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Martin Connor

Programming FMC with a track or heading

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Does anyone know how the FMC can be programmed in advance of arrival to fly a specific heading from an airport or vor?

 

e.g.  LOXIT DUXBY SFO .. then turn hdg 140

 

This is a standard approach on the Golden gate 5 arrival, ATC directing traffic over the airport, then to 140 with a descent to 4000.  During this 140 heading one is usually turned due east and then brought around to intercept runway 28L.  Golden gate 6 has changed this STAR, but I'd like to know how the FMC could be instructed to do this.  I suspect the answer may be that it can't.

 

Martin

 

 

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You can put a pseudowaypoint out there such as SFO140/10 will give you a 140 track from SFO for 10 nm.  See also: http://support.precisionmanuals.com/kb/a59/fmc-custom-waypoint-entry-notes.aspx , which is dated and I should update but you'll get the idea.  Otherwise, you are correct in that such instructions are normally contained in the sidstar file. Now, you can modify sidstar files and I've been down that rabbit hole for a couple years. It's fun if you like that kind of thing. 

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This is a standard approach on the Golden gate 5 arrival, ATC directing traffic over the airport, then to 140 with a descent to 4000.  During this 140 heading one is usually turned due east and then brought around to intercept runway 28L.

 

Dan mentioned how this could be done, but I do no not recommend it in situations like this. The reason is that any time you do this, the plane will track that value. This means that it will apply wind correction to continue on that track across the ground.  Controller assignments (or any time a chart says "fly heading" or any derivative of that) are always given as headings, which do not have wind correction. If you then track that direction (by making a PBD waypoint, as Dan mentioned), you will not be in the same position as those who are properly using HDG SEL. This could potentially put you in conflict with other aircraft.

 

Flying an assigned heading does not account for wind.  When instructed by a controller (or chart) to fly a heading, just use HDG SEL.  There's no reason to go all kinds of out of the way to add the instruction to the pretty magenta line.

 

So, while it can be done, it shouldn't be done.

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So, while it can be done, it shouldn't be done.

 

Good point, the sidstar syntax allows either TRK or HDG keywords for this reason... just depends on how much fidelity you want.  Realistically, we're allowed heading errors of +/- 5 deg and the VOR error can be +/- 6 deg so as often said, aviation is full of variance.

 

The track from KCRP TO KRBD (Corpus Christi to Dallas Executive TX) is 002 on the Garmin.... some days ATC will ask our heading to confirm we have correctly selected an odd altitude and I always reply with our track... seems to have always mollified them.

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Thanks Dan and Kyle, great advice as usual.  So glad I asked as I now have the link to Dan's entry point notes as well.  Never too old to learn some more.

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