Qalupalik wrote:
huv, I read your “track is what gets us where we want” as advocating for constant track values which is clearly an over-interpretation.
If you want to fly long distances efficiently, you would usually want to follow a Great Circle (I am sure that was your point also, Q). But a Great Circle is defined by its (ever changing) track, not by heading.
Did I drift off the thread subject too much by suggesting more “track” in practical navigation than “heading”, or did just no one else think this is worth discussing?
These days, whenever I train pilots to fly an ILS, I always make sure they include GPS track in the scan. It makes it so much easier than if you just chase the needle.
Another view: the G5 attitude indicator that was recently installed in one of our club Cherokee’s gives track and ground speed on the screen, and there is an easily selectable track bug, that the pilot, or the Garmin G500 autopilot, can follow easily. However, to install the G5 as an HSI, a “stabilised heading” is required for IFR, necessitating a time consuming installation and calibration of a remote magnetometer, costing much more than the price of the two G5’s combined.
“Stabilised heading” is still a requirement for IFR flight according to regulations, but is it really required for safe and practical IFR operation in the future?
Is it perhaps the change-over problems from one way of managing separation and navigation to another that is the problem, just like we are stuck with AM VHF radios instead of better FM radios because a gradual changeover is not possible?
(Peter, feel free to move this to a separate thread if you like)
whenever I train pilots to fly an ILS, I always make sure they include GPS track in the scan
Surely, they should fly the heading as the primary lateral reference. In all “instrument flight” you fly the heading as primary, laterally. Localiser, VOR tracking, NDB tracking…
Peter wrote:
Surely, they should fly the heading as the primary lateral reference. In all “instrument flight” you fly the heading as primary, laterally. Localiser, VOR tracking, NDB tracking…
Traditionally, yes. The question is if this is still a good idea when you have the actual track displayed.
You would want the heading bug driven from the GPS track, for a start… There is no such device. You can perhaps configure an RMI pointer presentation? Normally GPS lateral data is presented as a deviation bar, which is useless for flying a “direction”.
huv wrote:
But a Great Circle is defined by its (ever changing) track, not by heading.
Infinitely many geodesics satisfy that definition.
huv wrote:
but is [a stabilised heading] really required for safe and practical IFR operation in the future?
An alternative using GNSS-derived track is not resilient to remote interference or regional selective availability errors.
Peter wrote:
Surely, they should fly the heading as the primary lateral reference. In all “instrument flight” you fly the heading as primary
Yes, but the heading is mainly used for reference when making tracking adjustments. Use of GPS track takes the guesswork out of that so you can intercept and maintain localiser/radial/track with more precision and less effort.
Flying en-route, I am sure that most pilots agree that the desired track is followed easily using GPS track, without heading information. But I find that even flying an ILS based on GPS track only (without heading information) is quite easy. I would in fact prefer track-only information over heading-only to get and keep the needle in the middle.
Hence my question. Why do we base practical navigation on heading? Why not track?
Peter wrote:
bug driven from the GPS track, for a start… There is no such device
Yes, the Garmin G5 unit has that when used in AI/PFD mode. And certified autopilots are emerging that will fly “Track Hold”.
Qalupalik wrote:
An alternative using GNSS-derived track is not resilient to remote interference or regional selective availability errors.
I agree. That could very well be a reason for the “stabilised heading” requirement to remain for some time to come.
But even that I see that as an argument in favour of better navigation redundancy, not against using track rather than heading as a principle.
The tendency is there, in the equipment. When trained to fly e.g. the Garmin 1000 glass suite, some emphasis is on the “white line” on top of the HSI telling the GPS track, because using that makes any procedure easier to fly.
The question is whether it is desirable to speed up the transition towards flying track (vectoring: “fly track 220”?). Could we eventually fly IFR with (a crude) heading information only for line-up check and as a backup for use in emergencies. With a whiskey-compass, or maybe a cheap INS unit.
And certified autopilots are emerging that will fly “Track Hold”.
Autopilots have been able to intercept and track a GPS source ever since GPS came out. In terms of avionics wiring it is very similar to intercepting and tracking a VOR.
Peter wrote:
Autopilots have been able to intercept and track a GPS source ever since GPS came out. In terms of avionics wiring it is very similar to intercepting and tracking a VOR.
Exactly. Adding “track hold” mode is just one button and very little extra software. What has been missing is agreeing how best to use the ever more available track information in IFR flying techniques & procedures. Including when to downplay the role of heading.
