User's Manual

TT21/TT22 Transponder Installation Manual 13 July 2009
00560-00 Issue AF
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Page 32 Trig Avionics Limited
6.2.2.1 Calibration Equipment
To calibrate the encoder you will need to be able to power up the transponder
subsystem, and you will need a pitot-static test set with the appropriate adapters
to connect to the static port on the aircraft. The pitot-static test set should be
able to drive the altitude down to sea level, and above the service ceiling of the
aircraft.
No transponder test set is required – the calibration procedure displays all the
information you need on the screen of the TC20
6.2.2.2 Calibration Procedure
There are four adjustment points on the altitude encoder, a low altitude
adjustment point, two mid-level adjustments, and a high altitude adjustment
point. The low altitude point adjusts the correspondence at sea level, the first
mid level point adjusts the correspondence around FL100, the second mid level
point adjusts the correspondence at around FL200, and the high altitude point
adjusts the correspondence at FL300 and above. Since the altitude limit of the
encoder is likely to be higher than the service ceiling of the aircraft, it is
sufficient to set only those adjustment points at or below the service ceiling of
the aircraft.
Note: DO NOT EXCEED THE ALTITUDE OR RATE OF CLIMB
LIMITS OF THE PITOT-STATIC INSTRUMENTS OF THE
AIRCRAFT. The Trig altitude encoder is a solid state device and will
not be affected by excess altitude or rate of climb and descent, but the
mechanical instruments in the aircraft can easily be damaged by
being driven beyond their intended range.
Proceed as follows:
1. Set the primary altimeter subscale setting to 1013.2 hPa,
29.92 in hg.
2. Connect the pitot-static test set to the aircraft.
3. Power up the transponder and controller, whilst holding the
FN button down on the controller. This will enter SETUP