Arducopter 4.6.1 new 7 inch build, just takes off at alt hold

I just finished the build af a new 7 inch drone with a Speedeybee F405 V4 55A stack with Arducopter 4.6.1. I selected the the pre-calculated setting for a 7 inch quad with a 6S battery pack.
MOT_THST_HOVER = 0,15 which is default, I also tried raising it untill 0.68, but that even makes it worse. MOT_HOOVER_LEARN = 2 but it can’t learn this, because I have to disarm inmediately before it shoots to the moon.
Quad 7 inch.param (19.0 KB)
Log file:

The log file is very short, because I needed to disarm almost instantly.
Please help, whats wrong, I can’t figure it out.

You should not raise MOT_THST_HOVER, you should lower it. Try 0.10 or less.

Start with a hover in stabilized mode, this will take out the altitude hold and give us a look into the PID’s.
How much tuning have you complete on this?
@amilcarlucas is correct, my 7in is way over powered my hover is 0.05 I believe.

If you are new to the building drones with ardupilot try using the Methodic Config software.

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It’s definitly not the first drone I build with ardupilot, but this is the first time with a 7 inch drone with arducopter. I followed the manual and calibrated everything as usual. I never had this problem before. This are the rates:

ATC_ACCEL_P_MAX,146100
ATC_ACCEL_R_MAX,146100
ATC_ACCEL_Y_MAX,29700
ATC_ANG_LIM_TC,1
ATC_ANG_PIT_P,4.5
ATC_ANG_RLL_P,4.5
ATC_ANG_YAW_P,4.5
ATC_ANGLE_BOOST,1
ATC_INPUT_TC,0.15
ATC_LAND_P_MULT,1
ATC_LAND_R_MULT,1
ATC_LAND_Y_MULT,1
ATC_RAT_PIT_D,0.0036
ATC_RAT_PIT_D_FF,0
ATC_RAT_PIT_FF,0
ATC_RAT_PIT_FLTD,28.5
ATC_RAT_PIT_FLTE,0
ATC_RAT_PIT_FLTT,28.5
ATC_RAT_PIT_I,0.135
ATC_RAT_PIT_IMAX,0.5
ATC_RAT_PIT_P,0.135
ATC_RAT_PIT_PDMX,0
ATC_RAT_PIT_SMAX,0
ATC_RAT_RLL_D,0.0036
ATC_RAT_RLL_D_FF,0
ATC_RAT_RLL_FF,0
ATC_RAT_RLL_FLTD,28.5
ATC_RAT_RLL_FLTE,0
ATC_RAT_RLL_FLTT,28.5
ATC_RAT_RLL_I,0.135
ATC_RAT_RLL_IMAX,0.5
ATC_RAT_RLL_P,0.135
ATC_RAT_RLL_PDMX,0
ATC_RAT_RLL_SMAX,0
ATC_RAT_YAW_D,0
ATC_RAT_YAW_D_FF,0
ATC_RAT_YAW_FF,0
ATC_RAT_YAW_FLTD,0
ATC_RAT_YAW_FLTE,2
ATC_RAT_YAW_FLTT,28.5
ATC_RAT_YAW_I,0.018
ATC_RAT_YAW_IMAX,0.5
ATC_RAT_YAW_P,0.18
ATC_RAT_YAW_PDMX,0
ATC_RAT_YAW_SMAX,0
ATC_RATE_FF_ENAB,1
ATC_RATE_P_MAX,0
ATC_RATE_R_MAX,0
ATC_RATE_Y_MAX,0

In stabilize mode the drone flies OK, untill I switch to POSHOLD or any other nav mode.

Thanks I will try this

Post a link to that log as @prsh8ya suggested. It’s a simple matter to set the hover thrust value correctly from a Stabilize mode hover throttle value rather than guess at it or go the wrong way with the value as you did. Further, it will not learn a value below .125 so if the craft does have a thrust/weight below this you have to set it manually.

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@dkemxr You are right I completely forgot about it not learning hover below .125.

Why is that a hard lower limit?

I have seen that question answered here before by a Dev but I don’t recall what it was. I haven’t built a craft in some time that had a hover thrust value above .125 so it’s just routine for me to set it manually anyway.

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0.125 is the lowest value that allows for a smooth thrust expo curve with hover thrust at 50% stick position (0.5 cubed).

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00000003.BIN (740.5 KB)
Sorry for the late reply, I didn’t have a chance to do this before because of my work.

I attached the log file, and I lowered the MOT_THST_HOVER = 0,125 but it’s still taking off up when it’s switched in flight from stabilize to pos hold.
I had to disarm it quick, before I loose it.

Should I even go lower with the MOT_THST_HOVER ?

You should set it as suggested in the above post.

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Well that didn’t help anything either, I see not a single difference in behaviour, still shooting up to the stars even with 0.05
2025-07-06 11-14-30.bin (516 KB)

Start with basics, do a flight in stabilize mode not poshold mode.

get the craft to hover in stabilize mode for approx 1 min, check to see if the motors are hot and then post that bin file.

Post some photos of your craft, what controller are you using?
Did you calibrate the controller?

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Position Hold is good for nothing. Loiter replaced it for all uses years ago.

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I did calibrate the controller, and it is flying great in stabilize mode, no problem there.
I’m using a Radiomaster TX16S with Crossfire.
In any NAV mode I use pos hold, loiter alt hold, it takes off.
When I switch from stabilize to alt hold in flight it takes off.

It’s really weird, it’s not my first Arducopter quad, I also have another 5 inch that is flying great in any mode.

This is my second 7 inch quad, I have the exact same one setup with Inav and that one is flying awesome (right one is Inav, left one Arducopter).

Hover throttle looks to me to be around 0.02?

These are still at default and need to be set…

What do you think would happen with a situation like this?

@prsh8ya identified the problem. A hover throttle is ~ .02 and you have MOT_SPIN_MIN at default.
Standard procedure here Setting Motor Ranges
The vertical acceleration controller gains are at default. That’s one reason you have nothing but oscillation on the outputs along with default Rate PID’s.

Even with the Hover throttle set to .02 and the proper Motor Ranges set you may have some trouble with the thrust/weight you have. Suggest using a larger (heavier) battery.

You were both right, I set the Motor Range, totally forgot that one, and the MOT_THST_HOVER at 0,02 and it doesn’t take off anymore, but the oscillations are horrible.

Isn’t there a way to get this right with this battery and weight? I never heard that a quad could be too light…

Of course they are, it needs tuning. Drop the Rate PID’s in half and set the vertical acceleration controller gains based on hover thrust as per the docs. Standard pre-tuning steps.

With your level of tuning knowledge perhaps the Methodic Configurator would be a better route.