DOC AIRBUS | AMM A320FT/TISS - TRAFFIC COLLISION AVOIDANCE SYSTEM - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
A. Presentation
The T/TISS-TCAS is a function that detects and displays aircraft in the immediate vicinity and provides the flight crew with indications to avoid these intruders by changing the flight path in the vertical plane only.
TCAS change 7 has been mandatory in Europe since year 2000.
The T/TISS-TCAS complies with change 7.1 newly released through DO-185B. Change 7.1 introduces software modification to the TCAS algorithm, in particular on two items:
The system can establish individualized communications with each aircraft through ATC/Mode S transponders, thus permitting operation in dense traffic areas while avoiding an overload of radio-electric transmissions that would result from a general all-intruder response.
The T/TISS-TCAS has the capability to communicate with ATCRBS (Air Traffic Control Radar Beacon System) ground stations equipped with the Mode S system to indicate to them the vertical maneuver orders presented to the aircraft pilot. This information can facilitate the task of the ground station controller who, in turn, can modify the TCAS operating mode and cancel the avoidance orders if he deems it necessary for safety (as required in the DO-185B standard).
The system maintains surveillance within a sphere determined by the transmit power and receiver sensitivity of the T/TISS computer (TCAS function). The area in which a threat is imminent depends on the speed and path of the own A/C and the threat A/C.
There is an area defined as TAU (Ref. para.4.D.(2) ) within the surveillance arc which represents the minimum time the flight crew needs to discern a collision threat and take evasive action.
The T/TISS-TCAS can track up to 70 intruders at the same time (35 Mode S intruders and 35 ATCRBS intruders).
Its detection capability covers:
The T/TISS-TCAS is a function that detects and displays aircraft in the immediate vicinity and provides the flight crew with indications to avoid these intruders by changing the flight path in the vertical plane only.
An Airborne Traffic Situational Awareness (ATSAW) capability can be activated through pin programming: ATSAW concept is based on the display of traffic information provided by ADS-B Out and the display of the suitable information. Providing information on surrounding aircraft may bring safety and efficiency improvement in piloting task by helping the crew to have a better understanding of surrounding situation. Two applications are identified using ATSAW information:
The T/TISS-TCAS complies with change 7.1 newly released through DO-185B. Change 7.1 introduces software modification to the TCAS algorithm, in particular on two items:
In addition, the TCAS receives broadcast data from the transponder equipped with Enhanced Surveillance (EHS) function and capable of transmitting Automat Dependent Surveillance-Broadcast (ADS-B) messages. The TCAS uses this data to compute passive surveillance data.
Based on active and passive surveillance, hybrid surveillance can be performed to reduce the interrogation rate with farther transponder.
Their acquisition is achieved by means of two transmit/receive antennas, one located on the underside of the fuselage and the other on the top.
The system can establish individualized communications with each aircraft through ATC/Mode S transponders, thus permitting operation in dense traffic areas while avoiding an overload of radio-electric transmissions that would result from a general all-intruder response.
The T/TISS-TCAS has the capability to communicate with ATCRBS (Air Traffic Control Radar Beacon System) ground stations equipped with the Mode S system to indicate to them the vertical maneuver orders presented to the aircraft pilot. This information can facilitate the task of the ground station controller who, in turn, can modify the TCAS operating mode and cancel the avoidance orders if he deems it necessary for safety (as required in the DO-185B standard).
The system maintains surveillance within a sphere determined by the transmit power and receiver sensitivity of the T/TISS computer (TCAS function). The area in which a threat is imminent depends on the speed and path of the own A/C and the threat A/C.
There is an area defined as TAU (Ref. para.4.D.(2) ) within the surveillance arc which represents the minimum time the flight crew needs to discern a collision threat and take evasive action.
The T/TISS-TCAS can track up to 70 intruders at the same time (35 Mode S intruders and 35 ATCRBS intruders).
Its detection capability covers:
The T/TISS-TCAS is a function that detects and displays aircraft in the immediate vicinity and provides the flight crew with indications to avoid these intruders by changing the flight path in the vertical plane only.
TCAS change 7 has been mandatory in Europe since year 2000.
The T/TISS-TCAS complies with change 7.1 newly released through DO-185B. Change 7.1 introduces software modification to the TCAS algorithm, in particular on two items:
- improvement of the reversal logic
- replacement of "Adjust Vertical Speed, Adjust"(AVSA) order by "Level off" order.
The system can establish individualized communications with each aircraft through ATC/Mode S transponders, thus permitting operation in dense traffic areas while avoiding an overload of radio-electric transmissions that would result from a general all-intruder response.
The T/TISS-TCAS has the capability to communicate with ATCRBS (Air Traffic Control Radar Beacon System) ground stations equipped with the Mode S system to indicate to them the vertical maneuver orders presented to the aircraft pilot. This information can facilitate the task of the ground station controller who, in turn, can modify the TCAS operating mode and cancel the avoidance orders if he deems it necessary for safety (as required in the DO-185B standard).
The system maintains surveillance within a sphere determined by the transmit power and receiver sensitivity of the T/TISS computer (TCAS function). The area in which a threat is imminent depends on the speed and path of the own A/C and the threat A/C.
There is an area defined as TAU (Ref. para.4.D.(2) ) within the surveillance arc which represents the minimum time the flight crew needs to discern a collision threat and take evasive action.
The T/TISS-TCAS can track up to 70 intruders at the same time (35 Mode S intruders and 35 ATCRBS intruders).
Its detection capability covers:
- in range: an area of 30-40 NM around the aircraft
- in altitude: plus or minus 10000 ft.
- Above: -2700 ft to 9900 ft
- Below: -9900 ft to 2700 ft
- Normal: -2700 ft to 2700 ft
The T/TISS-TCAS is a function that detects and displays aircraft in the immediate vicinity and provides the flight crew with indications to avoid these intruders by changing the flight path in the vertical plane only.
An Airborne Traffic Situational Awareness (ATSAW) capability can be activated through pin programming: ATSAW concept is based on the display of traffic information provided by ADS-B Out and the display of the suitable information. Providing information on surrounding aircraft may bring safety and efficiency improvement in piloting task by helping the crew to have a better understanding of surrounding situation. Two applications are identified using ATSAW information:
- ATSA-AIRB : to improve situational awareness during general in-flight operations.
- ATSA-VSA : to improve visual acquisition and to maintain separation during visual separation approach.
The T/TISS-TCAS complies with change 7.1 newly released through DO-185B. Change 7.1 introduces software modification to the TCAS algorithm, in particular on two items:
- improvement of the reversal logic
- replacement of "Adjust Vertical Speed, Adjust"(AVSA) order by "Level off" order.
In addition, the TCAS receives broadcast data from the transponder equipped with Enhanced Surveillance (EHS) function and capable of transmitting Automat Dependent Surveillance-Broadcast (ADS-B) messages. The TCAS uses this data to compute passive surveillance data.
Based on active and passive surveillance, hybrid surveillance can be performed to reduce the interrogation rate with farther transponder.
Their acquisition is achieved by means of two transmit/receive antennas, one located on the underside of the fuselage and the other on the top.
The system can establish individualized communications with each aircraft through ATC/Mode S transponders, thus permitting operation in dense traffic areas while avoiding an overload of radio-electric transmissions that would result from a general all-intruder response.
The T/TISS-TCAS has the capability to communicate with ATCRBS (Air Traffic Control Radar Beacon System) ground stations equipped with the Mode S system to indicate to them the vertical maneuver orders presented to the aircraft pilot. This information can facilitate the task of the ground station controller who, in turn, can modify the TCAS operating mode and cancel the avoidance orders if he deems it necessary for safety (as required in the DO-185B standard).
The system maintains surveillance within a sphere determined by the transmit power and receiver sensitivity of the T/TISS computer (TCAS function). The area in which a threat is imminent depends on the speed and path of the own A/C and the threat A/C.
There is an area defined as TAU (Ref. para.4.D.(2) ) within the surveillance arc which represents the minimum time the flight crew needs to discern a collision threat and take evasive action.
The T/TISS-TCAS can track up to 70 intruders at the same time (35 Mode S intruders and 35 ATCRBS intruders).
Its detection capability covers:
- in range: an area of 30-40 NM around the aircraft
- in altitude: plus or minus 10000 ft.
- Above: -2700 ft to 9900 ft
- Below: -9900 ft to 2700 ft
- Normal: -2700 ft to 2700 ft
B. Principle
When an aircraft is airborne, its TCAS periodically transmits interrogation signals for all ATCRBS and Mode S transponder-equipped aircraft in the vicinity. These interrogations are received by the ATCRBS ground stations and by the transponders of the other aircraft.
In response to these interrogations, the transponders of nearby aircraft return signals containing their altitude value. The T/TISS-TCAS computes the range between the two aircraft by measuring the elapsed time between transmission of the interrogation and reception of the reply.
The altitude, altitude rate, range and range rate are determined by a periodic tracking of these exchanges and the data are used for intruder threat assessment.
Each threat is treated individually but the T/TISS-TCAS determines the best collision avoidance possibility with respect to all aircraft in its vicinity, while establishing maneuver coordination with the other TCAS-equipped aircraft. The optimum maneuver is the one that ensures an adequate separation of trajectories with a minimum vertical trend variation.
When an aircraft is airborne, its TCAS periodically transmits interrogation signals for all ATCRBS and Mode S transponder-equipped aircraft in the vicinity. These interrogations are received by the ATCRBS ground stations and by the transponders of the other aircraft.
In response to these interrogations, the transponders of nearby aircraft return signals containing their altitude value. The T/TISS-TCAS computes the range between the two aircraft by measuring the elapsed time between transmission of the interrogation and reception of the reply.
The altitude, altitude rate, range and range rate are determined by a periodic tracking of these exchanges and the data are used for intruder threat assessment.
Each threat is treated individually but the T/TISS-TCAS determines the best collision avoidance possibility with respect to all aircraft in its vicinity, while establishing maneuver coordination with the other TCAS-equipped aircraft. The optimum maneuver is the one that ensures an adequate separation of trajectories with a minimum vertical trend variation.
C. Advisories
Visual and aural advisories are supplied by the T/TISS computer(TCAS function) whenever assessment of the relative position of two aircraft reveals a potential collision hazard.
The Traffic Advisories (TA) indicate the position of nearby aircraft which are or may become a threat. Their display alerts the flight crew to the presence of intruders and facilitates their visual acquisition.
The Resolution Advisories (RA) may be divided into two categories:
Visual and aural advisories are supplied by the T/TISS computer(TCAS function) whenever assessment of the relative position of two aircraft reveals a potential collision hazard.
The Traffic Advisories (TA) indicate the position of nearby aircraft which are or may become a threat. Their display alerts the flight crew to the presence of intruders and facilitates their visual acquisition.
The Resolution Advisories (RA) may be divided into two categories:
- Corrective Advisories that instruct the pilot to deviate from current vertical rate
- Preventive Advisories that instruct the pilot to avoid certain maneuvers.
D. Display
Visual indications are presented on the Electronic Flight Instrument System (EFIS).
The Navigation Display (ND) is used to indicate the situation in the nearby traffic area : a symbol is displayed for each intruder on the image in the ARC or ROSE mode.
The avoidance maneuver indications, if any, are displayed on the vertical speed scale of the Primary Flight Display (PFD) by means of a band of colored sectors showing the vertical speed value to be adopted in order to avoid any risk of collision.
Visual indications are presented on the Electronic Flight Instrument System (EFIS).
The Navigation Display (ND) is used to indicate the situation in the nearby traffic area : a symbol is displayed for each intruder on the image in the ARC or ROSE mode.
The avoidance maneuver indications, if any, are displayed on the vertical speed scale of the Primary Flight Display (PFD) by means of a band of colored sectors showing the vertical speed value to be adopted in order to avoid any risk of collision.
E. Coordination
The avoidance maneuvers initiated by the T/TISS-TCAS could create a conflict situation if directed at another TCAS-equipped aircraft as this aircraft may also take similar evasive action, resulting in an unchanged situation.
To avoid this situation, a communication link between the two aircraft is established via the transponders, exchanging coordination messages.
The first aircraft to detect the other one initiates the communication procedure, indicates the maneuvers it intends to perform and communicates orders to the other aircraft requesting it to maintain its trajectory.
This necessarily involves the use of Mode S transponders, the only equipment of this type possessing the LINK function required for data exchange.
The Mode S transponders provide the capability to transmit a unique address (24 bits) assigned to each aircraft, permitting them to reply individually to other TCAS-equipped aircraft. It can respond to ground station interrogations in Mode A and Mode C and also in Mode S if the stations are suitably equipped.
The ground stations can modify the TCAS operating mode via the transponder link so as to inhibit resolution advisories in certain conditions.
The avoidance maneuvers initiated by the T/TISS-TCAS could create a conflict situation if directed at another TCAS-equipped aircraft as this aircraft may also take similar evasive action, resulting in an unchanged situation.
To avoid this situation, a communication link between the two aircraft is established via the transponders, exchanging coordination messages.
The first aircraft to detect the other one initiates the communication procedure, indicates the maneuvers it intends to perform and communicates orders to the other aircraft requesting it to maintain its trajectory.
This necessarily involves the use of Mode S transponders, the only equipment of this type possessing the LINK function required for data exchange.
The Mode S transponders provide the capability to transmit a unique address (24 bits) assigned to each aircraft, permitting them to reply individually to other TCAS-equipped aircraft. It can respond to ground station interrogations in Mode A and Mode C and also in Mode S if the stations are suitably equipped.
The ground stations can modify the TCAS operating mode via the transponder link so as to inhibit resolution advisories in certain conditions.
2. System Description
A. T/TISS-TCAS
The T/TISS-TCAS environment is composed of items closely associated with its operation, such as the transponders and the EFIS display units and peripherals supplying parameters or with maintenance functions.
The T/TISS-TCAS environment is composed of items closely associated with its operation, such as the transponders and the EFIS display units and peripherals supplying parameters or with maintenance functions.
B. Directional Antennas
The TCAS has two antennas of the transmit/receive type which provide azimuth information on aircraft located within the TCAS surveillance range.
The TCAS has two antennas of the transmit/receive type which provide azimuth information on aircraft located within the TCAS surveillance range.
C. ATC/TCAS Control Unit
The ATC/TCAS control unit, common to the ATC transponders and the T/TISS-TCAS, enables the operating modes of these two items of equipment to be selected. Information intended for the TCAS is transmitted via an ARINC 429 bus to the transponders which in turn transmit it to the T/TISS computer (TCAS function).
The ATC/TCAS control unit, common to the ATC transponders and the T/TISS-TCAS, enables the operating modes of these two items of equipment to be selected. Information intended for the TCAS is transmitted via an ARINC 429 bus to the transponders which in turn transmit it to the T/TISS computer (TCAS function).
D. TRAFFIC SELECTOR switches
Both TRAFFIC SELECTOR switches are rotary push/pull knobs (there is one switch for each pilot). They are installed in the cockpit:
Both TRAFFIC SELECTOR switches are rotary push/pull knobs (there is one switch for each pilot). They are installed in the cockpit:
- TRAFFIC SELECTOR switch 105SG1 on panel 301VU CAPT side.
- TRAFFIC SELECTOR switch 105SG2 on panel 500 VU F/O side.
E. Associated Items
(1) Mode S transponders
Two ATC/Mode S transponders, one active and the other on standby, are used with their antennas. Each transponder is linked to the TCAS by one high-speed ARINC 429 bus for transmission and another one for reception.
Apart from the specific transponder functions (response to ATC ground station interrogations) they permit communication between the TCAS and a TCAS-equipped detected aircraft.
Two ATC/Mode S transponders, one active and the other on standby, are used with their antennas. Each transponder is linked to the TCAS by one high-speed ARINC 429 bus for transmission and another one for reception.
Apart from the specific transponder functions (response to ATC ground station interrogations) they permit communication between the TCAS and a TCAS-equipped detected aircraft.
(2) Displays
Advisories are displayed by the Electronic Instrument System (EIS) by high-speed transmission of ARINC 429 messages on the buses linking the TCAS to the Display Management Computers (DMC) 1 and 3 on the one hand and to the DMC 2 on the other hand. The Flight Warning Computers (FWCs) connected in parallel on these buses monitor the validity of the information.
The NDs provide indications on the location of intruders in the traffic area. The Primary Flight Displays (PFDs) provide the flight crew with vertical speed correction information to avoid them.
The EWD also presents warning messages.
Advisories are displayed by the Electronic Instrument System (EIS) by high-speed transmission of ARINC 429 messages on the buses linking the TCAS to the Display Management Computers (DMC) 1 and 3 on the one hand and to the DMC 2 on the other hand. The Flight Warning Computers (FWCs) connected in parallel on these buses monitor the validity of the information.
The NDs provide indications on the location of intruders in the traffic area. The Primary Flight Displays (PFDs) provide the flight crew with vertical speed correction information to avoid them.
The EWD also presents warning messages.
(3) Mode S transponders
Two ATC/Mode S transponders, one active and the other on standby, are used with their antennas. Each transponder is linked to the TCAS by one high-speed ARINC 429 bus for transmission and another one for reception.
Apart from the specific transponder functions (response to ATC ground station interrogations) they permit communication between the TCAS and a TCAS-equipped detected aircraft.
Two ATC/Mode S transponders, one active and the other on standby, are used with their antennas. Each transponder is linked to the TCAS by one high-speed ARINC 429 bus for transmission and another one for reception.
Apart from the specific transponder functions (response to ATC ground station interrogations) they permit communication between the TCAS and a TCAS-equipped detected aircraft.
(4) Displays
Advisories are displayed by the Electronic Instrument System (EIS) by high speed transmission of ARINC 429 messages on the buses linking the TCAS to the Display Management Computers (DMCs) 1 on CAPT side and to the DMC 2 on F/O side. Depending on the EFIS DMC selection, the DMC 3 receives either the TA/RA display bus 1 or the TA/RA display bus 2. The DMC3 is connected to the bus TA/RA2 when the DMC reconfiguration switch is on position F/O/3. The FWCs connected in parallel on these buses monitor the validity of the information. The Navigation Displays (NDs) provide indications on the location of intruders in the traffic area. The Primary Flight Displays (PFDs) provide the flight crew with vertical speed correction information to avoid them.
The EWD also presents warning messages.
The DMC provides the TCAS with a list of intruders displayed on the ND.
Advisories are displayed by the Electronic Instrument System (EIS) by high speed transmission of ARINC 429 messages on the buses linking the TCAS to the Display Management Computers (DMCs) 1 on CAPT side and to the DMC 2 on F/O side. Depending on the EFIS DMC selection, the DMC 3 receives either the TA/RA display bus 1 or the TA/RA display bus 2. The DMC3 is connected to the bus TA/RA2 when the DMC reconfiguration switch is on position F/O/3. The FWCs connected in parallel on these buses monitor the validity of the information. The Navigation Displays (NDs) provide indications on the location of intruders in the traffic area. The Primary Flight Displays (PFDs) provide the flight crew with vertical speed correction information to avoid them.
The EWD also presents warning messages.
The DMC provides the TCAS with a list of intruders displayed on the ND.
F. Peripherals
The T/TISS-TCAS receives information from the following items of equipment :
The T/TISS-TCAS receives information from the following items of equipment :
(1) Radio altimeter
The radio altitude is an essential parameter for the T/TISS-TCAS. In the 0 to 2500 ft range it permits modulation of system sensitivity and triggering of inhibit orders. For this reason, two radio altimeters, one active and the other in standby, are linked to the T/TISS-TCAS via the low-speed ARINC 429 bus.
Radio Altimeter 1 is used first, and if not available (or if it is NCD), then Radio Altimeter 2 is used to calculate altitude, and compute inhibitions.
The radio altitude is an essential parameter for the T/TISS-TCAS. In the 0 to 2500 ft range it permits modulation of system sensitivity and triggering of inhibit orders. For this reason, two radio altimeters, one active and the other in standby, are linked to the T/TISS-TCAS via the low-speed ARINC 429 bus.
Radio Altimeter 1 is used first, and if not available (or if it is NCD), then Radio Altimeter 2 is used to calculate altitude, and compute inhibitions.
(2) Air data system
Barometric altitude information fulfils the same functions as radio altitude information but for the range over 2500 ft. The Air Data/Inertial Reference Unit (ADIRU), which is not directly linked to the T/TISS computer, transmits this information to the computer across the transponders via the ARINC 429 buses.
Barometric altitude information fulfils the same functions as radio altitude information but for the range over 2500 ft. The Air Data/Inertial Reference Unit (ADIRU), which is not directly linked to the T/TISS computer, transmits this information to the computer across the transponders via the ARINC 429 buses.
(3) Inertial reference system
The T/TISS-TCAS is linked by a high-speed ARINC 429 bus to the aircraft ADIRU1 which supplies the T/TISS-TCAS function with magnetic heading and pitch and roll attitude information.
The T/TISS-TCAS is linked by a high-speed ARINC 429 bus to the aircraft ADIRU1 which supplies the T/TISS-TCAS function with magnetic heading and pitch and roll attitude information.
(4) Landing Gear Control and Interface Unit (LGCIU)
The LGCIU provides the T/TISS-TCAS with the following discrete signals:
The LGCIU provides the T/TISS-TCAS with the following discrete signals:
- ground/flight signal (RH main landing gear compressed)
- landing gear extended signal (LH main landing gear downlocked).
(5) Centralized Fault Display Interface Unit (CFDIU)
The T/TISS-TCAS computer communicates with the Centralized Fault Display System (CFDS) via two low-speed ARINC 429 buses.
The T/TISS-TCAS computer communicates with the Centralized Fault Display System (CFDS) via two low-speed ARINC 429 buses.
(6) Flight Data Interface Unit (FDIU)
The FDIU receives T/TISS-TCAS data from the DMC.
The following parameters are recorded by the FDIU:
The FDIU receives T/TISS-TCAS data from the DMC.
The following parameters are recorded by the FDIU:
- RA related information (label 270):
. advisory rate to maintain
. combined control
. vertical control
. up advisory
. down advisory - manual Sensitivity Level (SL 0, 1, 2)
- TA issued or not.
(7) Various discrete signals
Discretes are used for the inhibition of certain advisories by equipment with higher priority than the TCAS (ref 34-72-00, Para. 7. A.).
Discretes are used for the inhibition of certain advisories by equipment with higher priority than the TCAS (ref 34-72-00, Para. 7. A.).
(8) Pin programming
For the TCAS function, ref 34-72-00, Para 5. C. (2).
For the TCAS function, ref 34-72-00, Para 5. C. (2).
(9) Pin programming
For the TCAS function, ref 34-72-00, Para 5. C. (2).
For the ATSAW function, ref 34-72-00, Para 5. C. (4).
For the TCAS function, ref 34-72-00, Para 5. C. (2).
For the ATSAW function, ref 34-72-00, Para 5. C. (4).
3. Component Description
A. TCAS Function FIN: 1000-SG
Ref 34-72-00,para. 6. B.
Ref 34-72-00,para. 6. B.
B. ATC/TCAS Control Unit FIN: 1000-SG
For detailed description, Ref. 34-52-00, Para. 6 and for TCAS operation, Ref. 34-72-10, Para. 4.H.
For detailed description, Ref. 34-52-00, Para. 6 and for TCAS operation, Ref. 34-72-10, Para. 4.H.
C. TCAS Antennas FIN: 7-SG-1 FIN: 7-SG-2
The directional antenna is composed of four passive vertically-polarized elements. This high-strength composite antenna is provided with a curved base, eight fuselage mounting screws and four color-coded connectors used to coaxially connect the four antenna elements to the T/TISS computer (TCAS function).
A Teflon gasket is mounted between the fuselage and the antenna in order to facilitate the removal of the antenna.
An O-ring is provided to seal the antenna to the fuselage. The antenna is used to receive and provide directional information for 1090 MHz Mode S squitters, Mode S and ATCRBS replies. Proper phasing of the four antenna elements enables omni or directional transmission of 1030 MHz broadcast or coordination messages and ATCRBS or mode S interrogations.
FOR 7SG1
The directional antenna has four passive vertically-polarized elements. This high-strength composite antenna has a curved base, eight fuselage mounting screws and four color-coded connectors. These connectors coaxially connect the four antenna elements to the Traffic and Terrain Integrated Surveillance System (T/TISS) computer (Traffic Alert and Collision Avoidance System (TCAS) function).
A Teflon gasket is installed between the fuselage and the antenna to make the removal of the antenna easier.
An O-ring seals the antenna to the fuselage. The antenna receives and sends directional information for 1090 MHz mode-S squitters, mode-S and air traffic control radar beacon system replies. A correct phasing of the four antenna elements makes possible the omnidirectional or directional transmission of 1030 MHz broadcast or coordination messages and air traffic control radar beacon system or mode-S interrogations.
FOR 7SG2
The omnidirectional antenna is an L-band antenna with a short stub, all-aluminum blade type which is fully sealed to prevent failure because of moisture.
It is vertically polarized, has an impedance of 50 ohms and a Voltage Standing Wave Ratio (VSWR) less or equal to 1.6. It operates in the 950 MHz to 1260 MHz frequency band. Lightning protection prevents damage to the antenna and the transponder.
The directional antenna is composed of four passive vertically-polarized elements. This high-strength composite antenna is provided with a curved base, eight fuselage mounting screws and four color-coded connectors used to coaxially connect the four antenna elements to the T/TISS computer (TCAS function).
A Teflon gasket is mounted between the fuselage and the antenna in order to facilitate the removal of the antenna.
An O-ring is provided to seal the antenna to the fuselage. The antenna is used to receive and provide directional information for 1090 MHz Mode S squitters, Mode S and ATCRBS replies. Proper phasing of the four antenna elements enables omni or directional transmission of 1030 MHz broadcast or coordination messages and ATCRBS or mode S interrogations.
FOR 7SG1
The directional antenna has four passive vertically-polarized elements. This high-strength composite antenna has a curved base, eight fuselage mounting screws and four color-coded connectors. These connectors coaxially connect the four antenna elements to the Traffic and Terrain Integrated Surveillance System (T/TISS) computer (Traffic Alert and Collision Avoidance System (TCAS) function).
A Teflon gasket is installed between the fuselage and the antenna to make the removal of the antenna easier.
An O-ring seals the antenna to the fuselage. The antenna receives and sends directional information for 1090 MHz mode-S squitters, mode-S and air traffic control radar beacon system replies. A correct phasing of the four antenna elements makes possible the omnidirectional or directional transmission of 1030 MHz broadcast or coordination messages and air traffic control radar beacon system or mode-S interrogations.
FOR 7SG2
The omnidirectional antenna is an L-band antenna with a short stub, all-aluminum blade type which is fully sealed to prevent failure because of moisture.
It is vertically polarized, has an impedance of 50 ohms and a Voltage Standing Wave Ratio (VSWR) less or equal to 1.6. It operates in the 950 MHz to 1260 MHz frequency band. Lightning protection prevents damage to the antenna and the transponder.
4. Operation/Control and Indicating
T/TISS-TCAS - Operation/Control and Indicating ** ON A/C NOT FOR ALL
T/TISS-TCAS - Operation/Control and Indicating ** ON A/C NOT FOR ALL
T/TISS-TCAS - Operation/Control and Indicating ** ON A/C NOT FOR ALL
T/TISS-TCAS - Operation/Control and Indicating ** ON A/C NOT FOR ALL T/TISS-TCAS - Operation/Control and Indicating ** ON A/C NOT FOR ALL T/TISS-TCAS - Operation/Control and Indicating ** ON A/C NOT FOR ALL A. Intruder Detection
The TCAS detects A/C equipped with Mode S transponders by listening for squitter transmissions DF11. Mode S transponders announce their presence by transmitting squitter messages once per second. The TCAS also detects A/C equipped with transponders that do not reply to Mode S interrogations but do reply to Mode A or C interrogations. The TCAS must actively search for Mode A or C equipped intruder aircraft because Mode A or C transponders do not transmit squitter messages. Once the presence of a Mode A or C intruder is confirmed, it is tracked by the TCAS. The TCAS is capable of tracking up to a combined total of 70 Mode S and Mode A or C intruders (35 Mode S intruders and 35 ATCRBS intruders).
Tracking is performed by repetitive TCAS interrogations in Mode S and Mode C format.
The TCAS detects A/C equipped with Mode S transponders by listening for squitter transmissions DF11. Mode S transponders announce their presence by transmitting squitter messages once per second. The TCAS also detects A/C equipped with transponders that do not reply to Mode S interrogations but do reply to Mode A or C interrogations. The TCAS must actively search for Mode A or C equipped intruder aircraft because Mode A or C transponders do not transmit squitter messages. Once the presence of a Mode A or C intruder is confirmed, it is tracked by the TCAS. The TCAS is capable of tracking up to a combined total of 70 Mode S and Mode A or C intruders (35 Mode S intruders and 35 ATCRBS intruders).
Tracking is performed by repetitive TCAS interrogations in Mode S and Mode C format.
(1) Interrogation of aircraft equipped with Mode A or Mode C transponders
With respect to aircraft equipped with Mode A or Mode C transponders, the TCAS is active and transmits Mode C only all-call interrogations (P1, P3 and P4 pulses). The code is similar to the one used by the Mode A and Mode C ground stations. The P4 pulse informs those Mode S transponders that this interrogation is not addressed to them.
The nominal time interval between two interrogations is one second. But, to limit radio-electric interference in dense traffic areas, each interrogation consists of a series of interrogations of increasing strength to reach more remote aircraft (whisper-shout) with 1 ms time periods inside the series.
The first transmission consists of relatively low power P1, P3 and P4 pulses only.
Therefore, only the nearest aircraft will receive and reply to these interrogations.
Then an S1 pulse is also transmitted. This pulse is at a lower amplitude, causing the close-in aircraft to interpret this as a side lobe from the transmitting station, requiring no reply. The purpose of the whisper- shout sequence is to reduce the number of aircraft replying to any one interrogation, thus limiting interference.
With respect to aircraft equipped with Mode A or Mode C transponders, the TCAS is active and transmits Mode C only all-call interrogations (P1, P3 and P4 pulses). The code is similar to the one used by the Mode A and Mode C ground stations. The P4 pulse informs those Mode S transponders that this interrogation is not addressed to them.
The nominal time interval between two interrogations is one second. But, to limit radio-electric interference in dense traffic areas, each interrogation consists of a series of interrogations of increasing strength to reach more remote aircraft (whisper-shout) with 1 ms time periods inside the series.
The first transmission consists of relatively low power P1, P3 and P4 pulses only.
Therefore, only the nearest aircraft will receive and reply to these interrogations.
Then an S1 pulse is also transmitted. This pulse is at a lower amplitude, causing the close-in aircraft to interpret this as a side lobe from the transmitting station, requiring no reply. The purpose of the whisper- shout sequence is to reduce the number of aircraft replying to any one interrogation, thus limiting interference.
(2) Replies of aircraft equipped with Mode A or Mode C transponders.
Aircraft equipped with Mode C transponders reply by transmitting their altitude, octal encoded in four digits ABCD, with a value of 100 ft for the LSB in the ATCRBS format.
For aircraft equipped with Mode A transponders with an altitude field empty (or with Mode C without altitude), the intruder presentation on the ND is limited to a display of its position in range and bearing.
Aircraft equipped with Mode C transponders reply by transmitting their altitude, octal encoded in four digits ABCD, with a value of 100 ft for the LSB in the ATCRBS format.
For aircraft equipped with Mode A transponders with an altitude field empty (or with Mode C without altitude), the intruder presentation on the ND is limited to a display of its position in range and bearing.
(3) Interrogation of aircraft equipped with Mode S transponders
(a) Transmission coding
The TCAS uses the Mode S function for certain identification of intruders as a 24-bit address is definitively assigned to each aircraft by air traffic control.
The interrogation comprises three pulses : P1, P2 and P6. P2 level is equal to or greater than the P1 level, which is the no-reply condition for the aircraft equipped with Mode A or C transponders. Therefore, only Mode S transponders reply to the interrogation.
The useful information is contained in P6 divided into 56 or 112 chips.
A chip is an unmodulated interval of 0.25 microseconds, preceded by possible phase reversals.
The message formats contain a number of bits permitting a more complete and diversified information exchange than in Mode C.
There are two distinct message formats :
The TCAS uses the Mode S function for certain identification of intruders as a 24-bit address is definitively assigned to each aircraft by air traffic control.
The interrogation comprises three pulses : P1, P2 and P6. P2 level is equal to or greater than the P1 level, which is the no-reply condition for the aircraft equipped with Mode A or C transponders. Therefore, only Mode S transponders reply to the interrogation.
The useful information is contained in P6 divided into 56 or 112 chips.
A chip is an unmodulated interval of 0.25 microseconds, preceded by possible phase reversals.
The message formats contain a number of bits permitting a more complete and diversified information exchange than in Mode C.
There are two distinct message formats :
- all Mode S interrogations (UPLINK format) are binary differential phase shift keying (DPSK) signals
- Mode S replies (DOWNLINK format) are formed by pulse position modulation (PPM) encoding the reply data.
(b) Squitters
The Mode S transponder participates actively in its own detection by transmitting signals, at one second intervals, intended to inform nearby aircraft of its presence.
This transmission, called squitter transmission, consists of a Format DF = 11 message, containing the Mode S 24-bit address assigned to the aircraft, whereas all the bits of the message PI field at zero indicates a squitter.
The Mode S transponder participates actively in its own detection by transmitting signals, at one second intervals, intended to inform nearby aircraft of its presence.
This transmission, called squitter transmission, consists of a Format DF = 11 message, containing the Mode S 24-bit address assigned to the aircraft, whereas all the bits of the message PI field at zero indicates a squitter.
(c) Mode S communication messages
The Mode S ATC communications system supporting personalized exchanges between ATC ground stations and Mode S transponder-equipped aircraft comprises :
In the Mode S message set, the TCAS uses only six UF-type messages and seven DF-type messages. These messages are :
The two tables below give the definition of the fields used in the messages.
The Mode S ATC communications system supporting personalized exchanges between ATC ground stations and Mode S transponder-equipped aircraft comprises :
- a set of 25 standard messages for station-aircraft uplinks (Uplink format) identified UFxx
- another set of 25 standard messages for downlinks (Downlink format) identified DFxx.
The message may be long or short and contain either 56 or 112 bits.
- the "message-type" field consisting of bits 1 to 5 whose coding translates the format decimal value into binary
- the address field containing the last 24 bits of the message (bits 33 to 56 or bits 89 to 112 depending on whether the message is short or long). These 24 bits contain the Mode S address of the transmitter.
In the Mode S message set, the TCAS uses only six UF-type messages and seven DF-type messages. These messages are :
- UF0, UF4, UF5, UF16, UF20, UF21
- DF0, DF4, DF5, DF11, DF16, DF17, DF20, DF21.
The two tables below give the definition of the fields used in the messages.
| ------------------------------------------------------------------------------- |
| ! DESIGNATOR ! FIELD ! INDICATION ! |
| !-------------!----------------!----------------------------------------------! |
| ! AP ! ADDRESS PARITY ! Coded address with parity check ! |
| ! AQ ! ACQUISITION ! Indicates if it is an interrogation message ;! |
| ! ! ! 1 = interrogation ! |
| ! DI ! DESIGNATOR ! Specifies type of information contained in SD! |
| ! ! IDENT ! field ! |
| ! MA ! MESSAGE ! Used by ground station to transmit a TCAS SL ! |
| ! ! Comm-A ! command to a TCAS-equipped aircraft ! |
| ! MU ! MESSAGE ! Used by TCAS to transmit to other aircraft RA! |
| ! ! Comm-U ! coordination information (under fields UDS, ! |
| ! ! ! MTB, CVC, VRC, CHC, HRC, HSB, VSB) ! |
| ! PC ! PROTOCOL ! Operating commands to the transponder ! |
| ! RL ! REPLY LENGTH ! Indicates if message is short (0) or long (1)! |
| ! RR ! REPLY REQUEST ! Length and content of reply information ! |
| ! ! ! requested by the interrogator ! |
| ! SD ! SPECIAL ! Contains control codes affecting the ! |
| ! ! DESIGNATOR ! transponder protocol ! |
| ------------------------------------------------------------------------------- |
| Table 1: N of uplink format message fields |
| ------------------------------------------------------------------------------ |
| ! DESIGNATOR ! FIELD ! INDICATION ! |
| !-------------!----------------!---------------------------------------------! |
| ! AA ! ADDRESS ! Mode S address in the clear in 24 bits ! |
| ! ! ANNOUNCED ! ! |
| ! AC ! ALTITUDE CODE ! Information indicating aircraft altitude ! |
| ! AP ! ADDRESS PARITY ! Coded address with parity check ! |
| ! CA ! CAPABILITY ! Transponder capability ! |
| ! DR ! DOWNLINK ! Requests extraction of downlink message by ! |
| ! ! REQUEST ! the interrogator (existing RA) ! |
| ! FS ! FLIGHT STATUS ! Flight status of the aircraft : ground, ! |
| ! ! ! flight, alert, SPI ! |
| ! ID ! IDENTIFICATION ! Contains the Mode A identification code ! |
| ! ! CODE ! ! |
| ! MB ! MESSAGE ! Indicates Advisory content to the ground ! |
| ! ! Comm-B ! station ! |
| ! MV ! MESSAGE ! Contains ARA, RAC, VDS subfields used for ! |
| ! ! Comm-V ! coordination ! |
| ! RI ! REPLY ! Type of reply and airspeed capability ! |
| ! ! INFORMATION ! ! |
| ! SL ! SENSITIVITY ! TCAS current sensitivity level ! |
| ! ! LEVEL ! ! |
| ! UM ! UTILITY MESSAGE! Transponder status readouts ! |
| ! VS ! VERTICAL STATUS! Aircraft status : 0 = airborne, 1 = ground ! |
| ------------------------------------------------------------------------------ |
| Table 2: N of downlink format message fields |
B. Measurement of Intruder Parameters
(1) Principle
(a) Determination of relative altitude
Upon confirmed transponder reception, the TCAS starts to interrogate the intruder. Its altitude is transmitted directly in the reply (standard barometric altitude) and this information is used to determine the relative altitude of the two aircraft, by calculating the barometric altitude difference.
This computation is, however, only possible with respect to Mode C or Mode S transponder equipped aircraft
Upon confirmed transponder reception, the TCAS starts to interrogate the intruder. Its altitude is transmitted directly in the reply (standard barometric altitude) and this information is used to determine the relative altitude of the two aircraft, by calculating the barometric altitude difference.
This computation is, however, only possible with respect to Mode C or Mode S transponder equipped aircraft
(b) Range measurement
The range is calculated by measuring the elapsed time between transmission of the interrogation signal and return of the reply transmitted by the intruder. Aircraft are detected from a minimum range of 14 NM.
The range is calculated by measuring the elapsed time between transmission of the interrogation signal and return of the reply transmitted by the intruder. Aircraft are detected from a minimum range of 14 NM.
(c) Determination of bearing
Two basic means exist for performing the direction finding function required by the TCAS: one based on phase and the other one based on amplitude.
The amplitude monopulse technique is used for the T/TISS. This system is a four element, vertically polarized, monopole array which is capable of transmitting in 4 selectable directions at 1030 MHz and receiving omnidirectionally with bearing at 1090 MHz.
The amplitude monopulse system generates four separate cardioid antenna patterns, each with its own receiver channel to view all four 90 degree sectors simultaneously (forward, aft, left and right sectors).
The bearing angle of a target is determined by the amplitude ratio of adjacent patterns.
The TCAS takes a ratio of the amplitude of the two strongest signals from two 90-degree antenna beams to determine a bearing angle.
This technique also prevents a bearing measurement from being reflected into a wrong quadrant. Because an amplitude ratio is used, distortions in the antenna patterns tend to be cancelled out.
When transmitting, the T/TISS computer(TCAS function) interrogates one sector at a time using a whisper-shout sequence of stepped power level interrogations.
Two basic means exist for performing the direction finding function required by the TCAS: one based on phase and the other one based on amplitude.
The amplitude monopulse technique is used for the T/TISS. This system is a four element, vertically polarized, monopole array which is capable of transmitting in 4 selectable directions at 1030 MHz and receiving omnidirectionally with bearing at 1090 MHz.
The amplitude monopulse system generates four separate cardioid antenna patterns, each with its own receiver channel to view all four 90 degree sectors simultaneously (forward, aft, left and right sectors).
The bearing angle of a target is determined by the amplitude ratio of adjacent patterns.
The TCAS takes a ratio of the amplitude of the two strongest signals from two 90-degree antenna beams to determine a bearing angle.
This technique also prevents a bearing measurement from being reflected into a wrong quadrant. Because an amplitude ratio is used, distortions in the antenna patterns tend to be cancelled out.
When transmitting, the T/TISS computer(TCAS function) interrogates one sector at a time using a whisper-shout sequence of stepped power level interrogations.
(d) Tracking
Once identified, the intruders are tracked by a series of interrogation-replies in Mode C only all-call for Mode C transponder-equipped aircraft, and in Mode S for Mode S transponder-equipped aircraft.
These exchanges permit the TCAS to periodically update the altitude, range and bearing data for each intruder and to compute the range rate and altitude rate variations. These data are then used to determine the time separating the two aircraft from their closest point of approach.
Once identified, the intruders are tracked by a series of interrogation-replies in Mode C only all-call for Mode C transponder-equipped aircraft, and in Mode S for Mode S transponder-equipped aircraft.
These exchanges permit the TCAS to periodically update the altitude, range and bearing data for each intruder and to compute the range rate and altitude rate variations. These data are then used to determine the time separating the two aircraft from their closest point of approach.
(e) Broadcast messages
Every ten seconds, the T/TISS-TCAS transmits a broadcast message intended to inform nearby aircraft, themselves equipped with a TCAS, of the presence of a TCAS-equipped aircraft in their traffic area.
These messages, received by the Mode S transponders, are communicated to the T/TISS computer (TCAS function) to enable it to know the number of TCAS-equipped aircraft in its detection envelope. This information is then used in the interference limitation formulas whose results modulate the Mode S interrogation output power level in inverse proportion to the number of aircraft. This reduces the number of non-elicited replies received by ground ATC stations.
The messages transmitted are of the uplink format type UF=16 with the Mode S 24 bit address of the interrogating TCAS included in the MID field (bits 65 to 88) with the UDS field (bits 33 to 40) containing the code F50. No response is expected for this type of message.
Every ten seconds, the T/TISS-TCAS transmits a broadcast message intended to inform nearby aircraft, themselves equipped with a TCAS, of the presence of a TCAS-equipped aircraft in their traffic area.
These messages, received by the Mode S transponders, are communicated to the T/TISS computer (TCAS function) to enable it to know the number of TCAS-equipped aircraft in its detection envelope. This information is then used in the interference limitation formulas whose results modulate the Mode S interrogation output power level in inverse proportion to the number of aircraft. This reduces the number of non-elicited replies received by ground ATC stations.
The messages transmitted are of the uplink format type UF=16 with the Mode S 24 bit address of the interrogating TCAS included in the MID field (bits 65 to 88) with the UDS field (bits 33 to 40) containing the code F50. No response is expected for this type of message.
(f) Communications frequencies
Communications between two aircraft are always crossed between transponder and TCAS. The T/TISS-TCAS transmits at a frequency of 1030 MHz to the transponder of the other aircraft, whose reply signals are at a frequency of 1090 MHz to the T/TISS-TCAS receiver. This choice allows system compatibility with ground station-transponder links as the ground stations use the same frequencies as the TCAS.
Communications between two aircraft are always crossed between transponder and TCAS. The T/TISS-TCAS transmits at a frequency of 1030 MHz to the transponder of the other aircraft, whose reply signals are at a frequency of 1090 MHz to the T/TISS-TCAS receiver. This choice allows system compatibility with ground station-transponder links as the ground stations use the same frequencies as the TCAS.
C. Coordination
Two TCAS-equipped aircraft must coordinate their maneuvers to avoid the flight path corrections ordered by each TCAS resulting in a hazardous situation.
Two TCAS-equipped aircraft must coordinate their maneuvers to avoid the flight path corrections ordered by each TCAS resulting in a hazardous situation.
(1) Coordination principle
In most cases of encounters between two TCAS-equipped aircraft, mutual identification is almost but not quite simultaneous, with sufficient time lag to establish the priority necessary for the coordination process.
The first aircraft to detect a potentially dangerous configuration computes a deviation maneuver sense and communicates it to the other aircraft.
This aircraft takes the information into account and in turn computes a correction.
If two aircraft detect each other at exactly the same time and simultaneously transmit coordination messages containing incompatible deviation senses it is, by convention, the aircraft that has the highest Mode S address that cancels its trajectory correction. A time delay in the display of orders on the display units avoids opposing orders.
In most cases of encounters between two TCAS-equipped aircraft, mutual identification is almost but not quite simultaneous, with sufficient time lag to establish the priority necessary for the coordination process.
The first aircraft to detect a potentially dangerous configuration computes a deviation maneuver sense and communicates it to the other aircraft.
This aircraft takes the information into account and in turn computes a correction.
If two aircraft detect each other at exactly the same time and simultaneously transmit coordination messages containing incompatible deviation senses it is, by convention, the aircraft that has the highest Mode S address that cancels its trajectory correction. A time delay in the display of orders on the display units avoids opposing orders.
(2) Communications protocol
Communications between two aircraft comprises three phases:
Communications between two aircraft comprises three phases:
(a) Detection phase
The T/TISS-TCAS receives squitter messages transmitted by the transponder of the intruder aircraft. These are DF11-type messages transmitted periodically at one second intervals and intended to enable its detection and identification.
This message essentially uses two fields:
The T/TISS-TCAS receives squitter messages transmitted by the transponder of the intruder aircraft. These are DF11-type messages transmitted periodically at one second intervals and intended to enable its detection and identification.
This message essentially uses two fields:
- an AA (Address Announced) field containing the Mode S address which must be acknowledged
- A PI (parity interrogator Identity) field which is the result of a parity encoding using a method of polynominal multiplication. On reception, the Address Announced field is multiplied by the same polynominal and the result is compared with the received value.
(b) Surveillance phase
After detection, a surveillance phase starts. This phase is composed of an acquisition part and a tracking part.
After detection, a surveillance phase starts. This phase is composed of an acquisition part and a tracking part.
1 Acquisition interrogation
When the TCAS receives a squitter and acquires the Mode S address of the intruder it enters into contact by transmitting a UFO-type message (Short special surveillance interrogation) with the following specific fields:
When the TCAS receives a squitter and acquires the Mode S address of the intruder it enters into contact by transmitting a UFO-type message (Short special surveillance interrogation) with the following specific fields:
- bit 9, RL = 0 : reply message length requested short (56 bits)
- bit 14, AQ = 1 : acquisition-type message indication.
2 Acquisition reply
The intruder's transponder replies to this request by a DFO message containing the following information:
The intruder's transponder replies to this request by a DFO message containing the following information:
- bit 6, VS : Vertical Status, = 1 if the aircraft is on the ground, = 0 if the aircraft is airborne
- bits 9 to 11, SL : Sensitivity level indicates in which sensitivity level its TCAS is operating
- bits 14 to 17, RI : combinations of bits, from values 8 to 15, specify the maximum speed the aircraft can reach. The other combinations are not used
- bits 20 to 32, AC : aircraft altitude code indicating the barometric altitude.
3 Tracking interrogation
After its acquisition, the intruder is tracked by UFO-type interrogations with the following field values:
After its acquisition, the intruder is tracked by UFO-type interrogations with the following field values:
- RL = 0 : reply message length requested short
- AQ = 0 : not an acquisition message.
4 Tracking reply
The intruder's transponder replies with a DFO message indicating altitude and TCAS sensitivity level by a combination of fields SL and RI:
The intruder's transponder replies with a DFO message indicating altitude and TCAS sensitivity level by a combination of fields SL and RI:
- SL : bits 9 to 11
- RI : bits 14 to 17, combination values 0 to 7. Values 8 to 15 are not used
- AC : bits 20 to 32, aircraft altitude code.
(c) Coordination phase
If the intruder becomes a threat, the TCAS programs a deviation maneuver to avoid a risk of collision. A coordination procedure is initiated between the two aircraft with an exchange of the following messages :
If the intruder becomes a threat, the TCAS programs a deviation maneuver to avoid a risk of collision. A coordination procedure is initiated between the two aircraft with an exchange of the following messages :
1 Coordination interrogation
The TCAS transmits a UF16 Long Special Surveillance message whose fields contain the following indications:
The TCAS transmits a UF16 Long Special Surveillance message whose fields contain the following indications:
| --------------------------------------------------------------------- |
| ! BITS ! FIELD ! INDICATION ! |
| !-------!-------!---------------------------------------------------! |
| ! 9 ! RL ! = 1 : reply message length requested long ! |
| ! 14 ! AQ ! = 0 : non-acquisition type interrogation ! |
| ! 33-40 ! UDS ! U Definition Subfield - defines the other data ! |
| ! ! ! in the MU field (Comm-U), composed of bits 42 ! |
| ! ! ! to 88 ! |
| ! 42 ! MTB ! Indicates multiple threat processing ! |
| ! 43-44 ! CVC ! Cancel Vertical resolution advisory Complement - ! |
| ! ! ! used to cancel an RA complement sent earlier to ! |
| ! ! ! an intruder ! |
| ! 45-46 ! VRC ! Vertical Resolution advisory Complement - used to! |
| ! ! ! transmit an RA vertical complement to the intru- ! |
| ! ! ! der requesting it not to modify its trajectory ! |
| ! ! ! (don't climb, don't descend) ! |
| ! 47-49 ! CHC ! Cancel Horizontal resolution advisory Complement-! |
| ! ! ! not used in T/TISS-TCAS ! |
| ! 50-52 ! HRC ! Horizontal Resolution advisory Complement - not ! |
| ! ! ! used in T/TISS-TCAS ! |
| ! 53-55 ! ! not used ! |
| ! 56-60 ! HSB ! Encoded Sense bits for Horizontal resolution ! |
| ! ! ! advisory complement - not used in T/TISS-TCAS ! |
| ! 61-64 ! VSB ! Encoded Sense Bits for Vertical resolution advi- ! |
| ! ! ! sory complement - parity code to protect the 4 ! |
| ! ! ! vertical command bits (43-46) ! |
| ! 65-88 ! MID ! Interrogator TCAS-equipped aircraft Mode S ! |
| ! ! ! address. ! |
| --------------------------------------------------------------------- |
2 Coordination reply
After acquisition of this message, the intruder's transponder replies with a Long Special Surveillance DF 16 type message, containing the information previously transmitted to it by its own TCAS:
After acquisition of this message, the intruder's transponder replies with a Long Special Surveillance DF 16 type message, containing the information previously transmitted to it by its own TCAS:
| --------------------------------------------------------------------- |
| ! BITS ! FIELD ! INDICATION ! |
| !-------!-------!---------------------------------------------------! |
| ! 6 ! VS ! Vertical Status - indicates whether aircraft is ! |
| ! ! ! on ground or airborne ! |
| ! 9-11 ! SL ! With RI, SL indicates the sensitivity level at ! |
| ! ! ! which the interrogated aircraft's TCAS is ! |
| ! ! ! operating ! |
| ! 14-17 ! RI ! Reply Information ! |
| ! 20-32 ! AC ! Altitude Code - contains aircraft altitude ! |
| ! ! ! encoded in 100 ft increments if bit 28 equals 0, ! |
| ! ! ! and in 25 ft increments if bit 28 equals 1 ! |
| ! 33-40 ! VDS ! V Definition Subfield defines the contents of the! |
| ! ! ! data and coding in the field MV (Comm V) composed! |
| ! ! ! of bits 41 to 88 ! |
| ! 41-54 ! ARA ! Active Resolution Advisory - indicates the RA ! |
| ! ! ! type currently generated by the T/TISS-TCAS ! |
| ! 55-58 ! RAC ! Resolution Advisory Complement - Indicates the RA! |
| ! ! ! complement type currently received from other ! |
| ! ! ! TCAS-equipped aircraft ! |
| ! 59-88 ! ! Not used ! |
| --------------------------------------------------------------------- |
(d) Correspondence of radio messages with Arinc 429 words
The coordination information exchanged between two aircraft transits via ARINC 429 buses linking the transponder to the T/TISS. The following table gives the correspondence between the two types of link:
The coordination information exchanged between two aircraft transits via ARINC 429 buses linking the transponder to the T/TISS. The following table gives the correspondence between the two types of link:
| --------------------------------------------------- |
| ! 1 - TRANSPONDER TO T/TISS-TCAS ! |
| !-------------------------------------------------! |
| ! ! RADIO MESSAGE ! ARINC MESSAGE ! |
| !---------!-------------------!-------------------! |
| ! FIELD ! MESSAGE ! BITS ! LABEL ! BITS ! |
| !---------!---------!---------!---------!---------! |
| ! MTB ! UF16 ! 42 ! 271 ! 09 ! |
| ! CVC ! ! 43-44 ! ! 10-11 ! |
| ! VRC ! ! 45-46 ! ! 12-13 ! |
| ! CHC ! ! 47-49 ! ! 14-16 ! |
| ! HRC ! ! 50-52 ! ! 17-19 ! |
| ! HSB ! ! 56-60 ! ! 20-24 ! |
| ! VSB ! ! 61-64 ! ! 25-28 ! |
| --------------------------------------------------- |
| --------------------------------------------------- |
| ! 2 - T/TISS-TCAS TO TRANSPONDER ! |
| !-------------------------------------------------! |
| ! ! RADIO MESSAGE ! ARINC MESSAGE ! |
| !---------!-------------------!-------------------! |
| ! FIELD ! MESSAGE ! BITS ! LABEL ! BITS ! |
| !---------!---------!---------!---------!---------! |
| ! SL ! DF16 ! 09-11 ! 274 ! 23-25 ! |
| ! RI ! ! 14-17 ! ! 26-29 ! |
| ! ARA ! ! 41-54 ! 273 ! 12-25 ! |
| ! RAC ! ! 55-58 ! ! 26-29 ! |
| --------------------------------------------------- |
D. Principles of Computation
In the T/TISS-TCAS, target aircraft are categorized depending on specific criteria varying in function of altitude.
The T/TISS-TCAS essentially uses two types of information to perform this classification:
This is the point of minimum distance between the two aircraft, assuming that their trajectories do not deviate.
The two criteria are:
In the T/TISS-TCAS, target aircraft are categorized depending on specific criteria varying in function of altitude.
The T/TISS-TCAS essentially uses two types of information to perform this classification:
- the relative altitude between two aircraft, known by the difference of their standard barometric altitudes
- the distance or range separating them.
- altitude rate
- range rate.
This is the point of minimum distance between the two aircraft, assuming that their trajectories do not deviate.
The two criteria are:
- vertical separation at CPA
- time left before reaching CPA.
(1) Projected vertical separation
The threat is evaluated by calculating the vertical separation between the two aircraft at the closest point of approach.
The T/TISS computer (TCAS function) processes the current altitude and altitude rate of the intruder to predict whether it will be within limits considered dangerous at the closest point of approach.
Intruder 1 penetrates the altitude zone delimited by the upper and lower thresholds but when it reaches CPA, it will be outside this zone.
Therefore no advisory will be issued.
However, when intruder 2 reaches CPA it is still inside this zone and therefore an advisory will be issued.
The threat is evaluated by calculating the vertical separation between the two aircraft at the closest point of approach.
The T/TISS computer (TCAS function) processes the current altitude and altitude rate of the intruder to predict whether it will be within limits considered dangerous at the closest point of approach.
Intruder 1 penetrates the altitude zone delimited by the upper and lower thresholds but when it reaches CPA, it will be outside this zone.
Therefore no advisory will be issued.
However, when intruder 2 reaches CPA it is still inside this zone and therefore an advisory will be issued.
(2) Time to intercept (TAU)
The TCAS does not need to locate the CPA in space, but rather it needs to know the time to intercept for two aircraft. For example, if two aircraft are approaching on the same axis on a collision course, this time is the ratio of distance between them to the sum of their speeds.
With the risk of collision being in inverse proportion to this time, trajectory correction orders are initiated by crossing predetermined time thresholds whose values depend on the altitude layer in which the aircraft is located.
This method of calculation avoids the initiation of corrections if, from a certain distance, the TAU trend is inverted even though the distance separating the two aircraft decreases. For example, in the case of two aircraft moving on parallel axes but in the opposite direction.
The curve represents the TAU variation before the closest point of approach.
This time decreases as the range decreases, reaches a minimum when the intruder's relative bearing is 45° and then increases rapidly. If the time corresponding to a predetermined threshold has not been reached before the minimum TAU value, a trajectory correction will not be initiated.
Certain conditions exist, however, in which this formula may prove insufficient. This may arise for example when two aircraft fly in the same direction with a very low closure rate. In this case, the range/range rate ratio gives a high TAU value whereas in fact, the two aircraft could be very near.
The TCAS uses a slightly different formula to preclude this situation:
This formula represents an estimate of the time the aircraft would take to penetrate a sphere around the intruder with a radius equal to (DMOD)expnt2/range. The DMOD coefficient is in function of altitude, ranging from 0.20 NM for 1000-2350 ft, to 1.1 NM above 20,000 ft as shown below:
The TCAS does not need to locate the CPA in space, but rather it needs to know the time to intercept for two aircraft. For example, if two aircraft are approaching on the same axis on a collision course, this time is the ratio of distance between them to the sum of their speeds.
| D |
| T = --------- |
| V1 + V2 |
| More generally, the TCAS uses range and range rate measurement to |
| compute this time : |
| RANGE R(NM) |
| TAU = ------------ i.e. TAU(s) = 3600 -------- |
| RANGE RATE RR (Kts) |
With the risk of collision being in inverse proportion to this time, trajectory correction orders are initiated by crossing predetermined time thresholds whose values depend on the altitude layer in which the aircraft is located.
This method of calculation avoids the initiation of corrections if, from a certain distance, the TAU trend is inverted even though the distance separating the two aircraft decreases. For example, in the case of two aircraft moving on parallel axes but in the opposite direction.
The curve represents the TAU variation before the closest point of approach.
This time decreases as the range decreases, reaches a minimum when the intruder's relative bearing is 45° and then increases rapidly. If the time corresponding to a predetermined threshold has not been reached before the minimum TAU value, a trajectory correction will not be initiated.
Certain conditions exist, however, in which this formula may prove insufficient. This may arise for example when two aircraft fly in the same direction with a very low closure rate. In this case, the range/range rate ratio gives a high TAU value whereas in fact, the two aircraft could be very near.
The TCAS uses a slightly different formula to preclude this situation:
| range - X (DMOD) expnt2 |
| TAU = ---------- with X = ---------------- |
| range rate range |
This formula represents an estimate of the time the aircraft would take to penetrate a sphere around the intruder with a radius equal to (DMOD)expnt2/range. The DMOD coefficient is in function of altitude, ranging from 0.20 NM for 1000-2350 ft, to 1.1 NM above 20,000 ft as shown below:
| -------------------------------------------------- |
| ! Altitude ! DMOD TA ! DMOD RA ! |
| ! (ft) ! (NM) ! (NM) ! |
| -------------------------------------------------- |
| ! 0-1000 ! 0.30 ! ---- ! |
| ! 1000-2350 ! 0.33 ! 0.20 ! |
| ! 2350-5000 ! 0.48 ! 0.35 ! |
| ! 5000-10000 ! 0.75 ! 0.55 ! |
| ! 10000-20000 ! 1.00 ! 0.80 ! |
| ! more than 20000 ! 1.30 ! 1.10 ! |
| -------------------------------------------------- |
E. Definition of Target Aircraft
Target aircraft are divided into four categories : OTHER - PROXIMATE - TRAFFIC ADVISORY (TA) - RESOLUTION ADVISORY (RA).
Target aircraft are divided into four categories : OTHER - PROXIMATE - TRAFFIC ADVISORY (TA) - RESOLUTION ADVISORY (RA).
(1) OTHER aircraft
Aircraft detected by the TCAS are defined as OTHER if they do not enter in PROXIMATE, TA or RA categories. They are displayed on the ND in:
The THRT/ALL/ABV/BLW switch on the ATC/TCAS control unit selects these configurations.
Aircraft detected by the TCAS are defined as OTHER if they do not enter in PROXIMATE, TA or RA categories. They are displayed on the ND in:
- normal configuration from -2700 ft to +2700 ft
- above configuration from -2700 ft to +9900 ft
- below configuration from -9900 ft to +2700 ft.
The THRT/ALL/ABV/BLW switch on the ATC/TCAS control unit selects these configurations.
(2) PROXIMATE aircraft
Targets are defined as proximate traffic if the difference between their altitude and that of the TCAS aircraft is less than 1200 ft and if their range is within 6 NM.
Their presentation on the ND is conditioned by the presence of another TA or RA intruder.
Generally aircraft not in the immediate vicinity enter into this category.
Depending on their trajectory, they may :
Targets are defined as proximate traffic if the difference between their altitude and that of the TCAS aircraft is less than 1200 ft and if their range is within 6 NM.
Their presentation on the ND is conditioned by the presence of another TA or RA intruder.
Generally aircraft not in the immediate vicinity enter into this category.
Depending on their trajectory, they may :
- conserve this status and move away without an advisory being declared.
In this case the pilot is informed of their presence on the ND by a white filled diamond symbol and can monitor their progress, or - have a trajectory liable to lead to a conflict situation and in this case they require a traffic advisory and their symbol changes.
(3) TRAFFIC ADVISORY aircraft
When an intruder is relatively near but does not represent an immediate threat, the TCAS issues a traffic advisory. Its presence is displayed on the ND by an amber filled circle. Its display is accompanied by an aural alert:
The pilot is therefore aware of its presence and knows its range and relative bearing. Its display is linked to vertical separation and time TAU before CPA values.
Depending on its trajectory, an intruder may conserve this status and move away, or it may become a collision threat. In this case avoidance maneuvers are suggested to the pilot via a resolution advisory.
When an intruder is relatively near but does not represent an immediate threat, the TCAS issues a traffic advisory. Its presence is displayed on the ND by an amber filled circle. Its display is accompanied by an aural alert:
| "Traffic Traffic". |
The pilot is therefore aware of its presence and knows its range and relative bearing. Its display is linked to vertical separation and time TAU before CPA values.
Depending on its trajectory, an intruder may conserve this status and move away, or it may become a collision threat. In this case avoidance maneuvers are suggested to the pilot via a resolution advisory.
(4) RESOLUTION ADVISORY aircraft
In resolution displays, the intruder is represented on the ND by a red filled square and corrective orders are issued on the vertical speed scale of the PFD. Crossing into resolution advisory occurs for a TAU time threshold 10 to 15 seconds lower than a traffic advisory threshold.
Vertical separation between the two aircraft is also taken into account for this category. There are two types of resolution advisory, in function of the vertical separation value:
- Preventive Advisories
- Corrective Advisories.
In resolution displays, the intruder is represented on the ND by a red filled square and corrective orders are issued on the vertical speed scale of the PFD. Crossing into resolution advisory occurs for a TAU time threshold 10 to 15 seconds lower than a traffic advisory threshold.
Vertical separation between the two aircraft is also taken into account for this category. There are two types of resolution advisory, in function of the vertical separation value:
- Preventive Advisories
- Corrective Advisories.
(a) Preventive advisory
In this case the vertical separation is less than a threshold S1 and greater than a threshold S2. The advisory instructs the pilot to avoid certain deviations from current vertical rate, this measure being sufficient to avoid a risk of collision. On the PFD speed scale, the forbidden values are indicated by red sectors.
In this case the vertical separation is less than a threshold S1 and greater than a threshold S2. The advisory instructs the pilot to avoid certain deviations from current vertical rate, this measure being sufficient to avoid a risk of collision. On the PFD speed scale, the forbidden values are indicated by red sectors.
(b) Corrective advisory
In this case, the vertical separation is lower than the threshold S2.
On the vertical speed scale of the PFD, colored sectors depict avoidance maneuvers to be performed:
- red sector = forbidden vertical speeds
- green "fly to" sector = a vertical speed range to be respected.
In this case, the vertical separation is lower than the threshold S2.
On the vertical speed scale of the PFD, colored sectors depict avoidance maneuvers to be performed:
- red sector = forbidden vertical speeds
- green "fly to" sector = a vertical speed range to be respected.
(c) Aural alerts
Trajectory correction or holding visual orders are accompanied by synthesized voice announcements whose level cannot be adjusted by the pilot. These announcements are generated by the T/TISS computer (TCAS function) and broadcast via the cockpit loud speakers. These messages and their meanings are described below:
Trajectory correction or holding visual orders are accompanied by synthesized voice announcements whose level cannot be adjusted by the pilot. These announcements are generated by the T/TISS computer (TCAS function) and broadcast via the cockpit loud speakers. These messages and their meanings are described below:
- "CLIMB, CLIMB":
Climb at the rate shown by the green sector on the PFD (1500 ft/min), - "CLIMB, CROSSING CLIMB, CLIMB, CROSSING CLIMB":
As above except that it further indicates that own flight path will cross through that of the intruder, - "INCREASE CLIMB, INCREASE CLIMB":
Follows a "climb" advisory. The vertical speed of the aircraft should be increased (2500 ft/min), - "CLIMB, CLIMB NOW, CLIMB, CLIMB NOW":
Follows a "descend" advisory when a reversal in sense is required to achieve safe vertical separation from a maneuvering intruder, - "DESCEND, DESCEND":
Descend at the rate indicated by the green sector on the PFD (-1500 ft/min), - "DESCEND, CROSSING DESCEND, DESCEND, CROSSING DESCEND":
As above except that it further indicates that own flight path will cross through that of the intruder, - "INCREASE DESCENT, INCREASE DESCENT":
Follows a "descend" advisory. The vertical speed of the descent should be increased (-2500 ft/min), - "DESCEND, DESCEND NOW, DESCEND, DESCEND NOW":
Follows a "climb" advisory when a reversal in sense is required to achieve safe vertical separation from a maneuvering intruder, - "LEVEL OFF, LEVEL OFF":
Reduce vertical speed to 0 ft/min, as shown on the PFD.
It can correspond to a level-off while climbing or descending.
It can also represent a weakening of corrective RA.
- "MONITOR VERTICAL SPEED":
Indicates that a forbidden vertical speed range exists (red sector) and that pilot must monitor vertical speed so as not to enter this range (Preventive Advisory). - "MAINTAIN VERTICAL SPEED, MAINTAIN":
Indicates a non-crossing advisory type, maintains rate (corrective). - "MAINTAIN VERTICAL SPEED, CROSSING MAINTAIN":
Indicates an altitude crossing advisory type, maintains rate (corrective).
These messages are spoken only once if softening from a previous corrective advisory - "CLEAR OF CONFLICT":
Indicates that separation has been achieved and range has started to increase.
(5) Advisory inhibit conditions
In certain particular conditions, certain advisories are not generated as they could lead to the pilot adopting flight conditions that are hazardous or outside the aircraft's performance capability.
In certain particular conditions, certain advisories are not generated as they could lead to the pilot adopting flight conditions that are hazardous or outside the aircraft's performance capability.
(a) Low altitude inhibitions
Ground proximity leads to the inhibition of those advisories liable to cause a hazardous situation at this level. In decreasing altitude, these are:
Ground proximity leads to the inhibition of those advisories liable to cause a hazardous situation at this level. In decreasing altitude, these are:
- below 1550 +/- 100 ft above ground level (AGL) inhibition of "Increase Descend" resolution advisories (RA)
- below 1100 +/- 100 ft AGL, inhibition of "Descend" resolution advisories (RA)
- TCAS automatic switching to TA Only mode below 1000 ft +/- 100 ft AGL (inhibition of all resolution advisories).
- inhibition of aural traffic advisories (TA) below 500 +/- 100 ft (600 ft in climb, 400 ft in descent).
(b) High altitude inhibition
Above 48,000 ft, limit given by pin program, further climb orders are inapplicable as the aircraft performance capability does not permit them to be taken into account.
"Climb" advisories are therefore inhibited above this altitude.
Above 48,000 ft, limit given by pin program, further climb orders are inapplicable as the aircraft performance capability does not permit them to be taken into account.
"Climb" advisories are therefore inhibited above this altitude.
NOTE: Other inhibitions exist for alert priority management (Ref 34-72-00,Para. 7. A.).
(c) Rejection of signals from aircraft on ground
Intruders declared to be on-ground can never cause proximate, traffic or resolution advisory (TA, RA.) and are not displayed on the Navigation Display. Determination of Airborne/On ground status:
In the figure, the intruder's height above ground level can be deduced:
Intruders declared to be on-ground can never cause proximate, traffic or resolution advisory (TA, RA.) and are not displayed on the Navigation Display. Determination of Airborne/On ground status:
- If the intruder is equipped with a Mode S transponder, the ground/flight status is sent in the DF message. The TCAS 7.0 directly knows if this intruder is on the ground.
NOTE: Former version of the TCAS applied the conversion algorithm as described below.
- If the intruder's ground/flight status is not directly available (Mode C Transponder for instance), the TCAS shall process the barometric altitude broadcast by the intruder (process described below) to convert it into height above ground level. Then, the intruder is declared to be on-ground if it is below 360 ft AGL when descending, and 400 ft AGL when climbing (380 +/- 20 ft).
In the figure, the intruder's height above ground level can be deduced:
| Z i/s = Z t/s -(Z t/m - Z i/m) |
| Where: Z i/s = height of intruder above ground level |
| Z i/m = altitude of intruder above sea level |
| Z t/s = height of TCAS above ground level measured by |
| radio altimeter |
| Z t/m = altitude of TCAS above sea level measured by |
| ADIRU |
F. Sensitivity Level
The notion of sensitivity level is very important in the TCAS as many of the operating modes depend on it.
The TCAS separates the surrounding airspace into altitude layers. A different Sensitivity Level (SL) threshold for issuing advisories is applied to each altitude layer.
The sensitivity level is decreased at low altitude to prevent unnecessary advisories in higher traffic densities such as terminal areas.
Generally, the level is determined automatically by the TCAS in function of:
1000 +/- 100 ft; 2350 +/- 200 ft; 5000 +/- 500 ft;
10000 +/- 500 ft; 20000 +/- 500 ft; 42000 +/- 500 ft.
For example, to switch from sensitivity level 3 to sensitivity level 2, the altitude must fall below 900 ft. However, to switch from sensitivity level 2 to sensitivity level 3, the altitude value must go above 1100 ft.
There are two other means of modifying the sensitivity level:
First a sensitivity level based on altitude is selected. Level 2 is selected if the radio altimeter altitude is less than 1000 ft. Level 2 is also selected if own aircraft is configured such that both CLIMB and DESCEND RAs are inhibited (e.g., below 1000 ft AGL with insufficient climb performance). Level 3 is selected if the aircraft is above 1000 ft and below 2350 ft AGL. If the aircraft is above 2350 ft AGL, barometric altitude is used to select either level 4 (from 2350 to 5000), level 5 (below 10,000 ft), 6 (from 10,000 to 20,000 ft), and 7 (above 20,000 ft).
ATC/TCAS control unit input is read by the T/TISS computer (TCAS function). If the pilot has selected Automatic Mode (TA/RA), then the altitude-based sensitivity level will be used in comparisons to determine the final level.
The notion of sensitivity level is very important in the TCAS as many of the operating modes depend on it.
The TCAS separates the surrounding airspace into altitude layers. A different Sensitivity Level (SL) threshold for issuing advisories is applied to each altitude layer.
The sensitivity level is decreased at low altitude to prevent unnecessary advisories in higher traffic densities such as terminal areas.
Generally, the level is determined automatically by the TCAS in function of:
- altitude values from the radio altimeter up to 2500 ft AGL
- barometric altitude values in the 2500 ft to 48,000 ft range. TAU values corresponding to each sensitivity level indicate the TA and RA thresholds. The vertical separation thresholds at CPA also vary in function of the sensitivity level for the different types of advisory.
| ---------------------------------------------------------------------- |
| ! ! TAU thresholds ! Vertical separation ! |
| ! ! ! thresholds ! |
| !----------------------------!-----------------!---------------------! |
| ! Source ! Altitude ! SL TA RA ! S0 S1 S2 ! |
| ! Altitude ! ! ! TA RA RA ! |
| ! ! ! ! prev cor ! |
| ! ! (ft) ! (sec) (sec) ! (ft) (ft) (ft) ! |
| !--------------------------------------------------------------------! |
| ! Radio Alt !less than 1000 ! 2 20 ! 850 ! |
| ! Radio Alt ! 1000-2350 ! 3 25 15 ! 850 600 300 ! |
| ! Baro ! 2350-5000 ! 4 30 20 ! 850 600 300 ! |
| ! Baro ! 5000-10000 ! 5 40 25 ! 850 600 350 ! |
| ! Baro ! 10000-20000 ! 6 45 30 ! 850 600 400 ! |
| ! Baro ! 20000-42000 ! 7 48 35 ! 850 700 600 ! |
| ! Baro !more than 42000! 7 48 35 ! 1200 800 700 ! |
| ---------------------------------------------------------------------- |
NOTE: Level 1 corresponds to Standby Mode in which no advisory is generated.
NOTE: This table indicates the threshold based on own aircraft altitude.
Each aircraft altitude depends on a hysteresis: 1000 +/- 100 ft; 2350 +/- 200 ft; 5000 +/- 500 ft;
10000 +/- 500 ft; 20000 +/- 500 ft; 42000 +/- 500 ft.
For example, to switch from sensitivity level 3 to sensitivity level 2, the altitude must fall below 900 ft. However, to switch from sensitivity level 2 to sensitivity level 3, the altitude value must go above 1100 ft.
There are two other means of modifying the sensitivity level:
- selecting TA only mode on the ATC/TCAS control unit forces level 2. In this case, intruders of all types are displayed but will not be transformed into RA symbols and no vertical speed modification indications will be issued.
- the ATC Mode S-equipped ground stations may modify the sensitivity level of the aircraft TCAS via the uplink without, however, having the capability to force the Standby Mode. If several ground stations command sensitivity levels, the TCAS logic selects the lowest level.
First a sensitivity level based on altitude is selected. Level 2 is selected if the radio altimeter altitude is less than 1000 ft. Level 2 is also selected if own aircraft is configured such that both CLIMB and DESCEND RAs are inhibited (e.g., below 1000 ft AGL with insufficient climb performance). Level 3 is selected if the aircraft is above 1000 ft and below 2350 ft AGL. If the aircraft is above 2350 ft AGL, barometric altitude is used to select either level 4 (from 2350 to 5000), level 5 (below 10,000 ft), 6 (from 10,000 to 20,000 ft), and 7 (above 20,000 ft).
ATC/TCAS control unit input is read by the T/TISS computer (TCAS function). If the pilot has selected Automatic Mode (TA/RA), then the altitude-based sensitivity level will be used in comparisons to determine the final level.
G. Information Display
The TCAS information is presented on the CAPT and F/O NDs. Additional messages can also be presented on the upper ECAM DU.
The TCAS information is presented on the CAPT and F/O NDs. Additional messages can also be presented on the upper ECAM DU.
(1) Traffic information on the ND
Target aircraft are presented on the ND in ROSE or ARC mode but not in PLAN mode.
These traffic indications show the situation in the surveillance zone.
The aircraft present in this zone are represented by symbols whose shape and color correspond to the type of intruders defined in the TCAS.
The symbols are positioned on the ND so as to depict their relative bearing and range. Data tags are associated with intruders.
These tags consist of:
Targets are symbolized according to their type:
Target aircraft are presented on the ND in ROSE or ARC mode but not in PLAN mode.
These traffic indications show the situation in the surveillance zone.
The aircraft present in this zone are represented by symbols whose shape and color correspond to the type of intruders defined in the TCAS.
The symbols are positioned on the ND so as to depict their relative bearing and range. Data tags are associated with intruders.
These tags consist of:
- two digits indicating their relative altitude in hundreds of feet
- a symbol indicating whether the intruder is above (+) or below (-) the aircraft.
Targets are symbolized according to their type:
- OTHER : white unfilled diamond, height 7 mm
- PROXIMATE TRAFFIC : white filled diamond, height 7 mm
- TRAFFIC ADVISORY : amber filled circle, diameter 5 mm
- RESOLUTION ADVISORY : red filled square, side 5 mm.
(2) The display only presents the eight most threatening intruders (number determined through program pins on the T/TISS computer).
The own aircraft is represented by the aircraft symbol at the center of the dial in ROSE mode and at the lower quarter and at the center of the image in ARC mode.
A white range ring with markings at each of the twelve clock positions is placed around the own aircraft symbol at a radius of 2.5 NM.
The following figure shows an example of the display on the ND:
These indications are only presented for the 10, 20 and 40 NM range selections. If a TA or RA type intruder is detected and the display range is at a higher scale, the following message comes into view at the center of the display, in red for RA and in amber for TA:
REDUCE RANGE
If a TA or RA type intruder is detected and the ND mode is inadequate for display, the following message comes into view at the center of the display in the same colors as above:
CHANGE MODE
The TCAS can detect an intruder without acquiring its bearing (for instance, multipath problem). In this case its range, relative altitude and an arrow are displayed in the TCAS area (at the bottom of the ND).
The color of the display is the same as the color of the intruder symbol.
OFF SCALE intruder: if only one half of the symbol is displayed, the target is defined as an off scale intruder. This calls for increasing the range selection on the ND.
The own aircraft is represented by the aircraft symbol at the center of the dial in ROSE mode and at the lower quarter and at the center of the image in ARC mode.
A white range ring with markings at each of the twelve clock positions is placed around the own aircraft symbol at a radius of 2.5 NM.
The following figure shows an example of the display on the ND:
These indications are only presented for the 10, 20 and 40 NM range selections. If a TA or RA type intruder is detected and the display range is at a higher scale, the following message comes into view at the center of the display, in red for RA and in amber for TA:
REDUCE RANGE
If a TA or RA type intruder is detected and the ND mode is inadequate for display, the following message comes into view at the center of the display in the same colors as above:
CHANGE MODE
The TCAS can detect an intruder without acquiring its bearing (for instance, multipath problem). In this case its range, relative altitude and an arrow are displayed in the TCAS area (at the bottom of the ND).
The color of the display is the same as the color of the intruder symbol.
OFF SCALE intruder: if only one half of the symbol is displayed, the target is defined as an off scale intruder. This calls for increasing the range selection on the ND.
(3) Traffic information on the ND
Target aircraft are presented on the ND in ROSE or ARC mode but not in PLAN mode.
These traffic indications show the situation in the surveillance zone.
The aircraft present in this zone are represented by symbols whose shape and color correspond to the type of intruders defined in the TCAS.
The symbols are positioned on the ND so as to depict their relative bearing and range. Data tags are associated with intruders.
These tags consist of:
Targets are symbolized according to their type:
Target aircraft are presented on the ND in ROSE or ARC mode but not in PLAN mode.
These traffic indications show the situation in the surveillance zone.
The aircraft present in this zone are represented by symbols whose shape and color correspond to the type of intruders defined in the TCAS.
The symbols are positioned on the ND so as to depict their relative bearing and range. Data tags are associated with intruders.
These tags consist of:
- two digits indicating their relative altitude in hundreds of feet
- a symbol indicating whether the intruder is above (+) or below (-) the aircraft.
Targets are symbolized according to their type:
- OTHER TRAFFIC: white outlined diamond or aircraft symbol, height 7 mm
- PROXIMATE TRAFFIC: white filled diamond or aircraft symbol, height 7 mm
- TRAFFIC ADVISORY: amber filled circle or aircraft symbol, diameter 5 mm
- RESOLUTION ADVISORY: red filled square or aircraft symbol, side 5 mm.
(a) Three aircraft symbols can be displayed on the ND
- TCAS only traffic: No ADS-B information is received from corresponding aircraft, or ADS-B and ACAS information is not correlated.
- ADS-B only traffic: Only ADS-B information is received. Corresponding aircraft may be out of TCAS range of detection.
- Dual traffic (TCAS + ADS-B): The corresponding traffic transmits ADS-B information within TCAS detection range and both ACAS and ADS-B information is correlated.
(4) The display only presents the eight most threatening intruders (number determined through program pins on the T/TISS computer).
The own aircraft is represented by the aircraft symbol at the center of the dial in ROSE mode and at the lower quarter and at the center of the image in ARC mode.
A white range ring with markings at each of the twelve clock positions is placed around the own aircraft symbol at a radius of 2.5 NM.
The following figure shows an example of the display on the ND:
These indications are only presented for the 10, 20 and 40 NM range selections. If a TA or RA type intruder is detected and the display range is at a higher scale, the following message comes into view at the center of the display, in red for RA and in amber for TA:
REDUCE RANGE
If a TA or RA type intruder is detected and the ND mode is inadequate for display, the following message comes into view at the center of the display in the same colors as above:
CHANGE MODE
The TCAS can detect an intruder without acquiring its bearing (for instance, multipath problem). In this case its range, relative altitude and an arrow are displayed in the TCAS area (at the bottom of the ND).
The color of the display is the same as the color of the intruder symbol.
The own aircraft is represented by the aircraft symbol at the center of the dial in ROSE mode and at the lower quarter and at the center of the image in ARC mode.
A white range ring with markings at each of the twelve clock positions is placed around the own aircraft symbol at a radius of 2.5 NM.
The following figure shows an example of the display on the ND:
These indications are only presented for the 10, 20 and 40 NM range selections. If a TA or RA type intruder is detected and the display range is at a higher scale, the following message comes into view at the center of the display, in red for RA and in amber for TA:
REDUCE RANGE
If a TA or RA type intruder is detected and the ND mode is inadequate for display, the following message comes into view at the center of the display in the same colors as above:
CHANGE MODE
The TCAS can detect an intruder without acquiring its bearing (for instance, multipath problem). In this case its range, relative altitude and an arrow are displayed in the TCAS area (at the bottom of the ND).
The color of the display is the same as the color of the intruder symbol.
(5) The TRAFFIC SELECTOR switch is a rotary knob with push/pull switch that allows interaction on the ND and has an impact on the ATSAW specific traffic pages on the MCDU:
- a clockwise rotation highlights the traffic displayed on the ND, from the closest to the farthest
- an counterclockwise rotation highlights the traffic displayed on the ND, from the farthest to the closest
- a quick rotation (whatever the direction) deactivates the highlight.
- a pull action selects the aircraft that is already highlighted.
- a push action deactivates the selection AND the highlight of the aircraft that is already selected and highlighted.
(a) The Highlight status is shown as follows:
- a cyan circle on the ND when aircraft is displayed on the ND
- cyan brackets on the TRAFFIC LIST page on the MCDU when the Highlight aircraft is displayed on the current TRAFFIC LIST page.
(b) The Selection status is shown as follows:
If the aircraft is displayed on ND, its flight ID is displayed in big characters on traffic list page.
Aircraft with flight ID displayed in small characters are not displayed on ND.
A prompt in front of one aircraft flight ID opens corresponding single aircraft page
- full label written in cyan on both NDs
- A/C Flight ID written in cyan on the TRAFFIC LIST page on the MCDU.
If the aircraft is displayed on ND, its flight ID is displayed in big characters on traffic list page.
Aircraft with flight ID displayed in small characters are not displayed on ND.
A prompt in front of one aircraft flight ID opens corresponding single aircraft page
(6) Aircraft control information on the PFD
Resolution advisories are represented on the vertical speed scale of the PFD by indications given in the form of a band made up of colored sectors:
Resolution advisories are represented on the vertical speed scale of the PFD by indications given in the form of a band made up of colored sectors:
- a red sector represents a forbidden vertical speed range
- a green sector indicates the vertical speed range the aircraft should fly in to avoid a collision threat represented by one or more intruders.
(7) Corrective advisory display
Corrective resolution advisories are displayed to advise the crew to perform an avoidance maneuver in the vertical sense.
This maneuver may take different forms:
The grey background is replaced by green and red sectors defining the optimum vertical speed values.
The pilot's task is to maneuver the aircraft to keep the needle out of the red sectors and place it in the adjacent green "Fly-to" sector.
The vertical speed information needle and digits is colored in red when the vertical speed is in the forbidden area. It becomes green when the vertical speed is in the authorized area.
Corrective resolution advisories are displayed to advise the crew to perform an avoidance maneuver in the vertical sense.
This maneuver may take different forms:
- climb or descent if the aircraft is in level flight
- reducing or increasing rate of climb or reversing to descent if the aircraft is in climb
- reducing or increasing rate of descent or reversing to climb if the aircraft is in descent.
The grey background is replaced by green and red sectors defining the optimum vertical speed values.
The pilot's task is to maneuver the aircraft to keep the needle out of the red sectors and place it in the adjacent green "Fly-to" sector.
The vertical speed information needle and digits is colored in red when the vertical speed is in the forbidden area. It becomes green when the vertical speed is in the authorized area.
(8) Preventive advisory display
Preventive resolution advisories advise the pilot to avoid vertical speeds that could lead to a hazardous situation.
They are represented by one or two red sectors on the vertical speed scale.
The pilot must keep the vertical speed of his aircraft outside these zones.
For example, if own and intruder's flight paths are horizontal and cross through each other, the intruder being at a higher flight level, if the vertical separation is sufficient it is not necessary to modify the aircraft flight path. The positive vertical speed sector is in red to indicate that the aircraft may remain at its present level or may descend but must not climb.
If intruders are detected above and below, two red sectors are displayed leaving an uncolored zone around the zero value on the vertical speed scale advising the pilot to maintain the aircraft at its current level.
The following figure shows several examples of corrective and preventive advisories.
Preventive resolution advisories advise the pilot to avoid vertical speeds that could lead to a hazardous situation.
They are represented by one or two red sectors on the vertical speed scale.
The pilot must keep the vertical speed of his aircraft outside these zones.
For example, if own and intruder's flight paths are horizontal and cross through each other, the intruder being at a higher flight level, if the vertical separation is sufficient it is not necessary to modify the aircraft flight path. The positive vertical speed sector is in red to indicate that the aircraft may remain at its present level or may descend but must not climb.
If intruders are detected above and below, two red sectors are displayed leaving an uncolored zone around the zero value on the vertical speed scale advising the pilot to maintain the aircraft at its current level.
The following figure shows several examples of corrective and preventive advisories.
(9) Messages annunciated on the ND
As well as intruder information, the ND also displays operating mode messages or fault data. This information is presented in the lower section of the ND (message zone):
As well as intruder information, the ND also displays operating mode messages or fault data. This information is presented in the lower section of the ND (message zone):
- TA ONLY - white - for the TA mode (automatic or manual switching)
- TCAS - red or amber - to indicate a T/TISS computer failure.
(10) Display on the PFD
A red or amber TCAS flag appears to the left of the vertical speed scale on the PFD if the TCAS cannot deliver RA data.
A red or amber TCAS flag appears to the left of the vertical speed scale on the PFD if the TCAS cannot deliver RA data.
(11) Display on the upper ECAM DU
- If a TCAS failure is detected, the amber warning message NAV TCAS FAULT is displayed on the upper ECAM DU and an amber Inop Sys "TCAS" is displayed on the lower ECAL DU.
- Selection of the TCAS STBY mode on the ATC/TCAS control unit results in the display of the TCAS STBY message (green) in the memo section of the upper ECAM DU. It will inhibit the NAV TCAS FAULT message on the upper ECAM DU.
H. ATC/TCAS Control Unit-Operational Use
The TCAS is a cooperative system whose operating mode is very close to the ATC Mode S transponder associated to it.
The main controls are thus grouped on the ATC/TCAS control unit and the traffic and conflict resolution information is presented on the EFIS displays.
The TCAS is a cooperative system whose operating mode is very close to the ATC Mode S transponder associated to it.
The main controls are thus grouped on the ATC/TCAS control unit and the traffic and conflict resolution information is presented on the EFIS displays.
NOTE: - Operation of the ATC Mode S transponder is described in 34-52.
- The EFIS components are also described in 31-64 for the PFD and 31-65 for the ND.
The manual operating modes of the TCAS are selected via the ATC/TCAS control unit. - The EFIS components are also described in 31-64 for the PFD and 31-65 for the ND.
(1) TCAS modes of operation
The TCAS mode of operation is selected by means of two selector switches:
The TCAS mode of operation is selected by means of two selector switches:
- STBY, TA and TA/RA
- THRT, ALL, ABV and BLW.
(a) STBY mode
In the Standby Mode, the advisory generation and surveillance functions are inhibited. No TCAS information can be displayed on the PFDs and NDs.
The aircraft symbol and the range ring remain on the ND and vertical speed information is not displayed on the PFD.
The green TCAS STBY message is displayed in the memo section of the upper ECAM DU.
In the Standby Mode, the advisory generation and surveillance functions are inhibited. No TCAS information can be displayed on the PFDs and NDs.
The aircraft symbol and the range ring remain on the ND and vertical speed information is not displayed on the PFD.
The green TCAS STBY message is displayed in the memo section of the upper ECAM DU.
(b) TA mode
In this mode, intruders are displayed on the ND according to their position in the airspace. The RA type intruder symbols are converted into TA type symbols. The TCAS performs surveillance functions but does not generate any resolution advisories.
The TA ONLY message is displayed in white on the NDs in the left corner of the TCAS message area.
In this mode, intruders are displayed on the ND according to their position in the airspace. The RA type intruder symbols are converted into TA type symbols. The TCAS performs surveillance functions but does not generate any resolution advisories.
The TA ONLY message is displayed in white on the NDs in the left corner of the TCAS message area.
(c) TA/RA mode
The TCAS performs all TA mode functions and also issues preventive or corrective resolution advisories, represented in the form of colored sectors along the vertical speed scale on the PFD.
The sensitivity level is determined automatically in function of altitude.
The TCAS performs all TA mode functions and also issues preventive or corrective resolution advisories, represented in the form of colored sectors along the vertical speed scale on the PFD.
The sensitivity level is determined automatically in function of altitude.
NOTE: The final mode of operation is a combination taking into account the aircraft altitude and any instructions received from ATC Mode S ground stations. For further information refer to the priority logic definition (Ref. Para. 4. F.).
(d) THRT mode
In this mode, TCAS intruders (proximate or/and other) are displayed if a TA or a RA is already displayed.
In this mode, TCAS intruders (proximate or/and other) are displayed if a TA or a RA is already displayed.
(e) ALL mode
This selection enables display of all intruders without any conditions (TCAS intruders are displayed when detected).
This selection enables display of all intruders without any conditions (TCAS intruders are displayed when detected).
(f) ABV and BLW modes
This selection controls the above and below vertical altitude for traffic advisory:
This selection controls the above and below vertical altitude for traffic advisory:
- ABV: altitude range is set to 9900 ft above the aircraft and 2700 ft below
- BLW: altitude range is set to 9900 ft below the aircraft and 2700 ft above.
(2) ATC mode of operation
The mode of operation of the transponder is selected by a switch with three positions STBY, AUTO, ON.
The mode of operation of the transponder is selected by a switch with three positions STBY, AUTO, ON.
(a) STBY mode
When the transponder is in standby it does not transmit either squitters or replies to ground station or other aircraft interrogations.
When the transponder is in standby it does not transmit either squitters or replies to ground station or other aircraft interrogations.
(b) AUTO mode
In flight, the aircraft operates as in the ON mode : all its functions are active.
When the aircraft touches down, the landing gear ground/flight relay disables the Mode A and C replies of the selected transponder from ground station interrogations.
However the Mode S replies and squitter are not inhibited when the A/C is on the ground.
In flight, the aircraft operates as in the ON mode : all its functions are active.
When the aircraft touches down, the landing gear ground/flight relay disables the Mode A and C replies of the selected transponder from ground station interrogations.
However the Mode S replies and squitter are not inhibited when the A/C is on the ground.
(c) ON mode
The Mode S transponder operates permanently, both in flight and on the ground. It periodically transmits squitters (at 1 second intervals) to be detected by other aircraft and replies to their interrogations and those from ground stations.
This function permits, on ground, to override the inhibition of replies from interrogations in Mode A or C. It is used by the air traffic controller to check the correct operation of the aircraft Mode A or C transponder prior to takeoff.
The Mode S transponder operates permanently, both in flight and on the ground. It periodically transmits squitters (at 1 second intervals) to be detected by other aircraft and replies to their interrogations and those from ground stations.
This function permits, on ground, to override the inhibition of replies from interrogations in Mode A or C. It is used by the air traffic controller to check the correct operation of the aircraft Mode A or C transponder prior to takeoff.
(3) Altitude reporting
(a) OFF position
Selection of the ALT RPTG switch OFF position has the following results:
Selection of the ALT RPTG switch OFF position has the following results:
- the Mode S transponder continues to transmit squitters and replies to Mode A, C and S interrogation but does not report altitude.
- the T/TISS-TCAS switches to STBY (TCAS STBY message in green on the upper ECAM DU)
- the PFD and ND display corresponds to the standby mode.
(b) ON position
The active transponder replies to interrogations and reports its altitude. The T/TISS-TCAS operates in the mode selected by its logic in function of information input from the control unit, ATCRBS/MODE S ground stations and in function of aircraft altitude.
The active transponder replies to interrogations and reports its altitude. The T/TISS-TCAS operates in the mode selected by its logic in function of information input from the control unit, ATCRBS/MODE S ground stations and in function of aircraft altitude.
(4) Selection of system 1/2 active transponder
The 1/2 switch permits selection of the active transponder. The non-selected transponder is placed in standby.
The 1/2 switch permits selection of the active transponder. The non-selected transponder is placed in standby.
(5) Identification code in Mode A
The Mode S transponder also replies to Mode A interrogations from ground stations. A keyboard permits the pilot to set the Mode A octal code assigned to the aircraft by the ATC ground station controller and included in the transmitted replies. A window on the control unit displays this code permanently as long as the content of the digital output message complies with the displayed data.
The Mode S transponder also replies to Mode A interrogations from ground stations. A keyboard permits the pilot to set the Mode A octal code assigned to the aircraft by the ATC ground station controller and included in the transmitted replies. A window on the control unit displays this code permanently as long as the content of the digital output message complies with the displayed data.
(6) IDENT pushbutton switch
On ground station request, an addition pulse must be included in the Mode A and Mode C replies transmitted by the transponder to enable a more precise location. This operation is performed by pressing the IDENT pushbutton switch on the control unit.
On ground station request, an addition pulse must be included in the Mode A and Mode C replies transmitted by the transponder to enable a more precise location. This operation is performed by pressing the IDENT pushbutton switch on the control unit.
I. T/TISS-TCAS part Air/Ground Determination
The TCAS air/ground state is based on the value present on the RMP-5K discrete, with the exception of the cases below:
The TCAS air/ground state is based on the value present on the RMP-5K discrete, with the exception of the cases below:
- If the radio altimeter is valid, and the RMP-5K indication is airborne, TCAS air/ground will transition to on-ground when the radio altitude becomes less than 50 ft.
- If the radio altimeter is valid, and the RMP-5K indication is on-ground, TCAS air/ground will transition to airborne when the radio altitude becomes greater than 60 ft.
5. BITE Test
A. Self Test
A quick check of the correct operation of the TCAS installation can be performed by activating the TEST function on the ground only:
A quick check of the correct operation of the TCAS installation can be performed by activating the TEST function on the ground only:
- either by pressing the pushbutton switch on the front of the T/TISS computer
- or through the Centralized Fault Display Interface Unit (CFDIU) by performing the TCAS Functional Test on the Multipurpose Control and Display Unit (MCDU).
The self-test sequence checks the main functions of the computer and transmits to the displays: - Labels 013, 015, 016, 203, 270, 274, 320, 350, 357 and 377 of TA/RA display bus according to the definition given in ARINC 735B attachment 18 (TCAS system functional test normal output definition)
- Label 270 of TA/RA display bus for resolution advisory characteristics (0 ft/mn advisory, up corrective advisory, don't descend, don't climb > 2000 ft/mn, rate to maintain)
- Labels 130, 131 and 132 .
-------------------------------------------------------------------------- ! INTRUDER ! TYPE ! RANGE ! REL ALT ! BEARING ! VERTICAL RATE ! ! ! ! (NM) ! (FEET) ! (DEG) ! ! !------------------------------------------------------------------------! ! 1 ! RA ! 2.00 ! +200 ! +90 !no vertical rate! ! 2 ! TA ! 2.00 ! -200 ! -90 !climbing ! ! 3 ! PROX ! 3.625 ! -1000 ! +33.75 !descending ! ! 4 ! OTHER ! 3.625 ! +1000 ! -33.75 !climbing ! --------------------------------------------------------------------------
- either by pressing the pushbutton switch on the front of the T/TISS computer
- or through the Centralized Fault Display Interface Unit (CFDIU) by performing the TCAS Functional Test on the Multipurpose Control and Display Unit (MCDU).
The self-test sequence checks the main functions of the computer and transmits to the displays: - Labels 013, 015, 016, 203, 270, 274, 320, 350, 357 and 377 of TA/RA display bus according to the definition given in ARINC 735B attachment 18 (TCAS system functional test normal output definition)
- Label 270 of TA/RA display bus for resolution advisory characteristics (0 ft/mn advisory, up corrective advisory, don't descend, don't climb > 2000 ft/mn, rate to maintain)
- Labels 130, 131 and 132 .
------------------------------------------------------------------- ! INTRUDER ! TYPE ! RANGE ! REL ALT ! BEARING ! VERTICAL ! TRACK ! ! ! ! (NM) ! (FEET) ! (DEG) ! RATE ! ANGLE ! !----------!------!-------!---------!---------!-----------!-------! ! 1 ! RA ! 2.00 ! +200 ! +90 ! no ! 0 ! ! 2 ! TA ! 2.00 ! -200 ! -90 ! climbing ! 90 ! ! 3 ! PROX ! 3.61 ! -1000 ! +33.75 !descending ! 180 ! ! 4 !OTHER ! 3.61 ! +1000 ! -33.75 ! no ! 270 ! -------------------------------------------------------------------
(1) ND image
The ND must display the images corresponding to the four types of intruders : Other, Proximate, TA and RA.
The shapes and colors of the traffic symbols are:
The ND must display the images corresponding to the four types of intruders : Other, Proximate, TA and RA.
The shapes and colors of the traffic symbols are:
- white unfilled diamond for Other traffic
- white filled diamond for Proximate traffic
- amber filled circle for TA traffic
- red filled square for RA traffic
(2) PFD image
At the beginning of the test sequence, green and red sectors must appear sequentially on the vertical speed scale of the PFD. Then a resolution advisory display is shown
At the beginning of the test sequence, green and red sectors must appear sequentially on the vertical speed scale of the PFD. Then a resolution advisory display is shown
(3) Failure indication
At the end of the test sequence the system generates a synthesized voice message:
In this case the NDs, the PFDs and the ECAM show the failure messages described in Para. 4.G.(5), (6) and (7).
There are several LEDs on the face of the T/TISS computer to identify the failed component when the test pushbutton switch is pushed (Ref 34-72-00,Para. 6. A.).
At the end of the test sequence the system generates a synthesized voice message:
| TCAS SYSTEM TEST PASS |
| if the system operates correctly or: |
| TCAS SYSTEM TEST FAIL |
| if an anomaly has been detected. |
There are several LEDs on the face of the T/TISS computer to identify the failed component when the test pushbutton switch is pushed (Ref 34-72-00,Para. 6. A.).
(4) ND image
The ND must display the images corresponding to the four types of intruders : Other, Proximate, TA and RA.
The shapes and colors of the traffic symbols are:
The ND must display the images corresponding to the four types of intruders : Other, Proximate, TA and RA.
The shapes and colors of the traffic symbols are:
- white unfilled diamond aircraft symbol for Other traffic
- white filled diamond aircraft symbol for Proximate traffic
- amber filled circle aircraft symbol for TA traffic
- red filled square aircraft symbol for RA traffic
(5) PFD image
At the beginning of the test sequence, green and red sectors must appear sequentially on the vertical speed scale of the PFD. Then a resolution advisory display is shown
At the beginning of the test sequence, green and red sectors must appear sequentially on the vertical speed scale of the PFD. Then a resolution advisory display is shown
(6) Failure indication
At the end of the test sequence the system generates a synthesized voice message:
In this case the NDs, the PFDs and the ECAM show the failure messages described in Para. 4.G.(5), (6) and (7).
There are several LEDs on the face of the T/TISS computer to identify the failed component when the test pushbutton switch is pushed (Ref 34-72-00,Para. 6. A.).
At the end of the test sequence the system generates a synthesized voice message:
| TCAS SYSTEM TEST PASS |
| if the system operates correctly or: |
| TCAS SYSTEM TEST FAIL |
| if an anomaly has been detected. |
There are several LEDs on the face of the T/TISS computer to identify the failed component when the test pushbutton switch is pushed (Ref 34-72-00,Para. 6. A.).
B. CFDS Interface
(1) Introduction
The BITE facilitates maintenance on in-service aircraft. It detects and identifies the faults related to the T/TISS-TCAS (TCAS in the maintenance menus, Ref NOTE). The BITE of the T/TISS-TCAS is connected to the CFDIU.
The BITE:
The BITE can operate in two modes:
The BITE facilitates maintenance on in-service aircraft. It detects and identifies the faults related to the T/TISS-TCAS (TCAS in the maintenance menus, Ref NOTE). The BITE of the T/TISS-TCAS is connected to the CFDIU.
The BITE:
- continuously transmits the T/TISS-TCAS status and its identification message to the CFDIU
- memorizes the faults which have occurred during the last 63 flight legs
- monitors data inputs from the various peripherals (RA, ATC and CFDIU)
- transmits to the CFDIU the result of the tests performed
- can communicate with the CFDIU through the interactive menu.
The BITE can operate in two modes:
- normal mode (the faults detected by the TCAS are sent to the CFDIU)
- interactive mode (on the ground, one can get access to TCAS internal fault logs and unit status information).
NOTE: No modification has been introduced in the CFDIU, therefore T/TISS-TCAS onboard maintenance interface can be accessed through the "TCAS" prompt.
(2) Fault listing
(a) Internal failures
Internal failures and associated messages are listed in the table below:
Internal failures and associated messages are listed in the table below:
| ----------------------------------------------------------- |
| ! LIST OF INTERNAL FAILURE MESSAGES ! |
| !---------------------------------------------------------! |
| ! ATA ! CLASS ! MESSAGE ! |
| !---------------------------------------------------------! |
| ! 344334 ! 1 ! TCAS(1000SG) ! |
| ! 344311 ! 1 ! ATC/TCAS TOP ANTENNA(7SG1) ! |
| ! 344311 ! 1 ! ATC/TCAS TOP ANTENNA(7SG1)COAXIAL J1 ! |
| ! 344311 ! 1 ! ATC/TCAS TOP ANTENNA(7SG1)COAXIAL J2 ! |
| ! 344311 ! 1 ! ATC/TCAS TOP ANTENNA(7SG1)COAXIAL J3 ! |
| ! 344311 ! 1 ! ATC/TCAS TOP ANTENNA(7SG1)COAXIAL J4 ! |
| ! 344311 ! 1 ! ATC/TCAS BOT ANTENNA(7SG2) ! |
| ! 344311 ! 1 ! ATC/TCAS BOT ANTENNA(7SG2)COAXIAL J1 ! |
| ! 344311 ! 1 ! ATC/TCAS BOT ANTENNA(7SG2)COAXIAL J2 ! |
| ! 344311 ! 1 ! ATC/TCAS BOT ANTENNA(7SG2)COAXIAL J3 ! |
| ! 344311 ! 1 ! ATC/TCAS BOT ANTENNA(7SG2)COAXIAL J4 ! |
| ----------------------------------------------------------- |
(b) External failures
| ---------------------------------------------------------- |
| ! LIST OF EXTERNAL FAILURE MESSAGES ! |
| !--------------------------------------------------------! |
| ! ATA ! CLASS ! MESSAGE ! |
| !--------------------------------------------------------! |
| ! 344233 !1 or 3 ! RA1 (2SA1)/TCAS(1000SG) (1)! |
| ! 344233 !1 or 3 ! RA2 (2SA2)/TCAS(1000SG) (1)! |
| ! 345233 !1 or 3 ! ATC 1(1SH1)/TCAS(1000SG) (2)! |
| ! 345233 !1 or 3 ! ATC 2(1000SG)/TCAS(1000SG) (2)! |
| ! 341234 !1 or 3 ! ADIRU1(1FP1) BUS IR/TCAS(1000SG) ! |
| ! 323171 ! 3 ! LGCIU1(5GA1)/CFDIU(1TW)/TCAS(1000SG) ! |
| ! 240000 ! 1 ! POWER SUPPLY INTERRUPT ! |
| ! 313234 ! 3 ! CFDIU (1TW)/TCAS (1000SG) ! |
| ! 316112 ! 3 ! MAST WARN(9WW)/TCAS(1000SG) ! |
| ! 316334 ! 3 ! DMC1/2/3(1WT1/2/3)/TCAS(1000SG) (3)! |
| ---------------------------------------------------------- |
NOTE: (1)
Failure of one radio altimeter is a class 3 failure whereas it becomes a class 1 failure when two radio altimeters are faulty.
Failure of one radio altimeter is a class 3 failure whereas it becomes a class 1 failure when two radio altimeters are faulty.
NOTE: (2)
Failure of the selected ATC is a class 1 failure. Failure of the ATC in standby is a class 3 failure.
Failure of the selected ATC is a class 1 failure. Failure of the ATC in standby is a class 3 failure.
NOTE: (3)
Only occurs if "NO" is answered on self-test validation pages, remain logged until "YES" is answered on self test validation pages.
Only occurs if "NO" is answered on self-test validation pages, remain logged until "YES" is answered on self test validation pages.
(3) Fault listing
(a) Internal failures
Internal failures and associated messages are listed in the table below:
Internal failures and associated messages are listed in the table below:
| ----------------------------------------------------------- |
| ! LIST OF INTERNAL FAILURE MESSAGES ! |
| !---------------------------------------------------------! |
| ! ATA ! CLASS ! MESSAGE ! |
| !---------------------------------------------------------! |
| ! 344334 ! 1 ! TCAS(1000SG) ! |
| ! 344311 ! 1 ! ATC/TCAS TOP ANTENNA(7SG1) ! |
| ! 344311 ! 1 ! ATC/TCAS TOP ANTENNA(7SG1)COAXIAL J1 ! |
| ! 344311 ! 1 ! ATC/TCAS TOP ANTENNA(7SG1)COAXIAL J2 ! |
| ! 344311 ! 1 ! ATC/TCAS TOP ANTENNA(7SG1)COAXIAL J3 ! |
| ! 344311 ! 1 ! ATC/TCAS TOP ANTENNA(7SG1)COAXIAL J4 ! |
| ! 344311 ! 1 ! ATC/TCAS BOT ANTENNA(7SG2) ! |
| ! 344311 ! 1 ! ATC/TCAS BOT ANTENNA(7SG2)COAXIAL J1 ! |
| ! 344311 ! 1 ! ATC/TCAS BOT ANTENNA(7SG2)COAXIAL J2 ! |
| ! 344311 ! 1 ! ATC/TCAS BOT ANTENNA(7SG2)COAXIAL J3 ! |
| ! 344311 ! 1 ! ATC/TCAS BOT ANTENNA(7SG2)COAXIAL J4 ! |
| ----------------------------------------------------------- |
(b) External failures
| ---------------------------------------------------------- |
| ! LIST OF EXTERNAL FAILURE MESSAGES ! |
| !--------------------------------------------------------! |
| ! ATA ! CLASS ! MESSAGE ! |
| !--------------------------------------------------------! |
| ! 344233 !1 or 3 ! RA1 (2SA1)/TCAS(1000SG) (1)! |
| ! 344233 !1 or 3 ! RA2 (2SA2)/TCAS(1000SG) (1)! |
| ! 345233 !1 or 3 ! ATC 1(1SH1)/TCAS(1000SG) (2)! |
| ! 345233 !1 or 3 ! ATC 2(1000SG)/TCAS(1000SG) (2)! |
| ! 341234 !1 or 3 ! ADIRU1(1FP1) BUS IR/TCAS(1000SG) ! |
| ! 323171 ! 3 ! LGCIU1(5GA1)/CFDIU(1TW)/TCAS(1000SG) ! |
| ! 240000 ! 1 ! POWER SUPPLY INTERRUPT ! |
| ! 313234 ! 3 ! CFDIU (1TW)/TCAS (1000SG) ! |
| ! 316112 ! 3 ! MAST WARN(9WW)/TCAS(1000SG) ! |
| ! 316334 ! 3 ! DMC1/2/3(1WT1/2/3)/TCAS(1000SG) (3)! |
| ! 343631 ! 3 ! GPS1(40RT1)/TCAS(1000SG) ! |
| ! 343631 ! 1 ! GPS1(40RT1)/TCAS(1000SG) ! |
| ! 343631 ! 3 ! GPS2(40RT2)/TCAS(1000SG) ! |
| ! 343631 ! 1 ! GPS2(40RT2)/TCAS(1000SG) ! |
| ! 228212 ! 3 ! MCDU1(3CA1)/TCAS(1000SG) ! |
| ! 228212 ! 3 ! MCDU2(3CA2)/TCAS(1000SG) ! |
| ! 316334 ! 3 ! DMC1(1WT1)/TCAS(1000SG) ! |
| ! 316334 ! 3 ! DMC2(1WT2)/TCAS(1000SG) ! |
| ! 344334 ! 3 ! TRAF SEL1 PUSH(105SG1)/TCAS(1000SG) ! |
| ! 344334 ! 3 ! TRAF SEL1 PULL(105SG1)/TCAS(1000SG) ! |
| ! 344334 ! 3 ! TRAF SEL2 PUSH(105SG2)/TCAS(1000SG) ! |
| ! 344334 ! 3 ! TRAF SEL2 PULL(105SG2)/TCAS(1000SG) ! |
| ---------------------------------------------------------- |
NOTE: (1)
Failure of one radio altimeter is a class 3 failure whereas it becomes a class 1 failure when two radio altimeters are faulty.
Failure of one radio altimeter is a class 3 failure whereas it becomes a class 1 failure when two radio altimeters are faulty.
NOTE: (2)
Failure of the selected ATC is a class 1 failure. Failure of the ATC in standby is a class 3 failure.
Failure of the selected ATC is a class 1 failure. Failure of the ATC in standby is a class 3 failure.
NOTE: (3)
Only occurs if "NO" is answered on self-test validation pages, remain logged until "YES" is answered on self test validation pages.
Only occurs if "NO" is answered on self-test validation pages, remain logged until "YES" is answered on self test validation pages.
(4) Normal mode
During normal mode, the BITE cyclically monitors the status of the T/TISS-TCAS.
In case of fault detection:
During normal mode, the BITE cyclically monitors the status of the T/TISS-TCAS.
In case of fault detection:
- It transmits its information to the CFDIU during the given flight. These items of information are transmitted to the CFDIU every 100 ms by an ARINC 429 message with label 356.
(5) Interactive mode
To gain access to the BITE, it is necessary to use one MCDU (Ref. ATA 22-82-00).
All information displayed on the MCDU during the BITE TEST configuration can be printed on the printer (Ref. ATA 31-35-00).
To gain access to the BITE, it is necessary to use one MCDU (Ref. ATA 22-82-00).
All information displayed on the MCDU during the BITE TEST configuration can be printed on the printer (Ref. ATA 31-35-00).
NOTE: No modification has been introduced in the CFDIU, therefore T/TISS-TCAS onboard maintenance interface can be accessed through the "TCAS" prompt.
(a) SYSTEM REPORT/TEST function
This function enables access to all the electronic systems and to the T/TISS computer.
The menu mode can only be activated on the ground.
This mode enables communication between the CFDIU, MCDU and the T/TISS-TCAS BITE.
The TCAS menu is composed of:
This function enables access to all the electronic systems and to the T/TISS computer.
The menu mode can only be activated on the ground.
This mode enables communication between the CFDIU, MCDU and the T/TISS-TCAS BITE.
The TCAS menu is composed of:
- LAST LEG REPORT
- PREVIOUS LEGS REPORT
- LRU IDENTIFICATION
- GROUND SCANNING
- CLASS 3 FAULTS
- GROUND REPORT
- TROUBLE SHOOTING DATA
- DISCRETE CONFIGURATION
- TEST.
(b) LAST LEG REPORT
This report contains the computer internal and external class 1 failures recorded during the last flight.
The failures are displayed in the chronological order (oldest first).
The following figure shows the sequence of menus.
This report contains the computer internal and external class 1 failures recorded during the last flight.
The failures are displayed in the chronological order (oldest first).
The following figure shows the sequence of menus.
(c) CLASS 3 FAULT
This report contains the last leg external class 3 failures recorded during the last flight.
The following figure shows the sequence of menus.
This report contains the last leg external class 3 failures recorded during the last flight.
The following figure shows the sequence of menus.
(d) PREVIOUS LEGS REPORT
The messages are identical to those shown in the Para. above but concern the last 63 flights if failures have occurred during these flights.
The messages are identical to those shown in the Para. above but concern the last 63 flights if failures have occurred during these flights.
(f) GROUND SCANNING
This function enables consultation of the T/TISS-TCAS failure recordings as defined by the Component Manufacturer.
The T/TISS peripheral monitoring and internal cyclic tests are used in order to detect transient failures.
This function enables consultation of the T/TISS-TCAS failure recordings as defined by the Component Manufacturer.
The T/TISS peripheral monitoring and internal cyclic tests are used in order to detect transient failures.
(g) GROUND REPORT
This report presents class 1, 2 or 3 internal failures when they are detected on the ground. These failures differ from those displayed on the LAST LEG REPORT page.
The figure shows examples of internal failures recorded on ground by the TCAS .
This report presents class 1, 2 or 3 internal failures when they are detected on the ground. These failures differ from those displayed on the LAST LEG REPORT page.
The figure shows examples of internal failures recorded on ground by the TCAS .
(h) TROUBLE SHOOTING DATA
This function analyzes the snapshot of the recorded fault to detect any software bug.
Two types of data are displayed:
This function analyzes the snapshot of the recorded fault to detect any software bug.
Two types of data are displayed:
- correlation parameters which are the date and UTC hour displayed in clear English
- snapshot data delivered in hexadecimal code or in clear messages.
(i) DISCRETE CONFIGURATION
This function presents the value or the status of several discretes. A report screen for each data shows the status of the discrete at the time this menu is selected.
This function presents the value or the status of several discretes. A report screen for each data shows the status of the discrete at the time this menu is selected.
(6) TCAS functional test
A T/TISS-TCAS built-in functional test can be initiated by pressing the line key adjacent to the TEST indication on the TCAS maintenance sub-menu.
The following sequence is then generated.
The test ends with the display of the following message on the MCDU:
. TEST OK OR TEST FAIL
at the end of the functional test the T/TISS-TCAS generates a complete sequence of synthesized voice messages.
When all the tests are completed and no failure has been detected the computer reports:
. TCAS SYSTEM TEST PASS
If one of the test criteria has not been met, this synthesized voice message is announced:
. TCAS SYSTEM TEST FAIL
Remarks:
This short test permits to check rapidly, on ground, the functionality of the TCAS and particularly that of the PFD/NDs via the DMC.
In addition it enables to check correct operation of the synthesized voice message system.
A T/TISS-TCAS built-in functional test can be initiated by pressing the line key adjacent to the TEST indication on the TCAS maintenance sub-menu.
The following sequence is then generated.
The test ends with the display of the following message on the MCDU:
. TEST OK OR TEST FAIL
at the end of the functional test the T/TISS-TCAS generates a complete sequence of synthesized voice messages.
When all the tests are completed and no failure has been detected the computer reports:
. TCAS SYSTEM TEST PASS
If one of the test criteria has not been met, this synthesized voice message is announced:
. TCAS SYSTEM TEST FAIL
Remarks:
This short test permits to check rapidly, on ground, the functionality of the TCAS and particularly that of the PFD/NDs via the DMC.
In addition it enables to check correct operation of the synthesized voice message system.