Primarily for general aviation discussion, but other aviation topics are also welcome.
By The Kissimmee Bum
FLYER Club Member (reader)  FLYER Club Member (reader)
#1472000
Anybody know what the symbol comprising two concentric turquoise rings means on SD?

Noticed two which were appearing this morning in the Yeovilton area. Now gone, but another still lurks just to the north of Liverpool.

Prob something obvious but it's not so obvious to me at the moment.