Saudi Arabian Airlines (Boeing 747)from New Delhi, India, to Dhahran, Saudi Arabia. Mid-air collision occurred on 12 November 1996 Kazakhstan Airlines (Ilyushin Il-76) from Kazakhstan to New Delhi Both aircrafts collided at India airspace. All 349 people on board both flights were killed, making it the WORST mid-air collision in history The causes of accident are: Failure of the Kazakh pilot to follow ATC instructions. Commanded by ATC to descend at altitude 15’000ft, but he descend to altitude 14’500ft. Lack of English Language Skills of Kazakh pilot. Indira Gandhi International Airport did not have secondary surveillance radar, which produces exact readings of aircraft altitudes; instead the airport had outdated primary radar, which produced approximate readings. No TCAS Bashkirian Airlines (Tupolev Tu-154M) passenger jet en route from Moscow to Barcelona. DHL Flight 611 (Boeing 757) cargo jet flying from Bergamo, Italy, to Brussels, Belgium. The two aircraft collided in mid-air on 1 July 2002, in Germany airspace killing all 71 aboard both aircraft. The Investigation found that the accident had been caused by problems within the air traffic control system and problems with the use of the Traffic alert and Collision Avoidance System (TCAS). On 24 February 2004, the ATC who was on duty at the time, was stabbed to death by a man who had lost his wife and two children in the accident.
The Traffic alert and Collision Avoidance System (or TCAS) is an aircraft collision avoidance system designed to reduce the incidence of mid-air collisions between aircraft. It monitors the airspace around an aircraft for other aircraft equipped with a corresponding active transponder, independent of air traffic control, and warns pilots of the presence of other transponder-equipped 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 with MTOM (maximum take-off mass) over 5700 kg (12,586 lbs) or authorized to carry more than 19 passengers. TCAS monitors the airspace around an aircraft for other aircraft equipped TCAS warns pilots of the presence of other aircraft (transponder-equipped) which may present a threat of mid-air collision (MAC). Intended as a last resort protection against risk of collision. Official definition from PANS-ATM (Nov 2007): ACAS / TCAS is an aircraft system based on secondary surveillance radar (SSR) transponder signals which operates independently of ground-based equipment to provide advice to the pilot on potential conflicting aircraft that are equipped with SSR transponders. In modern glass cockpit aircraft, the TCAS display may be integrated in the Navigation Display (ND); in older glass cockpit aircraft and those with mechanical instrumentation, such an integrated TCAS display may replace the mechanical Vertical Speed Indicator (which indicates the rate with which the aircraft is descending or climbing).
Traffic alert and Collision Avoidance System
Lecture 10: Traffic alertand Collision Avoidance System (TCAS)
AIR TRAFFIC CONTROL Home • ATC systems prevent aircraft collisions, organizePrevious and expedite the flow of traffic. • It also provides weather and navigational Next information. • Secondary surveillance radars are used for traffic Help control. • Modern ATC use air traffic control radar beacon system (ATCRBS) surveillance radar monitoring and separation of air traffic.
Secondary Surveillance RADAR Home • Primary RADAR measures position of targets by detection of reflected radio signals.Previous • SSR not only detects the aircraft but also gives its Next altitude and identity. • SSR makes use of RADAR transponders that replies to interrogation by transmitting an encoded data. Help • Transponder is a radio receiver and transmitter which receives request at 1090MHz and transmits at 1030 MHz.
Mid-Air Collision (MAC) HomePrevious Worst MAC in History •Saudi Arabian Airlines Next VS Kazakhstan Airlines , Help 1996 (349 people killed) A mid-air collision is an aviation accident in which two or more aircraft come into contact during flight.
What is TCAS Home • TCAS stand for Traffic alert and Collision Avoidance SystemPrevious • It is a transponder based interrogation system capable of displaying conflicting traffic and Next Help providing resolution advisory. • Provides an extra level of protection against mid-air collisions.
HOW TCAS WORKS Home • TCAS consists of antennas on aircraft body, computer processor & TCAS display inside cockpit.Previous • TCAS antenna continually surveys the airspace Next around an aircraft & transmit the signal. Help • Other aircraft that also equipped with TCAS in the surrounding area will reply the signal. • TCAS continuously calculates tracked aircraft position, therefore TCAS display constantly updated and provide real time position information.
HOW TCAS WORKS Home • TCAS operates similar as Secondary SurveillancePrevious Radar (SSR), but in air to air role. Next Help
HOW TCAS WORKS Home • Targets (other aircraft) are displayed on thePrevious TCAS screen as different symbols which show level of threat. • Aircraft relative altitude also will be displayed. Next Help – Relative altitude is the targets altitude in relation to the aircraft. EX: -03↑ depicts a target 300 feet below and climbing. • TCAS can not display aircraft without TCAS antenna/transponders.
Traffic Advisory (TA) & Resolution Advisory (RA) Home Determination of the alerts: TA & RA AUDIO WARNINGPrevious Traffic Advisory (TA) Intruder be at 45 “Traffic, Traffic” help the pilots in the visual search and 35 seconds for the intruder aircraft, and alert Next them to be ready for a potential from the collision resolution advisory area. Help Resolution Advisory (RA) Intruder be at 30 “Climb, Climb” avoidance maneuvers and 20 seconds “Descent, recommended to the pilot. from the collision Descent” area. • Maximum number of aircraft processed = 30
TCAS Advantages and Disadvantages Home • All threats taken into accountPrevious • Detection of all transponding aircraft, including those which are not displayed on the air traffic controller’s screen Next • Independent system, which acts as a last resort measure to Help avoid mid-air collision when other safety precautions fail. • TCAS reduced the risk of mid-air collision • TCAS can not display aircraft without TCAS antenna/transponders.
TCAS Limitations Home • No detection of aircraft without or notPrevious operating transponders . Next • No knowledge of the pilot’s intentions and of the ATC separation minima Help • Basic display: no identification, no past positions, no speed vector • Sometime generate unnecessary alerts.