IR - Baro Inertial Altitude Filter
 Figure 004

R 1EFF : 051-099, 106-149, 204-299, 301-399, 1 34-14-00Page 19 1401-499, 1Config-3 Aug 01/05 1 1 1CES 1 The ADR source to be used is selected according to the configuration of the discretes described in para. 2.B.(3)(d). When no ADR source is available, the labels 361 and 365 are sent with their status matrix coded NCD (No Computed Data).

 -magnetic deviation computation The principle of the inertial system is based on geographic referenced measurements and computation. To create the labels which are magnetic referenced (magnetic heading, magnetic track angle ; labels 320, 317) the IR computes a magnetic variation which is added to the true values (labels 314, 313). The magnetic variation is computed as a function of the present position (latitude and longitude) within the range of 82.N to 60.S excluding the magnetic polar region (latitude exceeds 73.N and longitude between 120.W and 90.W). The magnetic variation at any given point is calculated by using four grid intersection data values and a two-dimensional linear interpolation. The grid data comes from the National Oceanic and Atmospheric Administration and must be updated every 10 years in order to meet the accuracy requirements. The computation and display of navigation data by the FMGS and the EIS are in magnetic references (using magnetic referenced labels from the IR).
 -GPS/IRS hybridization computation At the end of GPIR NAV mode ground align processing, an 18-state PR/DR (Pseudo Range / Delta Range) mechanized Kalman filter is engaged to estimate the system error states. The hybrid solution is then corrected by removing its errors estimated from the Kalman filter.
 (3) Attitude mode The attitude mode is a reversionary mode which can be activated only by manual selection of the ATT mode on the CDU. The mode can be activated on the ground or in flight and is intended to provide a rapid attitude/heading restart capability if the IR has experienced total power shutdown or failures which do not disable the mechanization of the attitude computation. The necessity of selecting ATT is indicated by the IR on its action code (label 350 - code 04 = select ATT) and this data is used by the FWC to display a message on the ECAM displays. On the CDU, the STS-SELECT ATT indication comes into view if the DISPLAY/DATA selector switch is in STS (status) position. This mode needs a 20-second initialization phase with the aircraft in level flight. During this phase, all the ARINC bus outputs are sent with their status matrix coded NCD (No Computed Data). At the end of the initialization phase the IR sends valid outputs of:
 -body axis accelerations and angular rates
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 -pitch and roll attitude and rate
 -
vertical acceleration

 -
vertical velocity

 -baro-inertial altitude and vertical speed (Ref. para. D - IR output data, list of valid labels). The magnetic heading may also be valid if an initialization value has been sent by the FMGC (through the MCDU) or the CDU. (Ref. para. D - IR output data for the complete list of valid outputs).
 **ON A/C 005-049, 101-105, 151-199, 201-203,
 D. IR Output Data
 (1) Digital output characteristics The IRs have 4 independently buffered high-speed ARINC 429 digital output buses, designated bus output 1, 2, 3 and 4
 -digital output table: This table contains all the output parameters in the digital form. They are sorted as per the numerical order of their output label. The following table gives:
 -EQ.SYS.LAB.SDI : (SDAC, FWC, DMC...) output label for which the parameter is available
 -PARAMETER DEFINITION: parameter name
 -WORD RANGE/OPER RANGE/RESOLUTION ACCURACY: measurement range Maximum value transmitted. When the digital value changes, the change step is equal to the accuracy
 -UNIT : unit in which the digital value is transmitted
 -SIG BIT : indicates whether a sign bit is available
 -BITS : number of bits used by the parameter in the label
 -XMSN/INTV: output transmission interval. The refresh rate is given in milliseconds.
 -CODE:
 BNR: binary data word
 BCD: binary coded decimal data word
 ISO: data word coded in ISO5 code
 DIS: discrete data word
 HEX: hexadecimal coded
 HYB: mixed code.

 -ALPHA CODE: indicates the parameter mnemonic code
 -SOURCE ORIGIN: parameter source computer or system. When the input discretes of THE GPS PRESENT programming pins are grounded (indicating GPS present), both the MMR outputs and the GPIRS integrated navigation solution outputs are transmitted on the IR output buses with the IR output data.
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