Originally Posted by
nyalex
Just within the mode C veil, regardless of altitude. If you were required to have it below B airspace at anytime, what would the be the point of the veil in the first place?
heard this question too and I always thought that mode c was required below class b. If you look at a Seattle sectional at Seatac you will see that the lateral boundry of b goes beyond the mode c veil, so I thought that mode c would be required below the shelf there. And you can be within the 30 nm mode c veil and not be even in or below the class b, this is why the 30 nm magenta line is there.
I could be wrong but that is just what I was taught.