Aspen Avionics EFD1000H PFD, Руководство пилота

Страница: 74 / 213

CHAPTER 4
REFERENCE GUIDE
EFD1000H PFD Pilot’s Guide
Page 4-5
091-00012-001 REV C
4.1.3. Heading
The PFD ADAHRS also includes a slaved compass system that provides accurate
magnetic heading indications throughout most operating conditions and phases
of flight. Its electronic gyros compensate for turning and acceleration errors, and its
remote fluxgate compensates for gyroscopic precession errors, so there is no need for
the pilot to adjust heading throughout the flight. Nonetheless, all compass systems are
subject to some error, and the pilot should be aware of when and how the PFD heading
indication can be affected.
The earth’s magnetic field is measured directly by a 3-axis fluxgate magnetometer built
into the Remote Sensor Module (RSM), and magnetic heading is derived from the flux
on a plane perpendicular to gravity, providing immunity from pitching and rolling
effects. Electronic gyros and accelerometers in the PFD system are then used to stabilize
that raw heading data to eliminate the short-term turning and acceleration errors seen
in traditional magnetic compasses.
Together, these systems provide accurate heading indications even during aggressive
maneuvering. The gyros stabilize magnetic errors while maneuvering and are slaved
to the fluxgate, which continuously updates heading to compensate for gyroscopic
precession. The end result is a compass system that requires no pilot action to show
accurate magnetic heading throughout the flight.
Just like other compass systems, the accuracy of the fluxgate is affected by its location
on the airframe. Ferrous metal structures, electrical fields 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 affect the accuracy of the compass. The installer can compensate
for much of this interference when calibrating the RSM, but some effects cannot be
eliminated. Proper location of the RSM during installation of the PFD is critical to the
AHRS performance and accuracy.