Tcas - surveillance area General

The TCAS tracks and evaluates up to 30 airplanes that are in the surveillance area. Airplanes in the surveillance area are put into one of these four groups:

• Resolution advisory (RA) group

• Traffic advisory (TA) group

• Proximate traffic

• Other traffic.

TCAS has a maximum surveillance area that is 8700 feet above and below your airplane. It has a range of 40 nm.

Ra and ta Groups

The TCAS forms two protected areas around its own airplane. The dimensions of these protected areas change with airspeed and altitude of the TCAS airplane and the closure rate of the target.

The protected area represents the time until the target will be at the closest point of approach (CPA) to the TCAS airplane. This protected area is called the TAU area.

To calculate the TAU, the TCAS computer uses this data:

• Own airplane altitude

• Target closure rate

• Target range and altitude.

Traffic advisory TAU and resolution advisory TAU define areas around the TCAS airplane that, if penetrated by a target within the required altitude restrictions, would produce the appropriate warning from the TCAS computer.

The TCAS computer uses six sensitivity levels (2-7). Level 7 is the most sensitive. At level 2, no resolution advisories may occur. Below 1000 feet, level 2 is used and above 20000 feet, level 7 is used. Sensitivity levels are set by the TCAS computer based on own airplane altitude.

The TA and RA times vary with sensitivity level. At sensitivity level 3, RA TAU is 15 seconds while at sensitivity level 7, RA TAU is 35 seconds.

Proximate Traffic and Other Traffic

Proximate traffic is an airplane with a relative altitude

separation less than 1200 feet, is in a 6 nm radius of your

airplane, and is not a TA or RA threat.

Other traffic is an airplane with a range more than 6 nm that is not a TA or RA threat. If the range is less than 6 nm, the relative altitude must be more than 1200 feet.

TCAS - CONTROL AND DISPLAY

General

The EFIS control panel and the ATC control panel control the TCAS data that shows on the displays.

EFIS Control Panel

To show the TCAS data on the display, put the mode selector on the EFIS control panel in one of these modes:

• Expanded approach

• Expanded VOR

• Expanded map

• Centered map.

The range selector selects the range for the ND.

Push the TFC (traffic) switch on the range selector to let the ND show the TCAS data. When you do this, the TFC message and the TCAS symbols of any targets show on the display.

If the function selector on the ATC control panel is not in the TA or TA/RA position, the display does this:

• Shows an amber message, TCAS OFF (TCAS OFF shows in all ND modes)

• Removes all TCAS target symbols.

To remove the TCAS messages and symbols from the display, push the TFC switch again.

Atc/tcas Control Panel

The ATC/TCAS control panel sends control data through the ATC Mode S transponder to the TCAS computer. The TCAS computer sends this data to the DEU for display.

The function selector puts the TCAS computer in the TA only or TA/RA mode. In the TA only mode, the TCAS does not supply RA traffic symbols or advisories. It also does not supply RA aural messages. The function selector can also put the TCAS computer in the test mode.

The ND shows the relative altitude of the target above or below the symbol.