What was found
FIVE MINUTES AFTER TAKEOFF USING ONLY APU BLEED X FEED TO BOTH PACS, RT DUCT LEAK LIGHT, ILLUMINATED, TURNED OFF X FEED AND RT PAC, STARTED TIME AS PER CHECK LIST, AFTER 3 MINUTES BEGAN PRECAUTIONARY ENGINE SHUT DOWN CHECK LIST WITH ENGINE AT FLIGHT IDLE AS RT ENGINE PROP WAS FEATHERED, DUCT LIGHT WENT OUT. TROUBLESHOT SYSTEM, FOUND GASKET FOR RT DEICE PRESSURE REGULATING VALUE BLOWN, INSTALLED NEW GASKET, RAN ENGINE, OPS CKS GOOD.