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.
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
History
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.
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 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.
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.
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.
Communications
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.
Navigation
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.
Displays
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 within the last 5 years. The introduction of LCD or CRT displays was often backed up by conventional instruments.
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
Main article: 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.
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.
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.
To help avoid collision with terrain, aircraft use systems such as ground-proximity warning systems (GPWS), often combined with a radar altimeter. Newer systems use GPS combined with terrain and obstacle databases to provide similar alerting for light aircraft.
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 lightning activity are both indications of strong convective activity and severe turbulence, and weather systems allow pilots to deviate around these areas.
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.
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.).
Radar
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.
The military has used radar in fast jets to help pilots fly at low levels. While the civil market has had weather radar for a while, there are strict rules about using it to navigate the aircraft.
Sonar
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.
Electro-Optics
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.
ESM/DAS
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
AFDX: Specific implementation of ARINC 664(AND) 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
MIL-STD-1553: Military Aircraft
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
Aviation refers to flying using aircraft, machines designed by humans for atmospheric flight. More generally, the term also describes the activities, industries, and regulatory bodies associated with aircraft
Many cultures have built devices that travel through the air, from the earliest projectiles such as stones and spears, to more sophisticated buoyant or aerodynamic devices such as the boomerang in Australia, or kites. There are early legends of human flight such as the story of Icarus, and later, more credible claims of short-distance human flights including a kite flight by Yuan Huangtou in China,[1] the parachute flight of Armen Firman, and the glider flight of Abbas Ibn Firnas.
Santos-Dumont #6. Photo courtesy of the Smithsonian Institution.The modern age of aviation began with the first untethered human lighter-than-air flight on November 21, 1783, in a hot air balloon designed by the Montgolfier brothers, and balloon flight became increasingly common over longer and longer distances throughout the 19th century, continuing to the present.
The practicality of balloons was limited by the fact that they could only travel downwind. It was immediately recognized that a steerable, or dirigible, balloon was required. Although several airships, as steerable balloons came to be called, were built during the 1800s, the first aircraft to make routine flights were made by the Brazilian aviation pioneer Alberto Santos-Dumont. Santos-Dumont effectively combined an elongated balloon with an internal combustion engine. On October 19, 1901 he became world famous when he flew his airship "Number 6" over Paris to win the Deutsch de la Meurthe prize. Santos-Dumont's success with airships proved that controlled and sustained flight was possible.
First powered heavier-than air flight, December 17, 1903On December 17, 1903, the Wright brothers flew the first successful powered, heavier-than-air flight, though their aircraft was impractical to fly for more than a short distance because of control problems. The widespread adoption of ailerons made aircraft much easier to manage, and only a decade later, at the start of World War I, heavier-than-air powered aircraft had become practical for reconnaissance, artillery spotting, and even attacks against ground positions.
Aircraft began to transport people and cargo as designs grew larger and more reliable. In contrast to small non-rigid blimps, giant rigid airships became the first aircraft to transport passengers and cargo over great distances. The best known aircraft of this type were manufactured by the German Zeppelin company.
LZ 127 Graf Zeppelin.The most successful Zeppelin was the Graf Zeppelin. It flew over one million miles, including an around the world flight in August of 1929. However, the dominance of the Zeppelins over the airplanes of the that period, which had a range of only a few hundred miles, was diminishing as airplane design advanced. The "Golden Age" of the airships ended on June 6, 1937 when the Hindenburg caught fire killing 36 people. Although there have been periodic initiatives to revive their use, airships have seen only niche application since that time.
Great progress was made in airplane design during the 1920s and 1930s. One of the most successful designs of this period was the Douglas DC-3 which became the first airliner that was profitable carrying passengers exclusively, starting the modern era of passenger airline service. By the beginning of World War II, many towns and cities had built airports, and there were numerous qualified pilots available. The war brought many innovations to aviation, including the first jet aircraft and the first liquid-fueled rockets.
After WWII, especially in North America, there was a boom in general aviation, both private and commercial, as thousands of pilots were released from military service and many inexpensive war-surplus transport and training aircraft became available. Manufacturers such as Cessna, Piper, and Beechcraft expanded production to provide light aircraft for the new middle class market.
By the 1950s, the development of civil jets grew, beginning with the de Havilland Comet, though the first widely-used passenger jet was the Boeing 707. At the same time, turboprop propulsion began to appear for smaller commuter planes, making it possible to serve small-volume routes in a much wider range of weather conditions.
Yuri Gagarin was the first human to travel to space on April 12, 1961, while Neil Armstrong was the first to set foot on the moon on July 21, 1969.
Since the 1960s, composite airframes and quieter, more efficient engines have become available, but the most important innovations have taken place in instrumentation and control. The arrival of solid-state electronics, the Global Positioning System, satellite communications, and increasingly small and powerful computers and LED displays, have dramatically changed the cockpits of airliners and, increasingly, of smaller aircraft as well. Pilots can navigate much more accurately and view terrain, obstructions, and other nearby aircraft on a map or through synthetic vision, even at night or in low visibility.
On June 21, 2004, SpaceShipOne became the first privately funded aircraft to make a spaceflight, opening the possibility of an aviation market outside the earth's atmosphere.
Civil aviation
Main article: Civil aviation
Civil aviation includes all non-military flying, both general aviation and scheduled air transport.
Scheduled airline service
Main article: Airline
Swiss International Air Lines Airbus A330While there were many more in the past, there are currently only five major manufacturers of civil transport aircraft:
Airbus, based in Europe
Boeing, based in the United States
Bombardier, based in Canada
Embraer, based in Brazil
Tupolev, based in Russia (scheduled to be merged into the United Aircraft Building Corporation)
Boeing, Airbus, and Tupolev concentrate on wide-body and narrow-body jet airliners, while Bombardier and Embraer concentrate on regional airliners.
Until the 1970s, most major airlines were flag carriers, sponsored by their governments and heavily protected from competition. Since then, various open skies agreements have resulted in increased competition and choice for consumers, coupled with falling prices for airlines. The combination of high fuel prices, low fares, high salaries, and crises such as the September 11, 2001 attacks and the SARS epidemic have driven many older airlines to government-bailouts, bankruptcy or mergers. At the same time, low-cost carriers such as Ryanair and Southwest have flourished.
General Aviation
Main article: General aviation
1947 Cessna 120General aviation includes any flight that is not military and is not a commercial operation.
Because of the huge range of activities, it is difficult to cover general aviation with a simple description — general aviation may include business flights, private aviation, flight training, ballooning, parachuting, gliding, hang gliding, aerial photography, foot-launched powered hang gliders, air ambulance, crop dusting, charter flights, traffic reporting, police air patrols, forest fire flighting, and many other types of flying.
Each country regulates aviation differently, but typically, general aviation falls under several different types of regulations depending on whether it is private or commercial and on the type of equipment involved.
Many small aircraft manufacturers, including Cessna, Piper, Diamond, Mooney, Cirrus Design, Raytheon, and others serve the general aviation market, with a focus on private aviation and flight training.
The most important recent developments for small aircraft have been the introduction of advanced avionics (including GPS) that were formerly found only in large airliners, and the introduction of composite materials to make small aircraft lighter and faster. Ultralight and homebuilt aircraft have also become increasingly popular for recreational use, since in most countries that allow private aviation, they are much less expensive and less heavily regulated than certified aircraft.
This page is from http://en.wikipedia.org/wiki/Aviation All text is available under the terms of the GNU Free Documentation License. (http://en.wikipedia.org/wiki/Wikipedia:Text_of_the_GNU_Free_Documentation_License)
