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Is Magnetic Heading Obsolete in the Era of GPS?

R

RV9Otter

Active Member
I understand that when a controller gives you a heading to fly, they expect you to fly a magnetic heading. So, other than the legality of complying with the ATC instruction, is there any real benefit to flying headings instead of magnetic track in a GPS equipped aircraft? I can't think of any.

For example, on an instrument approach, let's say the course to fly from the approach fix to the missed approach point is 002 degrees. The autopilot is going to fly a 002 degree course (track) regardless of the aircraft heading necessary to fly the correct track. If you hand fly the approach, it would be much easier to just fly the 002 degree track on the EFIS (or the GPS display) than crab into the wind with a guessed at heading, and adjusting based on keeping the localizer centered, as was done in the pre-GPS days.

When flying to any waypoint, again, it is much easier to just fly the required magnetic track to that waypoint or destination.

Let's say the missed approach instructions for an instrument approach say to fly the runway heading until reaching a certain altitude. Again, it makes much more sense to me to fly the runway track from the GPS or the EFIS display, than fly the runway heading.

In summary, I can't think of one advantage to fly a magnetic heading instead of a magnetic track, other than legally complying with a controller's instructions. Is the whole idea of flying magnetic headings in GPS equipped aircraft obsolete in reality, again, except for he legal implications of following a controllers instruction?

Thanks...just looking to learn something here.

Curt
 
Controllers are expecting you to the fly the assigned heading, not a ground track. They are correcting for the winds and other traffic already.
Yes, once established on the final approach course you need to fly the course/ground track.

Vic
 
I Understand...but...

I understand the necessity to fly the heading requested by ATC, and that they try to compensate for winds. But, and this may be totally academic, in a GPS world, is this just a holdover? I also understand that not all aircraft have GPS, so, until the day everyone flying under ATC has GPS, and the rules of ATC guidance are changed, we'll need to fly magnetic heading when instructed to do so. But, bottom line, I still see no safety advantage of heading over track.

One bit of evidence that heading is obsolete in practice, is that very often a controller has to make adjustments to the heading assigned (because their compensation for wind was not perfect) to get the results they desire when vectoring me for the initial approach fix. If they were to assign a magnetic track (which I know they don't) there would be no compensating for wind and the results would be precisely accurate...you would hit the initial approach fix with the track assigned regardless of wind.

Curt
 
RV9Otter said:
In summary, I can't think of one advantage to fly a magnetic heading instead of a magnetic track, other than legally complying with a controller's instructions. Is the whole idea of flying magnetic headings in GPS equipped aircraft obsolete in reality, again, except for he legal implications of following a controllers instruction?
Click to expand...

Ever been in an area where GPS has been NOTAM'd as unavailable? It's probably more common than you think. Magnetic compasses continue to function fine in those areas.
 
Consider two airplanes taking off on parallel runways in IMC (27 L&R). Winds are from the north. Left runway flies a GPS track of 270. Right runway flies a heading of 270 as assigned by ATC. Bad things could ensue as the 27R airplane converges with the track of 27L airplane.

If every one had GPS and ATC assigned a track instead of a heading, life would be good. But that's not what happens today!
 
No...but that makes sense

O.K., had not thought of a situation where GPS is not available...But, in a world where everyone in the IFR system was required to have GPS, (at some point in the future when VOR's are decommissioned) I can see the controllers assigning magnetic tracks and only resort to magnetic headings when there is a failure of GPS. I'll let the go...as I realize the world without VOR's isn't here yet, but, I do believe the day is coming. At that point, I still see no advantage of magnetic heading being assigned instead of magnetic track.

Thanks,

Curt
 
RV9Otter said:
O.K., had not thought of a situation where GPS is not available...But, in a world where everyone in the IFR system was required to have GPS, (at some point in the future when VOR's are decommissioned) I can see the controllers assigning magnetic tracks and only resort to magnetic headings when there is a failure of GPS. I'll let the go...as I realize the world without VOR's isn't here yet, but, I do believe the day is coming. At that point, I still see no advantage of magnetic heading being assigned instead of magnetic track.
Click to expand...

When the military stops shutting down large swaths of airspace, then maybe. But it's not practical unless they stop doing that, and them doing that seems pretty unlikely.
 
Fact is, there are still a large number of aircraft without an IFR-TSO'd gps. Probably some of them are airliners! When the FAA mandates that all aircraft "in the system" (IFR, flight following, practice approaches, etc.) have an approach approved GPS, they'll probably switch to ground track for vectors.
BTW, I've seen plenty of "corrections" to heading issued by ATC. Sometimes they didn't get the wind correction right. But sometimes the pilot just doesn't hold the heading; sometimes the vacuum DG has drifted 5 deg off; sometimes the compass that the DG was set to was 5 deg off (who reads compass correction cards?).
 
BobTurner said:
Fact is, there are still a large number of aircraft without an IFR-TSO'd gps. Probably some of them are airliners! When the FAA mandates that all aircraft "in the system" (IFR, flight following, practice approaches, etc.) have an approach approved GPS, they'll probably switch to ground track for vectors.
Click to expand...
^^^^^^
THIS

And, there are still a large number of aircraft without ANY GPS.

:cool:
 
RV9Otter said:
O.K., had not thought of a situation where GPS is not available...But, in a world where everyone in the IFR system was required to have GPS, (at some point in the future when VOR's are decommissioned) I can see the controllers assigning magnetic tracks and only resort to magnetic headings when there is a failure of GPS. I'll let the go...as I realize the world without VOR's isn't here yet, but, I do believe the day is coming. At that point, I still see no advantage of magnetic heading being assigned instead of magnetic track.

Thanks,

Curt
Click to expand...

There are a lot of aircraft out there without electrical systems. If they have a radio, it will probably be a low power handheld radio and they will fly with their compass. (Or hand held GPS until the batteries die.)
 
When everyone has a GPS on board, why would we use a *magnetic* track at all? Why wouldn't we just switch to true headings, and forego correcting for magnetic deviations, and re-numbering runways from time to time when magnetic deviations change?
 
Snowflake said:
When everyone has a GPS on board, why would we use a *magnetic* track at all? Why wouldn't we just switch to true headings, and forego correcting for magnetic deviations, and re-numbering runways from time to time when magnetic deviations change?
Click to expand...

The issue is not true or magnetic heading but rather ground track versus heading. We know ground track is a result of heading flown plus the change that results from being blown around by the wind. An aircraft without a functioning means of establishing ground track (GPS, INS, Doppler, RNAV etc) can't readily fly a ground track "on command", as would be expected by ATC. Instead that aircraft would have to establish a heading, monitor their path over ground, and adjust as necessary. This process simply isn't viable in an ATC environment.

The comments about GPS outages are right on the mark, as are the comments about aircraft not equipped with GPS. We in the "experimental" world have become exceedingly accustomed to having multiple GPS sources feeding our gee-whiz EFIS equipment. Unfortunately there is a plethora of certificated aircraft which don't have this luxury and we still have to fly safely alongside them in the same airspace. Just like NORDO aircraft, we must cater to the lowest common denominator.
 
Almost irrelevant at RV speeds

Generally at 180 kts the difference between Mag HDG and Mag TRK are within 2 or 3 degrees of each other. I generally hate magnetometers with a passion for the PITA they are to install in a clean location and the extra plumbing and calibration. I personally think Garmin got the G5 just perfect to totally avoid a magnetometer. At the same time I like my SIRS whiskey compass and it makes for a good cross check in any case. Even in some stiff winds, there is not much discrepancy between the two (at RV speeds) and it never hurts to use the grey matter instead of looking for the little wind arrow on a glass display. In my 20 years of air time, electrics and more than a few EFIS top the list of failures. I doubt we will see the day when a Falcon 7X takes to the skies without a mag compass front and center above the panel. In a multi GPS RV one bad ant. can render all of the on board GPS useless.
 
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F1R said:
it never hurts to use the grey matter instead of looking for the little wind arrow on a glass display.
Click to expand...

Absent a magnetometer I don't think there could be any wind indication on the EFIS? It seems that magnetic heading is required for deducing the wind correction angle, which is useful for IFR approaches (which are typically flown at speeds much slower than cruise). True you could also get this from the whiskey compass, assuming one is installed.
 
Alan Carroll said:
Absent a magnetometer I don't think there could be any wind indication on the EFIS? It seems that magnetic heading is required for deducing the wind correction angle, which is useful for IFR approaches (which are typically flown at speeds much slower than cruise). True you could also get this from the whiskey compass, assuming one is installed.
Click to expand...

"A 15 knot cross wind at 180 KTAS needs closer to a 5 degree crab - enough to be noticeable."

Both of the above points are exactly why I said I like my SIRS whiskey compass.:D

On an IFR approach once established on the localizer, just keep the CDI needles centered and adjust accordingly. The GPS Mag Track makes this much easier at this point. You will know your low level winds before your arrival and the brain automatically crabs slightly into wind to freeze the needles

Mag heading however (IMHO) will never be obsolete.
 
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In Summary

So to summarize, all we need to do is:
  1. Ensure every aircraft has a GPS. This can be done by simply replacing the requirement for a "magnetic direction indicator" in FAR 91.205 with "GPS".
  2. End military-related GPS outages. Their silly ideas like "training in a GPS-denied environment" and whatever else is what wars are for anyway. MAGA!
  3. Change ATC procedures. Shouldn't take more than a few hours to ensure that every TRACON, ARTCC, etc. is aware of the new and simpler procedure.
  4. Convince the rest of the world to follow suit. An e-mail to the U.N. should suffice here - I'm sure they'd be happy to come along with us.
  5. Maybe update sectionals, approach plates, and whatever else. If we could convince ForeFlight to do this, everyone else would pretty much have to go along with it.

Besides, we're going to need to do this anyway: The Coming Geomagnetic Reversal.


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