Sandel
Avionics
SN3308 Navigation Display
Installation Manual
90106-IM-G(4) Installation Manual W SIG.doc
Appendix-A Page 3
Note: When installing to existing wiring, ensure that the fluxgate center tap
which exists on some Honeywell (Sperry) and Collins fluxgates is not
connected.
b) Ensure the compass card rotation is correct by observing that the displayed
heading increases/decreases properly as the aircraft heading is changed or
the fluxgate is rotated by hand. If increasing the heading of the fluxgate yields
decreasing
heading card indication, reverse the X/Y leads. This will not affect
North as identified in step ‘a’ above.
c) Proceed to the calibration adjustment.
Use of Signal indicators (with Quadrant set to 0):
300
q
X=100-250 Y=0
0
q
X =150-350 Y=identical but opposite to X.
60
q
X=0
Y=100-200
These readings are informational and approximate. The maximum X/Y signal
is dependent on the fluxgate and is not critical as long as it falls within the
above ranges.
Use of Peaking adjustment:
At a heading of North where X and Y are numerically equal but opposite,
changing the Peaking adjustment should not allow increasing the X or Y level
more than 10%. This does not normally require adjustment but can be used
to verify proper operation. The larger ARINC style Sperry, Honeywell, Collins
fluxgates use setting “0”, and the smaller King, STEC (Humphrey) fluxgates
use setting “6”.
Use of Excitation Lock indicators:
The EXC LOCK indicator shows the lock status of the internal fluxgate
demodulator and is shown for troubleshooting. When in normal operation, the
EXC LOCK will be a low number, ‘00’ being closer to perfect lock. Any
number 30 or above is considered out of lock and will after a three second
timeout cause a “Fluxgate Failed” error message to the pilot. If no fluxgate
excitation is present at all, the value will be ‘77’. It is normal for this number to
flicker from zero to a non-zero number during operation, and will depend on
the inverter/gyro used.
EXC VALID is the counter which counts up to 30 (three seconds) to trigger the
“Fluxgate Failed” error message to the pilot. If in the failed state the word
“INVALID” will show on the maintenance page.
