aviation electronics
Avionics is a portmanteau of "aviation electronics". It comprises electronic systems for use on aircraft, artificial satellites and spacecraft, comprising communications, navigation and the display and management of multiple systems. It also includes the hundreds of systems that are fitted to aircraft to meet individual roles; these can be as imple as a search light for a police helicopter or as complicated as the tactical system for an Airborne Early Warning platform.
Aircraft avionics
The cockpit of an aircraft is a major location for avionic equipment, including control, monitoring, communication, navigation, weather, and anti-collision systems. The majority of aircraft drive their avionics using 14 or 28 volt DC electrical systems; however, large, more sophisticated aircraft (such as airliners or military combat aircraft) have AC systems operating at 115V 400 Hz, rather than the more common 50 and 60 Hz of European and North American, respectively, home electrical devices.[1] There are several major vendors of flight avionics, including Honeywell (which now owns Bendix/King, Baker Electronics, Allied Signal, etc..), Rockwell Collins, Thales Group, Garmin, Narco, and Avidyne Corporation.
Communications
Communications connect the flight deck to the ground, and the flight deck to the passengers. On board communications are provided by public address systems and aircraft intercoms.
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 performed by simplex mode. Aircraft communication can also take place using HF (especially for trans-oceanic flights) or satellite communication.
Navigation
Main article: Radio navigation
Navigation is the determination of position and direction on or above the surface of the Earth. Avionics can use satellite-based systems (such as GPS and WAAS), ground-based systems (such as VOR or LORAN), or any combination thereof. Older avionics required a pilot or navigator to plot the intersection of signals on a paper map to determine an aircraft's location; modern systems, like the Bendix/King KLN 90B, calculate the position automatically and display it to the flight crew on moving map displays.
Radio navigation or radionavigation is the application of radio frequencies to determine a position on the Earth. Like radiolocation, it is a type of radiodetermination. The basic principles are measurements from/to electric beacons, especially directions, e.g. by bearing, radio phases or interferometry, distances, e.g. ranging by measurement of travel times, partly also velocity, e.g. by means of radio Doppler shift.
Monitoring
Glass cockpits started to come into being with the Gulfstream G-IV private jet in 1985. Display systems display sensor data that allows the aircraft to fly safely. Much information that used to be displayed using mechanical gauges appears on electronic displays in newer aircraft. Almost all new aircraft include glass cockpits. ARINC 818, titled Avionics Digital Video Bus, is a protocol used by many new glass cockpit displays in both commercial and military aircraft.
A glass cockpit is an aircraft cockpit that features electronic instrument displays. Where a traditional cockpit relies on numerous mechanical gauges to display information, a glass cockpit uses several displays driven by flight management systems, that can be adjusted to display flight information as needed. This simplifies aircraft operation and navigation and allows pilots to focus only on the most pertinent information. They are also popular with airline companies as they usually eliminate the need for a flight engineer. In recent years the technology has become widely available in small aircraft.
Early glass cockpits, found in the McDonnell Douglas MD-80/90, Boeing 737 Classic, 757 and 767-200/-300, and in the Airbus A300-600 and A310, used Electronic Flight Instrument Systems (EFIS) to display attitude and navigational information only, with traditional mechanical gauges retained for airspeed, altitude and vertical speed. Later glass cockpits, found in the Boeing 737NG, 747-400, 767-400, 777, A320 and later Airbuses, Ilyushin Il-96 and Tupolev Tu-204 have completely replaced the mechanical gauges and warning lights in previous generations of aircraft.
Future developments
Unlike the previous era of glass cockpits—where designers merely copied the look and feel of conventional electromechanical instruments onto cathode ray tubes—the new displays represent a true departure. They look and behave a lot like other computers, with windows and data that can be manipulated with point-and-click devices. They also add terrain, approach charts, weather, vertical displays, and 3D navigation images.
The improved concepts enables aircraft makers to customize cockpits to a greater degree than previously. All of the manufacturers involved have chosen to do so in one way or another—such as using a trackball, thumb pad or joystick as a pilot-input device in a computer-style environment. Many of the modifications offered by the aircraft manufacturers improve situational awareness and customize the human-machine interface to enhance safety.
As aircraft displays have modernized, the sensors that feed them have modernized as well. Traditional gyroscopic flight instruments have been replaced by Attitude and Heading Reference Systems (AHRS) and Air Data Computers (ADCs), improving reliability and reducing cost and maintenance. GPS receivers are frequently integrated into glass cockpits.
Modern glass cockpits might include Synthetic Vision (SVS) or Enhanced Vision systems (EVS). Synthetic Vision systems display a realistic 3D depiction of the outside world (similar to a flight simulator), based on a database of terrain and geophysical features in conjunction with the attitude and position information gathered from the aircraft navigational systems. Enhanced Vision systems add realtime information from external sensors, such as an infrared camera.
All new airliners such as the Airbus A380, Boeing 787 and private jets such as Bombardier Global Express and Learjet use glass cockpits. Certain general aviation aircraft, such as the 4-seat Diamond Aircraft DA40, DA42 and DA50 and the 4-seat Cirrus Design SR20 and SR22, are available with glass cockpits. Systems such as the Garmin G1000 are now available on many new GA aircraft, including the classic Cessna 172.
Glass cockpits are also popular as a retrofit for older private jets and turboprops such as Dassault Falcons, Raytheon Hawkers, Bombardier Challenger, Cessna Citations, Gulfstreams, King Airs, Learjets, Astras and many others. Aviation service companies work closely with equipment manufacturers to address the needs of the owners of these aircraft.
Aircraft flight control systems
Airplanes and helicopters have means of automatically controlling flight. They reduce pilot workload at important times (like during landing, or in 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 stabilization was used in a similar way. The old systems were electromechanical in nature until very recently.
The advent of fly by wire and electro actuated flight surfaces (rather than the traditional hydraulic) has increased safety. As with displays and instruments, critical devices which were electro-mechanical had a finite life. With safety critical systems, the software is very strictly tested.
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 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, (CFIT) aircraft use systems such as ground-proximity warning systems (GPWS), radar altimeter being the key element in GPWS. A major weakness of (GPWS) is the lack of "look-ahead" information as it only provides altitude above terrain "look-down". To overcome this weakness, modern aircraft use the Terrain Awareness Warning System (TAWS).
Modern aircraft can use several types of collision avoidance systems to prevent unintentional contact with other aircraft, obstacles, or the ground:
Airborne Radar can detect the relative location of other aircraft, and has been in military use since World War II, when it was introduced to help night fighters (such as the de Havilland Mosquito and Messerschmitt Bf 110) locate bombers. While larger civil aircraft carry weather radar, sensitive anti-collision radar is rare in non-military aircraft.
a Traffic alert and Collision Avoidance System (TCAS), which actively interrogates the transponders of other aircraft and negotiates collision-avoidance tactics with them in case of a threat. TCAS systems are relatively expensive, and tend to appear only on larger aircraft. They are effective in avoiding collisions only with other aircraft that are equipped with functioning transponders with altitude reporting.
Small PCAS device for use in light aircraft.
a Portable Collision Avoidance System (PCAS) is a less expensive, passive version of TCAS designed for general aviation use. PCAS systems do not actively interrogate the transponders of other aircraft, but listen passively to responses from other interrogations. PCAS is subject to the same limitations as TCAS, but also is ineffective if there is not at least one system (such as air traffic control or a TCAS-equipped aircraft) interrogating another aircraft's transponder.
a Ground proximity warning system (GPWS), or Ground collision warning system (GCWS), which uses a radar altimeter to detect proximity to the ground or unusual descent rates. GPWS is common on civil airliners and larger general aviation aircraft.
a Terrain awareness and warning system (TAWS) uses a digital terrain map, together with position information from a navigation system such as GPS, to predict whether the aircraft's current flight path could put it in conflict with obstacles such as mountains or high towers, that would not be detected by GPWS (which uses the ground elevation directly beneath the aircraft).
Synthetic vision provides pilots with a computer-generated simulation of their outside environment for use in low or zero-visibility situations.
Obstacle Collision Avoidance System is a ground based system that uses a low powered radar mounted on or near the obstacle. The radar detects aircraft in the proximity of the obstacle and firstly warns aircraft via flashing medium intensity lights and secondly warns aircraft of the obstacle via a VHF broadcast. No additional equipment is required on board the aircraft. Large, sophisticated aircraft may use several or all of these systems, while a small general aviation aircraft might have only PCAS or benefit from the OCAS system, or no collision-avoidance system at all (other than the pilot's situational awareness).
Weather systems
Weather systems such as weather radar (typically Arinc 708 on commercial aircraft) and lightning detectors are 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.
Lightning detectors like the Storm scope or Strike finder have become inexpensive enough that they are practical for light aircraft. In addition to 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. Modern displays allow weather information to be integrated with moving maps, terrain, traffic, etc. onto a single screen, greatly simplifying navigation.
Aircraft management systems
There has been a progression towards centralized control of the multiple complex systems fitted to aircraft, including engine monitoring and management. Health and Usage Monitoring Systems (HUMS) are integrated with aircraft management computers to allow maintainers early warnings of parts that will need replacement.
The Integrated Modular Avionics concept proposes an integrated architecture with application software portable across an assembly of common hardware modules. It has been used in Fourth generation jet fighters and the latests generation of Airliners.
Radar
Airborne radar was one of the first tactical sensors. The benefit of altitude providing range has meant a significant focus on airborne radar technologies. Radars include Airborne Early Warning (AEW), Anti-Submarine Warfare (ASW), and even Weather radar (Arinc 708) and ground tracking/proximity radar.
The military uses 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.
An airborne early warning and control (AEW&C) system is an airborne radar system designed to detect aircraft. Used at a high altitude, the radars allow the operators to distinguish between friendly and hostile aircraft hundreds of miles away. AEW&C aircraft are used for defensive and offensive air operations. The system is used offensively to direct fighters to their target locations, and defensively to counter attacks. It can also be used to carry out surveillance, and C2BM (command and control, battle management) functions.
Christian Argenis Umaña Zambrano
Ci:17678077
No hay comentarios:
Publicar un comentario