Iad controller described a minimal separation event involving two successive air carrier arrivals; t...

Narrative:

Aircraft X and aircraft Y were on approach to runway 19C. Aircraft X landed and due to a high speed taxiway closure rolled long and was instructed to exit the runway at taxiway D; which is a 90 degree turn off. Aircraft Y was short final and I was watching the situation develop. I knew that for aircraft X to be clear of the runway before aircraft Y crossed the landing threshold aircraft X had to keep his speed up and turn off without delay; which he was instructed to do. As aircraft X made his turn off the runway aircraft Y crossed the threshold. As aircraft X cleared; I transmitted to aircraft Y 'aircraft Y traffic clear of the runway; cleared to land runway 19C.' as aircraft X was approximately 8725' down the runway and turning off the runway I judged the situation to be safe and allowed aircraft Y to land. Looking back on the situation I was unsure if the aircraft X aircraft was entirely clear of the runway; although it appeared so; as he did not cross the runway hold bars prior to aircraft Y crossing the threshold. The asde-X was operating normally in full-core alerting and no alarm was generated. Recommendation; I always tell myself; and the developments that I instruct; to put safety above all else. In retrospect; although the aircraft had over a mile of runway separation between them; and the preceding aircraft appeared clear of the active runway; this situation could have easily been avoided by issuing go-around instructions to the arriving aircraft. Although I feel safety was never compromise and I exercised my best judgment at the time; perhaps sending the aircraft around would have been a better choice.aircraft X and aircraft Y were on approach to runway 19C. Aircraft X landed and due to a high speed taxiway closure rolled long and was instructed to exit the runway at taxiway D; which is a 90 degree turn off. Aircraft Y was short final and I was watching the situation develop. I knew that for aircraft X to be clear of the runway before aircraft Y crossed the landing threshold aircraft X had to keep his speed up and turn off without delay; which he was instructed to do. As aircraft X made his turn off the runway aircraft Y crossed the threshold. As aircraft X cleared; I transmitted to aircraft Y 'aircraft Y traffic clear of the runway; cleared to land runway 19C.' as aircraft X was approximately 8725' down the runway and turning off the runway I judged the situation to be safe and allowed aircraft Y to land. Looking back on the situation I was unsure if the aircraft X aircraft was entirely clear of the runway; although it appeared so; as he did not cross the runway hold bars prior to aircraft Y crossing the threshold. The asde-X was operating normally in full-core alerting and no alarm was generated. Recommendation; I always tell myself; and the developments that I instruct; to put safety above all else. In retrospect; although the aircraft had over a mile of runway separation between them; and the preceding aircraft appeared clear of the active runway; this situation could have easily been avoided by issuing go-around instructions to the arriving aircraft. Although I feel safety was never compromise and I exercised my best judgment at the time; perhaps sending the aircraft around would have been a better choice.

Original NASA ASRS Text

Title: IAD controller described a minimal separation event involving two successive air carrier arrivals; the reporter noting a landing clearance was issued without positive assurance the prior arrival had completely cleared the runway.

Narrative: Aircraft X and Aircraft Y were on approach to Runway 19C. Aircraft X landed and due to a high speed taxiway closure rolled long and was instructed to exit the runway at Taxiway D; which is a 90 degree turn off. Aircraft Y was short final and I was watching the situation develop. I knew that for Aircraft X to be clear of the runway before Aircraft Y crossed the landing threshold Aircraft X had to keep his speed up and turn off without delay; which he was instructed to do. As Aircraft X made his turn off the runway Aircraft Y crossed the threshold. As Aircraft X cleared; I transmitted to Aircraft Y 'Aircraft Y traffic clear of the runway; cleared to land Runway 19C.' As Aircraft X was approximately 8725' down the runway and turning off the runway I judged the situation to be safe and allowed Aircraft Y to land. Looking back on the situation I was unsure if the Aircraft X aircraft was entirely clear of the runway; although it appeared so; as he did not cross the runway hold bars prior to Aircraft Y crossing the threshold. The ASDE-X was operating normally in full-core alerting and no alarm was generated. Recommendation; I always tell myself; and the developments that I instruct; to put safety above all else. In retrospect; although the aircraft had over a mile of runway separation between them; and the preceding aircraft appeared clear of the active runway; this situation could have easily been avoided by issuing go-around instructions to the arriving aircraft. Although I feel safety was never compromise and I exercised my best judgment at the time; perhaps sending the aircraft around would have been a better choice.Aircraft X and Aircraft Y were on approach to Runway 19C. Aircraft X landed and due to a high speed taxiway closure rolled long and was instructed to exit the runway at Taxiway D; which is a 90 degree turn off. Aircraft Y was short final and I was watching the situation develop. I knew that for Aircraft X to be clear of the runway before Aircraft Y crossed the landing threshold Aircraft X had to keep his speed up and turn off without delay; which he was instructed to do. As Aircraft X made his turn off the runway Aircraft Y crossed the threshold. As Aircraft X cleared; I transmitted to Aircraft Y 'Aircraft Y traffic clear of the runway; cleared to land Runway 19C.' As Aircraft X was approximately 8725' down the runway and turning off the runway I judged the situation to be safe and allowed Aircraft Y to land. Looking back on the situation I was unsure if the Aircraft X aircraft was entirely clear of the runway; although it appeared so; as he did not cross the runway hold bars prior to Aircraft Y crossing the threshold. The ASDE-X was operating normally in full-core alerting and no alarm was generated. Recommendation; I always tell myself; and the developments that I instruct; to put safety above all else. In retrospect; although the aircraft had over a mile of runway separation between them; and the preceding aircraft appeared clear of the active runway; this situation could have easily been avoided by issuing go-around instructions to the arriving aircraft. Although I feel safety was never compromise and I exercised my best judgment at the time; perhaps sending the aircraft around would have been a better choice.

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.

Attributes
ACN	895261
Time
Date	201006
Local Time Of Day	1201-1800
Place
Locale Reference	IAD.Airport
State Reference	DC
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Landing Taxi
Route In Use	Other Instrument Approach
Flight Plan	IFR
Aircraft 2
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	Landing
Route In Use	Other Instrument Approach
Flight Plan	IFR
Person 1
Function	Local
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Deviation - Procedural Published Material / Policy

Iad controller described a minimal separation event involving two successive air carrier arrivals; the reporter noting a landing clearance was issued without positive assurance the prior arrival had completely cleared the runway.