I tried to print the Helicopter_fingerring.stl, and realized that the shaft with threads is not touching the build plate. It is almost 1 mm above. The finger ring is also above the build plate. These problems caused the print to fail. Included are the original stl files for the blades and front, so all of the files are together. The original Flying Helicopter Toy by 3DBROOKLYN works well - these changes make it work better (for Me)

I cut the bottom of the tail so that the shaft touches the build plate and added to the finger ring so it now touches. I have had good luck with printing at about 125%. I sliced in PrusaSlicer and printed on an Ender 5. Here are the actual scaling factors I used.

Settings for each part Helicopter_blades.stl 125% scale all axis Helicopter_Front.stl 125% all axis fixed finger ring V1.stl 124% X 124% Y 123% Z

My printers are all well calibrated and I used a value of -.09 for XY Size Compensation. First Layer Height .35 Layer height of .2 2 Perimeters (wall) 3 top and bottom layers

On the Helicopter blade I used 1 Perimeter (wall). This made it much lighter and fly better. You may have to play with some of the settings depending on your printer and slicer, but it is a great toy when you get it working