TT31 Service Bulletins for pilots

TT31 Transponder

Software versions run numerically, the higher the number the more recent the release – so the latest software will always include all the features of earlier versions.


01/10/2018          version 0.1

This Hardware Service Bulletin applies to TT31 transponders approved under ETSO authorisation EASA.21O.643 Rev B and EASA.21O.906 Rev A, part number 00220-00-(XX) and part number 00225-00-(XX) which are:

Serial number from 05767 to 09715;

Modification Level 6 or below; Installed in an orientation which is NOT a conventional aft-facing avionics stack mounting.


24.09.2018          version 3.18 – Current software version

TT31 software version 3.18 improves performance of Mode S replies to certain interrogations, correcting software versions 3.14, 3.15, 3.16 and 3.17.

05/12/2017          version 3.17

This software improves the automatic air / ground determination on the TT31.

24/08/2017         version 3.16

This software adds support for the Trig TN72 as a 14 CFR 91.227 compliant ADS-B position source. Adds GPS only air-ground determination algorithm for ADS-B Out.

13/08/2014         version 3.13

This adds compatibility with Garmin’s ADS-B Plus protocol for GNS and GTN navigators. This allows these Garmin units to be used as the GPS source for certified ADS-B Out. Improvements to front panel rotary knob functionality also added.

24/03/2014         version 3.11

Introduces user configurable serial ports, providing greater installation flexibility. Improves automatic dimming of the display backlight. Also adds automatic generation of the transponder Mode S address when a valid aircraft registration is configured (only applicable for ‘N’ registration aircraft). Adds support for the Trig ADS-B protocol which is used by various GPS position sources, including the Avidyne IFD440 and IFD540 for ADS-B.

03/08/2012         version 3.4

Improvements made to ADS-B Extended Squitter function to RTCA DO-260B standard (as required by 14 CFR 91.227). Support added for Garmin 4X0W and 5X0W GPS sources for ADS-B.

21/01/2010         version 2.5

This software adds the ability to receive TIS ‘A’ traffic in relevant US airspace, via RS232 output.

19/12/2008         version 2.3

Adds support for FreeFlight and NextNav GPS sources for ADS-B.

30/10/2008         version 2.2

This improves the timeout behaviour when a new Squawk code has been input.

13/02/2008         version 2.1

Improvements to Bendix King KLN94 GPS receiver support for ADS-B.

18/12/2007         version 2.0

This adds ADS-B Extended Squitter functionality for NMEA 0183 protocol output GPS sources. Also adds support for Squat switches and recall of previous squawk code after powering off.