TCASII performs as designed to solve a potential conflict for climbing air carrier traffic.

Attributes
ACN	183010
Time
Date	199107
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : zau
State Reference	IL
Altitude	msl bound lower : 16900 msl bound upper : 17600
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Route In Use	enroute airway : zau
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other cruise other
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : commercial pilot : atp pilot : cfi
Experience	flight time last 90 days : 60 flight time total : 14000 flight time type : 6000
ASRS Report	183010
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 600 vertical : 700
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation other

Narrative:

During climb to FL230 center advised traffic at 12 O'clock and 6 mi, and again at 3 mi appears to be circling at 17600'. We acquired traffic visly at 17500' and I slowed our rate of climb. TCAS issued an RA to descend, descend! I descended 600' and informed ATC and then continued climb to FL230 (my perception of evasive action matched RA).

Original NASA ASRS Text

Title: TCASII PERFORMS AS DESIGNED TO SOLVE A POTENTIAL CONFLICT FOR CLBING ACR TRAFFIC.

Narrative: DURING CLB TO FL230 CTR ADVISED TFC AT 12 O'CLOCK AND 6 MI, AND AGAIN AT 3 MI APPEARS TO BE CIRCLING AT 17600'. WE ACQUIRED TFC VISLY AT 17500' AND I SLOWED OUR RATE OF CLB. TCAS ISSUED AN RA TO DSND, DSND! I DSNDED 600' AND INFORMED ATC AND THEN CONTINUED CLB TO FL230 (MY PERCEPTION OF EVASIVE ACTION MATCHED 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.