Honeywell KLN 900s Pilot's Manual page 175

NOTE: If the present track does not intercept the arc,
then the KLN 900 will display NO INTRCPT in the
scratch pad area of the screen.
8. When the aircraft approaches the arc the KLN 900
will provide waypoint alerting and turn anticipation to join
the arc.
9. Once established on the arc the KLN 900 provides
left/right guidance relative to the curved arc. Distance to
the active waypoint is the distance from the present posi-
tion to the active waypoint, NOT the distance along the
arc. Refer to Appendix A for the geometry of the arc.
10. During the arc, the desired track will be constantly
changing. To help you keep the orientation correct the
Super NAV 5 will automatically display the desired track
(DTK) on the sixth line. It is not possible to change this to
something else while on the arc. The value displayed for
the desired track will flash when the difference between
the CDI or HSI and the current desired track is greater
than 10°.
11. Some DME arcs have defined radials that serve as
step down fixes. These points are not stored in the
database. To help you determine your position relative to
these step-down points along the arc, the KLN 900 will
display a new value on the bottom line of the display on
the Super NAV 5 page. This new bit of information is
denoted by the letters ARC followed by three numbers.
The three numbers represent the current radial that you
are on relative to the reference VOR/DME. It is not possi-
ble to select any other type of information to display on
this line like you normally can. The arc radial is forced into
this position when the aircraft is 30 NM from the arc. The
arc display is shown in figures 6-26 or in figure 6-27. Just
watch this value and when it reads the same as one of
the step-down points you can descend as necessary.
This particular example does not have such points, but
there are quite a few approaches that do.
NOTE: Autopilot performance may not be satisfactory if
coupled in the NAV mode while flying the arc. Many
autopilots were never designed to fly curved paths. If
autopilot performance is not satisfactory while flying DME
arcs, select the HDG mode and keep changing the head-
ing bug to keep the D-bar centered.
12. As the aircraft approaches the end of the arc, the
KLN 900 will provide waypoint alerting and turn anticipa-
tion to the next leg.
13. When the aircraft is 2 NM from FOW VOR, the FAF,
the KLN 900 will attempt to transition to the approach
active mode. Since the DME arc procedure is flown
entirely in the LEG mode the only possible problem would
be if the integrity monitoring did not check out.
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