Sandel
Avionics
SN3308 Navigation Display
Installation Manual
90106-IM-G(4) Installation Manual W SIG.doc
Page 11
Internal slaving requires connection of the flux gate excitation to the SN3308 flux gate
reference input P1-7. This input is used only to demodulate the flux gate signals.
Synchro DG’s require the master 400Hz inverter to be connected to the SN3308
400Hz reference input P2-4. This input is used to lock all 400Hz inputs and outputs
in the SN3308. This input presents no loading to the source.
Follow the information on the installation drawings, and plan to set up the appropriate
compass selections on the compass system maintenance page.
Slaving does not require the use of an external slaving accessory. Compass
calibration is performed using the SN3308 Compass maintenance page and offers a
unique 4-quadrant setup with no interaction between N-S-E-W. The SN3308 will
provide standby heading operation from the flux gate alone in the event of directional
gyro (DG) failure.
The SN3308 has a 3-wire ARINC 407 synchro bootstrap compass output if required.
(Software 1.05 and later).
1.4.2 GPS (Loran) Switching
The SN3308 has 3 Darlington open collector relay output discretes which operate
when the pilot selects NAV-2, GPS-1, or GPS-2 respectively. These outputs are
restricted to 35ma maximum current – do not exceed 35ma on serial numbers 2699
and below. These outputs pull only to within 1 volt of ground. Serial numbers 2700
and above have 250ma maximum current. Serials numbers 2700 and above outputs
pull to within 1 ohm of ground. Check to insure the remote switching relay is
compatible. If a multi-coil relay is used the SN3308 should be configured to drive the
first coil and a contact from the first coil can then be used to drive the remaining coils.
Nav 1 selection is the default selection and no relay driver output discrete is available.
The NAV-2, GPS-1, or GPS-2 outputs can be used to operate a switching relay for
each source, allowing the pilot to control the nav source selection from the front panel
of the SN3308. This is referred to as “master” mode and it is the preferred mode of
installation. In this configuration an additional remote switch/annunciator panel for a
GPS receiver is not required.
In the event the aircraft has an existing GPS switch/annunciator panel or it is desired
that one be installed, the “GPS SELECTED-” input (P2-30) on the SN3308 is used to
remote sense the selection of the GPS-1 and annunciate the selection. This is
referred to as “slave” mode. It allows annunciation of the selection on the SN3308
but does not use the front panel NAV switch to select the GPS receiver. This mode is
only available for use with a single GPS.
Master/Slave mode selection is done in the NAV maintenance page.
The SN3308 can be configured to accept a RELAY SENSE input, which provides
feedback as to the actual state of the switching relay. A single pole on the relay is
