Weather mins
Can someone in the 121 or 135 world help me (USN type) understand the rules about IFR takeoff mins, takeoff alternates and/or departure alternates. I think I understand the rules about destination alternate if weather is less than 2K and 3 then the airport needs to have 600-2 for precision and 800-2 for non-precision. The stuff that keeps coming back from internet searches says that it is all dependant on the Airlines Operating Specifications. For takeoff it mentions about having 1/2 mile for more than 2 engines and 1 mile vis for airplanes with 2 engines or less. I am trying to find out how you would look at a TAF/METAR and determine (other than being able to pick out the ceiling and vis) if you need a takeoff alternate and if you have the takeoff mins without knowing the Operating Specs and what type of airplane your are flying. Any info would be much appreciated.