When doing approaches, I do tend to mostly fly the track diamond on the HSI. Makes lateral guidance extremely easy.
Airborne_Again wrote:
if the GS is zero, then the heading is irrelevant!The track may be, but the heading is not.
Peter wrote:
You would want the heading bug driven from the GPS track, for a start… There is no such device.
EFIS systems have track indications, e.g. G5 and G1000. New autopilots like GFC500 have track hold mode in addition to heading hold mode.
I may have wires crossed but my KFC225 can fly a GPS track, etc.
What I was getting at earlier is that the heading bug is a very clear thing in your primary field of view and it is there for a reason – in most phases of flight one is flying a heading.
One could well argue that “classical IFR” is obsolete in places, and a track-driven “heading bug type object” would be more useful for some things, and indeed I use the GPS track value when flying e.g. the outbound leg of an IAP or a hold (because it gives me a wind-corrected track), but currently most people don’t have such a thing, and you still have to have a rough stab at the heading to fly, before tweaking it to achieve the desired track.
Peter wrote:
I may have wires crossed but my KFC225 can fly a GPS track, etc.
Yes, it can fly a track to a waypoint, but I’m talking about flying a track without reference to a waypoint.
OK, yes, though that can usually be adequately achieved (in most scenarios where it is required) by using the OBS mode.
There are some real challenges there for non-INS equipped aircraft. GPS will give you a true heading in general, but only when moving. To initialise the heading in some sort of AHRS you would need a dual GPS system like this (this uses a GPS phase difference; very clever – I spoke to the designer of that product the other day) and then it could use a fluxgate as normal followed by mag to true conversion based on GPS location. Or do all ground ops using mag heading.
No wonder it’s Canada who proposed it – they are the worst affected both by the magnetic declination as such and by its annual variation.
Interesting. I had no idea Canada was pushing for this. All fine when you are moving and have electricity for your avionics. What will replace the compass? Some form of mini GPS?
Interesting reference to professional mariners using only True North. I taught sailing while growing up, but don’t know anything about professional practices.
I was boating this summer on the West Coast of Canada (17 degrees of declination). Very foggy (IFR?) conditions. Navionics, a popular charting app, would only display my heading in True, I was steering with a big compass in front of me and was irritated that I couldn’t find the sub-menu to change the settings to display Magnetic headings. I have just looked it up now, and there is no such option! A brave new world!
Not such a big deal in London (UK – 0.44 degrees of variation), but it is interesting when the runway numbers in Canada change because of the rate of change in variation!!
Canuck wrote:
it is interesting when the runway numbers in Canada change because of the rate of change in variation!!
Our local airfield is changing runway numbers early next year from 05-23 to 04-22.
INS chips are so inexpensive and accurate I am surprised that they have not been more widely incorporated into GA avionics.
