Eventide ARGUS 5000 - Page 221

Heading Source Wiring Detail
Heading information, if available, is used by the Argus to orient the moving map in the
direction the aircraft is travelling. The Argus can also use GPS or Loran ground track
information for this purpose, and if heading is not connected or goes invalid, this is the
is^ only source of orientation. Heading is valuable when:
! The aircraft is not moving, moving slowly, or hovering, because there is no
ground track or track is unreliable.
! A non-GPS source (Loran) is being used, because there's a significant time lag
between aircraft maneuvering and Argus updating.
! It is used to orient the heading "card" behind the ADF needle. Heading MUST
be used for an installation to be IFR-approvable.
For the Argus to use heading information, it requires ARINC 407 Synchro output from
a bootstrap unit. (You cannot connect it directly to a heading gyro.) It also requires
a 28VAC 400Hz excitation signal to provide a reference for the synchro, and the
heading must be valid, as determined by the heading source.
Most heading problems are a result of using an excitation (reference) signal that is not
* j derived from the same source (frequency and phase) as that which drives the bootstrap.
If the needle slowly rotates or flips back and forth between one position and one 180
degrees opposite, this is the first thing to suspect. If the needle doesn't rotate with the
heading indicator, but suddenly flips 180 degrees as the compass is rotated, it usually
indicates that one synchro phase isn't connected. If there is a constant offset between
the compass and the Argus heading, it could mean that the bootstrap synchro is offset
on its shaft. An oscilloscope connected directly to the Argus pins is usually the best
way to troubleshoot heading problems.
If you cannot obtain a HDG indication, it may mean that the VALID line is "flagged."
The Argus is looking for, as determined in SETUP, either 28V or ground on this line.
If the line is floating or at the wrong voltage, the Argus reverts to TK (track). If the
heading source cannot be made to switch between these voltages when flagged and
valid, then the Argus valid line should be grounded and "LOW" should be selected in
— SETUP.
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July 1999 Argus 5000/7000 Ver. 5.xx Reference Manual Part#141003 217