Narrative:

Detroit approach control cleared us for a visual approach to runway 21C and switched us to tower control at about 12 mi out. Tower controller cleared us to land on runway 21C as soon as we checked in with him. When we were about 3 mi out, my first officer heard the tower controller clear another aircraft for takeoff from runway 21C. I did not hear this transmission. My first officer said he scanned the runway looking for an aircraft that might have been holding in position for takeoff but saw none and assumed he had misunderstood what he thought he heard. He did see an aircraft taxiing northeast on the 21C parallel taxiway but discounted it as one cleared to takeoff because of his relatively far distance from the runway entry point and our relatively close-in position on final approach. When we were at about 300 ft AGL, (approximately 1 mi on final) that aircraft turned onto the runway and began his takeoff roll. We initiated a go around and in the process descended to about 200 ft AGL. We over flew the other aircraft close enough to hear the engine noise from it. The aircraft was a medium size turbojet (two engines) type and identify unknown. I don't think that I or my first officer was at fault in this situation. That is, I believe we did everything required of us but if we simply had queried the tower controller about the transmission the first officer thought he heard, the near miss could have been avoided.

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Original NASA ASRS Text

Title: ACFT WAS CLRED FOR TKOF WHILE AN ACR WAS SHORT FINAL APCH RESULTING IN A GAR.

Narrative: DETROIT APCH CTL CLRED US FOR A VISUAL APCH TO RWY 21C AND SWITCHED US TO TWR CTL AT ABOUT 12 MI OUT. TWR CTLR CLRED US TO LAND ON RWY 21C AS SOON AS WE CHKED IN WITH HIM. WHEN WE WERE ABOUT 3 MI OUT, MY FO HEARD THE TWR CTLR CLR ANOTHER ACFT FOR TKOF FROM RWY 21C. I DID NOT HEAR THIS XMISSION. MY FO SAID HE SCANNED THE RWY LOOKING FOR AN ACFT THAT MIGHT HAVE BEEN HOLDING IN POS FOR TKOF BUT SAW NONE AND ASSUMED HE HAD MISUNDERSTOOD WHAT HE THOUGHT HE HEARD. HE DID SEE AN ACFT TAXIING NE ON THE 21C PARALLEL TAXIWAY BUT DISCOUNTED IT AS ONE CLRED TO TKOF BECAUSE OF HIS RELATIVELY FAR DISTANCE FROM THE RWY ENTRY POINT AND OUR RELATIVELY CLOSE-IN POS ON FINAL APCH. WHEN WE WERE AT ABOUT 300 FT AGL, (APPROX 1 MI ON FINAL) THAT ACFT TURNED ONTO THE RWY AND BEGAN HIS TKOF ROLL. WE INITIATED A GAR AND IN THE PROCESS DSNDED TO ABOUT 200 FT AGL. WE OVER FLEW THE OTHER ACFT CLOSE ENOUGH TO HEAR THE ENG NOISE FROM IT. THE ACFT WAS A MEDIUM SIZE TURBOJET (TWO ENGS) TYPE AND IDENT UNKNOWN. I DON'T THINK THAT I OR MY FO WAS AT FAULT IN THIS SITUATION. THAT IS, I BELIEVE WE DID EVERYTHING REQUIRED OF US BUT IF WE SIMPLY HAD QUERIED THE TWR CTLR ABOUT THE XMISSION THE FO THOUGHT HE HEARD, THE NEAR MISS COULD HAVE BEEN AVOIDED.

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.