Hello,When trying to build a flight plan...either via FS Build or straight into the FMC in my Dash 8 when it comes to the SID how do i know which one to select.For example when departing from RWY 27R from Heathrow i have a selection of 5 0r 6 SIDS to choose from how do i know which one is correct for my flight?Thank youDave

You have to choose one that finishes where your airway/flightplan starts. A good place to start is looking at the available charts and choosing the most appropriate one from there.... Try here:http://www.dc3airways.com/avcharts.html

And in real life too, just as a friendly reminder, on departure, clearance gives you your SID and the arrival airport's ATIS gives you your landing runway and star assignments, which are then just easily plugged into the FMC...on the more technically advanced airplanes like CRJ's and Airbus and such.Zach