Need help for analyzing strange altitude behavior in auto mission


I’m wondering since a while why my CUAV V5 Nano equipped quad do some strange altitude changes during start and RTL in auto mission

I fly today 4 times the same mission. According to my understanding, the CTUN.Dalt values should be the same for all 4 flights? But it varies from flight to flight…


  • What cause the drop during the start in 119.bin and 120.bin? 121.bin and 122.bin does not suffer from this drop.
  • Why CTUN.Dalt varies in RTL (5.2m, 5,6m, 6.2m)? CTUN.Dalt during the mission is stable on 10meters

Log files from all 4 flights:!AunrEY0aDm-hmRnlY5TdHkUMOHV3?e=LXxAVr

Many thanks in advance


Can you post a copy of the mission?

The altitude anomalies at the start are a little like the FC is expecting to overshoot the 10m altitude target (or the RTL alt) and throttles back but then doesn’t achieve the desired altitude - and yet the actual alt is following desired alt.
The only big differences I see between first and last flights are the baro and IMU temperatures - everything is hotter at the start, like it’s been sitting in the sun for a while - but it’s not too hot. Normally we like these things to heat up a little and stabilise.
According to baro the ground temp dropped 1 degree between 1st and last flights. Flying cooled everything off ?? I wonder if weather changed too, maybe less windy as time went on?

Looking through your parameters many are very standard and I think there’s more tuning you could do even though Roll and Pitch are tracking their desired reasonably well. Let us know what props, motors, and ESCs you have. Also take-off weight.

I’d be setting these right away:

Use this sheet to help, there’s even a MissionPlanner plug-in. My suggestion is to go over the tuning guide (if not already) and then run Autotune.

Maybe post a log of some manual flying around in AltHold and Loiter with a bit of hovering too.

Thanks for having a look. I did the flights all in a row, after landing I replaced the battery and up in the air again. The weather stayed very stable over the hole flights, so no big changes in temperature and wind.

Here a few data from my quad:
Takeoff weight: 3.8kg
Motor: SunnySky V4006-320KV
ESC: Hobbywing 4in1, 60A, normal PWM controlled, no DShot or similar
Prop: 16x5.4" T-Motor
Flightcontroller: CUAV V5 Nano

I do the tuning manually, never had great success with autotune. I also set the notch filter. To my opinion the drone fly very stable, I checked the Des.Roll/Pitch vs. the actual Roll/Pitch values and they look pretty good to my understanding.

My biggest question is, why the drone descends on the last waypoint and fly on this altitude back home… I also had the situation, that the drone climbs a few meters… I fly sometimes in areas where those difference in altitude could cause a crash. That’s the reason why I’m concerned about this behavior. I never know if the drone climbs or descends a few meters…

Here is my mission:

Thanks for the calculation sheet and the suggested parameters. I will change those values.