A320, cruising at FL350, experienced TCASII RA under ZAU control.

Attributes
ACN	585931
Time
Date	200306
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : mzv.vortac
State Reference	IL
Altitude	msl bound lower : 35000 msl bound upper : 36700
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau.artcc tracon : bwi.tracon
Operator	common carrier : air carrier
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zau.artcc
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : commercial pilot : atp pilot : multi engine
Experience	flight time last 90 days : 240 flight time total : 12500 flight time type : 2700
ASRS Report	585931
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : multi engine pilot : atp pilot : commercial
Experience	flight time last 90 days : 170 flight time total : 11453 flight time type : 1537
ASRS Report	586500
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : nmac non adherence : required legal separation
Independent Detector	aircraft equipment : tcas other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance flight crew : took evasive action flight crew : returned to assigned altitude
Consequence	faa : investigated
Miss Distance	horizontal : 0 vertical : 400
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Cruising at FL350, approximately 60 NM east of mvz, we had a TCASII TA. We reduced the range on the nd and observed a TCASII target about 10 NM, 900 ft below us and climbing. Target was at our 10 O'clock position and heading towards us on a collision course. Almost immediately, we received a TCASII RA directing us to 'climb.' power was advanced to toga, autoplt disconnected and we pitched up until we had a vertical speed in the 'green' zone. Chicago ARTCC was advised that we were responding to a TCASII RA warning. We received the 'clear of conflict' at approximately FL365 and leveled the aircraft at FL367. Once we were sure we were clear of the traffic, we received clearance back to FL350. Chicago ARTCC made no effort to inform us of the traffic until we had begun the RA evasive maneuver. At that time the controller directed us to turn left 30 degrees. We complied with the turn but continued to climb as directed by the TCASII. Information from the chicago ARTCC controller was not forthcoming as to who and why this conflict occurred. Both pilots estimated we passed directly over the other aircraft with a vertical clearance of approximately 400 ft. It was our considered opinion that this was a controller error which could have been catastrophic without the TCASII system.

Original NASA ASRS Text

Title: A320, CRUISING AT FL350, EXPERIENCED TCASII RA UNDER ZAU CTL.

Narrative: CRUISING AT FL350, APPROX 60 NM E OF MVZ, WE HAD A TCASII TA. WE REDUCED THE RANGE ON THE ND AND OBSERVED A TCASII TARGET ABOUT 10 NM, 900 FT BELOW US AND CLBING. TARGET WAS AT OUR 10 O'CLOCK POS AND HDG TOWARDS US ON A COLLISION COURSE. ALMOST IMMEDIATELY, WE RECEIVED A TCASII RA DIRECTING US TO 'CLB.' PWR WAS ADVANCED TO TOGA, AUTOPLT DISCONNECTED AND WE PITCHED UP UNTIL WE HAD A VERTICAL SPD IN THE 'GREEN' ZONE. CHICAGO ARTCC WAS ADVISED THAT WE WERE RESPONDING TO A TCASII RA WARNING. WE RECEIVED THE 'CLR OF CONFLICT' AT APPROXIMATELY FL365 AND LEVELED THE ACFT AT FL367. ONCE WE WERE SURE WE WERE CLR OF THE TFC, WE RECEIVED CLRNC BACK TO FL350. CHICAGO ARTCC MADE NO EFFORT TO INFORM US OF THE TFC UNTIL WE HAD BEGUN THE RA EVASIVE MANEUVER. AT THAT TIME THE CTLR DIRECTED US TO TURN L 30 DEGS. WE COMPLIED WITH THE TURN BUT CONTINUED TO CLB AS DIRECTED BY THE TCASII. INFO FROM THE CHICAGO ARTCC CTLR WAS NOT FORTHCOMING AS TO WHO AND WHY THIS CONFLICT OCCURRED. BOTH PLTS ESTIMATED WE PASSED DIRECTLY OVER THE OTHER ACFT WITH A VERTICAL CLRNC OF APPROX 400 FT. IT WAS OUR CONSIDERED OPINION THAT THIS WAS A CTLR ERROR WHICH COULD HAVE BEEN CATASTROPHIC WITHOUT THE TCASII SYS.

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.