(f)
CFDS message select
On the A/C, this discrete is open.
(g)
GPS present These discretes are used to activate GPS/IRS hybridization (computation, BITE function).
(h)
GPS priority select The GPIRS function uses this discrete to modify the GPS priority. Each ADIRU receives data from the two GPS portions of the MMRs on the primary and secondary inputs. For each ADIRU, the primary and secondary GPS inputs are defined as follows:
R 1EFF : 005-049, 051-099, 101-149, 151-199, 1 34-14-00Page 10 1201-299, 301-399, 401-499, 1Config-3 Aug 01/05 1 1 1CES 1 ---------------------------------------------| ADIRU | PRIMARY | SECONDARY | | SDI | INPUT | INPUT | ---------------------------------------------| 1 | GPSSU 1 (MMR 1) | GPSSU 2 (MMR 2) | | 2 | GPSSU 2 (MMR 2) | GPSSU 1 (MMR 1) | | 3 | GPSSU 1 (MMR 1) | GPSSU 2 (MMR 2) | ---------------------------------------------
Depending on the GPS validity and GPS priority select input discrete status, the GPS source is defined as follows:
---------------------------------------------------------------------| PRIORITY | PRIMARY | SECONDARY | GPSSU SOURCE | | STATUS | GPSSU | GPSSU |-----------------------------------| | | | GPS PRIORITY | GPS PRIORITY | | | | | SELECT = OPEN | SELECT = GROUND | ---------------------------------------------------------------------| 1 | Valid | Valid | Primary | Secondary | | 2 | Valid | Fail | Primary | Primary | | 3 | Fail | Valid | Secondary | Secondary | | 4 | Fail | Fail | Primary | Secondary | ---------------------------------------------------------------------
R **ON A/C 051-099, 106-149, 204-299, 301-399, 401-499,
C. Software Computation (Ref. Fig. 001, 002) The software contains the program memory and provides the following basic functions:
-real-time executive
-attitude integration
-velocity integration
-position integration
- output computation
-built-in test (Ref. 34-18-00).
The IR software operates in one of three basic modes: alignment,
navigation, or a reversionary attitude mode. These modes include various
portions of the major functions. The real-time executive and built-in
test functions interface with each function in each mode.
(1) Alignment mode The alignment is the initialization mode for the IR. Its primary function is to initialize the attitude, velocity and position integration functions implemented in the navigation mode. This mode operates on the ground only.
R 1EFF : 005-049, 051-099, 101-149, 151-199, 1 34-14-00Page 11 1201-299, 301-399, 401-499, 1Config-3 Aug 01/05 1 1 1CES 1
ADIRU - IR Block Diagram
Figure 001
R 1EFF : 051-099, 106-149, 204-299, 301-399, 1 34-14-00Page 12 1401-499, 1Config-3 Aug 01/05 1 1 1CES 1
ADIRU - IR Signal Flow Diagram
Figure 002
R 1EFF : 051-099, 106-149, 204-299, 301-399, 1 34-14-00Page 13 1401-499, 1Config-3 Aug 01/05 1 1 1CES 1 The IR alignment mode is divided into three parts:
-coarse level processing The coarse level processing is engaged during the first 30 seconds of the IR alignment mode. This processing estimates the local vertical using the three accelerometers and the measured gravity. During coarse level processing of the alignment mode, the software computes the level coordinate frame, pitch and roll, and associated rates and accelerations.
-gyro-compass (or azimuth) processing and level processing Gyro-compass processing is engaged after the 30 seconds of the IR alignment mode (coarse level complete) and runs for a minimum of
9.5 minutes.
Gyro-compass processing is used to orient body frame to North
(using earth rotation detection by gyros).
During this alignment submode, an estimated latitude is computed
using local vertical component of the earth rotation.
During this submode, the results of the coarse level processing are
sharpened to have a better knowledge of the coordinate frame.
-position entry data processing This position initialization can take place in coarse level processing or gyro-compass processing. The latitude and longitude pair processed for position initialization is received from the same source (FMGC 1, FMGC 2 or CDU). As soon as a valid position initialization pair is received, the software performs a BITE test to check if the entered latitude and longitude are within the following limits versus the position recorded at the end of the last power- up cycle:
Abs val( lat entered - lat recorded ) less than or equal to 1 deg.
Abs val( long entered - long recorded ) less than or equal to 1 deg (Ref. 34-18-00).
A second BITE test is performed on the entered latitude when an estimated latitude is available during the gyro-compass processing:
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