You accidentally misquoted Michael Yon when you chopped off the word MOST helicopter traffic ceases. Chopping off the word MOST makes your quote inaccurate.
You cannot have any combat rotary experience in Afghanistan if you never heard the term red illum. That would be like saying you drive a car but never heard of the term steering wheel. The term really is that common.
For instance, it is used here: http://www.mod.uk/DefenceInternet/DefenceNews/MilitaryOperations/RoyalNavySeaKingsFlyingOverAfghanistanForTwoYears.htm
"After 11 years, the Taliban realizes that most helicopter traffic ceases during red illum."
It's the third sentence of the fourth paragraph. Go check the excerpt for yourself.
1) Sorry I left off “MOST”.
2) Never claimed to have combat helo experience in Afghanistan
3) I stopped military flying in 1978, well before the US was operating helos in Afghanistan
4) You reference for “red illum” is a to British article. US folks generally use different terms than “spanner”, “boot”, “split pin” as used by our cousins across the pond. Does this also apply to “red illum”?
5) All my military combat experience was on the ground, in Vietnam. I did have a tiny bit of helo combat experience in Uganda, having been fired on by a ZU-23-2 at very close range. They missed. ;-)