TT31 Transponder (complete system)

Artikkelnr.: 00225-00-01

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.

NOK43 596,00 inkl. mva.
  • Produktinfo
  • Features
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  • Spesifications
  • FAQ


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.

The TT31 is compatible with many popular GPS position sources including Garmin GNS and GTN navigators and the Trig TN70. This makes installation flexibility the best in class. A free FAA STC allows the TT31 to be installed as a compliant ADS-B Out solution in 650 aircraft types for further information see our U.S. ADS-B page.

Talk to your Approved Trig Dealer now to find out how the TT31 can feature in your aircraft.

  • 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


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 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.


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.


Product Type ADS-B Supply Voltage Transmitter Output Options Sales Part Number
TT31 Mode S 1090ES    ADS-B Out capable Requires suitable GPS position source 12-33 Volts 240W at connector Available with tray 00225-00-01
          Available without tray 00220-00-01
Specification TT31 Transponder
Type Class 1 Mode S Level 2 els
Certification ETSO C166A, 2C112B and TSO-C112, C166b
Compliance 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
Weight 1.35 kg
Dimensions 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
  • Install manual and Operating manual (in English, German and French)
  • Installation kit (including plastic brackets for round mounts)
  • Tray
  • EASA Form One


Why do you call the TT31 the class leader?
The TT31 was also the first transponder in the world to achieve FAA TSO-C166b certification. It is the easiest retro-fit transponder on the market for the popular KT76A, KT76C and KT78A. Mode S is 'plug and play' and configurable serial ports enable the fastest ADS-B Out install, using the existing BK tray. The latest TT31 software also provides the widest compatibility with other third party avionics. In use the TT31 is one of the world’s most energy efficient transponders, producing less heat and using less power. This improves the overall reliability of your entire avionics stack.

How does “plug and play” work?
The TT31 has been specifically designed as a slide in replacement for the Bendix King KT76A, KT76C and KT78A. The transponder and can utilise the existing mounting tray, electrical connector and antenna connector.

The TT31 is also “plug and play” with the KT-76C. The mounting tray can sometimes be a snug fit as the size varies depending on the age of the KT-76C unit.

When I buy a TT31 what comes in the box?
When you purchase a TT31 Transponder (complete kit) you will receive the following items:  TT31 unit and tray, install kit, installation and user manuals (in English, German and French) and an EASA Form 1. You will need to supply wiring and have an existing or new antenna.

The TT31 can also be ordered as a kit without the Trig tray.

Should I buy a Trig tray with a new transponder?
If your old transponder is a different model than the KT76A, KT76C or KT78A, or if the condition of the tray is in doubt we would recommend that it is best to buy a new TT31 tray.

Can I get Mode S using my existing tray?
Yes – the TT31 really does provide Mode S straight out of the box. We would of course remind you to ensure compliance with local installation requirements via an approved facility if you have a certified aircraft. The latest version of the TT31 provides the most flexible installation options, that can include installing ADS-B Out using the original tray (this is subject to local STC regulations).

In Europe how do I get a free minor change?
We have an extensive list of free minor changes within our site available to download. If your aircraft type is not included give us a call, we usually know of other third parties who have a TT31 minor change that may be available. You may also consider the alternative EASA approval called CS-STAN this is especially suited to VFR aircraft.

Does the TT31 have an STC?
Yes, Trig has a free STC with an AML list of over 650 types.

You can find the TT31 STC here -

In the U.S. installing a compliant ADS-B Out solution (in a certified aircraft) requires your Trig transponder to utilise a certified WAAS GPS, this provides a compliant ADS-B position source. The FAA also requires that a certified ADS-B installation is completed in accordance with an FAA STC approval (Supplementary Type Certificate).

Our ADS-B STC’s are available free of charge and cover hundreds of aircraft types. Trig STC approvals allow the use of popular WAAS GPS navigators too – making installation more practical and cost-effective. Our TA70 GPS antenna has also been added to our STC equipment list.