Aspen Avionics Evolution EFD1000 VFR PFD - Free Gyro Mode

CHAPTER 4 REFERENCE GUIDE
EFD1000 VFR PFD Pilot’s Guide
Page 4-6
091-00028-001 ( )
Just like other compass systems, the accuracy of the uxgate is aected by its location
on the airframe. Ferrous metal structures, electrical elds produced by motors, pumps,
wiring, magnets in cabin speakers and other airframe-related sources of interference
either constant or momentary (i.e. operating an electric trim motor, windshield heat,
pumps, etc) can all aect the accuracy of the compass. The installer can compensate
for much of this interference when calibrating the RSM, but some eects cannot be
eliminated. Proper location of the RSM during installation of the PFD is critical to the
AHRS performance and accuracy.
Furthermore, all magnetic compass systems are susceptible to local disturbances in the
earth’s magnetic eld (some of which are shown on aviation charts or by NOTAM) and
will exhibit degraded performance when operating in extreme northern and southern
latitudes close to the earth’s magnetic poles.
4.1.4. Free Gyro Mode
When the PFD system detects that the horizontal component of the earth’s magnetic
eld is no longer strong enough to provide reliable heading data, the PFD will detect
the condition and annunciate that the heading system is no longer slaved to magnetic
north. If the condition persists, attitude and heading indications are removed.
While the condition can occur at greater distances, it is most likely to be observed
within 750 nautical miles from the magnetic poles. In the Northern Hemisphere, this
equates to operations in the Arctic Islands found north of continental North America.