Casey,

First the warnings and caveats: I have not had to fly a DME arc in 15 years
and I have never flown the KLN-89B.

Your idea of using VMG (velocity made good) is excellent for the DME arc.
From what I can quickly skim in the link to the .pdf operator's manual
provided in this thread by John Mireley,
http://riwg.cap.gov/docs/KLN89B_Manual.pdf, it appears that the KLN-89B does
not offer VMG. I don't know of any IFR receivers that do.

Go to 196 of 244 of the .pdf file where you will find the navigation terms
defined. In the second diagram of the page you will see the terminology for
a DME arc. If the approach has an arc and you have selected the approach on
the KLN-89B, I would think that you should be able to fly the arc leg just
like any other line, except that it curves. You should be able to turn so
the TK matches the DTK to parallel the arc. This DTK will change throughout
the arc to indicate the DTK for the tangent of the arc. Make slight
adjustments to the TK with respect to the DTK to manage the XTK, which
should be zero. To the best of my knowledge, most IFR receivers should work
in this way.

Back to your idea. A similar method to the one you described of flying with
a VMG of zero can be accomplished by flying with the BEARING and TRACK being
90 degrees apart when the VOR is the active waypoint. In the case of using
the KLN-89B or any IFR receiver for a DME arc on an approach in the database
this would not work because the reference VOR would not be the waypoint.
Most handheld GPS receivers have a data field called TURN. TURN is the
difference between TRACK and BEARING. Thus, keeping TURN at 90 should
accomplish this task when the active waypoint is the reference VOR.
Increase TURN to widen the arc and decrease TURN to tighten the ARC.

Targeting TURN to 90 instead of VMG to zero has an advantage in that TURN
is such a useful field it should be displayed already. VMG is not generally
useful and would require the extra distraction of changing a data field to
display it.

Obviously, a handheld GPS is not a substitute for either a DME or IFR
certified GPS and is strictly a tool for situational awareness.


John Bell
www.cockpitgps.com


"Casey Wilson" wrote in message
...
Hello all,

Anybody know of an available function in the KLN-89B that shows
'velocity made good?' That is, if you are not flying directly toward a
waypoint, what is the closing velocity? Groundspeed, as reported, is
relative to the velocity vector, so that isn't the correct figure.
Why? you ask. Well, I had a chance to fly a DME arc with a DME.
Don't
laugh, it was actually my first experience with DME. The instrument
reported
the heading and closing speed. Click, the light came on! When my
aircraft's
velocity vector was normal to the waypoint, the speed was zero. For me,
that
dropped the workload of flying the arc way, way down. The Skyhawk SP that
I
mostly fly ain't got no DME but it does have a KLN-89B. Unfortunately, the
limited user information available says nothing about the feature I'm
looking for.

Regards,

Casey Wilson
Freelance Writer and Photographer