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.