What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO ORD DUE TO THE FLIGHT CREW REPORTING A #1 ENGINE FAILURE AFTER TAKEOFF AT 5000FT. THE FLIGHT CREW REPORTED HEARING A LOUD BANG AND FELT VIBRATION, THE FLIGHT CREW SECURED THE ENGINE AND REPORTED 22 MINUTES SINGLE ENGINE FLIGHT. THE AIRCRAFT LANDED SAFELY AT ORD WITHOUT FURTHER INCIDENT. DURING THE POST FLIGHT INSPECTION THE #1 ENGINE OIL TANK WAS EMPTY WITH TURBINE BLADES AND OIL SITTING IN THE EXHAUST. MAINTENANCE REPLACED #1 ENGINE PER JOB CARD 26L40071001.