Thomas Borchert wrote:

John,

And you cannot do that with a map and compass?


Yes, you can. You can also ride into town on a horse. Do you?

Some people do ride horses. For fun. The map and compass will eventually
reach the same point.

But let's discuss why this will be (or perhaps already is) so. Someone
spoke of accuracy, which is a good point. The more precisely I know my
location, the more accurately I can follow an approach. And that,
typically, means that the approach is usable in lower weather.

Another major factor is time. The advantage of sophisticated RNAV (be it
the old fashioned kind or the kind silly enough to use only one input: GPS)
is that it leaves more time available to the pilot for other tasks. It
makes it easier to avoid issues like icing or CBs because it leaves more
time for "weather management", for example.

RNAV is one more tool for staying ahead of the airplane.

- Andrew