The TT21 and TT22 - smart and small
Both the TT21 and TT22 transponders are physically identical, a two part solution, with a separate control head and transponder box. The control head fits into a 57mm round hole, with the option of using a smaller compact mount hole. When fitted the depth of the controller is only 54mm, and connected to a wiring harness the depth is still only 85mm. The separate transponder box can be mounted anywhere within the airframe.
The complete system weighs less than 450 grams and is easily powered by an aircraft battery. Both transponders have an in-built altitude encoder saving space and simplifying installation. The TT21 has a nominal power output of 130 watts, whilst the TT22 has a power output of 250 watts. The TT22 is designed for high altitude and high performance aircraft operating above 15,000 feet and/or airspeed over 175 knots. The TT21 is popular amongst light sport, glider, balloon and foot launched pilots providing one of the most affordable ways to install Mode S. In use the TT21 and TT22 are simple to operate, with a positive control knob and push buttons for Squawk code and Flight ID input. The LCD display is bright and back lit, making it easy to read in flight. The transponder controller is splash proof making it suitable for use in open cockpit flying and ultra-light aircraft. A quick release latch secures the main hardware unit to the included mounting tray, allowing easy removal if required.