What was found
AT CRUISE FLIGHT AT FLT LEVEL 250 COULD NOT MAINTAIN PRESSURIZATION WITH SINGLE PACK OPERATION. AIRCRAFT RETURNED TO MSP AND LANDED WITHOUT INCIDENT. CLEANED OUTFLOW VALVE AND PRESSURIZED AIRCRAFT, OPERATIONAL CHECK OK.
As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
AT CRUISE FLIGHT AT FLT LEVEL 250 COULD NOT MAINTAIN PRESSURIZATION WITH SINGLE PACK OPERATION. AIRCRAFT RETURNED TO MSP AND LANDED WITHOUT INCIDENT. CLEANED OUTFLOW VALVE AND PRESSURIZED AIRCRAFT, OPERATIONAL CHECK OK.