| CHAPTER 3. Navigation
Common Error: Displaying the Wrong Navigation
Source
The annunciations showing which navigation sources are
displayed on which navigation instruments are often small, so
there is significant potential for displaying a navigation source
other than the one you intended to select. The consequences
of losing track of which navigation signals you are following can be significant: you may think you are steering along one
course when in fact you are steering along a different one.
Be sure to verify these settings prior to departure, and again
each time you make changes to any navigation instrument.
Some installations compound this potential with automatic
source switching. The most common switching mode is a
GPS source to be automatically deselected when the VOR is set to an ILS localizer frequency and a signal is present.
Typically, that is not a problem since the pilot intends to
switch to the ILS anyway. However, the error arises upon
missed approach, when the pilot selects another frequency
to follow a VOR missed approach routing. At that point,
some units revert back to the previous GPS or other RNAV routing selected instead of the VOR frequency that the
pilot just picked. This can result in gross navigation errors
and loss of obstruction clearances. In some units, this is a
shop programmable or jumper selected option. Check your
unit’s features. Always check for correct navigation source
selection and cross-check against the published procedure.
Be ready and able to fly and navigate manually.
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