BendixKing KLN 94 - Pilots Guide - Manual (Page 61)

3.7. INITIALIZATION AND TIME TO FIRST FIX
Since the KLN 94 stores its position and other required parameters in
memory when power to the unit is removed, it is seldom necessary to aid
the unit in reaching a NAV ready condition. The time required from power
on until the KLN 94 determines its present position and is therefore ready
to navigate is called “time to first fix.” The time to first fix is normally a few
minutes or less. In order for the KLN 94 to reach a NAV ready condition, it
is necessary to meet the following conditions:
1. The KLN 94’s “almanac” data should be current. Almanac data is
orbital information for all the satellites and is used for initial acquisition
when the KLN 94 is first turned on. This data is stored in the
KLN 94’s non-volatile memory and is considered current for up to six
months. Each satellite sends almanac data for all satellites. Since
the KLN 94 routinely updates the almanac data during normal opera-
tion, the almanac data will become out of date only if the KLN 94
hasn’t been used for the previous six months or longer. Collecting
new almanac data takes place automatically if the data is more than
six months old. If the almanac data is out of date and needs to be col-
lected, the KLN 94 will take approximately 12 minutes to acquire your
present position. The Self Test, Initialization, and Database pages
should be approved.
2. The aircraft must be located such that the GPS antenna has an unob-
structed view of the sky so that required satellite signals are not being
blocked. If possible, position the aircraft away from hangars or other
obstructions.
3. It is very helpful for the KLN 94 to have the correct time, date and
position to be able to determine which satellites should be in view.
This information is stored in the battery backed memory of the KLN 94
so it is not normally required to update it. If the KLN 94 has the correct
time, date and position, then the time to first fix will usually be less
than two minutes. If this information is not correct, then the KLN 94
will start to look for any satellites. Eventually, the KLN 94 will find
enough satellites to determine the position of the aircraft. This process
can take as long as 12 minutes. It is possible for you to update this
information manually, which will allow the KLN 94 to reach a NAV
ready status much faster. To set the time and date follow steps 5 and
6 in section 3.2, “Turn-On and Self-Test.” The initial position is usually
set during turn-on and self-test, but if for some reason it is necessary
to update the position after the power-on sequence, then use the fol-
lowing steps. Remember, if acquisition time is not important then it is
not necessary to update the time, date or position.
KLN 94 Pilot’s Guide Chapter 3 Basic GPS Operation
3-19