User's Manual

TT21 Transponder Installation Manual 19 January 2009
00560-00 Issue AA
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altitude point adjusts the correspondence at the altitude limit of the encoder. Since the altitude limit of
the encoder is likely to be higher than the service ceiling of the aircraft, it is sufficient to set the upper
adjustment at 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 mode on the controller.
4. Skip over the configuration modes until reaching the encoder calibration section.
5. Accept the Yes/No question; the LOW ALTITUDE set point will now be active, and
an altitude will be displayed.
6. On the static test set, drive the altitude to 0 feet.
7. Read the primary altimeter value, and turn the right knob on the TC20 until the
altitude displayed on the TC20 matches the altitude on the primary altimeter.
8. Press ENT on the TC20; the display will move to the HIGH ALTITUDE set point.
9. On the static test set, drive the altitude to the service ceiling of the aircraft.
10. Read the primary altimeter value, and turn the right knob on the TC20 until the
altitude displayed on the TC20 matches the altitude on the primary altimeter.
11. Press ENT on the TC20; the display moves to the TEST ALTITUDE screen.
To complete the testing you should leave the TC20 screen displaying the encoder altitude, and exercise
the altitude on the static test set across the altitude range of the aircraft. Use at least 10 test points, and
verify that in each case the altitude displayed on the primary altimeter and the altitude displayed on the
TC20 correspond within the 125 foot tolerance. Lightly tap the altimeter at each test point to eliminate
friction effects.
When the correspondence test is complete, press ENT again on the TC20, and power off the system.
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