How do I interpret ATC-directed headings?
Mike has a great question, one that is often brought up at the start of instrument training:
When given a heading by ATC, is it magnetic, true, or something else?
Whenever you are working with an air traffic control facility, any radar vectors they give you will be turns to magnetic headings only. This simplifies things, both on the ground and in the air, and means you don’t have to do math in the cockpit. It would be especially challenging over long distances, particularly east-west, as magnetic variation can change quite a bit. The only time you’ll typically encounter any kind of true headings will be during the planning phase of your flight.
Your question brings up another area of confusion that I see fairly often, especially in glass cockpits or in aircraft with GPS that provides ground track information: only use your ground track when you’re doing some kind of radio navigation! I can’t count the number of times we’ve gotten a vector and my student follows up by asking if we should fly a ground track of 340°.
So remember, if you get a vector, fly the magnetic heading. And don’t forget to update your heading indicator to your compass every 10 minutes or so!
Footnote: Blake makes a great point in the comments. Canada’s Northern Domestic Airspace, which includes the North Pole, contains such high amounts of deviation that all headings and tracks are requested in True, rather than the highly inaccurate Magnetic. Thanks, Blake!
Erik Johnson on Dec 26, 2008
Great Post! I am just starting instrument training here in Orlando and I was about to ask you the same question!
Blake on Dec 29, 2008
I would like to add one thing.
There is a time when a controller will give you headings in degrees true. It would be in the airspace designated as the (Canadian) Northern Domestic Airspace.
RAC 2.2.1 States:
“The Magnetic North Pole is located near the centre of the Northern Domestic Airspace, therefore magnetic compass indications may be erratic. Thus, in this airspace, runway heading is given in true and true track is used to determine cruising altitude for direction of flight in lieu of magnetic track.”
So all directions will be given with respect to the true track.
I guess a follow up question for you would be, does this also apply in Alaska?
A map of the area can be found here:
http://www.tc.gc.ca/CivilAviation/publications/tp14371/images/RAC2-2-1.gif
Eric on Dec 29, 2008
Thanks, Blake – Paul and I both fly in the US, so it’s great to get information about other countries’ regulations.
Head in the Clouds on Jan 06, 2009
A followup question– if a controller asks for “your on-course heading”, are they asking for your magnetic heading or your magentic course? These can easily be 10-20 degrees off if you’re flying in a strong crosswind, so I’m not sure what to answer.
Paul on Jan 06, 2009
Head in the Clouds:
Usually that is phrased, “State your on-course heading to XYZ.” XYZ being your next fix or destination. He is asking for your magnetic course to that fix not your actual heading. Because your right, in a strong crosswind it could be 10, 20 or even 30 degrees left or right of your course. You can find the answer quickly by looking at your GPS (if installed) and finding “DTK” or desired track.
Paul (aka instructor)