Narrative:

Captain requested and received (what I thought was) the ATR 221 degree radial. However, what he actually got was the sby 221 degree radial. Therefore, in about 5 mins, ATC told us that we were west of the airway. We corrected back to course after I recognized the error and switched to sby.

Google
 

Original NASA ASRS Text

Title: AFTER MD83 FLC REQUESTED AND RECEIVED AN ENRTE VOR COURSE RADIAL, THEY THEN TUNED IN THE WRONG VOR AND BECAME 5 MI OFF COURSE RESULTING IN ARTCC CTLR INTERVENTION.

Narrative: CAPT REQUESTED AND RECEIVED (WHAT I THOUGHT WAS) THE ATR 221 DEG RADIAL. HOWEVER, WHAT HE ACTUALLY GOT WAS THE SBY 221 DEG RADIAL. THEREFORE, IN ABOUT 5 MINS, ATC TOLD US THAT WE WERE W OF THE AIRWAY. WE CORRECTED BACK TO COURSE AFTER I RECOGNIZED THE ERROR AND SWITCHED TO SBY.

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.