Altitude decreasing and Crash in Loiter Mode

I took off in manual and i switched to loiter mode then the plane went as nose down and hit the ground. What is the problem ? Can anyone help me ?
Log File : 2021-09-05 15-57-18.tlog (723.3 KB)

Throttle goes from 75 to 40 suddenly when switchig

If you can get it, please post a .bin log file from the flight controller. .tlog files don’t have all the information.

Was this the first flight of the plane?

I tried some flights but had crashes. Sd card was broken so I couldn’t fetch the bin file. Can you analyze the tlog file. Is auto tunning is crucial because I havent done auto tunning yet. What should I do for autonomous flight I’m new on these things. Thx for your interest.

Did you set the servo reverses on transmitter or in arduplane ? Asking, as you have mentioned you are new to ardupilot.


@Sunnyfx79’s question is asking the same thing I was wondering about. Have you made sure the control inputs and the stabilized flight corrections are going in the correct direction? If the plan suddenly becomes uncontrollable after switching from Manual to any of the modes with flight control stabilization, it often means there is one of the controls reversed.

Some form of tuning is almost always needed. Auto tuning is the best for the vast majority of people and planes.

Make sure you follow these instructions:

A .tlog won’t tell me what was going on in the flight controller. Specifically between the flight controller and the servos vs inputs. For a crash like this it won’t do me any good. Maybe some of the smarter people around here can get more out of a .tlog than I can but I’ve never bothered with them for all but the most basic.

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Thanks for your replies. You are right I just forget to reverse the servo. It’s my fault.