Originally Posted by
megan
That piece of CASA's advice is bollox, light is an electromagnetic radiation of a frequency that the human retina is able to detect and form an image in the brain. From whence is the ground or water accessing this electromagnetic radiation in order for you to see same? The requirement is to be in sight, not to be able to see. With a half moon the entire moon is in your sight but you can only see half of it, because it's the only bit radiating electromagnetic radiation in the visible spectrum. To be able to see the ground or water the guy is saying you should be able to discern every tree, unlit house, chicken coop, horse and cow, or estimate the wind strength and direction over water by observation of the waves, and what is going to provide the source of illumination, only fly when no cloud and a full moon? Get real. Now if we were able to see in the infra red spectrum different story.
CASA's 'Regulatory Guidance Delivery' folk omitted what I consider to be fundamentally important, intersecting definitions:
visibility means the ability, as determined by atmospheric conditions and expressed in units of distance, to see and identify prominent unlighted objects by day and prominent lighted objects by night.
VMC (short for visual meteorological conditions) means meteorological conditions that meet the VMC criteria.
VMC criteria:
(a) for a class of aircraft (other than Part 131 aircraft) and a class of airspace (including flight visibility and distance from cloud)—means the criteria prescribed for the class of aircraft and class of airspace by the Part 91 Manual of Standards; and
(b) for Part 131 aircraft and a class of airspace (including flight visibility and distance from cloud)—means the criteria prescribed for the aircraft and class of airspace by the Part 131 Manual of Standards
(And "flight visibility" is defined to have the same meaning as in Annex 2 to the Chicago Convention. "The visibility forward from the cockpit of an aircraft in flight".)