Originally Posted by
Radu Poenaru
Is there a visibility requirement for CAT I approaches? Yes. And that visibility is measured by very smart people on the ground and then reported to the pilots.
That is not correct in the land of the FAA. The specific legal requirement is for "flight visibility" and flight visibility cannot, by definition, be measured by people on the ground or by RVR sensors. Yes, it is explicitly defined to be distinct from reported visibility, and the distinction is not trivial.
That distinction is crucial to the ability to legally land when the
reported visibility is below the specified minimum.