"Chris W" wrote in message
newsu6Vd.84$Ci7.63@lakeread07...
I guess I wasn't very clear in my first post.

Nope.

I know they all have the nearest airport feature and give runway length.
Lets say that I am flying along at 14,000ft and the engine starts doing
bad things. Since I was stupid and wasn't paying attention, I ask my GPS
where the nearest airport is. It tells me that there is an airport 5
knots to my left and 10 knots to my right.

You mean "nautical miles"? "Knots" is a measure of speed, not distance.

What it didn't tell me is the runway to the left was at an elevation of
10,000ft and the runway to the right was at an elevation of 5,000ft.

There aren't many airports around at 10,000'. And in mountainous terrain,
airports are usually (though not always, granted) found in the valley
floors. Terrain between you and a lower-altitude airport is probably more
likely to be a problem than a significant difference in altitude between two
choices.

Lets make the math simple and pretend there are 6000ft in a nautical mile.
To make the airport on the left you would have to maintain a glide ratio
of 7.5 to 1. To make the airport on the right you would need to maintain
a glide ratio of about 6.7 to.

So you actually want the least steep descent, not the steepest descent.

Obviously the runway to the right gives you more room to maneuver. This
is of course assuming there are no obstructions in your path. As another
poster pointed out, if you are flying over the rockies you better always
have a plan on where you are going to go if your loose power, you are just
asking for something bad to happen.

Now, you've written "loose" twice. It's "lose". I only "loose power"
during takeoffs and climbs.

Even from a single simulated flight over Colorado, it's pretty clear to
me, careful planing should go into any such flight in real life.

Indeed. That said, as I mentioned, there's at least one product out there
that displays 3D volumes (cones) to aid you in the exact decision making
you're asking about. Since your position relative to the cone depends not
only on your lateral distance, but your altitude above the airport as well,
it gives you the information you're thinking of. (Actually, while the data
is 3D, I believe it simply shows you a 2D cross-section of the cone on your
top-down map display)

That particular feature is not common though (only on one GPS navigation
unit that I'm aware of). I'm honestly not convinced it's really all that
necessary or useful except in very rare instances.

Pete