MEDIUM LARGE TRANSPORT FLT CREW ATTRIBUTES OBSCURED VISION TO RAIN REPELLENT COATING ON COCKPIT WINDSCREEN.

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DUE TO ENVIRONMENTAL CONCERNS; WINDSHIELD RAIN REPELLENT HAS BEEN REMOVED. IT HAS BEEN REPLACED BY A COATING THAT IS NOT EFFECTIVE. AIRSPEED SPREADS A SHEET OF WATER ACROSS THE WIND SCREEN THAT WIPERS CANNOT DISPERSE FOR ADEQUATE VISION. RAIN REPELLENT AND RAIN-X CAUSE THE WATER TO BREAK AND ALLOW THE WIPER BLADES TO BE EFFECTIVE. THE ACFT IN FRONT OF US WENT AROUND AND WE NEARLY DID FOR OBSCURED VISION. I HAVE SEEN THIS PROBLEM REPEATEDLY SINCE THE CONVERSION. IT IS NOT CAUSED BY THE WIPER BLADES; BUT BY THE LACK OF A WATER BREAK-FREE SURFACE ON THE GLASS. I FEEL THIS CHANGE IS A STEP BACK IN SAFETY. IT WILL EVENTUALLY RESULT IN AN ACFT ACCIDENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT HE WAS FLYING A B737-500 MODEL ACFT WHEN THE RPTED INCIDENT OCCURRED; BUT THAT HE HAS ENCOUNTERED THE SAME PROB IN 300; 500; 700; AND 900 SERIES ACFT AND IN ALL RAIN CONDITIONS; LIGHT TO HEAVY. RPTR ALSO STATES THAT HE DOES NOT KNOW WHETHER HIS COMPANY'S ACFT HAVE ORIGINAL FACTORY SPEC WINDSCREENS OR IF THEY HAVE BEEN MODIFIED WITH A REPELLENT COATING. THE RPTR STATED THAT THERE HAS BEEN A DIRECTIVE FROM HIS COMPANY'S MAINT DEP ADVISING THAT WINDSCREENS ARE NOT TO BE CLEANED WITH CARBONATED WATER AS THIS MAY DEGRADE THE EFFECTIVENESS OF THE WINDSCREEN COATING. RPTR STATED THAT THE PROBLEM OF RAIN 'SHEETING' ACROSS THE WINDSCREEN INSTEAD OF DISPERSING INTO DROPS HAS OCCURRED SINCE THE USE OF LIQUID REPELLENTS WAS DISCONTINUED. RPTR FEELS THAT OTHER PLTS MAY BE 'JUST TOLERATING' THIS PROB AND NOT RPTING IT. THE RPTR ADVISED THAT HE HAS NOT CONTACTED HIS COMPANY MAINT DEP REGARDING THE SIT; BUT HAS DISCUSSED IT WITH OTHER PLTS WHO CONCUR WITH HIS ASSESSMENT OF THE PROB.