What was found
ON ANNUAL INSPECTION, EMERGENCY AIR SHUT-OFF TO COCKPIT WAS DETERMINED NOT TO BE OPERATIVE. FURTHER INSPECTION FOUND BELLCRANK LOOSE FROM 'DOOR' BY RIVETS IN BELLCRANK HAVING COME OUT OF BELLCRANK. WHEN REMOVING UNIT FOR REPLACEMENT OF RIVETS, HINGE HOLDING DOOR IN PLACE HAD RIVETS, ALSO PULLED OUT, LEAVING DOOR AND ONE-HALF HINGE LOOSE. OTHER ONE-HALF OF HINGE ON DUCT FOUND CORRECTLY ATTACHED. MADE REPAIRS PER 43.13 AND RETURNED TO SERVICE. SYSTEM OPERATES NORMALLY.