Altitude reduces 1-2m in Loiter mode

I tested the loiter mode today morning. It was going smooth without big problem! :- But I found it was decrease the altitude regularly after the about 10 seconds of the loiter mode, the pattern is like ->

Loiter mode -> after 10 seconds -> decrease 1-2 m -> go back to stable in loiter mode -> after 10 seconds -> decrease 1-2m -> go back to stable in loiter mode -> …keep until reach onto the ground and landing automatically (disarm auto)

I guess the FS was triggered!

Do you guy any idea? or share your experience!

Merry Christmas!!!

Normally descent in Loiter is caused by the throttle not being in the middle. It sound silly but tons of people make this mistake because the mid throttle position while hovering in a manual flight mode (stabilize) is different than when in Loiter or AltHold. The mid-position while in the manual flight modes can be adjusted by following the instructions on this wiki page.

Now did the copter actually disarm after it landed? If it’s in Loiter mode it should only disarm if it thinks it’s landed and the pilot has put the throttle at zero for about 15 seconds. The other possibility is that the MOT_SPIN_ARMED parameter is set to zero so then it will shut down the motors when it thinks it’s landed but it won’t actually disarm (if you raised the throttle above mid it would restart the motors and take off).

The reason that this difference is that it tells whether it was in Loiter or whether a failsafe had triggered. It would only have disarmed if a failsafe had triggered and it was in LAND mode.

…but you know…instead of all this guess work, it would be better to attach logs file…

Thanks rmackay9

I think my copter is in underpowered situation. I have set the mid-thr to 700 now. It seems better! But the decrease altitude is still happen! I think I should upgrade the props size to 13 inch and use 4s battery. I will test it again and post the log next time. :slight_smile:

Today I just tested again my quadcopter. I found the decrease altitude problem is still there, but it’s better than last time. The mid-thr was set to 680. As below is my quadcopter spec:

12x3.8 props
30A simon ESC
4008 700kv
5000mah 30c battery
Total weight is 2200g

Log attached.

Do you have any advise for me? What should I upgrade? I think upgrading prop is easy to me! 15 inch - how do you think this? Thanks.

Sorry, I didn’t see this reply from you for some reason until just now.

 It looks like the problem is being caused by glitches on the radio input.  So graphing the CTUN message's ThrIn shows that the throttle is dropping suddenly and this corresponds with the drops in altitude during Loiter mode.

 I'm not sure the cause of these glitches but it could be that the TX/RX are losing contact for short periods of time.  Maybe there is some FPV gear or something else near the receiver that is causing interference.

Thanks for your indication. I never think it is caused by the RX.

I didn’t use the FPV gear! The RX satellite antenna is attached close to the ESC now! I’ll move it away the esc and test again!


Today I tested it again! I found the first 5 mins the copter is flight very stable in loiter or alt hold mode. I have moved the RX position and changed all the RX cables. After 5 mins, the altitude problem is happen. It would reduce about 1 meter during the loiter or alt hold mode! I have no idea! Now I believe it is caused by the battery performance. I will try to test it again in shortly to get the good tlogs data and more high performance battery later. :slight_smile:

Please give me advise if you faced this problem or any idea.