User's Manual

Table Of Contents
SYSTEM DESCRIPTION AND INSTALLATION MANUAL
T
3
CAS/Part No.9005000
The minimum External Sensor input accuracy accepted for True Track Angle is 1
degree from a primary source (GPS/FMS) and 5 degrees from a secondary
(Inertial) source.
(4) Radio Altitude (Digital/Analog)
T
3
CAS accepts up to 3 analog Radio Altitude inputs or 3 Digital ARINC 429
Radio Altitude inputs. Digital Radio Altitude Inputs 1 and 2 are shared with the
TCAS function. TAWS, TCAS and RWS require the Radio altitude input.
Radio altimeter equipment interfacing with T
3
CAS must be compliant with TSO-
C87 Airborne Low-Range Radio Altimeter, ETSO-2C87, Low Range Radio
Altimeters, or RTCA DO-155, Minimum Performance Standards Airborne Low-
Range Radar Altimeters.
The external LRUs/External Sensors providing the data parameters must provide
an input to the T
3
CAS that is within the range of ±3 feet (0.914 meters) or 4%
from 0 to 500 feet (152.4 meters) and 5% when above 500 feet (152.4 meters).
The electrical pin connections for the Digital/Analog Radio Altitude is listed under
Table 4-1 and Table 4-2 of sub-section 2 T
3
CAS Interface Description.
(a) Digital Input
The Table below shows the ARINC 429 digital interface characteristics
for the ARINC 707 radio altimeter system. Two of the ARINC 429 input
busses (RADIO_ALTITUDE_1 and RADIO_ALTITUDE_2) are shared
with the TCAS ARINC 429 Radio Altitude Inputs. The TAWS input
circuitry is independent from TCAS. (See Table 4-54.)
Table 4-54: Radio Altitude
429 Label: 164 Octal
Units: Feet
Max Range: ±8,192 Feet
Approx. LSB: 0.125
Data Bits:16
13(lsb) 28(msb)
Sign Bit:29
0 = Up, 1 = Down
Pad Bits: 11, 12
Transmit Interval:
25-50 ms
Data Type: Two’s
Complement Binary
(b) Analog Input
The Analog Radio Altitude inputs are compatible with an ARINC 552
Radio Altimeter system and may have a number of different input
formats as defined for specific aircraft requirements. The external
connector pins for Analog Radio Altitude Inputs #1 and #2 are shared by
TCAS and TAWS/RWS, both have independent circuitry.
The following common mode and differential mode inputs signals are
accepted by the T
3
CAS with the voltage ranges defined:
(+) input common mode range -5.0 to +40.0 V dc
(-) input common mode range -2.5 to +2.5 V dc
Differential (+ to -) range -2.5 to +37.5 V dc
Pub. No. 8600200-001, Revision 004
34-45-29
4-147
04 Nov 2014
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