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Nick Dobda

Flight Plan Changes mid-flight

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Sorry this post isn't really NGX related, so I guess feel free to delete, but the folks here are some of the most knowledgeable around (Kyle among others) so I have a question related to routes-

 

I am flying home in a week, KMSP to KPIT through KMDW. 

 

The second leg of the trip is KMDW to KPIT. Obviously I've been flying that route several times cause I want to be able to follow the flight while we're in the air. What I am seeing though on FlightAware, tracking that flight, over and over and over it seems the flight is taking a shortcut -

 

The planned route (the route I've been flying) is 

 

LEWKE GIJ OTENS ANEWA RIEKE DJB ACO JESEY2

 

It seems every single flight takes a shortcut and does this:

 

LEWKE GIJ OTENS ANEWA  ACO JESEY2

 

The route prior to departure shows the predicted path as the original route, but as the plane flies, the route always gets modified to the shortened version.

 

What's going on there? Its got to be more then coincidence that they are getting cleared direct to ACO from ANEWA every single time. 

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What's going on there? Its got to be more then coincidence that they are getting cleared direct to ACO from ANEWA every single time. 

 

One of a couple things is happening, and this is something I had a hand in when I was on my last contract with the FAA.

  1. If you're seeing a very constant route being filed, the dispatcher is likely filing what is called a "canned route." This is a route created by dispatchers - occasionally with the guidance of the local facilities (Tower, TRACON, ARTCC) - as the most X route, where X is "efficient, fastest, most acceptable, and so on" to fit the need. That is to say, it doesn't matter if it's the fastest route if ATC rejects it all the time and reclears the flight, which is a pain to ATC and the pilots for the full route clearance.

    These canned routes are stored in the dispatch program such that the dispatcher simply pulls the route for the city pair, checks the load numbers, assesses wind/weather delay, airport delay, taxi time, and so on, and builds the route. In other words, the route is a constant unless there is some huge reason to change it, like a giant thunderstorm parked on it, in which case, they route around. In some cases, over time, these routes fall "out of fashion" with the facilities due to how they structure the airspace, how a controller works the airspace, and so on, but this info never gets passed back to the dispatcher(s) or clearing facility, so the canned route never receives the change. The flight usually gets cleared as filed and then a direct, or a route amendment is given in flight.
     
  2. The route may also be an approved route by the facilities, but given the time of day, traffic loads may be conducive to route amendments. It's similar to the concept of an alternate: it's in the plan just in case you need to go there, but in practice you probably don't have to go there. The route itself is filed through what the operator and facility agreed upon, or simply what they've always filed and have not received any feedback about it. The controller sees light traffic such that giving a direct isn't an issue, coordinates with controllers up to the route mod end, and reclears the flight.

    Alternatively, one thing that a lot of operators and pilots don't think about is that ARTCCs ("centers") have agreed upon points where traffic enters their airspace if it's not on an airway. So, giving a flight a route mod off of an airway isn't a simple matter, particularly if it crosses facility boundaries. Inside the facility, the controller can just dial the next controller down the line (the "landline" you'll hear controllers referring to) to APPREQ the change, and then reclear the flight.

In the case of your route here, it looks more like the former. This isn't an inter-facility thing for the most part (the route change happens well before PIT TRACON picks the flight up. The facility (ZOA - Cleveland Center) might have a bunch of traffic going to DTW and transiting up to Canada, and the direct might cut the flight a little farther away from those traffic flows to help free up some airspace. This gets more and more important as spring turns to summer and you get popcorn storms to route around.

 

A bunch of dense info, but I hope it helps!

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Thanks Kyle I knew you would have a sold handle on what's going on and not give some generic answer, which is why I asked it here. 

The routes ... well future route, the dashed line ahead of the flight before it takes off, always follows the full route. Somewhere about ANEWA the predicted flight path changes, and the plane then follows it. That change happens just over the border of Indiana and Ohio, around Toledo. If the center boundaries are the same as vatsim, this is right about where you cross over into Cleveland center, which covers all the way to and through Pittsburgh.

Do you think its the Pilots (who I'm assuming are very familiar with the route and probably fly it very often) request the change to fly direct to ACO right when they enter Cleveland center airspace, or Cleveland Center making the change? Seems like a crafty pilot could ask for the shortcut and then sound like a hero to the cabin when they announce that "we'll get you into Pittsburgh 10 minutes early"

 

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The routes ... well future route, the dashed line ahead of the flight before it takes off, always follows the full route. Somewhere about ANEWA the predicted flight path changes, and the plane then follows it. That change happens just over the border of Indiana and Ohio, around Toledo. If the center boundaries are the same as vatsim, this is right about where you cross over into Cleveland center, which covers all the way to and through Pittsburgh.

 

Yeah, the way the FAA provides the data, the route will show the filed (full) route until an ATCO changes it in the system. The change is usually made right around the issuance of the instruction to the flight.

 

 

 


Do you think its the Pilots (who I'm assuming are very familiar with the route and probably fly it very often) request the change to fly direct to ACO right when they enter Cleveland center airspace, or Cleveland Center making the change? Seems like a crafty pilot could ask for the shortcut and then sound like a hero to the cabin when they announce that "we'll get you into Pittsburgh 10 minutes early"

 

I'm willing to bet that it was the ATCO who issued the instruction right after getting the flight from ZAU (Chicago center*) either for established traffic flows (as mentioned earlier), for general efficiency, or for sequencing (less likely if the flight is getting the shortcut all the time).

 

*ZAU and ZOB for Chicago and Cleveland, respectively, are two of the most nonsensical facility codes of the bunch, at least on the surface. Looking further, Chicago Center is in AUrora, Illinois; and Cleveland Center is in OBerlin, Ohio.

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There is no Cleveland Center feeds... but liveatc.net will let you listen to departure and center from the ORD area. You might be able to hear re-routings. I use liveatc when flying a route in real time, loads of fun.  - David Lee

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Next flight on that route is in an hour, ill listen in on ZAU see if I can pick anything up. I suspect the reroute is occurring in ZOB though.

 

EDIT - funny I finally pick a flight to follow and it gets delayed an hour and 20 mins. I have to leave my computer before it'll get there. Oh well.

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