Are there any conditions for changing flight mode?

Hello everybody.
I have come up with a little complicated problem this time.

This is a problem I had since I started the helicopter.

I used pixhawk to create fixed wings, quads, hexa, and so on.

They all had no problem changing the flight mode during flight.

But traditional heli is different.
flight mode change failed.

I think there are special conditions for changing modes.

I have compared the parameters of the helicopter with which the mode changes very well and the parameters of the current helicopter, but I did not see any abnormality.

I’ve looked into the forum, but no one has the same problem.

Would you be willing to share information about the traditional heli flight mode change?

I have not mastered this part yet.

My experience is that in the case of unarmed, the flight mode can be switched normally. If there are flight modes that are not available (such as insufficient number of satellites, high accuracy factor, etc.), the buzzer will sound twice. If it is unlocked, switch the flight mode, if there are insufficient conditions, the buzzer will prompt, but the mode will not switch to that mode!

How do i adjust the ‘high accuracy factor’ you are talking about?

So what situation do I have to make?
My helicopter then had a hdop of 0.6, and there was enough satellite.

Two buzzers you mentioned.

Sounds like a tearful beep sound to your ears?

It is very awkward to write.
:arrow_upper_right::arrow_lower_right: (1) :arrow_upper_right: (2)
My beep sounds roughly like this.