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Robinson Helicopter Company released Service Bulletin 85 for all of R44 model helicopters after receiving reports about deterioration and cracking of the rubberized seal where the filter assembly is fitted to the air box.  In researching the issue, RHC believes that the defect is limited to a specific lot of the C771-1 air filters.  If filters with a date code of 052311AY1 is identified, the filters should be removed from service and replaced with an airworthy unit.   Any spare units should also be checked for deterioration and if any are found, RHC requests that technical support be contacted to report the problem.