Hartington
The rules are quite simple - The commander must satisfy himself etc etc.....
Faily accurate is correct - say plus or minus 50feet or 50m visability.This represents 50% of the permitted cloudbase which is (100 feet) or 16% of the permitted visability (300m) for a CAT 2 approach.
At the planning stage, the weather needs to be forecast to be sufficient from an hour before to an hour after the estimated time of arrival. This must be the case for at least two airports and the requisite fuel must be carried to reach the furthest of the two (including sufficient reserves). One of the two airports may be the destination but not necessarily so. It may also be the departure airfield permitting a return to base. It is permissable to set off for your destination with the weather forecast to be below (and remain below) minima provided sufficient fuel is carried to reach the furthest of the two alternates, where the weather is deemed satisfactory. There is another whole set of rules which dictate (at the planning stage) what is and what is not satisfactory depending on the approach aids available at the alternate. This means that you can set off for a destintion in the knowledge that you might need to hold for a while in the hope of an improvement (which may or not be forecast) before diverting to an alternate with weather above minima/sufficient for landing.
It must also be noted that the requirements for planning (in the crewroom) are one thing but the rules can be changed once airborne. This because a forecast is a forecast and the weather is the weather!
The bottom line is that the crew get paid for making the decisions on a day like this. They likely have wives/husbands and kids at home too. The crew want to get their passengers to their destination but only if it is safe to do so. Days like this often cause disruption but that is life in this industry - it is better than dying.
You must trust the crew to make the right decisions on the day 'weather' or not you like the outcome because it will always be safety first.
Last edited by Grizzle; 18th Dec 2008 at 19:25.