New Goblin 380 will not hold position

motor KDE 500XF G3 925 (stock pinion)
ESC Jeti Spin 66 (5.5v BEC) Pixhawk indicates 5.4v
Futaba S-bus receiver
BK micro servos on collective BK mini on tail
Pixhawk with external GPS and telemetry radio

My problem is that the heli will not hold (X and Y) in loiter. It acts similar to althold, I see no pitch response to hold position. It has no problem holding altitude, alt hold works fine. In loiter, it just wanders in the direction of the wind and makes no real response to hold position.

The heli flies fine in stabilize, vibrations are good, tail is holding ok, It just will not hold position.

I attached my .log file and a few graphs. it has offsets between the roll and desroll, pitch and despitch parameters along with offsets in the GPS X and Y velocities.

any ideas?

.Log file is too big, will not attach, over 2MB, I will see if I can trim it down.

I attached the tuning screen. I doubled the loiter PID values as a test. it did not really make any noticeable change.

attached .log file


Could this be a trim problem with using RC1_TRIM?

I adjusted RC1_TRIM to 1590 and RC2_TRIM to 1400 to “trim” in the heli in stabilize mode. l think I should have used HS1_TRIM and HS2_TRIM to do this.

looking at the GPS velocity plots, it appears that the position is moving at a constant rate until I move the stick to bring it back. Is the RC1_TRIM, RC2_TRIM just giving the controller a constant diagonal input around 100PWM in loiter? My center stick PWM is 1494

This could explain the offset in the pitch and roll plots also.



I put the RC_TRIM numbers back to 1494, my center stick PWM along with HS_TRIM numbers and ran the auto calibration.

Arm the copter and hold collective stick full negative and right rudder for 15 seconds. Watch for the blinking colored lights, hover for 25 seconds, land, disarm and good to go. Pixhawk writes the trim to Eprom.

I guess reading the directions does work sometimes.

Glad you figured that out, the RC1 and RC2 trims are your inputs, and you need to leave these at the calibrated values, or else Arducopter will indeed think you are entering commands to move.

HS1_Trim, HS2_Trim and HS3_Trim are your swash servo trims, and you need to adjust these to trim the swashplate. One of your other logs shows pretty bad roll/pitch offsets in flight, which is usually caused by bad swashplate trim.

This bad roll/pitch control then makes the Loiter controller work very badly, as it can’t accurately guide the copter around. It acts… sort of drunk.