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Asked by: Dan Chitty
What is the purpose of vertical visibility? When is it applicable to a instrument approach? I have read the definition but would like more clarity.
Thank you for the feedback
John D. Collins
on Aug 03, 2013
A ceiling is defined when the clouds do not touch the surface and there is a distinct boundary between the cloud base and the air below. When there isn’t a distinct boundary and the obscuration is all the way to the ground, then vertical visibility is used to provide the pilot with an indication of how far one can see vertically. Its use is similar to a ceiling. The obscuration can be from various causes, such as smoke, fog, mist, etc., but the common thread is that the obscuration goes all the way to the ground. Flight visibility is always the determining factor for descending below the DA/MDA on an approach. The forecast or actual VV is used in the same manner as a ceiling when you are choosing whether or not to conduct an approach or go somewhere else.
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Dan Chitty on Aug 03, 2013
Thank you John. You explanation is very clear. Much appreciated.
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