B737 FLT CREW OVERSHOT LEVELOFF WHILE SEARCHING FOR TFC. THIS RESULTED IN AN RA FOR BOTH ACFT.

Narrative

WE WERE DSNDING TO FL330 FROM AN ORIGINAL ALT OF FL360 WITH THE AUTOPLT ENGAGED IN CTL WHEEL STEERING AND HDG SELECT. WE WERE IN A R TURN TO AN ASSIGNED HDG OF 270 DEGS. I BELIEVE I WAS DSNDING AT APPROX 300 KTS AND ESTIMATE THAT THE DSCNT RATE WAS ABOUT 3000 FPM. AT ABOUT 300 FT ABOVE FL320; WE RECEIVED A TA. THE CAPT AND I BEGAN SEARCHING FOR TFC. I DID NOT APPLY PWR DURING THE LEVELOFF. I DID NOT MONITOR THE AUTOPLT AS CLOSELY AS I NORMALLY DO DURING A LEVELOFF. I COULD NOT VISUALLY IDENT THE TFC AND WHEN I RETURNED TO MY NORMAL INST SCAN I SAW THAT THE ACFT WAS DSNDING THROUGH FL330. I AM NOT SURE WHAT THE VERT SPD WAS AT THIS TIME BUT IT 'FELT' LIKE WE WERE STILL DSNDING PRETTY RAPIDLY. I GRABBED THE YOKE AND PULLED UP TO ARREST THE DSCNT. ABOUT THIS TIME WE RECEIVED AN RA AND 'CLB' COMMAND. I PULLED MORE AND BEGAN A CLB. THE LOWEST WE EVER GOT WAS FL328. CTR WAS NOT AWARE OF THE DEV UNTIL THE ACFT BELOW US RPTED THE RA. THE CAPT AND I VERIFIED THAT THE MCP ALT WAS INDEED SET AT FL330 AT THE TIME OF THE INCIDENT. I BELIEVE THAT THE RELATIVELY HIGH RATE OF DSCNT; THE TURN; AND THE LACK OF ADDED PWR DURING THE LEVELOFF MADE IT IMPOSSIBLE FOR THE AUTOPLT TO COMPLETE THE LEVELOFF WITHOUT A DEV. IT SEEMED THAT THE AUTOPLT WAS LEVELING THE AIRPLANE; JUST NOT QUITE FAST ENOUGH. I ALLOWED THE TA TO DISTRACT ME FROM MONITORING THE AUTOPLT AT A CRITICAL TIME AND WITHOUT INTERVENTION; A DEV RESULTED. HAD I REALIZED THAT THE TA WAS LIKELY A RESULT OF MY DSCNT RATE VERSUS ACTUAL ALT; I MAY HAVE CONCENTRATED LESS ON IDENTIFYING THE TFC AND MORE ON CHANGING THE DSCNT RATE. THE IMPORTANCE OF VISUALLY LOCATING TA TFC CANNOT BE OVERSTATED. A HIGHER DEGREE OF SITUATIONAL AWARENESS ON MY PART MAY HAVE LED ME TO UNDERSTAND THAT ENSURING OUR AUTOPLT WOULD COMPLETE THE LEVELOFF AT THE ASSIGNED ALT ACTUALLY WOULD HAVE PREVENTED THE RA AND MADE THE LOCATION OF THE TFC A MOOT POINT.