How did you assign the channels for the helicopter? Are you using the basic setup or the advanced setup? Please read the manual on setting up and calibration procedures.

It will be more convenient to do a new setup if you disable all program mixes in your computer radio and do a recalibration first. Your throttle stick needs to be at mid position during calibration. Please go to the control panel in AFPD. In the advanced mode, find channel 20 and assign it to your throttle (channel 20 is for heli throttle while channels 1-4 are for plane throttle).