(6)
 Reconfiguration display In case of loss of inertial parameters on the CAPT or F/O PFD and ND, the IR3 can be used as a back up source by placing the ATT HDG selector switch in CAPT/3 position for the CAPT PFD and ND or in F/O/3 position for the F/O PFD and ND.

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 C. Warnings (Ref. Fig. 015, 016, 017, 018, 019)
 (1)
 In addition to the ATT or HDG flags displayed on the PFDs, NDs and on the CDU, warning messages are displayed on the lower part of the upper ECAM DU.

 (a)
 NAV IR 1(2)(3) FAULT
 NAV IR 1(2) + 2(3) FAULT
 When these messages are displayed:

 -
the MASTER CAUT lights on the glareshield come on

 -
the Single Chime (SC) sounds

 -
the IR FAULT legend flashes on the CDU.

 (b)
 NAV ATT DISCREPANCY This message is displayed when a difference higher than 5 deg. is detected by comparison inside the FWCs between the roll angle or the pitch angle provided by two IRs. When it is displayed:

 -
the MASTER CAUT lights on the glareshield come on

 -
the Single Chime (SC) sounds

 -
the CHECK ATT message appears on the PFD.

 (c)
 NAV HDG DISCREPANCY This message is displayed when a difference higher than 7 deg. (or 5 deg. in true heading) is detected by comparison inside the FWCs between the heading value provided by two IRs. When it is displayed:

 -
the MASTER CAUT lights on the glareshield come on

 -
the Single Chime (SC) sounds

 -
the CHECK HDG message appears on the PFDs and NDs.

 (d)
 NAV GPS 1(2) FAULT (Ref. Fig. 020) The GPSSUs are monitored by the three ADIRUs using the status word sent by the GPSSU and the BITE of the IR partion. This message is accompanied by:

 -activation of the MASTER CAUT lights on the glareshield panel
 -aural warning: single chime (SC).

 (2)
 When the CLR key is pushed on the ECAM control panel, a STATUS page is displayed on the lower ECAM DU and indicates the STATUS and INOP SYS (systems).

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 NAV IR 1 (2) (3) FAULT Message
 Figure 015

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 NAV IR 1+2 FAULT Message
 Figure 016

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 NAV IR 1+3 (2+3) FAULT Message
 Figure 017

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 NAV ATT DISCREPANCY Message
 Figure 018

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 NAV HDG DISCREPANCY Message
 Figure 019

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 NAV GPS - Fault Messages
 Figure 020

 1EFF : 001-004, 1 34-14-00Page 67 1 1 Config-1 Aug 01/03 1 1 1CES 1 D. ADIRUs Performance Criteria

 (1)
 History The inertial parameters to be considered to evaluate the level of performance of an inertial system after flight completion are:

 -
the radial position error (in NM)

 -
the residual ground speed error (in kts).
 Depending on their magnitude noticed at the end of the flight, the
 concerned inertial system(s) shall or shall not be removed from the
 aircraft.

 (2)
 Radial position error In order to address the statistical term of this requirement with the most relevant approximation, the removal criteria use a limit based on the recording of the radial position error on two consecutive flights. The use of a two-strike method presents the advantage to decrease the removal rate of healthy units that have shown, by chance, or by an inaccurate position entry at alignment, a radial position error beyond the specified criterion. The removal boundaries described on the figure present three different areas: (Ref. Fig. 021)

 -
Area 1 - ADIRU OK all the time

 -
Area 2 - ADIRU to be checked after second flight

 -
Area 3 - ADIRU to be replaced.

 NOTE : Area 2 is applicable when the residual radial position error
____ ranges within the limits described in following Para.
 (a) Lower limit for removal criteria The integration of the drift rate results in a lower limit for the radial position error: Radial position error (NM) = (2 (NM/h) * T (h)) + Offset (NM) The presence of an offset is necessary to avoid the unjustified removal of healthy units subject to the natural Schuler effects and to the Present Position inaccuracies entered during initialization. It should be pointed out that the adverse impacts of such inaccuracies over the radial position error will reveal stronger for short flight durations (below 1.5 hour).
　
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