Phl controller cleared a second aircraft for take off failing to note crossing traffic down field; t...

Narrative:

Phl on 9/35 configuration; new mitigated headings went into effect. Workload is very high on this configuration. It is the busiest position in the tower under these circumstances. I was working local east with traffic departing 9L and landing intersecting runway 35. Traffic on short final to runway 35 and an A321 in position on 9L; I crossed two aircraft at taxiway november; an E170 first then an A321 and one aircraft at taxiway 'east'. Landing traffic cleared the departure runway and I looked to see if my crossings were complete. I saw the first aircraft clearing the runway at november and though it was my second. I cleared the A321 for take off and immediately realized my error as the E170 was still moving. I immediately canceled the take off clearance. The aircraft had not appeared to move; but when the pilot was questioned; he said he moved about ten feet. The asde-X did not alarm; nor did the 'bars' go up. Don't have a complex operation during a procedure change. Taking the runway 35 arrivals out of the equation would have dramatically reduced the workload. New mitigated headings were taking attention away from other tasks. Having clearance or ground control write the heading on the departure strip would have been a big help.

Original NASA ASRS Text

Title: PHL Controller cleared a second aircraft for take off failing to note crossing traffic down field; the reporter issuing alternate instructions to secure separation.

Narrative: PHL on 9/35 configuration; new mitigated headings went into effect. Workload is very high on this configuration. It is the busiest position in the Tower under these circumstances. I was working Local East with traffic departing 9L and landing intersecting Runway 35. Traffic on short final to Runway 35 and an A321 in position on 9L; I crossed two aircraft at Taxiway November; an E170 first then an A321 and one aircraft at Taxiway 'E'. Landing traffic cleared the departure runway and I looked to see if my crossings were complete. I saw the first aircraft clearing the runway at November and though it was my second. I cleared the A321 for take off and immediately realized my error as the E170 was still moving. I immediately canceled the take off clearance. The aircraft had not appeared to move; but when the pilot was questioned; he said he moved about ten feet. The ASDE-X did not alarm; nor did the 'bars' go up. Don't have a complex operation during a procedure change. Taking the Runway 35 arrivals out of the equation would have dramatically reduced the workload. New mitigated headings were taking attention away from other tasks. Having clearance or Ground Control write the heading on the departure strip would have been a big help.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1013463
Time
Date	201206
Local Time Of Day	0001-0600
Place
Locale Reference	PHL.Airport
State Reference	PA
Aircraft 1
Make Model Name	A321
Operating Under FAR Part	Part 121
Flight Phase	Taxi
Route In Use	None
Flight Plan	IFR
Aircraft 2
Make Model Name	EMB ERJ 170/175 ER/LR
Operating Under FAR Part	Part 121
Flight Phase	Taxi
Route In Use	None
Flight Plan	IFR
Person 1
Function	Local
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Conflict Ground Conflict Less Severe Deviation - Procedural Published Material / Policy

Phl controller cleared a second aircraft for take off failing to note crossing traffic down field; the reporter issuing alternate instructions to secure separation.