APM 2.5 Alt Hold (SCARY!..)


I just set up my APM board for a quad. I flew a few times already in stabilize mode and it seems working just fine. Today, I wanted to try the "Alt-Hold" mode. 

I have read here a few times that the board has a tendency to shoot off when alt-hold is engaged. Knowing this, I wanted to test it. I raised the throttle (in Stabilize mode), till the craft gets to a hover. (I was holding the quad). I flipped the switched to "Alt-hold" and as I guessed, all 4 motors started running at full power till I flipped the switch back to stabilize mode.

I did it a few times with the same result:( 

Currently I didn't do any PID tuning. I flew the quad for about 30 minutes total. It is holding the heading pretty well. Responses are good. It hovers almost at mid throttle. But alt-hold is scary!!!

What should I do? I cannot even try the Loiter if I can not fix this issue.


P.S. Did the "altitude" test in CLI window. Did not get any negative value...

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  • I am very interested in this.


    Just curious but would the Vel Max/max  auto affect this?


    The pilot Vel Max is 16??? but the auto settings are -16???


    Is the negative correct?  The pilot version is positive.

  • Hello. This is my first time writing, so I really hope somebody can help me. I'm a beginner in this field.

    I have an APM 2.5 board with firmware 2.9.1b (and the latest version of Mission Planner) on a home-made quad and I'm having a very difficult time tuning it. I can't seem to get it to fly smoothly in stabilize  mode, and most of the times, in the alt hold mode, the copter accelerates upwards, instead of holding position. I wanted to check for existing vibrations and I have enabled raw and motors logs as indicated, but when I open the logs afterwards, it doesn't show me anywhere the raw values and the accel z, x, y values in the list. I don't know why that is... I've managed however to take a few snapshots of the accel values in real time by checking the tuning checkbox that I've attached below, but I can't tell whether the vibrations below are within acceptable range or not.

    Would you be kind enough as to take a look and tell me if i have any vibrations there that could affect the flight of the copter and thus making it really really hard to tune (I've been at it for 2 months already, changing PID values, and I can't seem to make it fly nicely). Any help is greatly appreciated!


  • hi alex

    follow richards advise and you will get good results .

    his advise as got me flying in alt/hold really well.

    I am using" moon gel " which is working well BUT after only

    about 15minutes flying i have noticed the "moon gel" as a split in 1 corner !

    And i found it difficult to glue. So if you go with gel give it a good wash with soap and water before


  • T3
    Did you check your zAcce value? Also what version of the firmware are you using?
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