Narrative:

Working local and ground control combined, a FBO tug requested and was given clearance to proceed to other ramp from taxiway C crossing runway 31, taxiway B to ramp. Tug was moving numerous aircraft all evening. My attention then was given to identifying an aircraft inbound for runway 18 that had dropped from my bright scope approximately 3 mi north of the airport. An small aircraft aircraft holding on taxiway D requested takeoff clearance on runway 31 at the intersection. After scanning appropriate txwys and runway, takeoff clearance was issued. Immediately after clearance was given, tug asked if I wanted him to hold short of runway 31. Looking towards taxiway C I now noticed the tug at the bend on taxiway C but towing an open staircase instead of an aircraft. Tug was advised to hold short and did so at the appropriate hold line. Factors contributing to the situation was assuming the tug had crossed the runway and was at the other ramp. Additionally, if the tug mentioned he was towing an open stairwell, my scan would not have been looking for an aircraft rather the combination of the small tug towing an open stairwell which is somewhat more difficult to spot considering the background on that taxiway. One way to prevent a recurrence would be ensuring a 'clear' acknowledgement is received prior to any operation which can be in conflict with any vehicle.

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Original NASA ASRS Text

Title: CTLR CLEARED A TUG TO CROSS A RWY THEN CLEARED AN ACFT FOR TKOF. POSSIBLE RWY INCURSION. OPERATIONAL DEVIATION.

Narrative: WORKING LCL AND GND CTL COMBINED, A FBO TUG REQUESTED AND WAS GIVEN CLRNC TO PROCEED TO OTHER RAMP FROM TXWY C XING RWY 31, TXWY B TO RAMP. TUG WAS MOVING NUMEROUS ACFT ALL EVENING. MY ATTN THEN WAS GIVEN TO IDENTIFYING AN ACFT INBND FOR RWY 18 THAT HAD DROPPED FROM MY BRIGHT SCOPE APPROX 3 MI N OF THE ARPT. AN SMA ACFT HOLDING ON TXWY D REQUESTED TKOF CLRNC ON RWY 31 AT THE INTXN. AFTER SCANNING APPROPRIATE TXWYS AND RWY, TKOF CLRNC WAS ISSUED. IMMEDIATELY AFTER CLRNC WAS GIVEN, TUG ASKED IF I WANTED HIM TO HOLD SHORT OF RWY 31. LOOKING TOWARDS TXWY C I NOW NOTICED THE TUG AT THE BEND ON TXWY C BUT TOWING AN OPEN STAIRCASE INSTEAD OF AN ACFT. TUG WAS ADVISED TO HOLD SHORT AND DID SO AT THE APPROPRIATE HOLD LINE. FACTORS CONTRIBUTING TO THE SITUATION WAS ASSUMING THE TUG HAD CROSSED THE RWY AND WAS AT THE OTHER RAMP. ADDITIONALLY, IF THE TUG MENTIONED HE WAS TOWING AN OPEN STAIRWELL, MY SCAN WOULD NOT HAVE BEEN LOOKING FOR AN ACFT RATHER THE COMBINATION OF THE SMALL TUG TOWING AN OPEN STAIRWELL WHICH IS SOMEWHAT MORE DIFFICULT TO SPOT CONSIDERING THE BACKGROUND ON THAT TXWY. ONE WAY TO PREVENT A RECURRENCE WOULD BE ENSURING A 'CLEAR' ACKNOWLEDGEMENT IS RECEIVED PRIOR TO ANY OPERATION WHICH CAN BE IN CONFLICT WITH ANY VEHICLE.

Data retrieved from NASA's ASRS site as of August 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.