[rumman1506]

I've built my first 250, here are the specs:

Frame: ZMR 250 Carbon Fiber
Motors: Emax 2204 2300KV
ESC: Emax 12A BLHeli
FC: CC3D (Mounted 90 Degrees, Yaw also changed to 90 degrees in attitude tab of GCS)
Props: Gemfan 5030
Battery: 1500 mAh 3S Battery

When I try to fly and take off with stock PID in CC3D (Roll: 0.00300, 0.00650, 0.000033; Pitch: Same as Roll; Yaw: 0.00620,0.01000, 0.000050), two problems occur:
1. Quad starts to drift left and side and slightly front side
2. With just little throttle stick input, the quad shoots in the air, lifts at high pace. When I try to compensate and lower the throttle, it bounces down very quickly. Basically it's quite impossible to make it hover, and it feels like the quad is floating

I wanted to tune the PIDs today but this behavior isn't letting me do so.
*The gyro is are okay and shows okay in LibrePilot GCS. I also give it time after plugging in battery before I arm
*The props are balanced
*The ESCs are calibrated
*There is no extra weight in one side which may cause unbalance and result in drift
*It was not so windy out there

I'm here dying with frustration. I need the help of you guys. Please enlighten me about what may be wrong so that I can correct them.

[TheOtherCliff]

If you think that this is a powerful quad that would shoot up like that at only 50% throttle, then be aware that vibration combined with PID D term too high can cause an invisible oscillation (very high frequency so it does not move far) that drives the throttle toward 50%.  For a test, cut all the PID D terms in half, or reduce them more, or set them all to zero.

I had some old ESC firmware (I don't remember if it was SimonK or BLHeli) make the ESCs very jumpy with the vertical difficult to control.  The problem went away when I flashed the latest ESC firmware.

Taking off from a slope and/or slowly increasing throttle for takeoff and/or trying to correct the quad roll/pitch while it is still on the ground will cause it to drift hard up hill.  I assume that you have not changed "always stabilize when armed" (should be off) or "zero the integral when throttle is low" (should be on).  From a level takeoff location, as soon as the motors start turning, you should jump the quad up to at least knee high without correcting roll or pitch or yaw until the quad is in the air.

Vibration higher than a certain level will cause gyro to go crazy, and drift badly or flip.  With marginal cases, it only happens at certain RPMs.

ESC calibration is stored inside the ESC and is not visible in any LP setting.  That can cause it to jump up.  Also, bad LP "output" settings can make that happen too.
https://librepilot.atlassian.net/wiki/display/LPDOC/ESC+Calibration

[rumman1506]

@TheOtherCliff
Thanks a lot for your response and advice!

I'll definitely try setting my D term low and test.

Can you please help me how do I flash the ESC? Mine are Emax 12A and it says BLheli.

What I do is, I gently push up the throttle, and don't put any roll, pitch or yaw commands. I try to increase the throttle than a bit for waist or chest high and it climbs fast towards the sky. And the drift happens the moment after the quad is in air. It's not vigorous but kind of gentle, as if it's floating, slowly and continuously to the left roll.
I haven't activated "always stabilize when armed" and "Zero the integral when throttle is low is turned on".
I'll try jumping the quad at knee high right after the motors starts to spin, next time I go out for testing.

Should I try changing the virtual roll? I've found an issue like mine in the forum and it worked for him.
Thanks a ton again for your suggestions.

[TheOtherCliff]

I would google for:
flash blheli
Many people use BLHeliSuite to do everything for BLHeli.  There are many options about what dongle to use, what operating system, etc.  I personally use Linux with an Arduino for a dongle.

The drift at takeoff is only a takeoff issue.  If it is consistent through the flight, and you are running Stabilized1 = Attitude mode then yes the fix for the drift is Attitude->Settings->RotatueVirtual...

[rumman1506]

Thanks I'll give that a try.

About virtual axis, I already have mounted my CC3D with the usb positioned at right, and I've set the virtual yaw 90 at attitude tab. My question is, now to solve this consistent drift issue in left roll axis, what should I change in the attitude mode? Roll or Pitch? I'm a bit confused, because original board roll axis is pitch axis now. It might sound silly but I'd really appreciate your help.

[TheOtherCliff]

So first be aware that you set your transmitter trims to center before running Wizard and never change the transmitter trims.  If you suspect that your transmitter trims have moved and don't know where to put them, you should run "transmitter wizard" or fly in Rate mode to adjust trims if you can.

I always mount my FC's with arrow forward (normal direction) and from my notes, this is what I use.
 - if it is drifting forward you subtract from pitch
 - if it is drifting left you subtract from roll
I believe/hope that also holds true if the board is mounted some other way, so subtract a large angle (say 3 degrees) from roll and subtract a small angle (say 1 degree) from pitch so that both of them are negative.

If you do roll only first and don't change pitch, it should become obvious whether you are changing the correct axis and in the correct direction. 

These angles do accept decimal parts of a degree, and I try to get it down to 0.1 degree.  I have a hard time seeing the difference in drift even with 0.1 degree change.

[rumman1506]

Thanks you very much. Really appreciate your helps.