• Enhances crew situational awareness of traffic situation
• Provides added safety by detecting and displaying potential collision threats
• Computes avoidance maneuvers with aural and visual commands
• Coordinates complementary commands in encounters with other TCAS II-equipped aircraft
• Provides flexibility with a wide variety of display and control options
• Contains extensive I/O capability with analog and digital system interfaces for universal application and fleet commonality
• Interfaces with single or dual Mode S transponders, including Collins TDR-94D
• Change 7 incorporated as standard
• Provides data load feature for shop or on-aircraft software revisions
• Provides internal diagnostics that allow accurate isolation of failed unit on the flight line and provides fault history to aid shop maintenance
• 4MCU version - common design with TTR-921 (6MCU)
• ACAS II compliant

The Rockwell Collins TCAS-4000 (TCAS II) is an airborne Traffic Alert Collision Avoidance System(also known as Airborne Collision Avoidance System (ACAS). The system operates as an airborne secondary surveillance radar that interrogates the ATC transponders of nearby aircraft. Range, relative bearing and altitude of the nearby aircraft are measured by the TCAS II system. The system provides both aural and visual warnings in the event TCAS II predicts a near miss or potential collision. TCAS II depicts aircraft with operating Mode C or Mode S transponders on one or more instrument panel displays.

TCAS II installation is mandated in United States airspace for aircraft with more than 30 passenger seats. TCAS II with Change 7 satisfies the requirements imposed by the International Civil Aviation Organization (ICAO) called Airborne Collision Avoidance System. ACAS has been mandated in Europe since January 2000.

The TCAS-4000 consists of a TTR-4000 TCAS Transmitter/Receiver, one or two TRE-920 TCAS Directional Antennas, two TDR-94 MODE S Transponders, a variety of control panels and a wide variety of traffic display options. TCAS-commanded avoidance maneuvers are in the vertical plane only, so Resolution Advisory (RA) commands appear on the two vertical speed instruments or the vertical speed display fields of integrated electronic flight display systems.

The TTR-4000 is a 4MCU package that weighs approximately 18 pounds and can be mounted in the electronic equipment bay or outside the pressure vessel. It incorporates Change 7 logic as standard, is software upgradeable to Change 7.1 logic, and can be powered from either an AC or DC source.

The TRE-920 is mounted on the top of the fuselage and a second may be installed on the bottom of the fuselage. If an omnidirectional antenna is installed on the bottom and nearby traffic is masked from the top mounted antenna, TCAS continues to compute avoidance maneuvers from range and altitude information but may not be able to display the relative bearing of the traffic.

The TVI-920D VSI/TA/RA Indicator is an active matrix liquid crystal display, optimized for wide viewing angles and high contrast. It incorporates all common electrical interfaces for the vertical speed functions and has an air pressure sensor for direct connection to the aircraft static system. The DC-powered TVI-920D is packaged in a standard three-inch (3ATI) aircraft instrument case for easy retrofit of conventional vertical speed indicators. An AC-powered version, the TVI-920 is also available.

The CTL-92T is a companion control to the standard Collins transponder control, the CTL-92E/93E. It controls TCAS functions with a rotary knob and is available with a variety of display control options. If equipped with display controls (range, mode and vertical surveillance range are available), the control information propagates through the Mode S transponder and TCAS receiver/transmitter to the displays.

The TCAS-4000 control is relayed through the Mode S transponder. Traffic display controls may be located on the display, the Electronic Flight Instrument System range and mode controller, or on the transponder control. Collins CTL-92T is the TCAS adjunct to the CTL-92E/93E transponder control and is one of many options for TCAS/transponder system control.

In order to comply with TCAS certification guidelines outlined in FAA Advisory Circular AC 20-151, both pilots must have visual access to a traffic display. This may take the form of a centrally located traffic display or individual traffic displays for each pilot. In addition, both pilots' vertical speed displays must incorporate resolution advisories.

There are four flight deck configurations available to meet the basic requirements. The configuration to be used depends on the aircraft type and the current flight deck configuration:

• The traffic information can be displayed on a centrally located multifunction display and the RA information can be displayed on a pair of ALI-850C Altitude/VSI/RA indicators.
• The traffic information and RA information can be displayed on a pair of TVI-920Ds.
• The traffic information can be displayed on a centrally located multifunction display and the RA information can be displayed on a pair of ALI-850C Altitude/VSI/RA indicators.
• The traffic information can be displayed on a Pro Line 4 or Pro Line 21 MFD and the RA information can be displayed on the pilot and copilot Primary Flight Displays (PFD).

The TCAS-4000 system interrogates nearby aircraft transponders in the same way as ATC radar but with an innovative architecture that realizes increased efficiency so as to avoid transponder overload. TCAS-4000 typically tracks transponder equipped aircraft traffic within 30 nautical miles. Traffic is displayed if the reported altitude is within ±2,700 feet of own aircraft (±9,900 feet if Above/Below feature is available and selected). TCAS can display up to 30 aircraft and tracks all aircraft within range. It selects for display those that pose the greatest collision threat to own aircraft.

See Transponder section for TDR-94D and CTL-92E specifications