What was found
LOUD AIR NOISE IN COCKPIT EVEN WITH RECIRCULATION OFF, MUCH LOUDER INFLT THAN ON GROUND. REPLACED LT PACK FLOW CONTROL AND SHUTOFF VALVE PER SERVICE TIP AND MM. LOW AND DEEP PITCHED SOUND HEARD WITH RECIRCULATION FANS OFF GONE.
As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
LOUD AIR NOISE IN COCKPIT EVEN WITH RECIRCULATION OFF, MUCH LOUDER INFLT THAN ON GROUND. REPLACED LT PACK FLOW CONTROL AND SHUTOFF VALVE PER SERVICE TIP AND MM. LOW AND DEEP PITCHED SOUND HEARD WITH RECIRCULATION FANS OFF GONE.