Narrative:

Was cleared for intersection departure runway 16 but turned onto runway 21 by mistake and unknowingly departed runway 21. Caught mistake once airborne. The intersection at night of runways 21 and 16 is confusing. Multiple txwys and runway exits and entrances. I could have avoided the mistake by double-checking directional gyroscope to runway heading. This would have provided a positive indication of departure. Problem was discovered after climb out. It is unknown if tower caught the mistake. I don't think that they did. No other traffic was involved.

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Original NASA ASRS Text

Title: PLT OF AN ATX CARGO C172 BECAME CONFUSED AT NIGHT AND TOOK OFF ON THE WRONG RWY THAN CLRED AT AN INTXN WHERE 2 RWYS CROSSED.

Narrative: WAS CLRED FOR INTXN DEP RWY 16 BUT TURNED ONTO RWY 21 BY MISTAKE AND UNKNOWINGLY DEPARTED RWY 21. CAUGHT MISTAKE ONCE AIRBORNE. THE INTXN AT NIGHT OF RWYS 21 AND 16 IS CONFUSING. MULTIPLE TXWYS AND RWY EXITS AND ENTRANCES. I COULD HAVE AVOIDED THE MISTAKE BY DOUBLE-CHKING DIRECTIONAL GYROSCOPE TO RWY HEADING. THIS WOULD HAVE PROVIDED A POSITIVE INDICATION OF DEP. PROB WAS DISCOVERED AFTER CLBOUT. IT IS UNKNOWN IF TWR CAUGHT THE MISTAKE. I DON'T THINK THAT THEY DID. NO OTHER TFC WAS INVOLVED.

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.