Narrative:

While I just began working local control and controller in charge in the tower; I had just received a relief briefing that included the information that a cessna aircraft was cleared for takeoff on runway 30 at pwk airport. My attention was to an aircraft circling to land; that I was watching on the d-brite to ensure that it did not fly into O'hare traffic. The ground controller asked me for permission to cross runway 30 at taxiway Y at the departure end of the runway 30. I gave him permission to cross runway 30; without scanning for the departing cessna. How it was discovered: after I watched the cessna cross the runway; the departing cessna came into view; and I realized that he was departing as the cessna was crossing runway 30 possibly. I have no way of knowing if he began his takeoff roll before or after the cessna was crossed or began crossing; he was already across when I saw him overfly the departure end of the runway. I then realized the possibilities of a conflict. The cessna was across the end of the runway when the overflying cessna reached the taxiway. Since I was not the controller that cleared him for takeoff; I had forgotten he was cleared; when I issued the crossing to the ground controller. Corrective actions: scan then approve a crossing local controller 1/ground controller scan before asking. I had been on position for 10 seconds or less when the aircraft crossing occurred.

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Original NASA ASRS Text

Title: PWK LCL CTLR EXPERIENCED OPERROR WHEN APPROVING TAXI RWY CROSSING WITH ACFT ON TKOF ROLL.

Narrative: WHILE I JUST BEGAN WORKING LCL CTL AND CIC IN THE TWR; I HAD JUST RECEIVED A RELIEF BRIEFING THAT INCLUDED THE INFO THAT A CESSNA ACFT WAS CLRED FOR TKOF ON RWY 30 AT PWK ARPT. MY ATTN WAS TO AN ACFT CIRCLING TO LAND; THAT I WAS WATCHING ON THE D-BRITE TO ENSURE THAT IT DID NOT FLY INTO O'HARE TFC. THE GND CTLR ASKED ME FOR PERMISSION TO CROSS RWY 30 AT TXWY Y AT THE DEP END OF THE RWY 30. I GAVE HIM PERMISSION TO CROSS RWY 30; WITHOUT SCANNING FOR THE DEPARTING CESSNA. HOW IT WAS DISCOVERED: AFTER I WATCHED THE CESSNA CROSS THE RWY; THE DEPARTING CESSNA CAME INTO VIEW; AND I REALIZED THAT HE WAS DEPARTING AS THE CESSNA WAS XING RWY 30 POSSIBLY. I HAVE NO WAY OF KNOWING IF HE BEGAN HIS TKOF ROLL BEFORE OR AFTER THE CESSNA WAS CROSSED OR BEGAN XING; HE WAS ALREADY ACROSS WHEN I SAW HIM OVERFLY THE DEP END OF THE RWY. I THEN REALIZED THE POSSIBILITIES OF A CONFLICT. THE CESSNA WAS ACROSS THE END OF THE RWY WHEN THE OVERFLYING CESSNA REACHED THE TXWY. SINCE I WAS NOT THE CTLR THAT CLRED HIM FOR TKOF; I HAD FORGOTTEN HE WAS CLRED; WHEN I ISSUED THE XING TO THE GND CTLR. CORRECTIVE ACTIONS: SCAN THEN APPROVE A XING LCL CTLR 1/GND CTLR SCAN BEFORE ASKING. I HAD BEEN ON POS FOR 10 SECONDS OR LESS WHEN THE ACFT XING OCCURRED.

Data retrieved from NASA's ASRS site as of January 2009 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.