Date: 201209
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Aircraft: Challenger CL600
Operator: Corporate
Operating under: Part 91
Flight plan: IFR
Flight phase: Takeoff / Launch
ATC / advisory: Tower ZZZ
Reporter organization: Government
Reporter function: Local
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Situational Awareness; Communication Breakdown
Second reporter function: Ground; Supervisor / CIC
Anomaly: Conflict Ground Conflict; Critical
Detector: Person Air Traffic Control
Result: General None Reported / Taken
Contributing factors: Procedure; Human Factors
Primary problem: Human Factors

Narrative: Controller In Charge (CIC) was combined at Ground Control (GC) for lunch breaks. I was working Local Control (LC) with no traffic on frequency. Ground Control requested to cross Runway 1 with a mower. I scanned the runway and final; checked my pad then approved the crossing. It seemed like a few minutes went by when a Challenger called ready and requested a back taxi for full length (about 800 FT) at Runway 1 Bravo Intersection; due to construction Alpha Taxiway for full length is closed. Again; I scanned the runway; final and checked my pad and cleared the Challenger for back taxi and takeoff. While the aircraft was back taxing; Approach called to APREQ an opposite direction arrival about 40 miles away. I expanded my RADAR to see the target. As I was approving the APREQ I observed the Challenger slowing to a stop about 2;500 FT from the approach end. I wondered why he was doing that until I saw the mower come from behind the Tower window stanchion. Delta Taxiway where the mower crossed runs east/west and is almost completely obscured by the window stanchion in front of the LC position. The GC/CIC was busy issuing clearances had apparently cleared the mower from a great distance from the runway and it took longer than I expected for him to get across. The GC/CIC was busy and did not observe the incident. The pilot turned around for full length and departed without further incident. The GC should have waited until the mower got to the runway before requesting the crossing. I should have slid the 12 inches to the right or left and looked at Delta Taxiway.


Second narrative: I was working Controller In Charge (CIC) and Ground Control (GC) combined. A mower asked to proceed south on Taxiway Lima and cross both runways at Delta. I said to Local Control (LC); 'Cross both runways at Delta?' and LC replied 'Cross both runways at Delta.' I cleared the mower across. I don't know how I missed this; but sometime soon after I cleared the mower; LC cleared a Challenger for take off on Runway 01. I did not hear this clearance. But I did hear the Challenger say something like; 'There's a mower on the runway in front of us.' Well; that got my attention. When I looked up; the Challenger was approximately 1;000 FT down the runway and moving at taxi speed; having obviously just aborted a takeoff; and the mower was still crossing his runway. I feel bad about not having LC's back as CIC; and embarrassed that the event occurred at all. I haven't yet listened to the tapes to determine exactly what was going on to account for why I didn't hear LC give that take off clearance; though I know that in that general time frame I was issuing a lot of IFR clearances. It is possible that I was issuing a clearance when LC spoke to the Challenger. Looking back; I remember that the mower asked to proceed some distance on a parallel taxiway and then cross. What I asked LC for was a crossing; and I did not indicate to LC that the crossing was not immediate. I think this probably contributed to the error. I suspect that the LC had assumed that enough time had elapsed by now that surely the mower had finished crossing; also; there is a pole in our Tower; from LC's seated position; blocks the view right down Delta Taxiway (which the mower was on; and I suspect that the mower was simply missed by LC when he did his runway scan. Had I indicated to LC that the crossing was not immediate; or had I waited until the mower was at the hold short lines before coordinating the crossing; perhaps this event would not have occurred.


Synopsis: Local Controller and Ground Controller described an aborted takeoff event when an aircraft observed a mower crossing down field.  Failed coordination between Local and Ground reportedly led to the occurrence.