User Guide

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CAL8 PAGE
Finally, this
is a handy one if
you want to avoid
those “fly-by
night” operations.
Since the GPS system has to maintain an accurate astronomical
almanac to know when and where to expect to find its satellites, it
didn’t take much additional computation power to add the
ephemeris figures for the sun.
When you first select this function, it displays predicted
sunrise and sunset for the flight-plan destination; based on current
date and current system time zone. Any of these values, however,
can be changed - for example, try checking it for your next birth-
day...in Paris! Click in the reference waypoint, date, and time
zone fields to get the corresponding sunrise and sunset.
NRST (NEAREST) PAGES
These pages
can be accessed
at any time by
pressing the NRST
key. When you
first access this
function, you’re given a list of categories - nearest airport, nearest
VOR, nearest CTR, etc. Just in case you’re in trouble, the page
always comes up with the cursor already sitting on APT, so if you
need directions to the nearest airport, fast - say, the engine just
quit! - all you need to do is hit NRST and select the desired way-
point type..
This will bring up a page showing the distance and bearing
to the nearest airport, as well as its identifier, name, altitude, and
the length and surface of its longest runway - all stuff it’s nice to
know in a hurry. You’ll also notice a number 1 next to the identi-
fier, indicating that it’s the “first nearest” of nine choices. Turning
the small right knob will scroll through the next choices, working
from nearer to further.
Now go to
the CAL 5 page;
the pressure alti-
tude will have
carried over from
CAL 4. Enter the current temperature, and the system will return
density altitude - the one that actually affects the performance of
your airplane. Click in the pressure altitude or temperature fields
to modify the density altitude.
CAL6 PAGE
This page
will figure out
your true airspeed
for you. Enter indi-
cated (calibrated)
airspeed at CAS by clicking in the corresponding field. If you’ve
used CAL 4 or CAL 5, the pressure altitude and temperature will
be carried over from them; otherwise, enter them now. The sys-
tem will return your true airspeed (TAS).
CAL7 PAGE
We can
continue to step
through these
linked calculator
functions; CAL 7
is used inflight to
determine actual (as opposed to forecast) winds aloft. If you’ve
used CAL 6 to determine your true airspeed, it’ll carry over; oth-
erwise, enter it at TAS by clicking in the corresponding field. Next,
enter an accurate heading from your directional gyro (you did
check it against the magnetic compass recently, didn’t you?). The
system will return actual wind, both in terms of headwind or tail-
wind component and in terms of true (not magnetic!) direction
and speed. Why true? Because that’s how winds aloft are report-
ed; magnetic directions are used only for airport surface wind
reports.
Appendices
Appendices