Cessna  

Maybe some downwash from the hovering heli......moved downwind into the path of landing plane?  Made plane cork screw?  

True story

I've been slung side ways 90 degrees in clear air after a heli crossed my path.  Turns out he was coming in from offshore....a 139,  He had a direct tail wind.  All his rotor wash was chasing him in a straight line.  I was at 1500ft agl and so was he.  He passed going towards LFT and I was over the Sugar mill in New Iberia just finished playing in the billowing smoke cloud from the stacks....was headed in the direction towards Lydia where I took off from.  Heli closest radius to me was about 2 miles away when it passed by.  I crossed his wake turb about 5 minutes after he had already left the area.....and HOLY S-HIT, DID I GET SLUNG.  I went from fat dumb and happy flying straight and level to as if I yanked full right brake toggle to stall the right side of the wing.  And just as soon as it hit me, it let me go.  I only lost about 200ft.  No collapse.  

Y'alls wake is no fkin joke.  When I see you coming I immediately do the wind calc and alt in my head and either climb or dive .  To get over it or under....but never around the same level.....especially heavies.

Paramotor Sparky out.