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Compact Transponders

TT21 and TT22 Transponders

Chosen by pilots around the world our compact transponders are the best choice for good reason.

Fitting in the tightest panel space our innovative design saves weight and space. Trig is ‘better by design’ our Mode S technology  makes you visible to commercial, military and GA traffic, as a result transiting busy airspace becomes more predictable and stress free. Our transponders are future proof too – the growing use of ADS-B further enhances your visibility and flight safety. Unlike other brands Trig transponders meet the very latest certification standard for ADS-B, FAA TSO-C166b.

Designed to be easier to use, with a clear bright display the controller even comes with a built in altitude encoder!  Join other pilots who have made Trig their compact transponder of choice – you’ll be in great company.

Contact your nearest Approved Trig Dealer to order your compact transponder.

  • Compact form factor – takes minimal panel space, fits in a compact or standard 57mm instrument hole.
  • Minimal depth – create space on your panel for other avionics.
  • Integrated altitude encoder
  • Certified for IFR / VFR flight
  • Manual dimming feature (adjustable backlight)
  • Low power consumption
  • EASA ETSO and FAA TSO Certification – includes TSO-C166b the latest ADS-B standard
  • Free European Minor Change approvals
  • Free FAA ADS-B STC for 576 aircraft types
  • Unbeatable value and quality – designed and manufactured in the U.K.

Product Design

Trig’s compact transponder is in two parts with a compact control head; this includes an inbuilt altitude encoder – saving further space and expense. A separate hardware box can be installed anywhere in the airframe. The mounted control head is only 54mm (2 3/25”) deep and can be fitted in panel using a 57mm (2 ¼”) round hole or smaller compact mount – the unit ships with the necessary fittings for both install options. Our compact transponders are highly efficient, whilst used in a wide range of GA types they are ideally suited for use in gliders and balloons, via an auxiliary battery.

Trig’s compact transponders are easy to operate and with a crisp, bright display. It is easy to read in all lighting conditions and features manual dimming. The transponder control head is splash proof too so it’s ideal for open cockpit and seaplane operations.

Power Output and ADS-B

Trig’s TT21 has a 130 watts nominal power output, making it a class 2 transponder that meets international standards for 1090ES ADS-B Out (TSO C166b). The TT21 is ideal for use in flight where a light weight Mode S solution is required and is suitable for both IFR and VFR use.

Compatible Trig products

ADS-B enhances safety and visibility, your investment in a compact transponder is future proof. Trig has a matching certified GPS position source that is highly affordable and simple to install. Our TN72 TABS GPS is ideal for ADS-B voluntary equipage and the TN72 X GPS can even be used to meet the 2020 mandate by light-sport and experimental types in the U.S.

Our TN70 GPS position source contains all the main components to provide an ADS-B Out solution in one box and is usually specified with a TT22 transponder. Customers in the U.S. should be aware that FAA, Federal Aviation Regulations (FAR) 91.227 requires that a compliant ADS-B Out solution uses a Class 1 transponder. The TT22 is a Class 1 device and meets this requirement. The TT21 is a Class 2 device and does not meet this regulation.

Product Model Type Meets TSO-C166b Suitable for 2020 ADS-B rule airspace (US) Transmitter Output
TT21 Class 2
Mode – S and 1090ES      ADS-B Out capable
Yes No – FAR 91.227 requires a Class 1 device – select the TT22. 130 W at connector
TT22 Class 1
Mode – S and 1090ES    ADS-B Out capable
Yes Yes 250 W at connector
Specification TT21 Transponder TT22 Transponder
Type Transponder Class 2 Mode S level 2els ADS-B Class B0 Transponder Class 1 Mode S level 2els
ADS-B Class B1S
Certification ETSO C88A, C112C, C166A
TSO C88b, C112c, C166b, approved for IFR and VFR flight
Compliance ED-73C, DO-160F, DO-178B Level B, DO-254
Level C, DO-260B, DO-181D
Supply voltage (DC) 9-33 V
Typical consumption (at 14v) idle: 0.15 A active: 0.28 A idle: 0.15A active: 0.34 A
Nominal Transmitter Power 130 W at connector 250 W at connector
Operating temperature for the transponder -40°C to +70°C
for the controller -25°C to +70°C
Cooling requirement no fan required
Weight 440g / 0.8 lbs
Dimensions (mm) controller: H 44 x W 63 x L 54 mm
transponder in tray: H 48 x W 68 x L 160 mm
Dimensions (inches) controller: H 1.8 x W 2.4 x L 2.1 inches
transponder in tray: H 1.8 x W 2.6 x L 6.2 inches

What's in the box

  • All Trig products come with a two year warranty, starting from the day of installation
  • Installation manual and Operating manual
  • Installation kit (including plastic brackets for round mounts)
  • Tray
  • EASA Form One

Frequently Asked Questions

What is the difference between the TT21 and the TT22?
Both models have the same physical dimensions and advantages of size and ease of installation. The TT21 is a 130 watt Class 2 transponder; this makes it ideal for light sports and regular GA use. The TT22 is a 250 watt Class 1 transponder, ideally suited to higher performance and/or high altitude performance types.

In the U.S. the FAA has stated that Class 1 transponders must be used to be ‘2020 complaint’ For U.S. customers Trig recommends the TT22 unit for this reason.

Is the controller display visible in all lightling conditions?
Yes! The LCD display is clear and crisp in all lighting, full sunlight generates a very clear contrast and in dull or dark lighting the inbuilt lighting ensures the unit remains clear and legible. The controller has a backlight and manual dimming can be selected to increase or decrease brightness.

Is the controller easy to use?
Yes! One handed operation is simple. The Squawk code is easily entered using fingers to rotate the ‘CODE’ dial whilst the thumb is used to press the ‘ENT’ key. All operations can be performed whilst wearing flying gloves.

How does the compact fit or the round mount installation work?
Complete units ship with the necessary parts to enable you to choose to install the transponder either as a compact mount or 2 ¼ “ full round. The kit includes a template to assist you in cutting an accurate compact mount hole in the panel. If a full round mounting is required then you simply fit the plastic blanks above and below the body on the TC20 controller (included in the box). Once installed the full round is a tough and durable solution and is particularly suited to classic and vintage types.

Can I use the Transponder in open cockpit fllying?
The TC20 controller is splash proof. This makes it suitable for use in open cockpit aircraft, where the weather can sometimes be in the cockpit and not just outside it!

In Europe, how do I get a free minor change?
Free minor changes for the TT21 and TT22 are available, see our minor change library. You may also consider the alternative EASA approval called CS-STAN this is especially suited to VFR aircraft.

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