Narrative:

On downwind, traffic was advised at approximately 1 O'clock. At about the same time as a visual on the traffic was acquired with simultaneous TCASII activation with a descend command (about 300 FPM indicated on the ivsi). I gently reduced altitude to 3800 ft and advised approach what we were doing. The TCASII then advised to monitor altitude (vertical rate). Approach gave us 3500 and the TCASII ceased RA's and returned to normal operation. The small aircraft type aircraft passing overhead (estimated 400 ft and behind my aircraft).

Google
 

Original NASA ASRS Text

Title: CAPT OF ACR MLG ACFT DEVIATED FROM ASSIGNED ALT WHEN RESPONDING TO A TCASII RA.

Narrative: ON DOWNWIND, TFC WAS ADVISED AT APPROX 1 O'CLOCK. AT ABOUT THE SAME TIME AS A VISUAL ON THE TFC WAS ACQUIRED WITH SIMULTANEOUS TCASII ACTIVATION WITH A DSND COMMAND (ABOUT 300 FPM INDICATED ON THE IVSI). I GENTLY REDUCED ALT TO 3800 FT AND ADVISED APCH WHAT WE WERE DOING. THE TCASII THEN ADVISED TO MONITOR ALT (VERT RATE). APCH GAVE US 3500 AND THE TCASII CEASED RA'S AND RETURNED TO NORMAL OP. THE SMA TYPE ACFT PASSING OVERHEAD (ESTIMATED 400 FT AND BEHIND MY ACFT).

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.