Narrative:

We crossed dawna at 12000 as assigned on a heading vector. We were soon cleared 'expedite' to 10000. Out of 10800, we were informed that there was traffic at 10500 that we needed to get below. Shortly thereafter, TRACON pointed out additional traffic at 9500, 12 O'clock. We were not visual on any of this traffic, but my impression was that we would be 'stacked.' within seconds after reaching 10000, we got a TCASII command (RA) 'climb!, climb!' at this point we had 2 targets on the HSI: 12 O'clock traffic at very close range (red) and 1130 O'clock traffic (yellow) with some separation. Copilot was flying and he responded to RA with gradual pull up. At about 10150, TCASII stopped annunciating, and reverted to 'monitor vertical speed' as he slowly let it settle back toward 10000. At about 10050 we got another RA. Þclb!' at this point, there were 3 targets: 2 red targets, very close range at 12 O'clock -- they were so close to each other as to be almost touching -- and still the traffic at 10500 was 1130 O'clock, yellow, and not on an apparent collision course. The copilot hesitated, so I pulled it up myself, added power, and he again resumed climb trying to satisfy the TCASII while not climbing any faster or higher than seemed necessary. Shortly, the controller demanded that we descend, informed us that separation had been violated. At about this time, the copilot saw an small aircraft fly under the nose. Observations: our initial pull-up at 10100 to 10150 probably did not prompt the separation alert. For the second RA there were 2 red targets, very close range, at 12 O'clock. I did not have or take the time to analyze their relative altitudes or trends. I knew that approach was controling 1 of these, but what about the other? With the presence of the second target, I pulled up more aggressively. The 10500 traffic was still yellow, still at 1130 O'clock and still not on an apparent collision course. The 2 targets at 12 O'clock, close range, were generating 'pull up' and either or both of these targets may well have been out of our visual range, below the nose. The 1130 O'clock traffic was above us, and though we didn't see it, it would at least be in a position where we could see it. We did not get an altitude alert, so we did not get to 10300. As this situation developed, it became clear to me that approach might have been controling us into trouble. None of this traffic was in sight, but it sounded like he may have been 'stacking' us. It occurred to me that TCASII may well not like this situation. I realize that ATC's separation guidelines allow 500 ft. But they must realize that, if they vector us into a stack with only 500 ft vertical and no lateral separation, we will get a TCASII alert and it will cause exactly this kind of trouble.

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Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION DURING FLC RESPONSE TO TCASII RA. EVASIVE ACTION CLB.

Narrative: WE CROSSED DAWNA AT 12000 AS ASSIGNED ON A HDG VECTOR. WE WERE SOON CLRED 'EXPEDITE' TO 10000. OUT OF 10800, WE WERE INFORMED THAT THERE WAS TFC AT 10500 THAT WE NEEDED TO GET BELOW. SHORTLY THEREAFTER, TRACON POINTED OUT ADDITIONAL TFC AT 9500, 12 O'CLOCK. WE WERE NOT VISUAL ON ANY OF THIS TFC, BUT MY IMPRESSION WAS THAT WE WOULD BE 'STACKED.' WITHIN SECONDS AFTER REACHING 10000, WE GOT A TCASII COMMAND (RA) 'CLB!, CLB!' AT THIS POINT WE HAD 2 TARGETS ON THE HSI: 12 O'CLOCK TFC AT VERY CLOSE RANGE (RED) AND 1130 O'CLOCK TFC (YELLOW) WITH SOME SEPARATION. COPLT WAS FLYING AND HE RESPONDED TO RA WITH GRADUAL PULL UP. AT ABOUT 10150, TCASII STOPPED ANNUNCIATING, AND REVERTED TO 'MONITOR VERT SPD' AS HE SLOWLY LET IT SETTLE BACK TOWARD 10000. AT ABOUT 10050 WE GOT ANOTHER RA. þCLB!' AT THIS POINT, THERE WERE 3 TARGETS: 2 RED TARGETS, VERY CLOSE RANGE AT 12 O'CLOCK -- THEY WERE SO CLOSE TO EACH OTHER AS TO BE ALMOST TOUCHING -- AND STILL THE TFC AT 10500 WAS 1130 O'CLOCK, YELLOW, AND NOT ON AN APPARENT COLLISION COURSE. THE COPLT HESITATED, SO I PULLED IT UP MYSELF, ADDED PWR, AND HE AGAIN RESUMED CLB TRYING TO SATISFY THE TCASII WHILE NOT CLBING ANY FASTER OR HIGHER THAN SEEMED NECESSARY. SHORTLY, THE CTLR DEMANDED THAT WE DSND, INFORMED US THAT SEPARATION HAD BEEN VIOLATED. AT ABOUT THIS TIME, THE COPLT SAW AN SMA FLY UNDER THE NOSE. OBSERVATIONS: OUR INITIAL PULL-UP AT 10100 TO 10150 PROBABLY DID NOT PROMPT THE SEPARATION ALERT. FOR THE SECOND RA THERE WERE 2 RED TARGETS, VERY CLOSE RANGE, AT 12 O'CLOCK. I DID NOT HAVE OR TAKE THE TIME TO ANALYZE THEIR RELATIVE ALTS OR TRENDS. I KNEW THAT APCH WAS CTLING 1 OF THESE, BUT WHAT ABOUT THE OTHER? WITH THE PRESENCE OF THE SECOND TARGET, I PULLED UP MORE AGGRESSIVELY. THE 10500 TFC WAS STILL YELLOW, STILL AT 1130 O'CLOCK AND STILL NOT ON AN APPARENT COLLISION COURSE. THE 2 TARGETS AT 12 O'CLOCK, CLOSE RANGE, WERE GENERATING 'PULL UP' AND EITHER OR BOTH OF THESE TARGETS MAY WELL HAVE BEEN OUT OF OUR VISUAL RANGE, BELOW THE NOSE. THE 1130 O'CLOCK TFC WAS ABOVE US, AND THOUGH WE DIDN'T SEE IT, IT WOULD AT LEAST BE IN A POS WHERE WE COULD SEE IT. WE DID NOT GET AN ALT ALERT, SO WE DID NOT GET TO 10300. AS THIS SIT DEVELOPED, IT BECAME CLR TO ME THAT APCH MIGHT HAVE BEEN CTLING US INTO TROUBLE. NONE OF THIS TFC WAS IN SIGHT, BUT IT SOUNDED LIKE HE MAY HAVE BEEN 'STACKING' US. IT OCCURRED TO ME THAT TCASII MAY WELL NOT LIKE THIS SIT. I REALIZE THAT ATC'S SEPARATION GUIDELINES ALLOW 500 FT. BUT THEY MUST REALIZE THAT, IF THEY VECTOR US INTO A STACK WITH ONLY 500 FT VERT AND NO LATERAL SEPARATION, WE WILL GET A TCASII ALERT AND IT WILL CAUSE EXACTLY THIS KIND OF TROUBLE.

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.