Beware the windmill effect! Bonus pic of a vortex ring.

[Ozzyguy]

Ok so while flying at the local dam on the dam wall embankment yesterday i came within centimetres(And only very few of them) from crashing.
I looked up an old episode of aircrash investigators and found the reason. It's called the windmill effect. It happens when wind comes up a ridge line and starts to tumble. It forced my quad down very rapidly(I wasn't descending). The following diagram shows the effect on a mountainside and at the top you will see a bonus depiction of the vortex ring state in the form of a down burst illustration.

 

[ianwood]

Mountain wave rotors. Dangerous and hard to identify unless you know what to look for. Even on a very small scale, they could take a Phantom for a ride into the abyss.

Bonus pic looks like wake turbulence to me. Same principle as VRS but wake turbulence is a trail of rotors whereas VRS is a single rotor that descends with your helicopter. Unless I am mistaken.

A Phantom in a decent wake turbulence would be ripped apart. Rightfully so.

 

[Ozzyguy]

True but it does illsutrate nicely whats going on in a VRS. Like in the opening scene of the first transformers movie. Your see a helicopter flying through smoke and you can see the air recirculaing. Wind rotors is the exact term I was tring to think of this morning