Please check out the flight in the link below:
http://flightaware.com/live/flight/DAL418/history/20060706/0551Z/KSLC/KATL
It’s a flight from Salt Lake City (KSLC) going to Atlanta (KATL). Its filed route is as follows:
TCH J173 EKR GCK MEM ERLIN2
Looking at my charts (it takes two - sorry 'bout that), J173 begins at TCH and ends at EKR. There are no other navaids or intersections in between TCH and EKR. So J173 is essentially going from TCH direct to EKR.
So why bother with inserting “J173” in between “TCH” and “EKR” in the flight plan? Why not just file it as:
TCH EKR GCK MEM ERLIN2
Seems like a waste of the pilot’s time to file it that way, and all of the controllers who have to deal with that extra data.
In today’s environment of PDC’s (pre departure clearances) the flight plan and clearance can be electronically downloaded to the cockpit and the controller (and pilot for that matter) may never even have to say the words “J173”. Also, I don’t know that this is the case here, but if it were a gov’t preferred route and you tried to shorten it as you suggest you would get a “full route clearance” which included the J173. In the aircraft I fly, a Falcon 2000EX, our flight planning service (GDP) comes up with the route, it is downlinked to the FMS in the cockpit and, if available, I get a PDC. All this cuts down on the workload for ATC.
Also, sometimes they might need you to re-intercept the airway after a vector. For instance, when leaving an airport with a VOR on the field, and the clearance included an airway that ran through that VOR, we put in the GPS the airport code, the VOR code, and then the next turn along the airway. After takeoff there are usually vectors around traffic or airspace or whatever but then ATC will clear you to resume own navigation, which mean re-intercepting the original airway. Sometimes they will clear you direct to the next fix, but not always.
Also, the route that is listed in FlightAware is often not what is actually flown. Changes to the routing while enroute are common, as is instructions to ‘cut the corner’ lots of times to fly direct to another fix way downstream. On one of my flights in the past month we had a full route planned out and loaded in the GPS. Once we were in radar contact (out of McComb, Mississippi) we were cleared direct to a fix over 600 miles away (to Lamar VOR in Colorado).
