Just curious how, during flight planning, which SID and STAR to be used is decided upon? Obviously when getting IFR clearance ATC can change what was requested, but initially, how does the flight crew decide which SID/STAR to request (besides the obvious such as direction of travel, etc). Let’s say you were going to be heading east and there were a few different STARs that aid in transition to enroute structure to the east, how do you decide which one to use?
As you said, most often the SID you choose depends most on which way you want to go. Weather can also play a part of it, but that is more often a last minute change.
Other times, it’s either a toss-up guess, or a personal choice. With many (dare I say most?) corporate and private jet pilots use Fltplan.com these days. With fltplan.com, you can see the most commonly flown routing for your direction of flight, even down to the A/C type that filed and flew that route.
Other times, like you said, you might file one routing and ATC comes back with an entirely different routing. Don’t even try to figure out all the thousands of variables to why ATC does what it does sometimes, but understand that they’re usually doing it for a pretty good reason.
There generally is only going to be one STAR/SID for each direction. Sometimes there may be two, one of them being an RNAV procedure that requires advanced GPS/INS navigation that not all aircraft are capable of flying, and thus, if you can’t fly the RNAV one, you file the other STAR suitable for all aircraft that only uses ground based VORs. I’ve seen a few instances where it is quit confusing, but on the actual chart, you’ll find notes that say “This STAR is for aircraft flying to xxx only”. The airspace is designed in a certain way to make it most safe and orderly for all aircraft, and these procedures make it more streamlined and less confusing.
When the departure or arrival procedure is changed by ATC, is it most likely due to weather along the filed route. When deviations get bad along a route, an alternate route is obviously needed. Some parts of the country are very flexibly (DEN comes to mind), but others aren’t (the Coasts). Often times, aircraft will be rerouted off the STAR/SID with weather and must use another procedure that normally wouldn’t even be considered, as it approaches/departs the terminal area from the other direction. This saturates the airspace running the open procedure, and thus delays must be incurred. This is one of the reasons flights are late alot in the summer.
OK I thought of another question along the same lines.
If there is a SID/STAR available for your airport, do you always plan to execute one or do you only plan a SID/STAR under certain conditions. Take ORD for instance - would you always plan for a STAR into ORD? If not, under what circumstances would you plan for the STAR and under what circumstances would you not?
May I recommend the FlightAware IFR Route Analysis tool, so you can see what ATC has been assigning to other aircraft on similar routes.
awesome, thanks for that.
The simple answer is yes. DP’s (or Departure Procedures as the FAA now calls them) and STAR’s provide several functions for ATC and pilots. But the main purpose is to help ATC efficiently route aircraft into and out of congested terminal and enroute airspace. Depending on traffic you may fly the entire procedure or abbreviations of it.
I was told, no first hand experiences on stars or dp, that if you put no star / no dp in your flight plan, you can just about expect to be vectored along those routes anyway so you might as well file for them. Of course, if I am poking along at 120 knots mixed in with jet jockies, my 120 knots just may gum up the works, so ATC may have something different for me, preferably shorter so I get there faster and not further gum up the system.
Very true… DP’s/STAR’s are typically (not always) assigned to turboprop and jet aircraft. And in alot of cases turboprops have modified if not separate procedures from jets due to their speed capabilities. In my experiences when flying a turboprop I’d be on a slightly different lateral course until a certain point, then 1000 ft. below overtaking jets. Then when I’m in a jet I’m looking out over the nose for TP coming up ahead and below. A fun perspective and view from either seat…