TCAS

[Slowly]

Paleso e ammeto la mia ingoranza circa tale manufatto elettronico, so cos'è e a cosa serve, ma come funziona?

Come si comporta se due aerei sono vicini? Avvisi acustici o "fa qualcosa di più"?

Se piove si rompe?

[Andrea F.]

Te lo spiego in 2 secondi:
Il Traffic Collision Avoidance Advice è un sistema che ti avvisa dei traffici vicini e in collisione, se etti in ta/ra ti fa anche gli avvisi di discesa o salita se ci sono traffici in collisione, e nell'80 si vedono i traffici sul variometro, mentre su aerei tipo a320 si vedono i traffici direttamente sul ND.

[patata]

esatto ti da gli avvisi di traffico TA circa 45 sec prima della possibile collisione e la manovra evasiva RA 25 sec prima.
il TCAS ti suggerisce di salire o scendere e quanto variometro mettere

[Manuelvi]

esatto ti da gli avvisi di traffico TA circa 45 sec prima della possibile collisione e la manovra evasiva RA 25 sec prima.
il TCAS ti suggerisce di salire o scendere e quanto variometro mettere

Ciao.pe rla precisione aggoiungerei anche se se nn hai un transponder in modo C attivo i resolution advisory (RA) nn li hai.
Sembra che con la futura implementazione del modo S si potrà avere anche il TCAS3 che darà avvisi di evitamento anche sul piano orizzontale in quanto ad oggi gli RA ti dicono solo "CLIMB CLIMB" "DESCEND DESCEND"

abbastanza preciso?

ciaoo

[Manuelvi]

Paleso e ammeto la mia ingoranza circa tale manufatto elettronico, so cos'è e a cosa serve, ma come funziona?

Come si comporta se due aerei sono vicini? Avvisi acustici o "fa qualcosa di più"?

Se piove si rompe?

A parte gli avvisi acustici dati dal Resolution advisory c'è anche una indicazione visiva sul TCAS basata su diversi colori.

Detta alla buona senza distanze e tempi, se un traffico è nel range ma nn è una possibile causa di TA o RA è disegnato come un triangolo BLU o BIANCO
se invece è un TA sarà un cerchio GIALLO e se è un RA un quadrato ROSSO

ciaoo

[Andrea F.]

esatto ti da gli avvisi di traffico TA circa 45 sec prima della possibile collisione e la manovra evasiva RA 25 sec prima.
il TCAS ti suggerisce di salire o scendere e quanto variometro mettere

Ciao.pe rla precisione aggoiungerei anche se se nn hai un transponder in modo C attivo i resolution advisory (RA) nn li hai.

ciaoo

Direi che sul 320 il trasponder in C ce l'hai...

[Manuelvi]

esatto ti da gli avvisi di traffico TA circa 45 sec prima della possibile collisione e la manovra evasiva RA 25 sec prima.
il TCAS ti suggerisce di salire o scendere e quanto variometro mettere

Ciao.pe rla precisione aggoiungerei anche se se nn hai un transponder in modo C attivo i resolution advisory (RA) nn li hai.

ciaoo

Direi che sul 320 il trasponder in C ce l'hai...

Direi proprio di si

ciao

[davierosoft]

Io direi che sul 320 hai il mode S visto che ce l'ha anche il 737, se il mode S sul 737 non funziona compare la scritta TCAS FAIL!

General
A.
The basic Traffic Alert and Collision Avoidance System (TCAS) supplies safe separation between your airplane and other airplanes that have ATCRBS or Mode S Transponders.
B.
One TCAS system is installed on the airplane. The TCAS system consists of one TCAS computer, two phased array directional antenna, and a control unit (ATC control panel). TCAS informations is shown on the EFIS EHSI and EADI displays.
C.
TCAS interrogates proximate airplanes and receives the altitude, bearing and other data from the intruder airplane via Air Traffic Control (ATC) system. The TCAS computer will analyze the data and determine if the intruder airplane is a threat to your airplane. If there is a potential threat, TCAS will issue resolution advisories which will instruct the pilot to avoid the conflict. If there is no threat TCAS will track the intruder airplane's position.
D.
TCAS operates in two modes: TA ONLY mode which only tracks the proximate airplane traffic and TA/RA mode which tracks intruder airplanes and issues resolution advisories.
E.
The TCAS uses this equipment (Fig. 1):
(1)
TCAS Computer
(2)
Two Phased Array Directional Antennas
(3)
Resolution Advisory/Vertical Speed Indicator (RA/VSI)
(4)
Traffic Advisory (TA) Display Indicator
(5)
Electronic Flight Instrument System (EFIS) Displays
(a)
Electronic Horizontal Situation Indicator (EHSI)
(b)
Electronic Attitude Director Indicator (EADI)
(c)
EFIS Control Panel.
(6)
A Mode S Transponder System that has this equipment:
(a)
Two Mode S Transponders
(b)
A TCAS/ATC Control Panel
(c)
Two Omnidirectional Antennas
F.
The TCAS computer and directional antenna are included in this section. Other TCAS equipment is included to a level necessary to understand the TCAS operation. See Chapter 34-53-00 for the mode S transponder and control panel description.
2.
TCAS Computer (Fig. 2)
A.
The TCAS computer is installed in the electronic compartment on shelf E3-4. The TCAS computer receives its primary power from the 115V AC ELEX PWR 1 Bus.
B.
The TCAS computer reads and keeps this information about your airplane:
(1)
Heading
(2)
Radio altimeter inputs from the left and right LRRA
(3)
Mode control requests and traffic display control inputs from the Mode S Transponder
(4)
Mode S identification code
(5)
Maximum airspeed data
(6)
Landing gear level position
(7)
Input from weight-on-gear (Air-Ground) strut switch.
(8)
Advisory Delay discrete inputs from the ground prox and wind shear system.
C.
TCAS gets IRS data from the left IRU. Heading, pitch, roll inputs used with the pressure altitude data lets the TCAS find your airplanes position, altitude and flight path.
D.
TCAS receives radio altitude from the left or right radio altimeter. TCAS normally uses the left radio altimeter. If the left radio altimeter fails, TCAS automatically switches to the right radio altimeter. TCAS uses the radio altitude to set sensitivity levels and to calculate intruder advisories.
E.
The traffic display control inputs from the EFIS control panel controls the TCAS traffic display formats shown on the navigation displays.
F.
The mode control data from the ATC control panel sets the mode of operation for the TCAS computer.
G.
The Mode S identification code comes from the ATC transponder. The identification code is permanently connected in the airplane with wire straps in the 24 discrete bit strapped inputs to the transponder. The Mode S identification code is used by the TCAS computer during collision avoidance routines with intruders.
H.
The maximum airspeed data is used in RA calculations and to make a projection of the maximum rate that two airplanes can come together.
I.
The Air/Ground input tells the TCAS whether your airplane is in-flight or on-ground. TCAS will not interrogate or reply when airplane is on ground. TCAS self-test is inhibited in-flight.
J.
The landing gear lever in the down position causes the bottom TCAS antenna to operate in an omnidirectional mode.
K.
The Advisory Delay signals suppress RA and TA indications if windshear or ground proximity conditions occur.
L.
The TCAS program pins set the audio level of voice outputs, the climb resolution advisories inhibit at an altitude of 48,000 feet, and the self-test inhibit in air mode.
M.
If a failure is found on any of these system failure inputs, the TCAS sends failure data to the RA/VSI and TA displays:
N.
If a failure is found on any of these system failure inputs, the TCAS FAIL indication is displayed on the EFIS display:
(1)
Failure inputs from the transponder, radio altimeters, RA/VSI and TA displays
(2)
Failure inputs from the transponder, radio altimeters, and EFIS displays
(3)
Continuity failure in the TCAS antennas or antenna cables
(4)
Failure data or data leakage on the ARINC 429 data bus from the Mode S Transponder.
(5)
Internal TCAS computer failures and failure of internal power supplies
(6)
Incorrect data from the magnetic heading or radio altimeter.
(7)
Failures that occur in the TCAS computer/transponder rf loop-around test
(8)
If a failure makes the TCAS operate unsatisfactorily, the TCAS computer stops all TCAS operations and shows the applicable indication on the display units.
O.
The TEST switch on the TCAS computer or the mode switch at the TEST position on the ATC control panel starts a self-test.
(1)
All of the LED indicators are normally off.
(2)
Push the TEST button on the front panel of the TCAS computer.
(3)
All of the LED indicators come on.
(4)
The TTR PASS LED indicator stays on if there is no failure to the TCAS computer or other essential system that interface with TCAS .
(5)
The applicable LED failure indicator comes on if there is a failure.

+-------------------------+---------------------------------+
| LEDs | FAILURE |
+-------------------------+---------------------------------+
| TTR PASS | TCAS OK (NO FAILURE) |
+-------------------------+---------------------------------+
| TTR FAIL | TCAS COMPUTER |
+-------------------------+---------------------------------+
| XPNDR | ATC TRANSPONDER OR DATA LINK |
| | INTERFACE |
+-------------------------+---------------------------------+
| UPPER ANT | TOP TCAS ANTENNA |
+-------------------------+---------------------------------+
| LOWER ANT | BOTTOM TCAS ANTENNA |
+-------------------------+---------------------------------+
| RAD ALT | NO RADIO ALTITUDE DATA |
+-------------------------+---------------------------------+
| HDNG | NO HEADING DATA |
+-------------------------+---------------------------------+
| R/A | RA DISPLAY |
+-------------------------+---------------------------------+
| T/A | TA DISPLAY |
+-------------------------+---------------------------------+

Figure 1
Sheet 1 - TCAS - Component Location Effectivity: AIRPLANES WITH COLLINS TCAS
Sheet 2 - TCAS - Component Location Effectivity: AIRPLANES WITH COLLINS TCAS
Sheet 3 - TCAS Component Location Effectivity: AIRPLANES WITH COLLINS TCAS
Sheet 4 - TCAS - Component Location Effectivity: AIRPLANES WITH COLLINS TCAS

Figure 2
Sheet 1 - TCAS Schematic (Example) Effectivity: AIRPLANES WITH COLLINS TCAS

3.
Directional Antenna (Fig. 2)
A.
The directional antenna is an electronically steerable phased array that has four top loaded monopole elements. The directional antenna is connected to the TCAS computer with four coaxial cables that have TNC plugs on the antenna end.
B.
The TCAS uses two directional antennas. One is installed on top and the other is installed on the bottom of the airplane. These antennas transmit to and receive signals from intruder airplanes.
C.
Each of the four elements of the directional antenna has a resistor that goes from the antenna element to ground. Each of the four resistors has a different value. The TCAS computer regularly does a continuity test on the antenna ports and will see the correct resistance value if the port is not shorted and not open.
D.
RA/VSI Display (Fig. 2)
(1)
The RA/VSI has these parts:
(a)
An electromechanical pointer to show vertical speed
(b)
An RA ring of red and green high brightness LEDs
(c)
An electromechanical TCAS flag, that shows normal, fail, and RA mode OFF conditions
(d)
A vertical speed failure flag.
(2)
A pointer and vertical speed scale, which are standard VSI features, show the instantaneous vertical speed of your airplane. The VSI used for TCAS applications has red and green LEDs around the edge of the vertical speed scale. When an arc of LEDs are lit, with the vertical speed scale tick marks, they resemble and are referred to as eyebrows.
(3)
The LEDs on the RA/VSI are the primary flight instrument indications for vertical movement RAs. When an RA shows on the RA/VSI a related number of the red LEDs come on to indicate the vertical speed rates not to use. This indication is used to maintain or get safe vertical separation between your airplane and an intruder.
E.
Traffic Advisory Display (TA display) (Fig. 2)
(1)
The TA display is installed in the center of the forward pedestal panel P9.
(2)
The traffic display helps the pilot see the intruder airplanes before RA threat conditions occur. The TA display supplies a display of up to 30 intruder airplanes that are equipped with Mode S or ATCRBS Transponders. The intruders must be detected on a directional antenna, and must be found within the display range.
(3)
Graphics shown on the traffic display tell the pilot about TA and RA conditions and show TCAS operation modes and failure conditions. Traffic displays are the secondary displays in the TCAS system.
4.
EFIS Displays (Fig. 2, Fig. 3)
A.
The EFIS displays are installed on the pilots' instrument panels.
B.
The traffic (TFC) switch on the EFIS control panel enable TCAS operations to be shown on the EHSI. TCAS traffic can only be shown on these EFIS modes: Expanded VOR/ILS mode, NAV mode, MAP mode, and CTR MAP mode.
C.
Traffic is shown on the EHSI to help the pilot see the intruder airplanes before RA threat conditions occur. The EHSI display supplies a display of up to 30 intruder airplanes that are equipped with Mode S or ATCRBS Transponders. The intruders must be detected on a directional antenna, and must be found within the display range.
D.
Graphics shown on the EHSI tell the pilot about TA and RA conditions and show TCAS operation modes and failure conditions.
E.
Graphics shown on the EADI tell the pilots to pull up (climb) or push down (descend). The graphics are represented as vertical pitch advisory to pilots must attain.
(1)
TCAS Indications (Message - Description):
(a)
TFC (GREEN) - Traffic display enable on the EHSI.
(b)
TCAS TEST (WHITE) - TCAS system on self-test mode.
(c)
TCAS FAIL (YELLOW) - TCAS computer fails.
(d)
TCAS OFF (WHITE) - TCAS system not active.
(e)
TA ONLY - Traffic Advisory ONLY mode.
(f)
OFFSCALE (YELLOW/RED) - When intruder airplane is out of display range or is within a display priority area. The OFFSCALE indication will be yellow if the intruder airplane is classified as a TA and red for RA.
(g)
TRAFFIC (YELLOW/RED) - TCAS system detects intruder airplane within the TCAS surveillance area. The TRAFFIC indication will be yellow if the intruder airplane is classified as a TA and red for RA.
1)
TA X.X ±XX++ (YELLOW) - A no bearing intruder airplane with a TA classification. Distance, relative altitude and arrow trend of the intruder airplane is also given.
2)
RA XX ±XX++ (RED) - A no bearing intruder airplane has a RA classification. Distance, relative altitude and arrow trend of the intruder airplane is also given.
(h)
OPENED WHITE DIAMOND - Non-threatening intruder airplane with range greater than 6 nm or relative altitude greater than ±1200 feet. traffic
(i)
FILLED WHITE DIAMOND - Non-threatening intruder airplane with range less than 6 nm and relative altitude less than ±1200 feet.
(j)
FILLED AMBER CIRCLE - Approaching intruder airplane close enough to be of concern. Accompanied by an aural caution TRAFFIC TRAFFIC.
(k)
FILLED RED SQUARE - An immediate threatening intruder airplane that requires evasive action. Accompanied by an aural command like CLIMB CLIMB or DESCEND DESCEND.
(l)
DOWN ARROW - Intruder airplane is descending at least 500 ft per minute.
(m)
UP ARROW - Intruder airplane is ascending at least 500 ft per minute.
(n)
RELATIVE ALTITUDE (+/- XX) - Intruder airplane is XX hundred of feet above (+) / below (-) you.
(o)
ABSOLUTE ALTITUDE (XX.X) - Intruder is at XX.X thousand of feet.
(p)
During an RA the graphics on the EADI show the pilot whether to climb or descend to avoid a collision.
(q)
The pilot must fly the airplane outside the RA flight boundary until the RA is resolved. Only climb and descent maneuver is required to resolve the RA.
Figure 3
Sheet 1 - TCAS EFIS Displays Effectivity: AIRPLANES WITH COLLINS TCAS

5.
TCAS Compatible Dual ATC Control Panel
A.
The TCAS compatible dual ATC control panel is located on the P8 electronic panel. The controls operate as follows:
(1)
Mode switch:
(a)
TEST - Initiates TCAS II and Mode S transponder self-test
(b)
STBY - Transponder does not transmit or reply to interrogation. All TCAS broadcast, surveillance and tracking operation are disabled.
(c)
TA - Enable TA ONLY mode
(d)
TA/RA - Enable TA and RA mode
(2)
Flight level switch:
(a)
ABSolute - Display intruder airplanes pressure (barometric) altitude.
(b)
RELative - Display intruder airplanes altitude relative to your own airplane.
(3)
ABOVE-N-BELOW switch:
(a)
ABOVE - Display intruder airplane from 9900 feet above to 2700 feet below you.
(b)
BELOW - Display intruder airplane from 2700 feet above to 9900 feet below you.
(c)
N - Display intruder airplane from 2700 feet above to 2700 feet below you.
(4)
GUI: Range Select Switch:
(a)
GUI: Selects 3, 5, or 10 mile range for traffic advisories.
6.
Operation
A.
Functional Description
(1)
The TCAS is an airborne traffic alert and collision avoidance system that does not use ATC ground stations. The system finds intruder airplanes that have transponders that reply to ATCRBS or Mode S interrogations. TCAS monitors and makes an analysis of the possible threat of other airplanes to your airplane. The TA display shows the intruder airplane's position. During threat situations, the system provides Traffic Advisories (TAs) and vertical movement Resolution Advisories (RAs) to help the pilot avoid mid-air collisions.

NOTE:
Only intruder airplanes with altitude data (Mode C or Mode S) in their transponder replies can cause RAs to occur in the TCAS. Intruders that do not have Mode C or Mode S transponders can only cause TAs to occur in the TCAS.


(2)
The TA display shows the position of near airplanes that are, or could become, collision threats. This makes it easier for the flight crew to see intruder airplanes before they respond to an RA. RA vertical speed indications show around the outer edge of the RA/VSI.
(3)
The EHSI shows the position of nearby airplanes that are, or could become, collision threats. This makes it easier for the flight crew to see intruder airplanes before they respond to an RA. RA pitch limit indications show on the EADI.
(4)
The directional antenna lets the TCAS computer transmit interrogations and receive replies on one of four antenna beams. The TCAS computer electronically points the antenna beam in one of four different directions to find the bearing of intruder airplanes. The antenna does not have to move. The TCAS adjusts the drive level and phase of each of the four antenna elements in the directional antenna to point the beam.
(5)
The TCAS finds airplanes that have a Mode S Transponder by listening for Mode S squitter transmissions. Mode S transponders transmit squitter data once every second. TCAS receives the airplane's mode S address and adds it to the interrogation list. TCAS could later interrogate those airplanes discreetly. The TCAS also finds airplanes that have transponders that do not reply to Mode S interrogations but do reply to ATCRBS interrogations. The TCAS must interrogate intruder airplanes that have Mode A and C transponders because they do not transmit squitter data. When an intruder is found, the TCAS monitors the intruder. The TCAS can monitor up to 30 intruders.
(6)
The TCAS interrogates intruders continuously to monitor the intruders. When an intruder is interrogated, transponders reply after a fixed delay. The TCAS measures the time between an interrogation and a reply to find the range of the intruder. The TCAS can find the relative altitude of the intruder if the intruder has a Mode C or Mode S transponder. The TCAS uses the directional antennas to find the bearing of the intruder.
(7)
The TCAS puts intruders into groups as non-threat, proximity, TA, or RA threat group airplanes. It uses the relative speed and position calculated from the reply data to put the intruder in the correct group. TCAS provides one or more of these data and instructions to the pilot:
(a)
The TCAS shows an intruder airplane as a symbol on the traffic advisory display. The symbol position on the display shows the range and bearing of the intruder. The symbol's shape and color tells if the airplane has been grouped as a non-threat, proximity, TA or RA threat. The intruder's altitude is shown above or below the symbol if the intruder makes its reply in Mode C or Mode S.

NOTE:
TCAS can only group and show an intruder airplane as an RA threat if the intruder is reporting altitude (Mode C or Mode S).


(b)
The TCAS shows an intruder airplane as a symbol on the EHSI. The symbol position on the display shows the range and bearing of the intruder. The symbol's shape and color tells if the airplane has been grouped as a non-threat, proximity, TA or RA threat. The intruder's altitude is shown above the symbol if the intrudes is above you, and below the symbol if the intruder is below you. A directional arrow trend next to the intruder airplane symbol shows if the intruder airplane is ascending (up arrow) or descending (down arrow) faster than 500 fpm.

NOTE:
TCAS can only group and show an intruder airplane as an RA threat if the intruder is reporting altitude (Mode C or Mode S).


(c)
The TCAS shows other traffic-related indications on the EHSI. When TCAS cannot determine the bearing of an intruder airplane, TCAS will display a no bearing message, red RA or yellow TA. There are a maximum of two no bearing messages. The one with the highest priority is displayed first. When a potential threat is out of the display area, the OFFSCALE indication will be displayed.
(d)
The TCAS supplies a TRAFFIC alert on the cockpit audio system if an intruder airplane enters the TAU area. If the intruder airplane is grouped as a TA, the TRAFFIC indication on the EHSI is colored yellow. If the intruder airplane is grouped as a RA, the TRAFFIC indication on the EHSI is colored red.

NOTE:
The TAU area represents the time to the closest point of approach by an intruder airplane. The TAU varies with the airplane altitude from 20 seconds to 45 seconds.


(e)
The TCAS supplies a TA alert on the cockpit audio system if the intruder is grouped as a TA.
(f)
The TCAS supplies an RA alert on the cockpit audio system and a vertical movement RA on the RA/VSI's if the intruder is grouped as an RA.
(g)
The TCAS supplies an RA alert on the cockpit audio system and a vertical movement RA on the EADI's if the intruder is grouped as an RA.
(8)
An airplane with TCAS has a Mode S Air Traffic Control (ATC) transponder and a TCAS/ATC control panel. The Mode S Transponder does the Mode S Transponder functions necessary for TCAS and the non-TCAS functions of ATCRBS (Modes A and C) Transponders.
(9)
When two airplanes with TCAS are threats to each other, the TCAS in each airplane supplies data to the other and they automatically make a decision which resolution advisory occurs in each airplane. The TCAS will not allow the same vertical movement RA to occur in both airplanes.
(10)
The TCAS operates at the same transmit and receive frequencies as ground stations (1030 MHz transmit and 1090 MHz receive). The TCAS and ground stations operate at transmit and receive frequencies that are opposite to the transponder transmit and receive frequencies as shown below.

+------------------------+-----------------------+----------------+
| SYSTEM | TRANSMIT FREQ | RECEIVE FREQ |
+------------------------+-----------------------+----------------+
| TCAS | 1030 MHz | 1090 MHz |
+------------------------+-----------------------+----------------+
| Ground Station | 1030 MHz | 1090 MHz |
+------------------------+-----------------------+----------------+
| ATC transponders | 1090 MHz | 1030 MHz |
+------------------------+-----------------------+----------------+

(11)
The TCAS transmits 1030 MHz messages from the top and bottom TCAS antennas to interrogate ATC transponders in other airplanes. The TCAS receives 1090 MHz messages from ATC transponders through the top and bottom directional antenna.
B.
TCAS Voice Alert
(1)
The TCAS system alerts the pilot with an audible caution or command during a traffic situation.
(2)
When an intruder airplanes projected path brings it close enough to be of concern (filled while diamond changing to filled yellow circle), a TRAFFIC TRAFFIC alert is sounded.
(3)
When a RA is encounter, the TCAS system will voice commands for the necessary corrective maneuvers. These voice commands are as follows:
(a)
Climb - climb - climb OR Climb - climb
(b)
Climb, crossing climb - climb, crossing climb
(c)
Descend - descend - descend OR Descend - descend
(d)
Descend, crossing descend - descend, crossing descend
(e)
Reduce climb - reduce climb
(f)
Reduce descent - reduce descent
(g)
Increase climb - increase climb
(h)
Increase descent - increase descent
(i)
Climb, climb now - climb, climb now
(j)
Descend, descend now - descend, descend now
(4)
After a RA is resolved, intruder airplane no longer a threat, the TCAS system will announce "clear of conflict".
C.
TCAS INHIBITS
(1)
When a ground proximity or windshear alert occurs, the TCAS will be set to the TA-ONLY mode and all TCAS voice alert are inhibited.
TCAS CHANGE 6.04A;

(2)
All TCAS audio messages are inhibited when the airplanes radio altitude is below 1100 feet during ascent and below 900 feet during descent.
TCAS CHANGE 7.0;

(3)
All TCAS audio messages are inhibited when the airplanes radio altitude is below 600 feet during ascent and below 400 feet during descent.
(4)
All resolution advisories are inhibited below 900 feet during descent and below 1100 feet during ascent.
(5)
No TCAS "Increase descent" commands are given when the airplane altitude is less than 1,450 feet.
(6)
No TCAS "Descend" commands are given when the airplane altitude is less than 1,000 feet.
(7)
TCAS CLIMB corrective action are inhibited above barometer altitude of 48,000 feet.
D.
BITE
(1)
The TCAS computer continuously runs BITE tests and monitors system functions when the microprocessor is not busy with system operations. The TCAS computer can detect any failure that would degrade the normal system operations. The TCAS computer also monitors the ATC system status. If a failure occurs in the ATC or TCAS systems these indications and system actions will occur in the TCAS:
(a)
TCAS FAIL will show on the TA display
(b)
TCAS FAIL or TCAS OFF will show on the EHSI display
(c)
A TCAS fail flag will show on the RA/VSI
(d)
Normal TCAS display indications are stopped
(e)
Stops interrogations by your airplane TCAS
(f)
Sends TCAS fail or TCAS OFF status in the Mode S transmission when interrogations are received from other airplanes.
(2)
There are two ways to start the BITE test manually:
(a)
Push the TEST switch on the front panel of the TCAS computer
(b)
Turn the mode select switch on the control module to TEST and hold it for at least one second.
(3)
If there is a failure during the BITE test, a failure LED indicator will come on on the front panel of the TCAS computer.
(4)
The RA/VSI has failure flags that show an indication of the system status.
(5)
The EFIS displays show an indication of the system status.
E.
Control
(1)
Provide electrical power (Ref 24-22-00)
(2)
Close this circuit breaker:
(a)
On the P18 Circuit Breaker Panel:
1)
TCAS
(3)
System control is provided by the mode select switch on the TCAS/ATC control panel.
(a)
Set the mode switch to TA/RA for normal TCAS operation.
(b)
Set the mode switch to TA for TA only mode. This mode keeps the TCAS from giving RAs.
(4)
The L/R switch selects the left or right ATC transponder as the active transponder.
(5)
The TFC switch on the EFIS control panel controls the display mode for the TCAS display on the EFIS.

[Slowly]

Mizzeca.grazie, ho capito.