An anc controller described a loss of separation event occuring when a take off clearance was issued...

Narrative:

Air carrier X landed runway 14 and was at taxi speed. Since there was no reason to withhold departure clearance; I cleared air carrier Y for take-off; checking the position and status of another aircraft flying a grid pattern overhead the field at one thousand eight hundred. Another air carrier checked on frequency. I then instructed air carrier X to exit the runway. Approximately nine seconds elapsed from the time air carrier Y completed his read back to the time I instructed air carrier X to exit. Traffic was somewhat complex due to an aircraft's mapping mission. [They were] flying lines with very wide teardrop turns at relatively low altitude for several hours. We did not have staffing available for a local assist. I have reviewed the 7110.65 and been instructed by my operations manager that I cannot anticipate the aircraft will be able to exit in a timely fashion even though it appears under control. Unless we allow anticipated separation to be used for exiting aircraft; all I can do is ensure the aircraft has acknowledged runway exiting instructions prior to clearing the departure for take-off. We can educate the controller(s) who actually saw the event developing to speak up in a timely fashion.

Original NASA ASRS Text

Title: An ANC controller described a loss of separation event occuring when a take off clearance was issued to Runway 25R traffic with Runway 14 landing traffic still on the runway. Photo mission distractions were listed as causal factors.

Narrative: Air Carrier X landed Runway 14 and was at taxi speed. Since there was no reason to withhold departure clearance; I cleared Air Carrier Y for Take-Off; checking the position and status of another aircraft flying a grid pattern overhead the field at one thousand eight hundred. Another Air Carrier checked on frequency. I then instructed Air Carrier X to exit the runway. Approximately nine seconds elapsed from the time Air Carrier Y completed his read back to the time I instructed Air Carrier X to exit. Traffic was somewhat complex due to an aircraft's mapping mission. [They were] flying lines with very wide teardrop turns at relatively low altitude for several hours. We did not have staffing available for a Local Assist. I have reviewed the 7110.65 and been instructed by my Operations Manager that I cannot anticipate the aircraft will be able to exit in a timely fashion even though it appears under control. Unless we allow anticipated separation to be used for exiting aircraft; all I can do is ensure the aircraft has acknowledged runway exiting instructions prior to clearing the departure for Take-Off. We can educate the controller(s) who actually saw the event developing to speak up in a timely fashion.

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	893381
Time
Date	201006
Local Time Of Day	1801-2400
Place
Locale Reference	ANC.Tower
State Reference	AK
Aircraft 1
Make Model Name	B747 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Landing
Flight Plan	IFR
Aircraft 2
Make Model Name	Saab 340 Undifferentiated
Operating Under FAR Part	Part 121
Flight Phase	Takeoff
Flight Plan	IFR
Person 1
Function	Local
Person 2
Function	Supervisor / CIC
Events
Anomaly	ATC Issue All Types Conflict Ground Conflict Less Severe

An anc controller described a loss of separation event occuring when a take off clearance was issued to runway 25R traffic with runway 14 landing traffic still on the runway. Photo mission distractions were listed as causal factors.