https://www.youtube.com/watch?v=PqewZDoOIuE
This isn't the usual "tip vortice" spiral pictures and there're plenty of youtube clips of boat propellors showing the spiral path of tip cavitation but this isn't one of them.
What you have in the above clip is the water that's being pushed back is also spinning around as evidenced by the action of the engines exhaust. Granted water is a bit more viscous than air, but as has been pointed out in previous posts, stator vanes are needed in axial flow turbines and compressors because the airflow does not leave the blade perpendicular to the shaft axis and needs to be straightend, and surfaces placed above/below the engine thrustline influence a plane in opposite ways.
Spiral slipstream is real, it exists, but an rc prop in air isn't going to create a spiral that wraps around a plane 4-5 times. It'd be lucky to be only a fraction of a full rotation over the length of the fuselage but a fraction of a degree can created ounces of force imbalance.
https://www.youtube.com/watch?v=N3WwQKZ05Uk
The above is a slo-mo of the spiral path of tip cavitation but is in no way "evidence" supporting spiral slipstream, it's just the path of the prop tip "drawn" in the moving water....