General Yo-Yo Effect

[RMB677]

When practicing hovering with my Blade 450 3D, about 5' off the deck, I get what I call the yo-yo effect. Without any throttle, and thus no pitch change, using only roll, elev, and rudder the heli changes altitude sinking to withing a foot or so of the ground and back up. I can understand this happening when there is a breeze but not with dead calm. Is this still ground effect at 5' or something abnormal?

Roger

 

[Virtibird]

When practicing hovering with my Blade 450 3D, about 5' off the deck, I get what I call the yo-yo effect. Without any throttle, and thus no pitch change, using only roll, elev, and rudder the heli changes altitude sinking to withing a foot or so of the ground and back up. I can understand this happening when there is a breeze but not with dead calm. Is this still ground effect at 5' or something abnormal?

Roger

Ok I am new to this forum and heli's so what I am about to say could be totally wrong but I think I know what is happening. When you are in a hover and you give any cyclic input you are trading vertical lift for horizontal lift so the heli decends, plus all else being equal when the heli gets into ground affect less lift is required to hover with a givin collective input so the heli rises out of ground affect then settles back down again. totally normal.

 

[callsign4223]

That is true about the lift loss , but I wouldn't think it should be that drastic. How much drop are you getting? Also, how far are you pushing the heli over, what kind of angle is it getting to?

 

[RMB677]

The drop is usually 2' to 3' and is associated with small movements of the right stick, only enough to try holding in one spot. Usually there is a small amount of roll or elevation associated. My thinking is that the change in attitude of the rotor affects the lift eventhough the balde pitch is unchanged.

 

[callsign4223]

The small changes you are making to the cyclic(right stick) should not create a 3 foot drop. If you were making drastic movements, causing the rotor disc to tilt at large angles( 20-30 degrees) then you would see large altitude drops. But small cyclic corrections should not cause such drastic altitude loss.

 

[murankar]

don't forget you are going to get some translational lift from the wind also. a little breeze can rob you of a little lift so keep that in mind.

 

[Lee]

You dont need much cyclic movement for the heli to bob up and down. Especially if you are a bit slow with your collective control. Think of the air under the heli like a trampoline. The heli is bouncing up and down on this cushion of air. Depending what you do with your legs, you can bounce higher, or you can absorb the bounce and stop. If your reactions are slow on the sticks this bounce will get worse. If your timing is right, you will dampen the bounce and come back to a steady hover.