'Copter Conundrum

I know there is a flat car launched version.....not sure stand alone.

They don't fly the best, usually the body of the helicopter is spinning as much as the blade! But I can in most cases get them to fly 5-6 feet off the launcher. Even once in a great while the helicopter will land on it's skids! If your helicopter just flops off the car or helipad, I assuming you are using a repo copter. Check that the blade is not too tight that it doesn't spin free. Be sure the clutch on the helicopter is engaged with the clutch on the launcher. Wind spring tight, but don't force. A very small shot of WD-40 (not oil) on the winding spring will lube it and unwind faster. 

My experience matches Chuck's. I have had many helicopter cars, and a few heliports. I even had some of the ones that were recently made by Lionel LLC. The launching mechanism on the Lionel LLC ones seemed to bind. I did not try to fix them, I just sold them off.
The Satellite cars work much better.

A few of the postwar copter cars I've serviced have had to have a new 3419-26 Helicopter Car Main Winding Spring.

The MTH 'coptor car launches it's chopper and it flies quite well.  Obviously, it normally doesn't land where you'd want it to...