Northern Airborne Technology THxxx - Manual (Page 33)

SM06 Rev. 4.10 Tac/Com Control Head Manual
aircraft, such as Aerospatiale airframes, there are two dimmers, one of which MUST be
ON for normal daylight flight, to drive engine instruments. If this line is accidentally
used, then the display will always be at half intensity. A dimmer must be used that is
OFF during normal daylight flying, and ON during night flying for correct control head
operation. Early control heads (prior to Tac/Com II) did not have this automatic feature,
which has been added to improve night visibility by reducing display glare in the cockpit.
2.5.5
Amber (RX) Squelch light comes on, but no RX audio is heard.
Press the HELP/SQ button. If audio is heard, this means there is a problem either with
the subaudible tones, or with the AUDIO squelch setting. Refer to the CTCSS or
Subaudible Tone Table in Section 3.5.4.2 of this manual to check the CTCSS tone
format and frequency, and/or refer to the Power On Checks section (2.4.2) to check the
audio squelch.
2.6 Final Inspection
During the test flight, check levels and operation of all functions. Display brightness or
contrast may have to be tailored for adequate viewing by the flight crew. Ensure there
is no interaction between any transmit functions and received NAVAIDS, or any other
communication receiver functions. Antenna placement or cable routing may have to be
changed if these problems are encountered. Closely spaced antennas or coax cable
runs may cause problems, especially between VHF systems (AM & FM), and between
VHF transmissions and UHF receiving (due to third harmonic relationship), particularly if
the RT406F (with its less selective front end) is used in a complex system.
Ensure that there is no interaction between Tac/Com control head operation and ADF
performance. If interference exists, relocation or re-routing of the interconnect cabling
may be required.
Before leaving the aircraft, ensure that all the mating connectors are securely fastened
to the Tac/Com control head. Also ensure that the unit is securely fastened to the
aircraft from the front panel, and that all Dzus fasteners are locked.
If all functions are satisfactory, the aircraft may be released for service once all required
log entries, electrical load and weight and balance amendments are made, the flight
manual supplement is updated, and the required local regulatory paperwork is
completed. There is currently no Technical Standing Order (TSO) for FM
Communication systems, regardless of manufacturer.
2.7 Continued Airworthiness
Maintenance of the Tac/Com Series control heads is ‘on condition’ only. Periodic
maintenance of this product is not required.
Jan 4, 2006 Page 2-7
ENG-FORM: 805-0108.DOT
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