I suppose the downdraft from the helicopter caught the sail, and blew the thing over... By the way, what's the extra (4th) wheel for?
so can we learn from this from a design or usage point of view 
(don't sail under choppers)
when your mast tip hits a chopper the pilots absolutely freak out
. they move over a bit and drop the chopper to the ground like its made of lead[}:)]. having stopped the rotors, the go over the fuselage looking for the dent.
It certainly teaches them to stay further away
Many Adelaide land sailors did a commercial shoot for Labatts Beer (Canadian company) many years ago, they wanted landyachts lifting wheels and sailing around a hot air baloon just off the ground.....
Problem was land yachts need wind, hot air balloons want little or no wind, I dont know it the commercials ever went to air but it was fun making them
