Narrative:

During a routine inspection task card 21-20-04 - cabin air distribution check valves detailed inspection; it was discovered that the emergency pressurization check valve flappers would not freely open. Also discovered that rtv sealant had apparently seeped into the flapper openings during a previous maintenance visit where the rtv was used as a fay seal. The installer unknowingly squeezed the excess sealant when installing which had penetrated the flapper opening and during the curing process adhered to both the flapper face and the flapper opening; thus preventing the flapper from performing as potentially required. The previous installer followed the MM 21-12-00 as written; but did not verify that flappers would open freely or close as they should.a suggestive corrective action would be to change the cessna ce-560XL maintenance manual (M/M) to:1.) add a warning not to use excessive rtv or flapper will not open. 2.) do not fay seal; edge seal.3.) add a note to verify that flappers 'open' freely and 'close' as they should. 4.) step missing on 21-12-00 paragraph 3; a-(5) which states to 'discard the gaskets.' where is the step to replace the gaskets? Reference: ce-560XL MM 21-22-00 task 21-22-00-210. Ce-560XL MM 21-12-00. Maintenance inspector. Missing documentation.

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Original NASA ASRS Text

Title: An Aircraft Maintenance Inspector (AMI) reports finding Emergency Pressurization Check Valve flappers on a Cessna CE-560XL aircraft would not open freely; during a Detailed Inspection of the Cabin Air Distribution Check Valves. Previous application of RTV sealant had penetrated the flapper opening and secured the flapper to the opening; preventing movement.

Narrative: During a Routine Inspection Task Card 21-20-04 - Cabin Air Distribution Check Valves Detailed Inspection; it was discovered that the Emergency Pressurization Check Valve Flappers would not freely open. Also discovered that RTV Sealant had apparently seeped into the flapper openings during a previous maintenance visit where the RTV was used as a fay seal. The installer unknowingly squeezed the excess sealant when installing which had penetrated the flapper opening and during the curing process adhered to both the flapper face and the flapper opening; thus preventing the flapper from performing as potentially required. The previous installer followed the MM 21-12-00 as written; but did not verify that flappers would open freely or close as they should.A suggestive Corrective Action would be to change the Cessna CE-560XL Maintenance Manual (M/M) to:1.) Add a Warning not to use excessive RTV or flapper will not open. 2.) Do not fay seal; edge seal.3.) Add a note to verify that flappers 'open' freely and 'close' as they should. 4.) Step missing on 21-12-00 Paragraph 3; A-(5) which states to 'Discard the Gaskets.' Where is the step to replace the gaskets? Reference: CE-560XL MM 21-22-00 Task 21-22-00-210. CE-560XL MM 21-12-00. Maintenance Inspector. Missing documentation.

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.