Narrative:

We were climbing out of mem on the mem 275 degree radial at approximately 30 mi from mem when we received a TCASII TA. After selecting a closer range we saw an amber diamond showing traffic at 11-11:30 O'clock, 2 mi and our altitude, 11000 ft. Immediately the captain requested a vector from ATC for traffic avoidance, and copilot prepared to turn aircraft to avoid traffic. We then got a TCASII RA commanding a 1500 FPM descent to get into the 'green' area. The first officer (me) immediately began a 1500 FPM descent to comply with the advisory when we got the message 'increase descent.' I pushed the nose over to comply and get back into the green, but at 7000 FPM descent, there was only red (ie, TCASII was commanding higher descent rate). At this point I spotted the other aircraft at 10 O'clock and 1/2 mi still at our altitude. I continued an aggressive descent and made a slight right turn to avoid the conflicting aircraft. The other aircraft appeared to be a cessna 172 or 150. He passed approximately 1/4 mi to the left and 200 ft above us. I believe the TCASII advisory was wrong. If we had increased our climb rate, I believe we could have avoided the traffic without incident. As it was, it took an aggressive maneuver and aircraft overspd (370-375 KTS) to avoid the other aircraft. Earlier ATC warning and vectoring would also have helped. Other notes: we recovered from descent at approximately 9000 ft MSL. Maximum speed in descent 370-375 KTS. Maximum descent rate 7000-13000 FPM. No 'G' limits exceeded. No passenger injured. ATC notified during and after RA.

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Original NASA ASRS Text

Title: TCASII RA COMMANDS EXCESSIVE DSCNT WHICH APPEARED TO RPTR TO BE ERRONEOUS.

Narrative: WE WERE CLBING OUT OF MEM ON THE MEM 275 DEG RADIAL AT APPROX 30 MI FROM MEM WHEN WE RECEIVED A TCASII TA. AFTER SELECTING A CLOSER RANGE WE SAW AN AMBER DIAMOND SHOWING TFC AT 11-11:30 O'CLOCK, 2 MI AND OUR ALT, 11000 FT. IMMEDIATELY THE CAPT REQUESTED A VECTOR FROM ATC FOR TFC AVOIDANCE, AND COPLT PREPARED TO TURN ACFT TO AVOID TFC. WE THEN GOT A TCASII RA COMMANDING A 1500 FPM DSCNT TO GET INTO THE 'GREEN' AREA. THE FO (ME) IMMEDIATELY BEGAN A 1500 FPM DSCNT TO COMPLY WITH THE ADVISORY WHEN WE GOT THE MESSAGE 'INCREASE DSCNT.' I PUSHED THE NOSE OVER TO COMPLY AND GET BACK INTO THE GREEN, BUT AT 7000 FPM DSCNT, THERE WAS ONLY RED (IE, TCASII WAS COMMANDING HIGHER DSCNT RATE). AT THIS POINT I SPOTTED THE OTHER ACFT AT 10 O'CLOCK AND 1/2 MI STILL AT OUR ALT. I CONTINUED AN AGGRESSIVE DSCNT AND MADE A SLIGHT R TURN TO AVOID THE CONFLICTING ACFT. THE OTHER ACFT APPEARED TO BE A CESSNA 172 OR 150. HE PASSED APPROX 1/4 MI TO THE L AND 200 FT ABOVE US. I BELIEVE THE TCASII ADVISORY WAS WRONG. IF WE HAD INCREASED OUR CLB RATE, I BELIEVE WE COULD HAVE AVOIDED THE TFC WITHOUT INCIDENT. AS IT WAS, IT TOOK AN AGGRESSIVE MANEUVER AND ACFT OVERSPD (370-375 KTS) TO AVOID THE OTHER ACFT. EARLIER ATC WARNING AND VECTORING WOULD ALSO HAVE HELPED. OTHER NOTES: WE RECOVERED FROM DSCNT AT APPROX 9000 FT MSL. MAX SPD IN DSCNT 370-375 KTS. MAX DSCNT RATE 7000-13000 FPM. NO 'G' LIMITS EXCEEDED. NO PAX INJURED. ATC NOTIFIED DURING AND AFTER RA.

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.