Narrative:

Mis-heard heading from approach control. During approach to runway 9L at ord, controller gave us heading and altitude change. We apparently mis- heard controller and turned to the incorrect heading and started to descend. I believe we read back what we thought the controller said and he mis-heard us. When the controller saw that we were not doing what he had intended, he gave us a climb and a vector to runway 9R. Remainder of flight completed without incident. We received no TCASII alerts during this incident. Controller did an excellent job recognizing our error and vectoring us back for approach to runway 9R.

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Original NASA ASRS Text

Title: READBACK HEARBACK PROB LEADS TO ALT AND TRACK DEV.

Narrative: MIS-HEARD HDG FROM APCH CTL. DURING APCH TO RWY 9L AT ORD, CTLR GAVE US HDG AND ALT CHANGE. WE APPARENTLY MIS- HEARD CTLR AND TURNED TO THE INCORRECT HDG AND STARTED TO DSND. I BELIEVE WE READ BACK WHAT WE THOUGHT THE CTLR SAID AND HE MIS-HEARD US. WHEN THE CTLR SAW THAT WE WERE NOT DOING WHAT HE HAD INTENDED, HE GAVE US A CLB AND A VECTOR TO RWY 9R. REMAINDER OF FLT COMPLETED WITHOUT INCIDENT. WE RECEIVED NO TCASII ALERTS DURING THIS INCIDENT. CTLR DID AN EXCELLENT JOB RECOGNIZING OUR ERROR AND VECTORING US BACK FOR APCH TO RWY 9R.

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.