Narrative:

Air carrier X 737 was holding 340 degrees, climbing to 17000 ft. Instructed to 'expedite through 12000 ft.' air carrier X B757 departed 8 mi southwest of the B737 heading 345 degrees, climbing to 10000 ft. The B757 was turned to heading 260 degrees 4 mi north of the airport. At approximately 7000 ft the B737 advised that he was responding to an RA and descending. The B737 was filed as a 300 series but failed by far to meet my expectations of an expeditious climb. The 737 was either very heavy or not really a 300. The B757 was climbing at a very high rate, possibly affecting his rate of turn also. At the point of the RA, a B737-300 would normally be above 11000 ft. I failed to recognize this discrepancy. Controllers place a great deal of importance on aircraft type. Many times a climb will be issued to a B737-300 or B757 that would not be given to a B727 or DC9. I've rarely heard an aircraft asked what his rate of climb will be, but through experience, controllers know what to expect. Any time circumstances exist that prevent an aircraft from performing normally the pilot should be prepared to advise, particularly when instructed to 'expedite.' if the pilot had said 'we'll expedite but we're a dash 200 today (as is often heard) this may have been prevented. Equally, if I had been more attentive to actual performance instead of relying on what always worked in the past, no corrective action would have been required.

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Original NASA ASRS Text

Title: ACR X TCASII RA HAD LTSS FROM ACR Y SYS ERROR. EVASIVE ACTION TAKEN.

Narrative: ACR X 737 WAS HOLDING 340 DEGS, CLBING TO 17000 FT. INSTRUCTED TO 'EXPEDITE THROUGH 12000 FT.' ACR X B757 DEPARTED 8 MI SW OF THE B737 HDG 345 DEGS, CLBING TO 10000 FT. THE B757 WAS TURNED TO HDG 260 DEGS 4 MI N OF THE ARPT. AT APPROX 7000 FT THE B737 ADVISED THAT HE WAS RESPONDING TO AN RA AND DSNDING. THE B737 WAS FILED AS A 300 SERIES BUT FAILED BY FAR TO MEET MY EXPECTATIONS OF AN EXPEDITIOUS CLB. THE 737 WAS EITHER VERY HVY OR NOT REALLY A 300. THE B757 WAS CLBING AT A VERY HIGH RATE, POSSIBLY AFFECTING HIS RATE OF TURN ALSO. AT THE POINT OF THE RA, A B737-300 WOULD NORMALLY BE ABOVE 11000 FT. I FAILED TO RECOGNIZE THIS DISCREPANCY. CTLRS PLACE A GREAT DEAL OF IMPORTANCE ON ACFT TYPE. MANY TIMES A CLB WILL BE ISSUED TO A B737-300 OR B757 THAT WOULD NOT BE GIVEN TO A B727 OR DC9. I'VE RARELY HEARD AN ACFT ASKED WHAT HIS RATE OF CLB WILL BE, BUT THROUGH EXPERIENCE, CTLRS KNOW WHAT TO EXPECT. ANY TIME CIRCUMSTANCES EXIST THAT PREVENT AN ACFT FROM PERFORMING NORMALLY THE PLT SHOULD BE PREPARED TO ADVISE, PARTICULARLY WHEN INSTRUCTED TO 'EXPEDITE.' IF THE PLT HAD SAID 'WE'LL EXPEDITE BUT WE'RE A DASH 200 TODAY (AS IS OFTEN HEARD) THIS MAY HAVE BEEN PREVENTED. EQUALLY, IF I HAD BEEN MORE ATTENTIVE TO ACTUAL PERFORMANCE INSTEAD OF RELYING ON WHAT ALWAYS WORKED IN THE PAST, NO CORRECTIVE ACTION WOULD HAVE BEEN REQUIRED.

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.