User's Manual

SYSTEM DESCRIPTION AND INSTALLATION MANUAL
TCAS 3000 Traffic Alert and Collision Avoidance System
34−43−23
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Page 1−21
15 Dec 2005
Table 1−6. TCAS 3000 Computer Unit Leading Particulars (cont)
Item Specification
• Extended Range Reception Capability . . . . . . . . . . .
(Optional Mode)
−82 ± 2 dBm (≥90% Mode S squitter
replies decoded)
• Low Level Receiver Signal Rejection . . . . . . . . . . . . .
(Normal Operation)
−81 dBm (≤10% Mode S and ATCRBS
replies decoded)
• Receiver Signal Processing . . . . . . . . . . . . . . . . . . . . . Amplitude Mono−pulse
• System Bearing Accuracy . . . . . . . . . . . . . . . . . . . . . . Error less than 9 degrees RMS, 27
degrees peak from −10 to +10 degrees
elevation
(1) System Interfaces
The TCAS 3000 Computer Unit supports the external system interfaces that follow.
Unless otherwise specified, the specifications apply to both the 6−MCU and 4−MCU
computers. All interfaces are per ARINC 735A.
(a) Radio Altimeter Interface
The TCAS 3000 Computer Unit accepts either analog or digital radio altimeter
inputs. For each type of input, dual input ports are provided.
Each of the military radio altimeter types provide two outputs that are connected
to the TCAS CU input pins. The two altimeter outputs are the Analog Data
Output and Analog Data Reliability signal. The TCAS CU uses the Data
Reliability signal in conjunction with the Analog Data Output to determine radio
altimeter failures.
A condition exists for several military radio altimeters known as Out of Track.
This condition occurs when the radio altimeter has not failed and the altimeter is
not reading a valid altitude. Altitude data for an Out of Track condition should be
considered invalid and not used.
The digital radio altimeter interface accepts inputs from an ARINC 707 radio
altimeter on ARINC 429 low speed input busses.
(b) Mode S Transponder Interface
The TCAS 3000 computer contains two sets of ARINC 429 high speed busses
for communication with two Mode S transponders. It uses ARINC 718−A/735
communication protocol (2 inputs, 2 outputs).
(c) Onboard Maintenance System Interface
The TCAS 3000 computer contains a set of ARINC 429 low speed busses for
communication with an onboard maintenance system (1 input, 1 output). The
unit interfaces with all major airframe manufacturers maintenance computer
systems. Since the maintenance computer protocol for each airframe
manufacturer is different, the TCAS 3000 automatically detects the type of
airframe from the data received from the maintenance computer and sets its
protocol accordingly.