TRA-67A aviation surveillance device

The TRA-67A is a Mode S air traffic control transponder from Honeywell Aerospace for transport aircraft. It is an ATC Mode S transponder that is mounted remotely in the avionics bay and operated from a panel-mounted control unit, and it forms the transponder element of a surveillance installation that includes antennas, air data sources and a collision avoidance computer.

Its function is to answer interrogations from ground radar and from other aircraft. Honeywell describes the TRA 67 and TRA 100 family as an air transport Mode S transponder that provides the data capability to identify the aircraft to surrounding aircraft equipped with an airborne collision avoidance system (ACAS). Paired with the CAS-100A system, the transponder supplies the data squitter capability used for this identification. An enhanced version of the TRA-67A supports the DO-185A TCAS interface protocol and broadcasts ADS-B extended squitter messages, which adds automatic position reporting to its transponder role.

For installation, the unit contains an L-band receiver-transmitter and works with two antennas in a diversity arrangement. It uses ARINC 429 for two-way communication with the TCAS and the maintenance bus, and for receive-only inputs from the control unit, the air data sources and the flight identification source. It meets ARINC 735-2, which is required for operation with the CAS-81 collision avoidance system, and ARINC 604 for the centralised fault data system. Aircraft wiring is made through a size 2 ARINC 600 multiple-section connector at the rear of the unit.

The mechanical and electrical data support installation planning. The case is a 4 MCU unit to ARINC 600, 4.88 inches wide, 7.64 inches high and up to 12.76 inches long, with a mass of 13.5 lb plus or minus 0.4 lb. The unit runs from a 97 to 134 V AC supply at 380 to 420 Hz and draws 60 W, or 95 W with the fan. The operating temperature range is -55 C to +70 C for most part numbers and -40 C to +70 C for the -0000 version, with a maximum humidity of 95%.

The TRA-67A is listed to TSO C112, the standard for air traffic control radar beacon system and Mode S airborne equipment. Honeywell lists several part numbers for the product, including a variant for the Boeing 777, which shows that the unit is offered as a line-replaceable item for fitted fleets. Its typical application is the transponder position in a commercial or regional transport aircraft; it is not a small unmanned-aircraft transponder, and buyers of drone-class equipment should treat it as a reference for the Mode S transport class.