Narrative:

An A330 waiting to depart runway xxl. I was working local control east and owned runway xxl and a crossing runway for aircraft arriving. I coordinated with local control west to go in a hole between an arrival to a crossing runway and an arrival to runway xxl. I told the arrival on a crossing runway to plan on rolling through runway xxl without delay and exit at kilo. I put an A330 in position on runway xxl with a B747 on a 5 mile final going 180 KTS. I prepped an A330 to be ready for an immediate departure and went back to the B747 to start slowing a little bit and then told him to maintain his slowest speed which he came back and said his approach speed was 140 KTS. I was expecting him to actually slow down to his approach speed a lot sooner than he did. He was still at 160 KTS inside a three mile final with the arrival on a crossing runway still rolling out to clear the runway xxl intersection. I then went to the A330 and told him to start bringing up his power and plan on rolling without delay and then cleared him for takeoff on runway xxl when the arrival on a crossing runway was clear of his intersection. The A330 started his roll right away with the B747 inside a 2 mile final. To the naked eye the A330 was 6;000 ft and airborne. I cleared the B747 to land on runway xxl. I feel that the B747 did not respond right away when given control instructions to maintain his slowest approach speed. I do feel that if he would have slowed to his approach speed in a timelier manner; this would never have been an issue. However; I also understand that; since the traffic volume was so light that I did not need to go in that hole and could have waited.

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Original NASA ASRS Text

Title: Tower Controller reported marginal runway separation when an arrival did not slow as quickly as expected to allow room for the preceding departure. Traffic on a crossing runway complicated the scenario.

Narrative: An A330 waiting to depart Runway XXL. I was working Local Control East and owned Runway XXL and a crossing runway for aircraft arriving. I coordinated with Local Control West to go in a hole between an arrival to a crossing runway and an arrival to Runway XXL. I told the arrival on a crossing runway to plan on rolling through Runway XXL without delay and exit at Kilo. I put an A330 in position on Runway XXL with a B747 on a 5 mile final going 180 KTS. I prepped an A330 to be ready for an immediate departure and went back to the B747 to start slowing a little bit and then told him to maintain his slowest speed which he came back and said his approach speed was 140 KTS. I was expecting him to actually slow down to his approach speed a lot sooner than he did. He was still at 160 KTS inside a three mile final with the arrival on a crossing runway still rolling out to clear the Runway XXL intersection. I then went to the A330 and told him to start bringing up his power and plan on rolling without delay and then cleared him for takeoff on Runway XXL when the arrival on a crossing runway was clear of his intersection. The A330 started his roll right away with the B747 inside a 2 mile final. To the naked eye the A330 was 6;000 FT and airborne. I cleared the B747 to land on Runway XXL. I feel that the B747 did not respond right away when given control instructions to maintain his slowest approach speed. I do feel that if he would have slowed to his approach speed in a timelier manner; this would never have been an issue. However; I also understand that; since the traffic volume was so light that I did not need to go in that hole and could have waited.

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.