"Hi Andy,
Indoor test just now.
How are the IMU params looking? esp. AccY
TIA2015-05-07 12-13-07 1.bin.logAccXYZ.png"

"@Andy - to your post on AccY ( not GyrY ), let me check why I am getting this despite mounting on a anti-vibration ( Anti-vibration Shock Absorber ). Thx"

"By lifting the copter the mag interference is ruled out I think.
IMU->GrY seems to be ranging between +1 and -1. It does hit +2 just before line 25 and -4 just before 35. That is when the quad hits the ground - bouncy landing. Unless I am reading…"

"This is getting even more frustrating. I changed my APM board ( but again 2.6 ). Reflashed it to AC 3.2.1, Reset the board and did a full set up - all 9 yards including compass calibration and compassmot. So now I have a new APM, new GPS+DCM, height…"

"Disabled ECC check and downloading log works and no timeouts. But the radio range is still a problem."

"As I mentioned, I got a new compass and the problem persists. Raising the GPS+DC unit to about 10 cm has not helped either. The dataflash log auto-analysis is showing 3%-9% interference. The same auto-analysis is showing  Test: IMU Mismatch = NA for…"

"No such luck for me... I am out of ideas!"

"I borrowed a GPS+DCM and I am still getting a DCM Bad Heading and EKF_CHECK=2 errors!!
Needless to say I did a compass recalibration and compassmot again.
Do I have a bad APM? or is it a software / config issue?
The GPS/DCM is raised up 10cm"

"Post above, took her in the air. Pretty OK with AltHold. Switched to Land and it started to descend nicely and then suddenly tilted, banked and began to drift until I took control in stabilize. Log with MAG on attached  (23.log ). ErrYaw has come…"

"@Cala/Andy - I am not able to reply to your posts So the thread will go a bit haywire.
I just did a static test i.e. quad is held secure ( not in flight ) and I ran the throttle up with props down and shifted for a short while. The DCM line stays…"

"#2 - Bolts are OK. Not magnetised.
#3 - Orientation is fine - double checked.
#4 - Did compass calibration again. Did not notice any lag. Offsets -60, -34, 43 ( previous -63, -31, 43)
#5 - North (on DCM) to North on my phone compass matches
#6 - Ran…"

"I just realized that I was not getting this issue in AC 3.1.5 but I had not flown that much so difficult to say with certainty.
I did find a discussion on DIY drones here 
Could this be a 3.2.1 problem?"

"Andy - This is what I am going to do:
1. Have already raised the GPS+Compass unit a few cms up.
2. Basis Cala's suggestion, demag the bolts if required
3. Double check orientation
4. Rerun calibration and check for any lags
5. Recheck calibration…"

"Hi Cala - Let me check on the bolts also but I have secured the caddy using just two ( using M3x10 ) . Maybe I will heat them to get rid of any magnetism since I may not have nylon ones. Will use a compass to check for any magnetic field.
Will…"

"You won't believe this but due to this we are very scared of quad flying off and hurting someone. So all our  tests have a long but loose tethered harness. In case the beast flies off, we can pull it back :-)"

"Red is front - X config.
Good catch on compass. I had turn the caddy slightly to calibrate the North of DCM to North of my phone shown by Compass 360 app. You will see an abandoned screw hole. Ideally I should have turned the whole unit but the zip…"