Why i loss throtle control when i switch to altitude hold mode irrespective dead band or within dead band

I am using ardupulot2.8 borad with latest firmware v3.3,i have very good control on stablize mode.but when i switch apm to altitute hold mode it maintain its alt position and i happly flying it.but as soon as i try back to switch it to stablize mode i loss control on throttle while pitch roll yaw is responding except throttle.even if i trun off transmitter hope that it fall down ,nothing happen its hovering at constant altitude.
Please help me i could have loss my quadcopter. I made crash to wall to land it and finally it land with crash landing


In case you are using some clone of APM2 FMC board the most recent version of firmware you could be able to flash is 3.2.1 and not 3.3.x. So I believe you mean 3.2.1. https://github.com/ArduPilot/ardupilot/blob/master/ArduCopter/ReleaseNotes.txt (search there for “drop support for APM1, APM2”)

It needs to be explained on more details what exactly do you mean as “i loss control on throttle”. How exactly does it looks like?

AltHold automatically keeps drone hovering at constant altitude in a middle position of throttle stick.

If your drone needs really high throttle value for hovering in stabilize mode then you may have not enough throttle for hovering drone in a middle position of throttle stick. So drone may go down immediately after you switched it to stabilize. The same time it will respond ok on roll/pitch actions. Is it your case?

Also you receiver may have failsafe features and here is a chance it could provide some “safe values” to FMC in case of signal loss. For some receivers there could be “presumably safe values” of controls implemented, for other receivers a “last received values” could be used. Once you turned your transmitter off, receiver may detect it and use failsafe feature to keep drone in air.


Thanks for reply
Sir its right that i am using clone of apm 2.8 but in this case i have successfully install ardupilot firmware 3.3 and obviously i had put throttle stick within 40 to60% range of throttle ,my question is my drone has locked alt postion after switching from stablize to althold mode even if i make throtle stick to full down position or full high.i am using FS TH9x transmitter i thing it does not have faile safe feature. Please help me still waiting to make my next fly.

I cannot state anything definitely about your case, because support for APM has been dropped in 3.3-rc1

How do you flashed it with 3.3?

No, AltHold mode doesn’t mean altitude will be locked for any position of throttle stick. It just make drone hovering at some locked altitude for some range of throttle stick position about its middle one. And drone will go down/up as soon as you will move throttle stick up/down.

Failsafe feature is related to receiver, not transmitter.

I think you have answered your own question.

There is good reason the APM support was stopped with 3.2.1
And I would say you have NOT successfully installed 3.3.3.
And as you have managed to shoehorn 3.3.3 into an APM there is going to be issues.
You have found one of the issues.
There will likely be others as well.

As it is openly stated that FW3.3.3 is for 32bit hardware I don’t think it likely that there is a straight answer to your question other than reflash with 3.2.1

Thank you sir so much
I am new to ardupilot if you have not toll me about apm support i.e apm can’t support copter 3.3 and so i could have waste my time in this nonscense really thak you. So my last question is which firmware is better to install either 3.2.1 or previous version

So far I remember 3.2.1 was really stable version. It may have lack of new features, but it was good.

The reason @dipspb (Dmitry Prokhorov) could tell you had a clone, is that 3DR never produced a 2.8 version of the APM.

Also, the 9x radio does have failsafe modes with the right R/X.