"Say the other chopper's blades weren't spinning and she parks in her spot without incident,...they're still too close. Now the other chopper starts to spin up and WHACK they hit! Who's to blame now"
I would think that regardless of what markings are painted on the ground, the arriving machine has a duty to stay far enough away from the parked machine so that both can be safely operated. But: in addition, the parked machine should not , thereafter, spool up unless it knows that it can do so safely. It's like driving your car--"who has the right of way" becomes secondary when one has the opportunity to avoid an accident. The doctrine is called "last clear chance".