Now the enquiring minds are getting technical - good for you!
Here goes; Licensed aerodromes have to conform to CAP 168 and Runways are coded from 1 to 4.
Now I can't speak on grass runways, but the same probably applies. (Always in something a bit heavy for potentially damp grass and I hate to think about all the performance issues regarding whether its wet and how long etc.)
Back to the point all runways are (should be) safeguarded with a "strip area" around the runway. This ranges from 40m up to 150m for a precision app. runway. Best way to visualise this is usually by noting where any runway holding points/stop bars/wig wags are located. Inside ot these and you have not "vacated" the runway.......so in this instance, it was still mine.
I'll try and look through the books and see if same applies to grass runways........don't suppose their are any precision approaches on to grass
No it was not a helicopter - and don't be fooled by them either. Just remember, and I was useless at physics, the forces required to kep them airborne have to exceed the equivalent of their weight hence rotor wash can do a lot of damage. Please excuse my lay interpretation, but the nett result may not be pretty/
Got to go to a meeting.......other side of airfield!