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lift, can extend the achieved glide considerably.
Many models of electronic glide calculators now exist.
Often coupled with an electronic variometer, they
display the altitude necessary for distance and wind
as input by the pilot. In addition, many electronic
glide calculators feature speed-to-fly functions that
indicate whether the pilot should fly faster or slower.
Most electronic speed-to-fly directors include audio
indications, so the pilot can keep eyes outside the
cockpit. The pilot should have manual backups for
electronic glide calculators and speed-to-fly directors
in case of a low battery or other electronic system
failure.
Figure 11-2. Navigational plotter.
Figure 11-3. Circular glide calculator.
11-4
Other equipment may be needed to verify soaring performance
for Federation Aeronautique Internationale
(FAI) badge or record flights. These include turn-point
cameras, barographs, and GPS flight recorders. For
complete descriptions of these items, as well as badge
or record rules, check the Soaring Society of America
web site (www.ssa.org).
Finally, a notepad or small leg-attached clipboard on
which to make notes before and during the flight is
often handy. Notes prior to flight could include weather
information like winds aloft forecasts or distance
between turn points. In flight, noting takeoff and start
time, as well as time around any turn points, is useful to
gauge average speed around the course.
NAVIGATION
Airplane pilots navigate by pilotage (flying by reference
to ground landmarks) or dead reckoning
(computing a heading from true airspeed and wind,
then estimating time needed to fly to a destination).
Glider pilots use pilotage since they generally cannot
remain on a course line over a long distance and do not
fly one speed for any length of time. Nonetheless, it is
important to be familiar with the concepts of dead reckoning
since a combination of the two methods is sometimes
needed.
USING THE PLOTTER
Measuring distance with the plotter is accomplished by
using the straight edge. Use the Albuquerque sectional
chart and measure the distance between Portales Airport
(Q34) and Benger Airport (Q54), by setting the plotter
with the zero mark on Portales. Read the distance of 47
NM to Benger. Make sure to set the plotter with the sectional
scale if using a sectional chart (as opposed to the
WAC scale), otherwise the measurement will be off by
a factor of two. [Figure 11-4]
The true heading between Portales and Benger can be
determined by setting the top of the straightedge along
the course line, then slide it along until the index hole is
on a line of longitude intersecting the course line. Read
the true heading on the outer scale, in this case, 48°. The
outer scale should be used for headings with an easterly
component. If the course were reversed, flying from
Figure 11-4. Measuring distance using the navigational plotter.
11-5
Benger to Portales, use the inner scale, for a westerly
component, to find 228°. [Figure 11-5]
A common error when first using the plotter is to read
the course heading 180° in error. This error is easy to
make by reading the scale marked W(270°) instead of
the scale marked E (090°). For example, the course
from Portales to Benger is towards the northeast, so the
heading should be somewhere between 30° and 60°,
therefore the true heading of 48° is reasonable.
Calculating heading and groundspeed when there is a
crosswind component along the course can be done by
using the wind triangle. [Figure 11-6] Suppose the
course is 50°, the true airspeed (TAS) is 70 knots, and
the wind at cruise altitude is 190° at 20 knots. On a sheet
of paper, draw a line representing north-south. Mark a
reference point midway along the north-south line, and
draw a line along 50° using the plotter and label it C
for course. Designate the original point along the
north-south line as point A. Next, using either the WAC
or sectional scale on the plotter, draw a line from the
reference point A along 190°. Make this line 20 miles
long and label it W for wind. Mark the end of the line
point B. Set the 0-mile mark on the plotter straightedge
at point B and rotate the plotter until the 70-mile mark
intersects line C. The heading can be obtained from the
new line (label it H) and is found to be 61°. The
groundspeed is determined by measuring the distance
point B and where the H line intersects line C and is
found to be 84 knots.
Construction of the wind triangle is useful if cruising in
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Glider Flying Handbook(151)
