Narrative:

The captain informed me about 10 mins after takeoff that we would be returning to ord. He said we had lost 1 of our 2 hydraulic system and he was declaring an emergency landing, but not to prepare the passenger. He said we had 10 mins and he did not anticipate evacing. We arrived back in ord without incident.

Google
 

Original NASA ASRS Text

Title: F100 CREW HAD HYD FAILURE DEPARTING ORD.

Narrative: THE CAPT INFORMED ME ABOUT 10 MINS AFTER TKOF THAT WE WOULD BE RETURNING TO ORD. HE SAID WE HAD LOST 1 OF OUR 2 HYD SYS AND HE WAS DECLARING AN EMER LNDG, BUT NOT TO PREPARE THE PAX. HE SAID WE HAD 10 MINS AND HE DID NOT ANTICIPATE EVACING. WE ARRIVED BACK IN ORD WITHOUT INCIDENT.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.