Trig TT31 Transponder Unit Only

£1,980.00 Incl VAT £1,650.00 Excl VAT

The TT31 can be used as a direct plug and play replacement for the KT76A, KT76C & KT78A or can be used to replace any other transponder. We therefore offer the TT31 in two versions, with (complete) or without (only) the mounting tray.

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Part number: 00220-00-01

TT31 Transponder

The TT31 stack transponder has unparalleled installation benefits and class leading performance.

Trig’s TT31 transponder is the ideal retro-fit for the popular Bendix King legacy transponders. The TT31 will ‘plug and play’ straight into an existing KT76A, KT76C and KT78A tray. This significantly reduces both installation time and cost. It provides pilots with Class 1 Mode S technology that is also 1090ES ADS-B Out capable too – to the latest international standard.

  • Improved retrofit performance – ‘plug and play’ Mode S installation for KT76A, KT76C and KT78A
  • Certified for IFR / VFR flight
  • Amongst the lowest power consumption in class
  • TIS traffic capabilities – portable and/or panel mounted avionics
  • Backlit LED display
  • No cavity tube – no warm up time required (no need for dropper resistors)
  • Free European Minor Change approvals
  • Free FAA ADS-B STC for 650 aircraft types
  • Software provides the widest compatibility with third party avionics
  • Unbeatable value and quality – designed and manufactured in the U.K.
  • Two year worldwide warranty

Additional Features

The TT31 is a highly efficient class leading transponder. It’s easy to use and operate, with a clear bright display and simple user interface. Features include a flight timer, stop watch and altitude monitor (can alert you of a deviation from your selected altitude). The TT31 includes data link support for the U.S. TIS traffic service, up-linked from approach radars. TIS traffic can be displayed on a variety of portable and panel mount displays, coverage includes most US terminal areas. The latest performance upgrades are available during the life of your product via Trig software upgrades, avoiding the need for expensive hardware upgrades.

Mode – S And ADS-B

Mode A and C transponders are now being replaced by Mode S transponders, this technology is optimised for tomorrow’s airspace requirements. The introduction of ADS-B surveillance technology means the modern transponder has now become the hub of future airspace compliance requirements. Here the TT31 remains the class leader, it was the world’s first transponder certified to TSO-C166b. This is latest FAA standard for the U.S. 2020 ADS-B mandate and demonstrates Trig’s advanced levels of compliance. It’s worth remembering that to receive all ADS-B In traffic transmissions in the U.S. the FAA requires a functioning certified ADS-B Out device.

Product Design

The TT31 uses half the electrical power of legacy transponders, whilst still transmitting at a higher signal power, its efficient design reduces waste heat in the avionics stack. This reduces the load on the aircraft electrical system improving overall reliability. The flexible power input means that both 14 and 28 volt systems can be used without special configuration or dropper resistors (we recommend that any dropper resistor fitted for a previous transponder should always be removed). The TT31 is compatible with both parallel and serial altitude encoders; it can even act as a serial altitude repeater to provide a convenient altitude source for your GPS.

ADS-B Express Lane

In North America the 2020 mandate is fast approaching, ADS-B will be required by most pilots.

Our TT31 transponder is a class leader as it provides a highly practical 2020 ADS-B upgrade option. With the right avionics in your aircraft and our latest TT31 software you can get ADS-B installed up to three times faster than alternative solutions – saving time and money.

Additional information


Class 1 Mode S Level 2 els


ETSO C166A, 2C112B and TSO-C112, C166b


ED-73B, DO-160E, DO-178B Level B, DO181C, DO-260B Class B1S, DO-254 Level C

Supply Voltage (DC)

11 – 33 V

Typical Current Consumption (at 14V)

idle: 0.22 A, active: 0.45 A

Nominal Transmitter Power

240 W at connector

Operating Temperature

-20°C to + 70°C

Cooling Requirement

No fan required


1.35 kg


In tray – H 40 x W 160 x L 239 mm
In tray – H 1.57 x W 6.30 x L 9.4 inches

  • All Trig products come with a two year warranty, starting from the day of installation
  • EASA Form One
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