibrate the ESC's to your throttle?
    Did you use the hand held programmer for the Turnigy ESC'sto set them all the same?.
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