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There may come
a time when a pilot is not able to make it to
the planned destination.
This can be the result of unpredicted weather
conditions, a system malfunction, or poor preflight
planning.
In any case, the pilot needs to be able to safely
and efficiently divert to an alternate destination.
Risk management procedures become a priority
during any type of flight diversion and should
be used the pilot. For example, the hazards
of inadvertent VFR into IMC involve a risk that
the pilot can identify and assess and then mitigate
through a pre-planned or in-flight diversion
around hazardous weather. Before any cross-country
flight, check the charts for airports or suitable
landing areas along or near the route of flight.
Also, check for navigational aids that can be
used during a diversion.
Risk management is explained in greater detail
in Chapter 2, Aeronautical Decision-making.
Computing course, time, speed, and distance
information in flight requires the same computations
used during preflight planning. However, because
of the limited flight deck space and because
attention must be divided between flying the
aircraft, making calculations, and scanning
for other aircraft, take advantage of all possible
shortcuts and rule-of-thumb computations.
When in flight, it is rarely practical to actually
plot a course on a sectional chart and mark
checkpoints and distances.
Furthermore, because an alternate airport is
usually not very far from your original course,
actual plotting is seldom necessary.
The course to an alternate destination can be
measured accurately with a protractor or plotter
but can also be measured with reasonable accuracy
using a straightedge and the compass rose depicted
around VOR stations.
This approximation can be made on the basis
of a radial from a nearby VOR or an airway that
closely parallels the course to your alternate
destination.
However, remember that the magnetic heading
associated with a VOR radial or printed airway
is outbound from the station.
To find the course to the station, it may be
necessary to determine the reciprocal of that
heading.
It is typically easier to navigate to an alternate
airport that has a VOR.
After selecting the most appropriate alternate
destination, approximate the magnetic course
to the alternate using a compass rose or airway
on the sectional chart. If time permits, try
to start the diversion over a prominent ground
feature.
However, in an emergency, divert promptly toward
your alternate destination.
Attempting to complete all plotting, measuring,
and computations involved before diverting to
the alternate destination may only aggravate
an actual emergency.
Once established on course, note the time, and
then use the winds aloft nearest to your diversion
point to calculate a heading and GS.
Once a GS has been calculated, determine a new
arrival time and fuel consumption.
Give priority to flying the aircraft while dividing
attention between navigation and planning.
When determining an altitude to use while diverting,
consider cloud heights, winds, terrain, and
radio reception.
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