Re: [Flightgear-devel] RFD: FlightGear and the changing state of air navigation

[Stuart B. <stu...@gm...>]

Hi David,

On Tue, Jul 4, 2017 at 12:29 PM, David Megginson wrote:
> To make the discussion a little more concrete, here's an example. When
> you're flying an IFR approach with a GPS navigator, you can use RNAV for the
> transitions, but need to switch to the ground ILS transmitter for the actual
> approach (they both use the same CDI on many planes, so it's easy to miss).
> The GTN 650 that I'm installing in my plane will switch CDI mode
> automatically under certain conditions, but it's not guaranteed.

The FG Route Manager provide the RNAV function
(http://wiki.flightgear.org/Route_manager), plus logic to connect it as an
autopilot source. Switching the CDI to an ILS at the end of the route is pretty
straightforward: just put a Nasal listener on
/route-manager/signals/finished and
then check for a decent ILS signal.

>From a quick glance looking at the GTN 650 and seeing what it does, and thinking
of how each of the main pages would map to FG function, I think we've
got most/all
of the underlying generic function and data  sources required.  "All"
that is required
is connecting them together into a coherent instrument.

Here's the list of main pages and how they would map:
1) Map - We already have mapping solutions, and the canvas one would
seem to get most of the way there
2) Traffic - Again, we've already got AI objects displayed on in-sim
maps, so this is done
3) Terrain - Slightly trickier.  Depending on the resolution required,
we could do some terrain sampling and colour a canvas?
4) Weather - This looks much more challenging.  Not sure if we could do this.
5) Default Nav - this is just some straightforward property display
6) Flight Plan - This is a UI interfacing the FG Route manager.
Frankly, I suspect we'd
probably just bring up the existing Route Manager dialog at this
point, as entering a
route via a simulated touchscreen doesn't sound like a fun way to
spend a Sunday afternoon! :)
7) Proc - Setting the STAR/SID to use.  We already have this function
in the Route Manager.
There is an issue with getting the underlying data, though there are
tools to upload Navigraph into
the Route Manager.
8) Nearest - This is just a lookup into our existing airport and fix DBs.

So, I think most of the fundamentals are there - it's "just" a case of
combining them into an
instrument that mimics the GTN 650.

James Turner would hopefully have useful input, but given he hasn't responded
already I suspect he's on holiday.

-Stuart