Avionics

The onboard electronics used for piloting an aircraft are called avionics (AVI-ation electr-ONICS). Avionics include communications and navigation systems, autopilots, and electronic flight management systems (FMS). more...

Onboard electronics that are unrelated to piloting tasks, such as video systems for passengers, are sometimes considered avionics as well. Many of these devices include embedded computers.

History

Radiotelephone (two way voice radio) systems have been installed in aircraft since before World War II, and have been widely used for mission coordination and air traffic control. Early systems used vacuum tubes, and because of their weight and size, were installed out of the way with only a control head in place in the flight deck. Standardization on VHF frequences occurred shortly after World War II, and transistor radio systems replaced the tube-based systems shortly afterward. Only minor changes have been made to these systems since the 1960s.

The earliest navigation systems required the pilot or navigator to wear headphones and listen to the relative volume of tones in each ear to determine which way to steer on course.

Later, navigation systems developed along five separate paths:

• NDB/ADF systems
• VOR systems
• ILS systems
• ATCRBS Transponders
• Distance Measuring Equipment
• GPS receivers

Non-Directional Radiobeacon

The NDB (non-directional radiobeacon) was the first electronic navigation system in widespread use. The original radio range stations were high-power NDBs, and followed nighttime routes previously delineated by colored light beacons. DF (direction finder) and ADF (Automatic Direction Finder) avionics can receive signals from these. A needle shows the pilot the relative heading toward the station compared to the centerline of the aircraft. NDBs use the LF and MF bands, and are still in use today (2005) at smaller airports because of their low cost but their use is quickly being supplanted by GPS. This is due mostly from the higher cost of ADF equipment in the aircraft and maintaining the NDB stations.

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