CHANGEOVER POINTS
When flying airways, pilots normally change frequencies
midway between navigation aids, although there
are times when this is not practical. If the navigation
signals cannot be received from the second VOR at the
midpoint of the route, a changeover point (COP) is
depicted and shows the distance in NM to each NAVAID,
as depicted in Figure 3-15 on page 3-12. COPs indicate
the point where a frequency change is necessary to
receive course guidance from the facility ahead of the
aircraft instead of the one behind. These changeover
points divide an airway or route segment and ensure
continuous reception of navigation signals at the prescribed
minimum en route IFR altitude. They also
ensure that other aircraft operating within the same portion
of an airway or route segment receive consistent
azimuth signals from the same navigation facilities
regardless of the direction of flight.
![](images/chapter_3_11.jpg)
Where signal coverage from two VORs overlaps at the
MEA, the changeover point normally is designated at
the midpoint. Where radio frequency interference or
other navigation signal problems exist, the COP is
placed at the optimum location, taking into consideration
the signal strength, alignment error, or any other
known condition that affects reception. The changeover
point has an effect on the primary and secondary obstacle
clearance areas. On long airway or route segments,
if the distance between two facilities is over 102 NM
and the changeover point is placed at the midpoint,
the system accuracy lines extend beyond the minimum
widths of 8 and 12 NM, and a flare or spreading outward results at the COP, as shown in Figure 3-16.
Offset changeover points and dogleg segments on airways
or routes can also result in a flare at the COP.
![](images/chapter_3_11_1.jpg)
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