Narrative:

During a busy arrival bank to runway 35; the 4 miles behind a B757 was lost. The weather was VFR and because of a strong quartering tailwind the compression rate was high. As controller in charge I was helping the approach controller when able to provide visual between arrivals with a high compression rate that would not affect safe landing. In the case of these two aircraft; the pilot had changed to tower frequency early but did not immediately check on. The radar controller attempted to break out the B737 because of the potential loss of 4 miles but received no response. It was about this time I over heard the local controller transmitting with the B737 about visual separation and the B757. The fact was that the controller had them both in sight but the B737 did not yet see the B757. A heading for pull out was issued and coordinated with satellite radar. The separation went as low as 3.6 before the B737 turned to avoid wake.it's hard to determine an exact recommendation since everyone involved tried hard to make this work. The mitigating factors of the non-responsive pilot due to radio change and the quartering tailwind had a lot to do with this ops error. In hindsight an immediate break out by local may have saved this from being an ops error but is not guaranteed. Because of the high quartering tailwind is was common for overtakes to reflect 40-90 knot overtakes until at lower altitudes inside the marker. An unfortunate event where everyone was aware and did their best to have a solution that didn't get the results needed for written requirements.

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Original NASA ASRS Text

Title: Tower Controller-in-Charge reported a wake turbulence separation operational error; B737 following a B757; due to several contributing factors.

Narrative: During a busy arrival bank to RWY 35; the 4 miles behind a B757 was lost. The weather was VFR and because of a strong quartering tailwind the compression rate was high. As CIC I was helping the Approach Controller when able to provide visual between arrivals with a high compression rate that would not affect safe landing. In the case of these two aircraft; the pilot had changed to Tower frequency early but did not immediately check on. The Radar Controller attempted to break out the B737 because of the potential loss of 4 miles but received no response. It was about this time I over heard the Local Controller transmitting with the B737 about visual separation and the B757. The fact was that the Controller had them both in sight but the B737 did not yet see the B757. A heading for pull out was issued and coordinated with satellite radar. The separation went as low as 3.6 before the B737 turned to avoid wake.It's hard to determine an exact recommendation since everyone involved tried hard to make this work. The mitigating factors of the non-responsive pilot due to radio change and the quartering tailwind had a lot to do with this ops error. In hindsight an immediate break out by Local may have saved this from being an ops error but is not guaranteed. Because of the high quartering tailwind is was common for overtakes to reflect 40-90 knot overtakes until at lower altitudes inside the marker. An unfortunate event where everyone was aware and did their best to have a solution that didn't get the results needed for written requirements.

Data retrieved from NASA's ASRS site as of July 2013 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.