Lowrance 100 Installation And Operation Instructions Manual page 76

Vertical Navigation
The AirMap 100 can help you decide when to let down
for an approach to an airport. To use this feature, first
press the MENU key, then highlight the "E6B Computer"
label. Now highlight the "Vertical Navigation" label as
shown at right and press the right arrow key. A screen
similar to the one at right appears. It's inactive at this
time.
We are travelling to the Wichita Mid-Continent airport
in Wichita, Kansas. It's identifier is shown at the bottom of the screen -
ICT. We are travelling at 4500 feet, and need to be at the pattern altitude
(about 2300 feet) by 5 nautical miles from the airport using a 450 fpm
descent.
After determining the above data, highlight each item
on this screen and enter the data. When you're finished,
highlight the "Vertical Nav" label at the top of the screen
and press the right arrow key. A screen similar to the
one below appears.
The solution to our vertical navigation problem shows
at the bottom of the screen. Our current altitude is 4500
feet and at our current airspeed, we should begin our
descent in 41 minutes and 8 seconds. If we maintain a
450 fpm descent in about 48 minutes, then we should
reach pattern altitude 5 nautical miles before we reach
the airport.
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