What was found
ON OPERATIONAL CHECK FLIGHT FOR PRESSURIZATION CHECKOUT, AIRCRAFT FAILED TO MAINTAIN MAXIMUM CABIN PRESSURE ON SINGLE ENGINE BLEED AIR. MAINT DISCOVERED MULTIPLE CRACKS ON FORWARD PRESSURE BULKHEAD, LOWER RT CORNER OF P/N 114-410026-6, WEB ASSY AT UPPER END OF STIFFENER P/N 114-410026-55 AND AT STA 84. THIS CRACK WAS APPROX 7 INCHES LONG. AN ADDITIONAL CRACK WAS DISCOVERED THAT RAN ALONG UPPER JOGGLE OF P/N 114-410026-6. THIS CRACK WAS ALSO APPROX 7 INCHES LONG. BOTH CRACKS WERE THEN REPAIRED IAW B1900C STRUCTURAL REPAIR MANUAL WITH A SINGLE SURFACE PATCH. ANTICIPATE FINDING THAT THERE WAS A RIVET MISSING AT MANUFACTURE THAT WOULD ATTACH PIN 114-410026-23 STIFFENER TO ANGLE P/N 114-410026-9. (M)