.
Two ADR outputs are erroneous but different and the remaining ADR is correct, or if all three ADR outputs are erroneous but different. The AP and A/THR will disconnect. If the disagreement lasts for more than 10 seconds, the PRIM triggers the NAV ADR DISAGREE ECAM caution. Flight controls revert to ALTN 2 law. The SPD LIM flag is displayed on both PFDs, however VLS and VSW are not displayed. This condition is latched until a PRIM reset is performed on ground without any hydraulic pressure. However, if the disagreement was transient, the AP and A/THR can be re-engaged when the NAV ADR DISAGREE message has disappeared.
.
One ADR is correct but the other two ADRs provide the same erroneous output, or if all three ADRs provide consistent and erroneous data. The PRIMs and FEs will reject the “good” outlier ADR and will continue to operate normally using the two consistent but faulty ADRs.
Any erroneous speed/altitude indication will always be associated with one or more of the following cues:
. Fluctuations in airspeed indications
. Abnormal correlation of basic flight parameters (IAS, pitch, attitude, thrust, climb rate); e.g IAS increasing with large nose-up pitch attitude, IAS decreasing with large nose down pitch attitude, IAS decreasing, with nose down pitch attitude and aircraft descending
. Abnormal AP/FD/A/THR behavior . Stall or overspeed warnings . Reduction in aerodynamic noise, with increasing IAS . Increase in aerodynamic noise, with decreasing IAS
8.110.4
A330/A340 Non-normal Operations
REV 1 (6 JUN 05)
FCTM Miscellaneous
The ADRs provide a number of outputs to many systems and a blockage of the pitot and/or static systems may also lead to the following:
. SPD LIM flag on PFD
.
Alpha floor activation (because AOA outputs from the sensors are
corrected by speed inputs) . Wind shear warning (due to Mach input) . Flap load-relief activation . Flap auto-retraction from 1+F to 1
.
Alpha lock on slats retraction (due to the speed logic part of the alpha lock
function) . ALTI DISCREPANCY on ECAM . RUD TRV LIM FAULT ON on ECAM
Always apply the ECAM procedure. If the failure is not annunciated on ECAM, crosscheck all IAS/ALTITUDE sources (ADR 1, 2, & 3, and ISIS/STBY INST).
Early recognition of erroneous airspeed indications requires some familiarity with the relationship between attitude, thrust setting and airspeed. If it is positively confirmed that the outlier ADR is at fault and that the other two ADRs are correct, select the faulty ADR OFF. This action will generate an ECAM procedure, which should be applied in order to reconfigure the PFD to display correct information.
However, in very extreme circumstances, two or all three ADRs may provide identical but erroneous data. If there is any doubt, then do not instinctively reject the outlier ADR, although the temptation may exist if the other two ADR outputs are consistent. In most cases, this decision would be correct, but not in the case where two speed/altitude indications are consistent but wrong. Apply the initial actions of the UNRELIABLE SPEED INDICATION QRH procedure from memory as they quickly provide a safe flight condition in all phases of flight and aircraft configuration. Rely on the primary flight parameters of pitch attitude and thrust setting.
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