Narrative:

Approaching stl terminal area. Kansas city gave a late descent clearance to several aircraft including ours. The clearance required a descent from FL350 to FL270 in 15 mi. We then received a similar late clearance to cross qball intersection at 11000 ft. Center was informed that we could not comply and an off course vector was issued. After we could make the crossing restr, we were cleared direct qball and switched to stl approach. The frequency was very busy and our check-in was delayed. 2 mi from qball, a TCASII TA appeared for an aircraft at 11 O'clock position, our altitude. The TA quickly changed to an RA, requiring a 500 ft descent. The aircraft passed off to the left about 1 mi. Approach's response to RA 'didn't see aircraft.' we don't know if the aircraft was being controled. Possible cause: center controller understanding of distance required for a normal descent and/or aircraft position relative to fix. Workload prevented center or approach controller from seeing or calling traffic. Frequency congestion also a factor on approach. Possible training taking place. Corrective actions: timely clrncs to avoid delaying vectors, frequency congestion, and disruption of smooth traffic flow.

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Original NASA ASRS Text

Title: B757 FLC BELIEVE ZKC LATE DSCNT AND T75 FREQ CONGESTION ON COM XFER ARE CONTRIBUTING FACTORS TO A TCASII TA-RA.

Narrative: APCHING STL TERMINAL AREA. KANSAS CITY GAVE A LATE DSCNT CLRNC TO SEVERAL ACFT INCLUDING OURS. THE CLRNC REQUIRED A DSCNT FROM FL350 TO FL270 IN 15 MI. WE THEN RECEIVED A SIMILAR LATE CLRNC TO CROSS QBALL INTXN AT 11000 FT. CTR WAS INFORMED THAT WE COULD NOT COMPLY AND AN OFF COURSE VECTOR WAS ISSUED. AFTER WE COULD MAKE THE XING RESTR, WE WERE CLRED DIRECT QBALL AND SWITCHED TO STL APCH. THE FREQ WAS VERY BUSY AND OUR CHK-IN WAS DELAYED. 2 MI FROM QBALL, A TCASII TA APPEARED FOR AN ACFT AT 11 O'CLOCK POS, OUR ALT. THE TA QUICKLY CHANGED TO AN RA, REQUIRING A 500 FT DSCNT. THE ACFT PASSED OFF TO THE L ABOUT 1 MI. APCH'S RESPONSE TO RA 'DIDN'T SEE ACFT.' WE DON'T KNOW IF THE ACFT WAS BEING CTLED. POSSIBLE CAUSE: CTR CTLR UNDERSTANDING OF DISTANCE REQUIRED FOR A NORMAL DSCNT AND/OR ACFT POS RELATIVE TO FIX. WORKLOAD PREVENTED CTR OR APCH CTLR FROM SEEING OR CALLING TFC. FREQ CONGESTION ALSO A FACTOR ON APCH. POSSIBLE TRAINING TAKING PLACE. CORRECTIVE ACTIONS: TIMELY CLRNCS TO AVOID DELAYING VECTORS, FREQ CONGESTION, AND DISRUPTION OF SMOOTH TFC FLOW.

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.