Idle up is a flight mode where the throttle will not return to idle so you never loose your head speed.

Most radios have 5 point pitch and throttle curves read from left to right as bottom stick; 1/4 stick; 1/2 stick; 3/4 stick and full throttle.

So in normal flight mode you have idle/25 percent throttle/50%/75%/100% and on the pitch you have -4, 0, +5, +7, +9 degrees.

In idle up you would have 100%, 75%, 50%, 75%, 100% and -9, -5, 0, +5, +9

The machine would hover in normal at half stick and the blades would slow down and stop at bottom stick.

In idle up the machine would hover upright at 3/4 stick and inverted at 1/4 stick. Full down stick would be full power and full inverted pitch to climb while upside down. Full up stick would be full power and full pitch to climb upright.

The idea is to get your headspeed and then set the throttle curves up and down so that the head speed remains constant at any stick setting. A weak engine would need higher throttle points, maybe 100, 80, 60, 80, 100 where a strong engine, like my 50 hyper will over speed at anything over 85, 60, 44, 60, 85