Narrative:

Descending through approximately 32;000 feet we received an IAS disagree. I hand flew the airplane; comparing the stand-by a/south (airspeed) indicator to our instruments and the first officer (first officer) a/south dropped to 50 knots and the captain side was somewhat close in speed to the stand-by. We also had an engine light and soon after had altitude disagree with the first officer side losing its altimeter. The speeds and altitude disagree lights came on 3 different times on descent and approach; followed by momentary corrections before disagreeing again for longer durations. The captain side was more aligned to the stand-by than the first officer side; but it wasn't clearly reliable either. We had a slightly higher approach than normal based on lack of confidence in the airspeed but had a smooth and uneventful landing.this same exact scenario happened in [this same aircraft last week] upon descent. The aircraft sat overnight during heavy rain the night before and the mechanics said they drained the tat (total air temperature) line; which was full of fluid and they opened an 'access panel' and water rushed out. The system appeared to work normally after clearing the water and it was signed off for service with no issues on the return flight. The aircraft also sat the night before our flight; but we did not experience heavy rain overnight.the mechanic did a bite test before we left the cockpit and said both air data computers were fried. Being the rainy season and this issue happening twice in a week; leads to questions as to the safety of the operation of this aircraft until the cause is clearly determined and corrected.

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Original NASA ASRS Text

Title: B737NG First Officer reported experiencing erroneous airspeed indications later traced to water in the pitot-static system.

Narrative: Descending through approximately 32;000 feet we received an IAS Disagree. I hand flew the airplane; comparing the stand-by A/S (airspeed) indicator to our instruments and the FO (First Officer) A/S dropped to 50 knots and the Captain side was somewhat close in speed to the stand-by. We also had an ENG light and soon after had ALT disagree with the FO side losing its altimeter. The speeds and altitude disagree lights came on 3 different times on descent and approach; followed by momentary corrections before disagreeing again for longer durations. The Captain side was more aligned to the stand-by than the FO side; but it wasn't clearly reliable either. We had a slightly higher approach than normal based on lack of confidence in the airspeed but had a smooth and uneventful landing.This same exact scenario happened in [this same aircraft last week] upon descent. The aircraft sat overnight during heavy rain the night before and the mechanics said they drained the TAT (Total Air Temperature) line; which was full of fluid and they opened an 'access panel' and water rushed out. The system appeared to work normally after clearing the water and it was signed off for service with no issues on the return flight. The aircraft also sat the night before our flight; but we did not experience heavy rain overnight.The mechanic did a bite test before we left the cockpit and said both Air Data Computers were fried. Being the rainy season and this issue happening twice in a week; leads to questions as to the safety of the operation of this aircraft until the cause is clearly determined and corrected.

Data retrieved from NASA's ASRS site 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.