WEATHER FACTORS 1Gp
Take-Off. The following are minimum conditions for aircraft take-offs:
• Green rated pilots. Sufficient visibility for the aircraft to be kept straight without reference to instruments. At night, this is considered to be 3 consecutive side or centreline runway lights.
• White Rated pilots. Minimum Met Vis of 1000 m and cloudbase not lower than 200 ft.
• 1G310.140.10 Circling Approach Minima. The minimum reported Met Vis for all categories of circling approaches is 2500 m.
• The minimum actual and forecast weather for a diversion airfield is to be as follows:
• One airfield with no significant cloud below 700 ft and a minimum visibility of 3700m (Green or better); or,
• Two airfields, which can be in close proximity, with no cloud below 500 ft and minimum visibility of 2500m (Yellow 1), however only Green Rated pilots are permitted to operate under these conditions.
• When selecting a diversion, stations are to consider the minimum weather, both actual and forecast for the operating period, is no worse that the pilot’s instrument rating limit.
• An independent subsidiary runway may be nominated as the diversion when the actual and forecast weather is White or better.
Use of Civilian Airports as Diversions.
Unlike UK military METARs that report the lowest visibility that cause a colour state change, civilian METAR will only report the lowest visibility if this is less than 50% of the Prevailing Visibility (PREVIS) or less than 1500M. Therefore, unless the visibility reduces to 1500M (Amber), you can only guarantee that the visibility is actually half of the PREVIS. As a result, when selecting a Civilian diversion, Sqns are to factor any PREVIS such that only half the declared visibility is guaranteed.
This may be out of date.
Etc etc