User manual

8 Avionics and Airframe
This chapter discusses XCSoar as a subsystem of the aircraft. It
covers the integration of XCSoar with external devices, includ-
ing GPS, switches and sensors, and aircraft radio transceivers and
other devices. Integration with FLARM is covered in Chapter 7,
and integration with variometers is covered in Chapter 6.
8.1 Battery life
Most modern PDAs are designed for short sporadic use and so do
not have a very good battery capacity when considering the dura-
tion of cross-country soaring flights. It is recommended to power
the PDA externally, via a transformer connected to the glider bat-
tery. This installation should be performed by appropriately qual-
ified personnel, and should contain a fuse and a manual isolation
switch.
The greatest cause of power drain by the PDA is the LCD back-
light, however domestic PDAs are not particularly bright so they
may need to have the back-light up full. However, for EFIS sys-
tems such as Altair, it is recommended to use the lowest back-light
settings that are comfortable.
When operating PDAs under internal battery, XCSoar detects a
low battery condition and allows the operating system to shut down
and preserve the memory. In addition, it can be set up to blank the
screen after a period of inactivity, so that it can reduce the power
consumption. When the screen is blanked, pressing one of the
hardware buttons on the PDA activates the screen again.
Another way to help conserve battery power is to reduce the com-
putational load by turning off certain features. Drawing terrain and
long snail trails contribute the most to the CPU load.
For Altair/Vega systems, the external supply voltage is displayed
on the system status dialog (see Section 8.8).
8.2 GPS connection
XCSoar requires a 3D GPS fix for its navigation functions.
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