Narrative:

Aircraft had MEL [applied for] windshield and windows defogging system; clear view windows. Uneventful flight until descending below 5;000 feet for hot and humid approach into [destination]. Both the first officer's windshield and clear view windows began to fog in the high humidity environment and selecting high function on the window anti-ice panel did not improve the condition. The captain's window defog was working properly. The first officer unsuccessfully tried to manually clean his windshield several times but could not keep up with the quick rate of fogging and at the same time perform his assigned duties. The runway environment was barely visible through the first officer's windshield for landing and taxi in; creating a safety issue for the crew.the active MEL for the airplane only referred to the clear view window; but the lack of defog was also present for the windshield; which is covered by MEL windshield and windows defogging system; main windshield; and not present in the ard. Deferring an inoperative windshield defog system poses a significant safety of flight risk and is contrary to the company's mindset of 'safety first'! As the meteorological conditions at any given location change daily; it is impossible to predict when the windshield anti-ice system will or will not be able to keep the windshield clear and should not be solely relied upon. It is not safe to be able to defer the windshield defog system and relying on the window anti-ice to keep the window clear when arriving at high humidity destinations. Recommend that an inoperative windshield defog system not be a deferrable item and must be repaired prior to aircraft dispatch.

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Original NASA ASRS Text

Title: MD-11 Captain reported the aircraft was dispatched with the FO's windshield defogging system deferred inoperative; and the window fogged up on arrival to the hot and humid destination airport; causing a safety concern.

Narrative: Aircraft had MEL [applied for] Windshield and Windows Defogging System; Clear view Windows. Uneventful flight until descending below 5;000 feet for hot and humid approach into [destination]. Both the FO's windshield and clear view windows began to fog in the high humidity environment and selecting High function on the Window Anti-Ice panel did not improve the condition. The Captain's window defog was working properly. The First Officer unsuccessfully tried to manually clean his windshield several times but could not keep up with the quick rate of fogging and at the same time perform his assigned duties. The runway environment was barely visible through the FO's windshield for landing and taxi in; creating a safety issue for the crew.The active MEL for the airplane only referred to the clear view window; but the lack of defog was also present for the windshield; which is covered by MEL Windshield and Windows Defogging System; Main Windshield; and not present in the ARD. Deferring an inoperative Windshield defog System poses a significant safety of flight risk and is contrary to the company's mindset of 'safety first'! As the meteorological conditions at any given location change daily; it is impossible to predict when the windshield anti-ice System will or will not be able to keep the windshield clear and should not be solely relied upon. It is not safe to be able to defer the windshield defog system and relying on the window anti-ice to keep the window clear when arriving at high humidity destinations. Recommend that an inoperative windshield defog System NOT be a deferrable item and must be repaired prior to aircraft dispatch.

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.