-Simple paragraph, long answer-
The simple paragraph:
91.126(b)(2) - "Each pilot of a helicopter or powered parachute must avoid the flow of fixed-wing aircraft."
-The long answer-
The FAA, in a rare instance, has placed the above paragraph in the FAR's to give us helicopter pilots additional abilities in regards to the law as to create a safer airport environment for all aircraft. Most pilots view this as a good thing, but let me enhance your understanding and add some insight. The flowing are my opinions and not a final ruling or based on case law.
My interpretation of the law:
You would be Required to Avoid the fixed wing flow (if any) but how you do that is not mentioned. This basically allows us to do direct approaches, fly under or above the pattern and also to determine our own flow or use the published helicopter patterns (if published).
How to proceed:
Consider that the basic class G airport and its airspace (up to 2,500 AGL within 4 NM) usually has fixed wing somewhere and you should account for their speed and maneuverability limitation against your own. Then you can assess the usability of the fixed wing pattern given the current weather and airport conditions. If you deem, at anytime, that you may conflict with fixed wing aircraft during your approach to land or take-off, you should deviate from within the fixed wing pattern as safely as possible with the intent of improving the safety to all aircraft and the airport environment as a whole.
Below is how it reads to me and is confusing so read it twice and consider it’s the FAA-
In a helicopter, if you are unable to maneuver safely and maintain outside the fixed wing pattern at an airport then you are not allowed to enter the fixed wing pattern without using the authority granted by FAR:91.3. You should also consider that any class G airport that has overlying class E airspace has the same rules as the class G plus the additional restrictions of class E airspace.
It should be pointed out that it is only a pattern when aircraft are in it. Otherwise it is just navigable airspace.
Fix wing patterns are not the published pattern and are subject to changes by fixed wing pilots.
All in all:
Use your good judgment and fly safely, Helicopters are magnetic to the eye and the camera and you will be judged by all those fixed wing pilots that can't see over the dash and have no idea why helicopters are allowed to fly anyway. So, always keep in mind that we are a small community and have great powers that will someday be taken from us. Let's do our best to postpone that day as long as possible and avoid the fixed wing aircraft without undo noise and endangerment to the airport vicinity.