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Encyclopedia > Avionics

Avionics is a portmanteau which literally means aviation electronics. In essence it comprises all electronic systems designed for use on an aircraft. At a basic level this comprises communications, navigation and the display and management of multiple systems. It also comprises the literally hundreds of systems that are fitted to aircraft to meet individual roles. These can be as simple as a search light for a police helicopter or as complicated as the tactical system for an Airborne Early Warning platform. Avionics also refers to the electronics on artificial satellites and spacecraft. This article is about blends. ... Look up aviation in Wiktionary, the free dictionary. ... This article is about the engineering discipline. ... The term communications is used in a number of disciplines: Communications, also known as communication studies is the academic discipline which studies communication, generally seen as a mixture between media studies and linguistics. ... Table of geography, hydrography, and navigation, from the 1728 Cyclopaedia. ... MBB/Kawasaki BK117 - callsign Polair 61 (Western Australia Police). ... United States Air Force E-3 Sentry An Airborne Early Warning (AEW) system is a radar system carried by an aircraft which is designed to detect other aircraft. ...

The study of avionics and its impact on aerospace technology has grown at an amazing rate. Initially the ancillary part of an aircraft, avionics has, for many aircraft, become the sole reason for its existence. Increasingly, military aircraft become the means of placing powerful and sensitive sensors into a tactical environment.



The term avionics did not gain any credence or general use until the early 1970s. Up to this point instruments, radios, radar, fuel systems, engine controls and radio navigation aids had all formed individual and often mechanical systems.

In the 1970s avionics was born. Driven by changes in the electronics industry as a whole, the avionics market boomed. However, where once aircraft and space flight set the standard, it was not long before the rest of the industry was in control. In the early 1970s military aircraft consumed 90% of the world’s semiconductor production. By the mid 1990s it was less than 1%. Airframers started to bring together its specialists. They formed Avionics Departments and by the end of the 1970s a whole new segment of the aviation industry had been formed. A semiconductor is a solid whose electrical conductivity is in between that of a conductor and that of an insulator, and can be controlled over a wide range, either permanently or dynamically. ...

This was mostly driven by military need rather than civil airliner development (the cold war). A large number of aircraft had become flying sensors platforms, and making large amounts of electronic equipment work together had become the new challenge. Today, avionics as used in military aircraft almost always forms the biggest part of any development budget. Aircraft like the F-15E and the now retired F-14 have roughly 80% of their budget spent on avionics. Most modern helicopters now have budget splits of 60/40 in favour of avionics. (F-22?) For other uses, see Cold War (disambiguation). ... See F-15 Eagle for main F-15 page. ... Sailors prepare an F-14 Tomcat for flight on the aircraft carrier USS Abraham Lincoln, in support of Operation Iraqi Freedom (2003). ... ...

The civilian market has also seen a massive growth in cost of avionics. Flight control systems (fly-by-wire) and new navigation needs brought on by tighter airspaces, have pushed up development costs accordingly. The major change has been the recent boom in consumer flying. As more people begin to use planes as their primary method of transportation, more elaborate methods of controlling aircraft safely in these high restrictive airspaces have been invented. Whilst the nature of civil aircraft means that avionics is almost always confined to the cockpit, the budgets and development made in the civil market has for the first time started to influence the military. A flight control system consists of the flight control surfaces, the respective cockpit controls, connecting linkage, and necessary operating mechanisms to control aircraft in flight The basic fundamentals of aircraft controls has been explained in aeronautics. ...

Main categories

Avionics, like electronics, is a massive subject that does not easily lend itself to simple categorisation. The headings below try to allocate areas of interest, from which you can delve deeper into the subject areas.

Aircraft avionics

The cockpit of any aircraft is the most obvious location for avionics. It is also the most contentious and difficult. Systems that allow the aircraft to fly safely or have direct control over the aircraft are all directly controlled by the pilot. These safety critical systems and the items that support them are all referred to as aircraft avionics.


Probably the first piece of avionics to exist, the ability to communicate from the aircraft to the ground has been crucial to aircraft design since its inception. The boom in telecommunications has meant aircraft (civilian and military) fly with a vast array of communication devices. A small number of these provide the critical air to ground communications systems for safe passage. On board communications are provided by public address systems and aircraft intercoms. A public address system, abbreviated PA system, is an electronic amplification system used as a communication system in public areas. ... Intercom system in the Pittock Mansion An intercom is an electronic communications system within a building or group of buildings. ...

The VHF aviation communication system works on the Airband of 118.000 MHz to 136.975 MHz. Each channel is spaced from the adjacent by 8.33 kHz. Amplitude Modulation AM is used. The conversation is perfomed by simplex mode. A Bendix/King KY197 Airband VHF communication radio mounted above a Cessna ARC RT-359A Transponder (the beige box) in a light airplane instrument panel. ... Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. ... Look up AM, A.M., Am, am, a. ...

See also: Aircraft Communication Addressing and Reporting System

Aircraft Shyamala Communication Addressing and Reporting System (or ACARS) is a digital datalink system for transmission of small messages between aircraft and ground stations via radio or satellite. ...


This article concerns navigation in the sense of determination of position and direction on or above the surface of the Earth.

Soon after communications the envelope within which an aircraft could be operated was limited by the conditions. Navigation sensors have been developed from the early days to assist pilots in safe flight. As with communications, there is a vast array of radio navigation and relative aircraft based navigation devices that can be fitted to an aircraft. One of the most important ways in which aircraft navigation is done today is with the aid of the GPS system. Radio navigation is the application of radio frequencies to determining a position on the earth. ... Over fifty GPS satellites such as this NAVSTAR have been launched since 1978. ...


The advent of avionics as a separate entity was quickly followed by integration of these functions. The drive to manufacture more reliable and better quality means of displaying flight critical information to pilots started very early on. True glass cockpits have only started to come into being since the G-IV in 1985. The introduction of LCD or CRT displays was often backed up by conventional instruments. The Gulfstream IV (or G-IV) and derivatives are a family of private jet aircraft produced by Gulfstream Aerospace, a General Dynamics company based in Savannah, Georgia, United States. ... This article is about the year. ...

Today the reliability of LCDs means that even these flight critical back ups are 'glass'. But this is only the superficial element. Display systems carry out checks of key sensor data that allows the aircraft to fly safely in very aggressive environments. Display software is often written in the same way as that for flight control software, as essentially the pilot will follow it. The display systems can take multiple different methods of determining attitude, heading and altitude that the aircraft use, and provide them in a safe and easy to use manner to aircrew.

Aircraft flight control systems

Aeroplanes and helicopters have had different means of automatically controlling flight for many years. They reduce pilot workload at useful times (like on landing, or in the hover), and they make these actions safer by 'removing' pilot error. The first simple auto-pilots were used to control heading and altitude and had limited authority on things like thrust and flight control surfaces. In helicopters, auto stabilisation was used in a similar way. The old systems were all electromechanical in nature until very recently. A flight control system consists of the flight control surfaces, the respective cockpit controls, connecting linkage, and necessary operating mechanisms to control aircraft in flight. ...

The software driven systems fitted to almost all new major aircraft today have made a significant leap forward. The advent of fly by wire and electro actuated flight surfaces (rather than the traditional hydraulic) has massively increased safety. As with displays and instruments, critical devices which were electro-mechanical had a finite life which was very restrictive. Electronic systems are not limited by the mechanical constraints. With safety critical systems, the software is written in very strict conditions, where the ideal scenario is that it will never fail. A flight control system consists of the flight control surfaces, the respective cockpit controls, connecting linkage, and necessary operating mechanisms to control aircraft in flight The basic fundamentals of aircraft controls has been explained in aeronautics. ...

Collision-avoidance systems

To supplement air traffic control, most large transport aircraft and many smaller ones use a TCAS (Traffic Alert and Collision Avoidance System), which can detect the location of other, nearby aircraft, and provide instructions for avoiding a midair collision. Smaller aircraft may use simpler traffic alerting systems such as TPAS, which are passive (they do not actively interrogate the transponders of other aircraft) and do not provide advisories for conflict resolution. For the Canadian musical group, see Air Traffic Control (band). ... TCAS and IVSI Indicator The Traffic Collision Avoidance System (or TCAS) is a computer system installed on board many large aircraft, designed to prevent mid-air collisions. ...

To help avoid collision with terrain, (CFIT) aircraft use systems such as ground-proximity warning systems (GPWS), radar altimeter being the key element in GPWS. Newer systems (EGPWS) use GPS combined with a terrain and obstacle databases to provide more warning time. A controlled flight into terrain (CFIT) describes an unintentional crash by an airworthy aircraft into the ground (usually a Antarctica on November 28, 1979. ... Ground Proximity Warning System (GPWS) monitors an aircrafts height above ground as determined by a radio altimeter. ... Ground proximity warning system (GPWS) is a system designed to alert pilots if their aircraft is in immediate danger of flying into the ground. ... Over fifty GPS satellites such as this NAVSTAR have been launched since 1978. ...

Weather systems

Weather systems such as weather radar (typically Arinc 708 on commercial aircraft) and lightning detectors are especially important for aircraft flying at night or in Instrument meteorological conditions, where it is not possible for pilots to see the weather ahead. Heavy precipitation (as sensed by radar) or severe turbulence (as sensed by lightning activity) are both indications of strong convective activity and severe turbulence, and weather systems allow pilots to deviate around these areas. Weather radar in Norman, Oklahoma with rainshaft (Source: NOAA) Environment Canada King City (CWKR) weather radar station. ... ARINC 708 is a specification for airborne pulse Doppler Weather radar systems primarily found on commercial aircraft. ... Lightning detector at the Kennedy Space Center in Florida. ... Instrument meteorological conditions (IMC) are weather conditions that require aircraft pilots to fly primarily by reference to instruments rather than outside visual references, as they could in Visual meteorological conditions (VMC). ...

Recently, there have been three important changes in cockpit weather systems. First, the systems (especially lightning detectors like the Stormscope or Strikefinder) have become inexpensive enough that they are practical for light aircraft. Second, in addition to the traditional radar and lightning detection, observations and extended radar pictures (such as NEXRAD) are now available through satellite data connections, allowing pilots to see weather conditions far beyond the range of their own in-flight systems. Finally, modern displays allow weather information to be integrated with moving maps, terrain, traffic, etc. onto a single screen, greatly simplifying navigation. NEXRAD Radar at NSSL NEXRAD or Nexrad (Next-Generation Radar) is a network of 158 high-resolution Doppler radars operated by the National Weather Service, an agency of the National Oceanic and Atmospheric Administration (NOAA), in the United States. ...

Aircraft management Systems

As integration became the buzzword of the day in avionics, and as PCs came onto the market, there was a natural progression towards centralized control of the multiple complex systems fitted to aircraft. Combined with displays and flight control systems, these three core systems allow all the aircraft systems (not just avionics) to have their data compiled and manipulated to make it easier to maintain, easier to fly and safer.

Engine monitoring and management was an early progression into aircraft management for ground maintenance. Now the ultimate extension of this is total management of all the components on the aircraft, giving them longer lives (and reducing cost). Health and Usage Monitoring Systems (HUMS) are integrated with aircraft management computers to allow maintainers early warnings of parts that will need replacement.

The aircraft management computer or flight management systems are used by aircrew in place of reams of maps and complex equations. Combined with the digital flight bag they can manage every aspect of the aircraft chock to chock.

Although avionic manufacturers provide flight management systems, aircraft management and HUMS tend to be specific to the airframe as the design of the software is dependent on the aircraft it is fitted to.

Mission or tactical avionics

The major developments in avionics have tended to happen 'in the back' before the cockpit. Military aircraft have been designed either to deliver a weapon or to be the eyes and ears of other weapon systems. The vast array of sensors available to the military (as for the front) is then used for whatever tactical means required. As with aircraft management, the bigger sensor platforms (like the E-3D, JSTARS, ASTOR, Nimrod MRA4, Merlin HM Mk 1) have mission management computers.

As the sophistication of military sensors increases and they become more ubiquitous, the pseudo-military market has started to dip into the product. Police and EMS aircraft can now carry some very sophisticated tactical sensors.

Military communications

While aircraft communications provide the backbone for safe flight, the tactical systems are designed to withstand the rigours of the battle field. UHF, VHF Tactical (30-88 MHz) and SatCom systems combined with ECCM methods, and cryptography secure the communications. Data links like Link 11, 16, 22 and BOWMAN, JTRS and even TETRA provide the means of transmitting data (such as images, targeting information etc.). This article is about the radio frequency. ... Very high frequency (VHF) is the radio frequency range from 30 MHz to 300 MHz. ... Electronic counter-countermeasures (ECCM) describes a variety of practices which attempt to reduce or eliminate the effect of Electronic countermeasures ( ECM) on sensors aboard vehicles, ships and aircraft and especially seekers on weapons such as missiles. ... The German Lorenz cipher machine, used in World War II for encryption of very high-level general staff messages Cryptography (or cryptology; derived from Greek κρυπτός kryptós hidden, and the verb γράφω gráfo write or λεγειν legein to speak) is the study of message secrecy. ... TADIL-A/Link 11 is a secure half-duplex TADIL radio link used by the U.S. military that receives or transmits--but not both simultaneously--a sequential data exchange digital link. ... Link 16 is a military inter-computer data exchange format of NATO, the North Atlantic Treaty Organisation. ... Link 22 is an upcoming NATO standard for wireless information interchange between military units. ... Bowman is the name of the new tactical communications system being deployed by the British Armed Forces. ... The Joint Tactical Radio System (JTRS) is planned as the next-generation radio for use by the U.S. military in field operations for the second decade of the 21st century. ... Genera More than 150[1] Look up tetra in Wiktionary, the free dictionary. ...


Airborne radar was one of the first tactical sensors. As with its ground based counterpart it has grown in sophistication. The obvious massive benefit of altitude providing massive range has meant a significant focus of developing airborne radar technologies. The general ranges of radar of Airborne Early Warning (AEW), Anti-Submarine Warfare (ASW), and even Weather radar (Arinc 708) and ground tracking/proximity radar. For other uses, see Radar (disambiguation). ... United States Air Force E-3 Sentry An Airborne Early Warning (AEW) system is a radar system carried by an aircraft which is designed to detect other aircraft. ... “A/S” redirects here. ... Weather radar in Norman, Oklahoma with rainshaft (Source: NOAA) Environment Canada King City (CWKR) weather radar station. ... ARINC 708 is a specification for airborne pulse Doppler Weather radar systems primarily found on commercial aircraft. ...

The military has used radar in fast jets to help pilots fly at low levels in several operations. While the civil market has had weather radar for a while, there are strict rules about using it to navigate the aircraft.


Soon after radar came sonar. Dipping sonar fitted to a range of military helicopters allows the helicopter to protect shipping assets from submarines or surface threats. Maritime support aircraft can drop active and passive sonar devices (Sonobuoys) and these are also used to determine the location of hostile submarines. For other uses, see Helicopter (disambiguation). ... Sonarbuoy loaded on aircraft A sonobuoy (a portmanteau of sonar and buoy) is a relatively small (typically 4 7/8 inches, or ~124 mm, in diameter and 36 inches, or ~914 mm, long) expendable sonar system that is dropped/ejected from aircraft or ships conducting anti-submarine warfare or underwater... USS Los Angeles A submarine is a specialized watercraft that can operate underwater. ...


Electro-optic system covers a wide range of systems, including Forward Looking Infrared (FLIR), and Passive Infrared Devices (PIDS). These are all used to provide imagery to crews. This imagery is used for everything from Search and Rescue through to acquiring better resolution on a target. A forward looking infrared (FLIR) system is a television camera that takes pictures in infrared. ...


Electronic support measures and defensive aids are used extensively to gather information about threats or possible threats. Ultimately they can be used to launch devices (in some cases automatically) to counter direct threats against the aircraft. They are also used to determine the state of a threat or even identify it.

Aircraft Networks

The avionics systems in military, commercial and advanced models of civilian aircraft are interconnected using an avionics databus. These network protocols are similar in functionality as an in-home network connecting computers together, however, the communication and electrical protocols can be very different. Here is a short list of some of the more common avionics databus protocols with their primary application:

  • Aircraft Data Network (ADN): Ethernet derrivative for Commercial Aircraft
  • Avionics Full-Duplex Switched Ethernet (AFDX): Specific implementation of ARINC 664 (ADN) for Commercial Aircraft
  • ARINC 429: Commercial Aircraft
  • ARINC 664: See ADN above
  • ARINC 629: Commercial Aircraft (Boeing 777)
  • ARINC 708: Weather Radar for Commercial Aircraft
  • ARINC 717: Flight Data Recorder for Commercial Aircraft
  • IEEE 1394b: Military Aircraft
  • MIL-STD-1553: Military Aircraft
  • MIL-STD-1760: Military Aircraft

Aircraft Data Network (ADN) is a concept introduced by the ARINC Airline Electronics Engineering Committee (AEEC) in the ARINC 664 Specification. ... Aircraft Data Network (ADN) is a concept introduced by the ARINC Airline Electronics Engineering Committee (AEEC) in the ARINC 664 Specification. ... Avionics Full-Duplex Switched Ethernet (AFDX) is a standard (ARINC 664) for a low-level network and protocol to communicate between avionics devices in aircraft. ... Aircraft Data Network (ADN) is a concept introduced by the ARINC Airline Electronics Engineering Committee (AEEC) in the ARINC 664 Specification. ... ARINC 429 is a data format for aircraft avionics. ... Avionics Full-Duplex Switched Ethernet (AFDX) is Part 7 of the ARINC 664 Specification which defines how Commercial Off-the-Shelf (COTS) networking technology will be used for future generation Aircraft Data Networks (ADN). ... ARINC 708 is a specification for airborne pulse Doppler Weather radar systems primarily found on commercial aircraft. ... FireWire (also known as i. ... MIL-STD-1553 is military standard published by the United States Department of Defense that defines the mechanical, electrical and functional characteristics of a serial data bus. ... The MIL-STD-1760 communications bus is derived from the earlier MIL-STD-1553 and provides additional safety features such as message integrity validation using CRCs. ...

Police and Air Ambulance

Police and EMS aircraft (mostly helicopters) are now a significant market. Military aircraft are often now built with a role available to assist in civil disobedience. Police helicopters are almost always fitted with video/FLIR systems to allow them to track suspects or items they or their command are interested in. They can also be fitted with searchlights and loudspeakers for the very same reason police cars are.

EMS helicopters obviously need medical equipment, which is rarely classified as avionics. However, many EMS and Police helicopters will be required to fly in unpleasant conditions, this may require more aircraft sensors, some of which were until recently considered purely for military aircraft.

External links

  • Space Shuttle Avionics
  • Aviation Today Avionics magazine
  • RAES Avionics homepage

See also

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