Narrative:

I was working the burne radar position. I issued a crossing restriction to medium large transport X to cross 10 DME south of tys at FL320. The pilot acknowledged the clearance. Sep was lost between medium large transport X and medium large transport Y when medium large transport X was 5 NM south of tys (not corrected for slant range). Mathematical calculations show that at the time sep was lost the slant range corrected distance between small aircraft X and the tys VORTAC was approximately 7.33 NM and at an altitude of FL326. Therefore, it appears to be a mathematical impossibility that small aircraft X complied with his clearance. Due to the fact that small aircraft X never stated he would have a problem making his restriction after he acknowledged his clearance no alternative instructions. I assumed small aircraft X was going to make his restriction and was basing sep on that assumption. Callback conversation with reporter revealed the following: reporter stated the closest point was 1700' and 1.7 north. Traffic was light and he was watching an overtake situation with another aircraft. He issued traffic to small aircraft X and the pilot wasn't too concerned of not making his altitude crossing restriction. C/a alarmed. Management filed a pilot deviation and an operational error.

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Original NASA ASRS Text

Title: STANDARD SEPARATION WAS LOST WHEN PLT FAILED TO COMPLY WITH CROSSING RESTRICTION.

Narrative: I WAS WORKING THE BURNE RADAR POS. I ISSUED A XING RESTRICTION TO MLG X TO CROSS 10 DME S OF TYS AT FL320. THE PLT ACKNOWLEDGED THE CLRNC. SEP WAS LOST BTWN MLG X AND MLG Y WHEN MLG X WAS 5 NM S OF TYS (NOT CORRECTED FOR SLANT RANGE). MATHEMATICAL CALCULATIONS SHOW THAT AT THE TIME SEP WAS LOST THE SLANT RANGE CORRECTED DISTANCE BTWN SMA X AND THE TYS VORTAC WAS APPROX 7.33 NM AND AT AN ALT OF FL326. THEREFORE, IT APPEARS TO BE A MATHEMATICAL IMPOSSIBILITY THAT SMA X COMPLIED WITH HIS CLRNC. DUE TO THE FACT THAT SMA X NEVER STATED HE WOULD HAVE A PROB MAKING HIS RESTRICTION AFTER HE ACKNOWLEDGED HIS CLRNC NO ALTERNATIVE INSTRUCTIONS. I ASSUMED SMA X WAS GOING TO MAKE HIS RESTRICTION AND WAS BASING SEP ON THAT ASSUMPTION. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR STATED THE CLOSEST POINT WAS 1700' AND 1.7 N. TFC WAS LIGHT AND HE WAS WATCHING AN OVERTAKE SITUATION WITH ANOTHER ACFT. HE ISSUED TFC TO SMA X AND THE PLT WASN'T TOO CONCERNED OF NOT MAKING HIS ALT XING RESTRICTION. C/A ALARMED. MGMNT FILED A PLT DEVIATION AND AN OPERROR.

Data retrieved from NASA's ASRS site as of July 2007 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.