cannot maintain inversion, heads down to ground no matter wh

[turnbui]

Hi folks,
I am using a 6 channel Tx made by Awesome RC Products which has a 3D switch and a port on the back for the USB cable. It came with my "Twister" heli. Everything in FMS works without fault but I cannot maintain inverted flight. When I cut the power once inverted [to give me time] I can change the orientation of the heli but it just floats down to the ground everytime. Can anyone tell me what I might be doing wrong? I have tried with both the 3D switch on and off and am using the ThreeDee heli.
Thanks