On 09/15/09 06:31, Curtis Olson wrote:
> I believe the original intent was to make the system function in away that
> made it appear that whatever approach you were trying to fly was the one
> that was turned on.
We agree that was the original intent. However it
was doomed from the start, because navradio.cxx
has never had any workable way of divining which
approach "you were trying to fly".
> So biasing the choice based on which approach you are
> most likely to be flying seems to make some sense. You don't care about
> aircraft heading because (I don't know) maybe you do a 180 because you get
> lost or you want to fly back and start over again, or whatever. The active
> glideslope & dme & ils transmitters should change when you turn away from
> the airport. The important thing is which end of the runway you are off of.
We agree that basing it on heading doesn't work,
because you might be approaching the airport from
upwind and need to make a 180 to get established
on the final approach course.
But basing it on position doesn't work either, and
is arguably worse, because
a) You might be approaching the airport from upwind,
and
b) more importantly, you might need to fly the missed
approach segment. Missed approaches are a matter
of life and death in the real world. As the saying
goes, if you are not prepared for the miss, you are
not prepared for the approach.
> I think we can concede that we don't have real world controllers turning
> approaches and lighting on and off for us on the ground.
That's not the right question to be asking. There
are ways of achieving acceptable verisimilitude without
having to hire actual real-world certified tower
controllers. FGFS already solves problems that are
vastly more complicated than reversible ILSs.
> So either we
> create an elaborate system and force the user to make all these detailed
> choices every time we start up the sim, or we create some functional
> defaults that behave like people would expect, and allow people to easily
> use the simulation to practice flying any published approach.
No, those are not the only options.
No, a workable system does not have to be elaborate.
No, we do not need to force ordinary users to do
anything at startup.
> I think it's pretty important to be able to fire up FlightGear and practice
> any published approach without needing to go through contortions or
> elaborate setup proceedures,
Agreed. Right now *none* of the reversible ILSs are
flyable, because of the aforementioned unrealistic
behavior when approaching from upwind, and wildly
unrealistic behavior on the missed approach segment.
> or having to repeatedly restart the sim until
> the particular approach we are interested randomly is enabled.
Flying an ILS with a tailwind and then following the
published circle-to-land procedure is not unreasonable.
Indeed it is a good thing to practice.
In the real world you cannot just show up at KJFK and
demand that they turn on the ILS "you are interested in".
It is realistic to choose what airport you are interested
in flying to. It is not realistic to dictate that the
approach in use will be the one "you are interested in".
Glendower: I can call spirits from the vasty deep.
Hotspur: Why, so can I, or so can any man;
But will they come
when you do call for them?
> FlightGear
> is used as part of FAA certified flight training devices so this is an area
> of the code where the basics need to work and be solid, and then if we want
> to get fancy and add additional realism, that's great.
There is a lot of room for compromise between "fancy"
and "wrong". Right now it is wrong, as has been
pointed out repeatedly over the years. It can be
improved quite a bit without getting fancy.
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