Narrative:

Aircraft X had just landed on runway 7L and was holding between the runways waiting to cross at B9. I was providing OJT instruction at the time with my developmental on the local south position. The developmental then cleared aircraft Y (C172) for departure off runway 7R; full length. Aircraft Y was slow to depart and my developmental was scanning his pattern containing 4 airplanes. My developmental then picked up his runway crossing placard; in my mind; anticipating going to cross aircraft X after aircraft Y had passed him on his departure. The developmental then keyed the mic; again I am thinking he is going to confirm aircraft X is on frequency; instead keyed the mic and said; 'aircraft X; without delay cross runway 7R and contact ground .8.' as soon as he said the word 'cross' I was in the process of keying my mic to stop his taxi but aircraft X was already moving onto the runway and was past the hold bar and first white line of the runway. I knew aircraft Y was airborne about 200 ft in the air approaching B5 and realized that stopping aircraft X was futile and unnecessary as doing so would have stopped him on the runway and if by chance aircraft Y had to abort his take off; aircraft X would be in his path. My developmental saw the situation as I was alerting him as to where aircraft Y was and keyed the mic and said; 'aircraft X hold position; disregard.' after getting off position; we debriefed the incident and talked about ways to visually scan first and then get crossing placard second; so that you are sure that the runway is clear. We discussed numerous different scanning techniques; utilizing the crossing placards in a more effective way and emphasized how important scanning the runway is at all times.

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Original NASA ASRS Text

Title: DVT Controller providing OJT described a loss of separation event when the developmental issued a runway crossing clearance with conflicting traffic on takeoff; the reporter electing not to issue alternate instructions because of aircraft locations.

Narrative: Aircraft X had just landed on Runway 7L and was holding between the runways waiting to cross at B9. I was providing OJT instruction at the time with my developmental on the Local South position. The developmental then cleared aircraft Y (C172) for departure off Runway 7R; full length. Aircraft Y was slow to depart and my developmental was scanning his pattern containing 4 airplanes. My developmental then picked up his runway crossing placard; in my mind; anticipating going to cross aircraft X after aircraft Y had passed him on his departure. The developmental then keyed the mic; again I am thinking he is going to confirm aircraft X is on frequency; instead keyed the mic and said; 'Aircraft X; without delay cross Runway 7R and contact Ground .8.' As soon as he said the word 'cross' I was in the process of keying my mic to stop his taxi but aircraft X was already moving onto the runway and was past the hold bar and first white line of the runway. I knew aircraft Y was airborne about 200 FT in the air approaching B5 and realized that stopping aircraft X was futile and unnecessary as doing so would have stopped him on the runway and if by chance aircraft Y had to abort his take off; aircraft X would be in his path. My developmental saw the situation as I was alerting him as to where aircraft Y was and keyed the mic and said; 'Aircraft X hold position; disregard.' After getting off position; we debriefed the incident and talked about ways to visually scan first and then get crossing placard second; so that you are sure that the runway is clear. We discussed numerous different scanning techniques; utilizing the crossing placards in a more effective way and emphasized how important scanning the runway is at all times.

Data retrieved from NASA's ASRS site as of April 2012 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.