Narrative:

Aircraft X was on the PLAIN4 departure from bjc (bjc.PLAIN4.gld./...) at 9;000; requesting climb to 10;000. Aircraft Y was on the PLAIN4 departure from den (den.PLAIN4.gld...) at 10;000. Routes on the two aircraft diverged after gld. Aircraft Y was filed 77 KTS faster than aircraft X and was behind aircraft X. The area were the two aircraft were in when the clearance was given is known to be non radar at 9;000 and marginal radar coverage at 10;000. Prior to the clearance; my estimation is that the two aircraft were 1-2 miles lateral based on their positions just prior to losing aircraft X on radar. The controller asked aircraft Y if he had aircraft X in sight. Aircraft Y replied in the affirmative. Aircraft Y was then instructed to maintain visual separation from aircraft X. Aircraft X was issued climb to 10;000. Clearance was issued when both aircraft were approximately 27 to 29 nautical miles from gld on the PLAIN4 departure. When the clearance was issued; aircraft X was non radar; and then aircraft Y went non radar. When radar contact was reestablished; aircraft X was approximately 7 miles in front of aircraft Y and standard separation existed. In applying paragraph 7-2-1 of the 7110.65; the controller explained that there is no time limit or distance limit specified. Thus; because the routes diverge after gck; the application of the rule was correct; according to him; because aircraft Y was instructed to maintain visual separation. I have never heard of an interpretation of visual separation that would permit it to be applied as in this circumstance and in this manner. Because of the clearance from the controller; aircraft Y had no choice but to reduce speed in order to keep aircraft X in sight. Recommendation; a clarification in the 7110.65 should be made.

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Original NASA ASRS Text

Title: ZDV Controller chronicled a debate on the use of visual separation; 7110.65. 7-2-1; and application of same; with regard to a crossover situation as experienced in this case.

Narrative: Aircraft X was on the PLAIN4 departure from BJC (BJC.PLAIN4.GLD./...) at 9;000; requesting climb to 10;000. Aircraft Y was on the PLAIN4 departure from DEN (DEN.PLAIN4.GLD...) at 10;000. Routes on the two aircraft diverged after GLD. Aircraft Y was filed 77 KTS faster than Aircraft X and was behind Aircraft X. The area were the two aircraft were in when the clearance was given is known to be non radar at 9;000 and marginal RADAR coverage at 10;000. Prior to the clearance; my estimation is that the two aircraft were 1-2 miles lateral based on their positions just prior to losing Aircraft X on RADAR. The Controller asked Aircraft Y if he had Aircraft X in sight. Aircraft Y replied in the affirmative. Aircraft Y was then instructed to maintain visual separation from Aircraft X. Aircraft X was issued climb to 10;000. Clearance was issued when both aircraft were approximately 27 to 29 nautical miles from GLD on the PLAIN4 departure. When the clearance was issued; Aircraft X was non radar; and then Aircraft Y went non radar. When RADAR contact was reestablished; Aircraft X was approximately 7 miles in front of Aircraft Y and standard separation existed. In applying paragraph 7-2-1 of the 7110.65; the Controller explained that there is no time limit or distance limit specified. Thus; because the routes diverge after GCK; the application of the rule was correct; according to him; because Aircraft Y was instructed to maintain visual separation. I have never heard of an interpretation of visual separation that would permit it to be applied as in this circumstance and in this manner. Because of the clearance from the Controller; Aircraft Y had no choice but to reduce speed in order to keep Aircraft X in sight. Recommendation; A clarification in the 7110.65 should be made.

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.