GRS attitude and heading reference system (AHRS) The GRS system uses solid-state sensors to measure aircraft attitude, rate of turn, and slip and skid. This data is then provided to all the integrated avionics units and GDU display units. Unlike many competing systems, the AHRS can be rebooted and recalibrated in flight during turns of up to 20 degrees. GMU magnetometer The GMU magnetometer measures aircraft heading and is a digital version of a traditional compass. It does so through aligning itself with the magnetic flux lines of the earth. GTX transponder Either the GTX 32 or GTX 33 transponder can be used in the G1000 system, although the GTX 33 is far more common. The GTX 32 provides standard mode-C replies to ATC interrogations while the GTX 33 provides mode-S bidirectional communications with ATC and therefore can indicate traffic in the area as well as announce itself spontaneously via "squittering" without prior interrogation. GEA engine/airframe unit The GEA unit measures a large variety of engine and airframe parameters, including engine RPM, manifold pressure, oil temperature, cylinder head temperature, exhaust gas temperature, and fuel level in each tank. This data is then provided to the integrated avionics units. GSD data aggregator The GSD is a data aggregator system included on complex G1000 systems, such as that found on the Embraer Phenom 100. It serves as a point of connection which allows external systems to communicate with the G1000. Backup systems As a condition of certification, all aircraft utilizing the G1000 integrated cockpit must have a redundant airspeed indicator, altimeter, attitude indicator, and magnetic compass. In the event of a failure of the G1000 instrumentation, these backup instruments become primary. In addition, a secondary power source is required to power the G1000 instrumentation for a limited time in the event of a failure of the aircraft's alternator and primary battery. Certification The Garmin G1000 is generally certified on new general aviation aircraft, including Beechcraft, Cessna, Diamond, Cirrus, Mooney, Piper, Quest (the Quest Kodiak), and Tiger. In late 2005, Garmin first announced in the G1000 in the Columbia Aircraft Model 400, later sold to Cessna. Garmin announced its first G1000 retrofit program for the Beechcraft C90 King Air in 2007. That same year the Garmin G1000 became a jet platform, as the avionics system for the Cessna Citation Mustang very light jet. Versions of the G1000 are also used in the Embraer