TCAS and IVSI Indicator

The Traffic alert and Collision Avoidance System (or TCAS) is a computerised avionics device which is designed to reduce the danger of mid-air collisions between aircraft. It monitors the airspace around an aircraft, independent of air traffic control, and warns pilots of the presence of other aircraft which may present a threat of mid-air collision (MAC). It is an implementation of the Airborne Collision Avoidance System mandated by International Civil Aviation Organization to be fitted to all aircraft over 5700 kg or authorised to carry more than 19 passengers. TCAS Indicator Photo and edit by user Meggar File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... TCAS Indicator Photo and edit by user Meggar File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... This article is about the machine. ... This article does not cite any references or sources. ... For the Canadian musical group, see Air Traffic Control (band). ... The doomed Boeing 727, PSA Flight 182, crashes in flames after colliding with another aircraft in 1978 A mid-air collision (MAC) is an aviation accident where two or more aircraft come into unplanned contact during flight. ... Airborne Collision Avoidance System (ACAS) is an ICAO (International Civil Aviation Organization) standard specified in ICAO Annex 10 Vol IV which provides pilots with a system independent of air traffic control to detect the presence of other aircraft which may present a threat of collision. ... The International Civil Aviation Organization (ICAO), an agency of the United Nations, codifies the principles and techniques of international air navigation and fosters the planning and development of international air transport to ensure safe and orderly growth. ...

In modern glass cockpit aircraft, the TCAS display may be integrated in the Navigation Display; in older glass cockpit aircraft and those with mechanical instrumentation, a TCAS display replaces the mechanical Instantaneous Vertical Speed Indicator (which indicates the rate with which the aircraft is descending or climbing). This article does not cite any references or sources. ...

Impetus for a collision prevention system

Although research into collision avoidance systems has been ongoing since at least the 1950s, authorities such as the Federal Aviation Administration were only spurred into action after several major mid-air collisions involving great loss of life. Some of these tragic mid-air accidents include: “FAA” redirects here. ...

• Grand Canyon midair collision in 1956;
• The Zagreb mid-air collision in 1976;
• PSA Flight 182, a Boeing 727 which collided with a Cessna 172 in 1978;
• Aeroméxico Flight 498, a 1986 collision similar to PSA Flight 182, which finally spurred the US Congress and other regulatory bodies into action and led to mandatory collision avoidance equipment.

United Airlines Flight 718, Mainliner Vancouver, registration N6324C, was a Douglas DC-7 en route from Los Angeless International Airport to Chicago, Newark and Philadelphia on June 30, 1956. ... Year 1956 (MCMLVI) was a leap year starting on Sunday (link will display full calendar) of the Gregorian calendar. ... Zagreb FIR in 1976, showing route of BEA476 (red) and JP550 (green) The Zagreb mid-air collision refers to one of the worst accidents in aviation history. ... Year 1976 Pick up sticks(MCMLXXVI) was a leap year starting on Thursday (link will display full calendar) of the Gregorian calendar. ... Pacific Southwest Airlines (PSA) Flight 182, registration N533PS, was a Boeing 727-214 commercial airliner that collided over San Diego, California with a private Cessna 172 on September 25, 1978. ... The Boeing 727 is a mid-size, narrow-body, three-engine commercial jet airliner. ... Cessna 172RG 1964 Cessna 172E 1965 Cessna F172G 1971 Cessna 172 The early Cessna 172 Skyhawks had no rear window and featured a square fin design, like this 1957 model 1977 Cessna 172XP 1977 Cessna 172M Cessna 172R Panel of C-GLFC The Cessna 172 Skyhawk is a four-seat... Year 1978 (MCMLXXVIII) was a common year starting on Sunday (link displays the 1978 Gregorian calendar). ... Aeroméxico Flight 498 was a scheduled commercial airline flight, a McDonnell Douglas DC-9-32 bound for Los Angeles International Airport (LAX) in Los Angeles, California, USA from Mexico CityMexico. ... Year 1986 (MCMLXXXVI) was a common year starting on Wednesday (link displays 1986 Gregorian calendar). ... The Congress of the United States is the legislative branch of the federal government of the United States of America. ...

TCAS Basics

TCAS involves communication between all aircraft equipped with an appropriate transponder. Each TCAS-equipped aircraft "interrogates" all other aircraft in a determined range about their position (via the 1030 MHz radio frequency), and all other craft reply to other interrogations (via 1090 MHz). This interrogation-and-response cycle may occur several times per second. An Ontario Highway 407 toll transponder In telecommunication, the term transponder (short-for Transmitter-responder and sometimes abbreviated to XPDR, XPNDR or TPDR) has the following meanings: An automatic device that receives, amplifies, and retransmits a signal on a different frequency (see also broadcast translator). ... A megahertz (MHz) is one million (106) hertz, a measure of frequency. ... FreQuency is a music video game developed by Harmonix and published by SCEI. It was released in November 2001. ...

Through this constant back-and-forth communication, the TCAS system builds a three dimensional map of aircraft in the airspace, incorporating their bearing, altitude and range. Then, by extrapolating current range and altitude difference to anticipated future values, it determines if a potential collision threat exists. In mathematics, extrapolation is the process of constructing new data points outside a discrete set of known data points. ...

It should be noted that TCAS and its variants are only able to interact with aircraft that have a correctly operating transponder.

The next step beyond identifying potential collisions is automatically negotiating a mutual avoidance maneuver between the two (or more) conflicting aircraft. These avoidance maneuvers are communicated to the flight crew by a cockpit display and by synthesized voice instructions.

Safety Aspects of TCAS

Safety studies on TCAS estimate that the system improves safety in the airspace by a factor of between 3 and 5.

However, it is well understood that part of the remaining risk is that TCAS may initiate midair collisions: "In particular, it is dependent on the accuracy of the threat aircraft’s reported altitude and on the expectation that the threat aircraft will not make an abrupt maneuver that defeats the TCAS RA. The safety study also shows that TCAS II will induce some critical near midair collisions..." (See page 7 of Introduction to TCAS II Version 7 (PDF) in external links below).

One potential problem with TCAS II is the possibility that a recommended avoidance maneuver might direct the flight crew to descend toward terrain below a safe altitude. Recent requirements for incorporation of ground proximity mitigate this risk. Ground proximity warning alerts have priority in the cockpit over TCAS alerts.

Some pilots have been unsure how to act when their aircraft was requested to climb whilst flying at their maximum altitude. The accepted procedure is to follow the climb RA as best as possible, temporarily trading speed for height. The climb RA should quickly finish. In the event of a stall warning, the stall warning would take priority.

Relationship to Automatic Dependent Surveillance (ADS)

Automatic Dependent Surveillance-Broadcast (ADS-B) messages are transmitted from aircraft equipped with suitable transponders, containing information such as identity, location, and velocity. The signals are broadcast on the 1090 MHz radio frequency. ADS-B messages are also carried on a Universal Asynchronous Transmitter (UAT) in the 900 MHz band. Automatic Dependent Surveillance-Broadcast (also called ADS-B) is a system by which airplanes constantly broadcast their current position and altitude, category of aircraft, airspeed, identification, and whether the aircraft is turning, climbing or descending over a dedicated radio datalink. ... Automatic Dependent Surveillance-Broadcast (also called ADS-B) is a system by which airplanes constantly broadcast their current location, type of aircraft, airspeed, flight number, and whether the aircraft is turning, climbing or descending. ...

TCAS equipment which is capable of processing ADS-B messages may use this information to enhance the performance of TCAS, using techniques known as "hybrid surveillance". As currently implemented, hybrid surveillance uses reception of ADS-B messages from an aircraft to reduce the rate at which the TCAS equipment interrogates that aircraft. This reduction in interrogations reduces the use of the 1030/1090 MHz radio channel, and will over time extend the operationally useful life of TCAS technology. The ADS-B messages will also allow low cost (for aircraft) technology to provide real time traffic in the cockpit for small aircraft. Currently UAT based traffic uplinks are provided in Alaska and in regions of the East coast.

Hybrid surveillance does not include the use any of the aircraft flight information in the TCAS conflict detection algorithms; ADS-B is used only to identify aircraft that can safely be interrogated at a lower rate.

In the future, prediction capabilities may be improved by using the state vector information present in ADS-B messages. Also, since ADS-B messages can be received at greater range than TCAS normally operates, aircraft can be acquired earlier by the TCAS tracking algorithms.

The identity information present in ADS-B messages can be used to label other aircraft on the cockpit display (where present), improving situational awareness.

Drawbacks to TCAS and ADS-B

The major demonstrated problem of the ADS-B protocol integration is this added verbosity of the extra information transmitted, which is unnecessary for collision avoidance purposes. The more data transmitted from one aircraft in accordance with the system design, the lesser the number of aircraft that can participate in the system, due to the fixed and limited channel data bandwidth (1 megabit/second with the 26/64 data bits to packet length bit capacity of the Mode S downlink data format packet). For every Mode S message of 64 bits, the overhead demands 8 for clock sync at the receiver and Mode S packet discovery, 6 for type of Mode S packet, 24 for who it came from. Since that leaves only 26 for information, multiple packets must be used to convey a single message. The ADS-B "fix" proposal is to go to a 128 bit packet, which is not an accepted international standard. Either approach increases channel traffic above the level sustainable for environments such as the Los Angeles Basin.^{[citation needed]}

Versions of TCAS

PASSIVE

Collision Avoidance systems which rely on transponder replies triggered by ground and airborne systems are considered passive. Ground and airborne interrogators query nearby transponders for mode C altitude information, which can be monitored by third-party systems for traffic information. Passive systems display traffic similar to TCAS, however generally have a range of less than 7 nautical miles. Portable Collision Avoidance System. A Cessna ARC RT-359A Transponder (the beige box) mounted beneath a Bendix/King KY197 VHF communication radio in a light airplane instrument panel A transponder is an electronic device that produces a response when it receives a radio-frequency interrogation. ... PCAS, which stands for Portable Collision Avoidance System, a technology similar in function to TCAS (Traffic Collision Avoidance System). ...

TCAS I

TCAS I is the first generation of collision avoidance technology. It is cheaper but less capable than the modern TCAS II system, and is mainly intended for general aviation use. TCAS I systems are able to monitor the traffic situation around a plane (to a range of about 40 miles) and offer information on the approximate bearing and altitude of other aircraft. It can also generate collision warnings in the form of a "Traffic Advisory" (TA). The TA warns the pilot that another aircraft is in near vicinity, announcing "traffic, traffic", but does not offer any suggested remedy; it is up to the pilot to decide what to do, usually with the assistance of Air Traffic Control. When a threat has passed, the system announces "clear of conflict". General aviation (abbr. ...

TCAS II

TCAS II is the second and current generation of TCAS, used in the majority of commercial aviation aircraft (see table below). It offers all the benefits of TCAS I, but will also offer the pilot direct, vocalised instructions to avoid danger, known as a "Resolution Advisory" (RA). The suggestive action may be "corrective", suggesting the pilot change vertical speed by announcing, "descend, descend", "climb, climb" or "Adjust Vertical Speed Adjust" (meaning reduce or increase vertical speed). By contrast a "preventive" RA may be issued which simply warns the pilots not to deviate from their present vertical speed, announcing, "monitor vertical speed" or "maintain vertical speed". TCAS II systems coordinate their resolution advisories before issuing commands to the pilots, so that if one aircraft is instructed to descend, the other will typically be told to climb — maximising the separation between the two craft. Aviation or Air transport refers to the activities surrounding mechanical flight and the aircraft industry. ...

As of 2006, the only implementation that meets the ACAS II standards set by ICAO is Version 7.0 of TCAS II, produced by three avionics manufacturers: Rockwell Collins, Honeywell, and ACSS (Aviation Communication & Surveillance Systems; an L-3 Communications and Thales Avionics company). Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... The International Civil Aviation Organization (ICAO), an agency of the United Nations, develops the principles and techniques of international air navigation and fosters the planning and development of international air transport to ensure safe and orderly growth. ... Rockwell Collins (NYSE: COL) is a large United States-based international company headquartered in Cedar Rapids, Iowa, primarily providing aviation and information technology systems, solutions, and services to governmental agencies and aircraft manufacturers. ... Honeywell Heating Specialties Company Stock Certificate dated 1924 signed by Mark C. Honeywell - courtesy of Scripophily. ... L-3 Communications Holdings, Inc. ... The Thales Group (Euronext: HO) is a global electronics company serving aerospace, defence, and information technology markets worldwide. ...

TCAS III

TCAS III was the "next generation" of collision avoidance technology which underwent development by aviation companies such as Honeywell. TCAS III incorporated technical upgrades to the TCAS II system, and had the capability to offer traffic advisories and resolve traffic conflicts using horizontal as well as vertical manouevring directives to pilots. For instance, in a head-on situation, one aircraft might be directed, "turn right, climb" while the other would be directed "turn right, descend." This would act to further increase the total separation between aircraft, in both horizontal and vertical aspects. All work on TCAS III is currently suspended and there are no plans for its implementation.^{[citation needed]} Honeywell Heating Specialties Company Stock Certificate dated 1924 signed by Mark C. Honeywell - courtesy of Scripophily. ...

Current implementation

Although the system occasionally suffers from false alarms, pilots are now under strict instructions to regard all TCAS messages as genuine alerts demanding an immediate, high-priority response. (Only stall warnings and Ground Proximity Warning System warnings have higher priority than the TCAS.) The FAA and most other countries' authorities' rules state that in the case of a conflict between TCAS RA and air traffic control (ATC) instructions, the TCAS RA always takes precedence. If one aircraft follows a TCAS RA and the other follows conflicting ATC instructions, a collision can occur, such as the July 1, 2002 Überlingen disaster. In this mid-air collision, both airplanes were fitted with TCAS II systems which functioned properly, but one obeyed the TCAS advisory while the other ignored the TCAS and obeyed the controller; both aircraft descended into a fatal collision. Ground Proximity Warning System (GPWS) is a system designed to alert pilots if their aircraft is in immediate danger of flying into the ground. ... “FAA” redirects here. ... For the Canadian musical group, see Air Traffic Control (band). ... is the 182nd day of the year (183rd in leap years) in the Gregorian calendar. ... Also see: 2002 (number). ... Bashkirian Airlines Flight 2937, registration RA-85816, was a Tupolev 154M passenger jet en route from Moscow, Russia to Barcelona, Spain. ...

Regulatory situation around the world

FAA may refer to: Federal Aviation Administration in the United States Fleet Air Arm in the UK Royal Navy Fuerza Aérea Argentina in Argentina This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... You may want one of: European Aviation Safety Agency English Academy of Southern Africa, discussed in the article South African English European Architecture Students Assembly This is a disambiguation page — a list of pages that otherwise might share the same title. ... You may want one of: European Aviation Safety Agency English Academy of Southern Africa, discussed in the article South African English European Architecture Students Assembly This is a disambiguation page — a list of pages that otherwise might share the same title. ... This article is in need of attention. ... The Civil Aviation Department (Chinese: 民航處) is responsible for providing air traffic control services to all aircrafts operating within the Hong Kong Flight Information Region. ...

References

See also

• Mid-air collision
• Flight 1907
• 1996 Charkhi Dadri air mishap - November 12, 1996
• Bashkirian Airlines Flight 2937 - July 1, 2002
• Gol Transportes Aéreos Flight 1907 - September 29, 2006

• Bitching Betty
• Ground Proximity Warning System
• Portable Collision Avoidance System

The doomed Boeing 727, PSA Flight 182, crashes in flames after colliding with another aircraft in 1978 A mid-air collision (MAC) is an aviation accident where two or more aircraft come into unplanned contact during flight. ... Flight 1907 may refer to: Air Kazakhstan Flight 1907 Gol Transportes Aéreos Flight 1907 Category: ... Saudi Arabian Airlines Flight 763 (SV 763), registration HZ-AIH, was a Boeing 747-168B en route from New Delhi, India to Dhahran, Saudi Arabia on November 12, 1996. ... Bashkirian Airlines Flight 2937, registration RA-85816, was a Tupolev 154M passenger jet en route from Moscow, Russia to Barcelona, Spain. ... Gol Transportes Aéreos Flight 1907 was a Boeing 737-800 SFP, registration PR-GTD, on a scheduled passenger flight from Manaus, Brazil to Rio de Janeiro, which collided in mid-air with an Embraer Legacy business jet on September 29, 2006 over the Brazilian state of Mato Grosso. ... There are very few or no other articles that link to this one. ... Ground Proximity Warning System (GPWS) is a system designed to alert pilots if their aircraft is in immediate danger of flying into the ground. ... PCAS, which stands for Portable Collision Avoidance System, a technology similar in function to TCAS (Traffic Collision Avoidance System). ...

External links

• Discussion of TCAS
• AIS-P/TailLight alternative to TCAS and ADS-B without the problems of TCAS and ADS-B
• Use of ADS-B as a weapon system or billing for service