Air carrier has TCASII RA, responds.

Attributes
ACN	186891
Time
Date	199108
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : oxi
State Reference	IN
Altitude	msl bound lower : 28000 msl bound upper : 28200
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zau
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 5000 flight time type : 150
ASRS Report	186891
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : flight engineer pilot : cfi
Experience	flight time last 90 days : 200 flight time total : 5200 flight time type : 200
ASRS Report	187079
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were approaching O'hare airport at FL280 (cruise) on a clear night and could visually see several other aircraft around us, above and below. At location noted above, we were issued a TA by TCASII on account of a target at 12 O'clock, FL270, going the opposite direction. We returned to our other duties and a few seconds later, TCASII issued an RA and commanded a 2000 FPM climb. We immediately initiated a climb and notified ATC of our action. They told us we were not in conflict and to return to FL280. At that time TCASII commanded a descent and terminated its conflict alert. Our deviation was only 200 ft above FL280. Controller was very upset as he was working '29 aircraft' in his sector, some of which were 1000 ft above and below us. However, directives issued to us both in training and through official channels are quite specific. All RA's must be followed unless the pilot is certain that no conflict exists. At the instant the RA occurred we were not absolutely certain that the previous TA had not started a climb toward us, and therefore we elected to follow the RA. Supplemental information from acn 187079: in my opinion TCASII is a worthless, expensive distraction in the cockpit that we do not need.

Original NASA ASRS Text

Title: ACR HAS TCASII RA, RESPONDS.

Narrative: WE WERE APCHING O'HARE ARPT AT FL280 (CRUISE) ON A CLR NIGHT AND COULD VISUALLY SEE SEVERAL OTHER ACFT AROUND US, ABOVE AND BELOW. AT LOCATION NOTED ABOVE, WE WERE ISSUED A TA BY TCASII ON ACCOUNT OF A TARGET AT 12 O'CLOCK, FL270, GOING THE OPPOSITE DIRECTION. WE RETURNED TO OUR OTHER DUTIES AND A FEW SECONDS LATER, TCASII ISSUED AN RA AND COMMANDED A 2000 FPM CLB. WE IMMEDIATELY INITIATED A CLB AND NOTIFIED ATC OF OUR ACTION. THEY TOLD US WE WERE NOT IN CONFLICT AND TO RETURN TO FL280. AT THAT TIME TCASII COMMANDED A DSCNT AND TERMINATED ITS CONFLICT ALERT. OUR DEV WAS ONLY 200 FT ABOVE FL280. CTLR WAS VERY UPSET AS HE WAS WORKING '29 ACFT' IN HIS SECTOR, SOME OF WHICH WERE 1000 FT ABOVE AND BELOW US. HOWEVER, DIRECTIVES ISSUED TO US BOTH IN TRAINING AND THROUGH OFFICIAL CHANNELS ARE QUITE SPECIFIC. ALL RA'S MUST BE FOLLOWED UNLESS THE PLT IS CERTAIN THAT NO CONFLICT EXISTS. AT THE INSTANT THE RA OCCURRED WE WERE NOT ABSOLUTELY CERTAIN THAT THE PREVIOUS TA HAD NOT STARTED A CLB TOWARD US, AND THEREFORE WE ELECTED TO FOLLOW THE RA. SUPPLEMENTAL INFO FROM ACN 187079: IN MY OPINION TCASII IS A WORTHLESS, EXPENSIVE DISTR IN THE COCKPIT THAT WE DO NOT NEED.

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.