How
to interpret the
Along
TLacklCrosstrack Error chart
The illustrationshows four (4) flight
pathsto waypoints being offset varying
distancesfrom the VORTAC. You will
note that in flight path1the offset
distance iszero. Or, inother words, the
waypoint
is
locatedover the VORTAC.
Inthis case the along-track and
crosstrack error is minimum.This is
becausethe along-track error istotally
derived from the DME and the cross-
track error from the VOR.
Please note that the along-track and
crosstrack errors increase inflight
paths
2,
3
and
4,
as the waypoint off-
set perpendicular
to
the flight path
increases. For example, on flight path
4
where the waypoint isoffset
100
nm
perpendicular
to
the flight pathand
the aircraft is
100
nm from the way-
point. the aircraft can beanywhere
within a
5.7
nm square when the
crosstrack needle iscenteredand
the along-track (distance)indicator
is showing exactly
100
nmto go.
In summary, the illustration shows
that the accuracyof the RNAV system
is poorest when the waypoint offset
distance and the aircraft distancefrom
the VORTAC is large. On the other
hand, the RNAV accuracy
is
greatest
when the waypoint offset distance and
the distancefrom the VORTAC is small.
CAUTION: Like all RNAV installations,
each KNS
80
installationmust be
demonstratedto meet FAA Advisory
Circular 90-45A for IFR approval.
KNS
80
Systemapplications
The KNS
80
System, in addition
to conventional VOR/DME/ILS
navigation, providesmany advantages
related
to
its
RNAV functions:
Direct route navigation from point
of originto destination without following
the frequently circuitousVictor airways
is a basic use of RNAV. Determineyour
most direct route and set up waypoints
at intervals along that route.
(Remember, the KNS
80
stores the
frequency of each waypoint. You need
only to change waypoints.Other
systems require you
to
change
waypoint and VORTAC frequency.)
Location
of
airfields that are not
equippedwith navigation aids is a
common use of RNAV. Locatethe
airfield on your navigation chart and
place a waypoint at that location.
Set
up a holding pattern at any
geographic point convenientto you or
ATC. Simply establish awaypoint at
that location,then fly your patternjust
as
if
it were a real VOR station using
your course deviation needleand DME
for reference.
Locateweather breaks reported by
an
FSS
or controller. Establish a
waypoint at that location andfly directly
to it.
Determine time
of
ADlZ or
restrictedarea penetration. Establish a
waypoint at your planned point of
penetration. Fly directly
to
that
waypoint and you
will
be provided
continuousdistance and time-to-
waypoint on your KNS
80.
be established simply by using the
KNS
80
in VORlPAR function and
maintaining a constant course
deviationon your CDI (one nm per dot,
up to
&
5
nm full scale).
A route parallel
to
the airway but
farther out may be accomplished by
establishing waypointsthe same
distance out from each of the
VORlDME stations that define the
airway.
RNAV chartsfor RNAV Airway
HighAltitude), Approaches. SID’Sand
8
TAR’S are available.
A route parallel tg an airway may
9
