Narrative:

At 37;000 ft received flashing IAS alert on the pfd followed by intermittent sps advanced EICAS message. Compared airspeed and altimeters and believed the #1 air data computer was malfunctioning. Received descent clearance and the #1 IAS began to rapidly decrease. Selected the #2 air data computer on the reversion panel and recovered air data. At 28;200 ft looked at the standby and it was frozen at 32;000 ft and within 10 seconds began to catch up to the current altitude assigned. Water began to drain over our respective kit bags from the top of the window crevice. Landed and contacted maintenance. The following trip a week later experienced a several hundred foot fluctuation on the vsi and also over speed warnings on the IAS as a result of problem with air data computer. Contacted maintenance. On preflight for another flight; after reviewing log as required found this aircraft experienced a similar air data computer failure. In each case; maintenance stated it was probably water.

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Original NASA ASRS Text

Title: EMB145 Captain experiences ADC failure at FL370 causing erroneous airspeed and altimeter indications. Switching to #2 ADC eliminates problems. Maintenance believes water is causing the ADC's to fail. Other instances of water caused ADC failures are experienced and viewed in aircraft log.

Narrative: At 37;000 FT received flashing IAS alert on the PFD followed by intermittent SPS advanced EICAS message. Compared airspeed and altimeters and believed the #1 ADC was malfunctioning. Received descent clearance and the #1 IAS began to rapidly decrease. Selected the #2 ADC on the reversion panel and recovered air data. At 28;200 FT looked at the standby and it was frozen at 32;000 FT and within 10 seconds began to catch up to the current altitude assigned. Water began to drain over our respective kit bags from the top of the window crevice. Landed and contacted maintenance. The following trip a week later experienced a several hundred foot fluctuation on the VSI and also over speed warnings on the IAS as a result of problem with ADC. Contacted maintenance. On preflight for another flight; after reviewing log as required found this aircraft experienced a similar ADC failure. In each case; maintenance stated it was probably water.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.