Garmin - HIRF Air Data System (Unit P/N)

The Garmin GDC 74(X) Air Data Computer is a remote mounted device that provides air data for flight instrumentation. The system measures aircraft static and impact pressure information from pressure transducers and raw air temperature from an outside temperature probe. Using the raw data from the appropriate sensors, the unit computes pressure altitude, vertical speed, airspeed values, air temperature information and density altitude. Aircraft specific configuration parameters are stored in an external configuration module to make the GDC 74(X) a Line Replaceable Unit (LRU). The system provides pitot-static and temperature derived air data to the G1000 GIA 63 Integrated Avionics Unit and the GDU Primary Flight Displays. 

The GDC 74(X) provides the following information in ARINC 429 format: 

• Air Temperature (total air temperature, outside/static air temperature) 

• Corrected Static Pressure 

• Density Altitude 

• Impact Pressure Uncorrected 

• Indicated Airspeed 

• Mach Number 

• Pressure altitude 

• Total Pressure 

• True Airspeed 

• Vertical Speed 

In addition to providing all the above listed functions of the GDC 74A and GDC 74H, the GDC 74B is RVSM (Reduced Vertical Separation Minimums)-capable. Also, the GDC 74B’s software implements airframe-specific SSEC (Static Source Error Correction) equations that correct for changes in the measured air pressure. These changes in pressure are due to disturbances created by the aircraft in flight. Additionally, the GDC 74B supports installation-specific external sensor data, such as angle of attack.