Narrative:

This situation happened while working local control in a VFR tower. -- A loss of separation with 2 aircraft at a runway intersection. Small aircraft X ILS runway 8, was instructed to come overhead for left traffic runway 13. While small aircraft X came up over runway 8, an small transport was put into position and hold runway 8, as small aircraft X started his left turn over the tower roof for runway 13. I cleared the small transport for takeoff and put an small aircraft Y into position and hold runway 8. It's about 500 ft to the runway 8/13 intersection. As the small transport lifted off and approached the distance needed for runway separation, I checked runway 13 final approach for small aircraft X, did not see him, so I cleared small aircraft Y for takeoff. Went back to look for small aircraft X on base leg, then final, then I looked back at small aircraft Y on runway 8 and saw small aircraft X overflying small aircraft Y, then landed. I should have found small aircraft X in my scan before I cleared small aircraft Y for takeoff. From my position in the cabin attendant, small aircraft X could have been behind a support pole to the roof, possibly short final. Small aircraft X made a very short approach which was unexpected and I was looking for him further out on his circling approach, instead of over the runway.

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Original NASA ASRS Text

Title: SMA X LANDED ON OCCUPIED RWY WITH SMA Y IN POS CLRED FOR TKOF. LTSS. NMAC. SYS ERROR. PLTDEV.

Narrative: THIS SITUATION HAPPENED WHILE WORKING LCL CTL IN A VFR TWR. -- A LOSS OF SEPARATION WITH 2 ACFT AT A RWY INTXN. SMA X ILS RWY 8, WAS INSTRUCTED TO COME OVERHEAD FOR L TFC RWY 13. WHILE SMA X CAME UP OVER RWY 8, AN SMT WAS PUT INTO POS AND HOLD RWY 8, AS SMA X STARTED HIS L TURN OVER THE TWR ROOF FOR RWY 13. I CLRED THE SMT FOR TKOF AND PUT AN SMA Y INTO POS AND HOLD RWY 8. IT'S ABOUT 500 FT TO THE RWY 8/13 INTXN. AS THE SMT LIFTED OFF AND APCHED THE DISTANCE NEEDED FOR RWY SEPARATION, I CHKED RWY 13 FINAL APCH FOR SMA X, DID NOT SEE HIM, SO I CLRED SMA Y FOR TKOF. WENT BACK TO LOOK FOR SMA X ON BASE LEG, THEN FINAL, THEN I LOOKED BACK AT SMA Y ON RWY 8 AND SAW SMA X OVERFLYING SMA Y, THEN LANDED. I SHOULD HAVE FOUND SMA X IN MY SCAN BEFORE I CLRED SMA Y FOR TKOF. FROM MY POS IN THE CAB, SMA X COULD HAVE BEEN BEHIND A SUPPORT POLE TO THE ROOF, POSSIBLY SHORT FINAL. SMA X MADE A VERY SHORT APCH WHICH WAS UNEXPECTED AND I WAS LOOKING FOR HIM FURTHER OUT ON HIS CIRCLING APCH, INSTEAD OF OVER THE RWY.

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.