User's Manual

TT21/TT22 Transponder Installation Manual 13 July 2009
00560-00 Issue AF
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Page 12 Trig Avionics Limited
provided. The screws supplied are appropriate for panel thicknesses from 3
mm to 5 mm. If a thinner panel is used, you may need to exchange the screws
for shorter versions since they can bottom out in the mounting holes.
If alternate screws are required, please note that the mounting thread in each
case is 4-40.
5.3 Transponder Main Unit Mounting
The TT21/TT22 Mode S transponder is designed to be mounted in any
convenient location in the cockpit, the cabin, or an avionics bay.
The following installation procedure should be followed, remembering to allow
adequate space for installation of cables and connectors.
 Select a position in the aircraft that is not too close to any high
external heat source. (The TT21/TT22 is not a significant heat
source itself and does not need to be kept away from other devices for
this reason).
 Avoid sharp bends and placing the cables too near to the aircraft
control cables.
 Secure the mounting tray (p/n 00667-00) to the aircraft via the three
(3) mounting holes in the tray. The tray should be mounted to a flat
surface - it is important that the tray is supported at the dimples as
well as the three mounting points.
 Put the TT21/TT22 transponder into the secured mounting tray by
hooking the connector end under the lip on the tray.
 Lock the TT21/TT22 transponder into the mounting tray by clipping
the retaining wire over the lugs on the opposite end.
5.4 Cooling Requirements
The TT21/TT22 Mode S transponder meets all applicable ETSO requirements
without forced air-cooling.
Attention should however be given to the incorporation of cooling provisions