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Posted for "John Barrett" <2thman@olympus.net>:
This is an interesting topic because it's now been almost 15 years since GPS
became available to us GA guys (I bought my Garmin 150 in 1989) and now GPS
is used probably by 90% or more of all aircraft flying in the US (my guess).
Still the AIM and the powers behind it tell us they want heading and
indicated a/s instead of ground track and ground speed. The latter two
pieces of info are of infinitely greater value. Following the official
rules requires the controller to interpolate, calculate and use the SWAG
mtehod (scientific wild ass guess) to determine your trajectory. His CRT
is not accurate enough to do this with particularly great precision, so he
ends up with a rather fuzzy idea of what's really happening - sort of like
the difference between an NDB approach and an ILS.
We'll continue to follow the rules but maybe some day the FAA will
accidentally fall awake and make the simple improvement of allowng the
controller and pilot to work with the best data available to them..
BTW, when I ask for a direct clearance on an IFR flight plan, whether I'm
in VFR or IFR conditions, I tell the controller the intended track over the
ground and the distance to the asked for fix, and 9 times out of 10 I get
the clearance. I still use the /A code in my flight plan so there is no
confusion about my GPS not being IFR approved.
I believe most controllers are likely to use the best information you give
them - just make sure you clearly let them know what data you are passing
on - don't let them think you're giving them a heading when you mean your
track over the ground, etc.
Regards,
John Barrett
Actually a controller is not interested in the ground track that you
intend
to fly. The pilot/controller glossary ...snip...
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