A B737 flight crew receive a TCASII TA while cruising at FL310 under ZTL control.

Attributes
ACN	622204
Time
Date	200212
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ztl.artcc
State Reference	GA
Altitude	msl single value : 31000
Environment
Flight Conditions	Mixed
Weather Elements	Turbulence Thunderstorm Rain Ice
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : ztl.artcc tower : atl.tower
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : ztl.artcc
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 2000 flight time total : 20000 flight time type : 200
ASRS Report	622204
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	conflict : airborne critical non adherence : required legal separation non adherence : published procedure
Independent Detector	aircraft equipment : tcas
Resolutory Action	none taken : anomaly accepted
Miss Distance	horizontal : 12000 vertical : 0
Supplementary
Problem Areas	Weather ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

We were en route in LNAV at FL310, 30 mi north of atl. As center was giving us a frequency change, we got a TA on the TCASII. Both my first officer and I had to turn our map range down to 10 mi because the TA target was so close. I told ZTL to 'stand by, we have a TA on the TCASII.' the target was at 12 O'clock position and 5 mi. Approximately 1 second later, the target was at 12:30 O'clock position and 4 mi. The target passed less than 2 mi off our right at our altitude. Our heading was 210 degrees, the target heading was approximately 340 degrees. I reported to center that the traffic passed less than 2 mi off our right and the other aircraft agreed, less than 2 mi. I then asked center what that was all about, and they said that they were taking care of it. We then received a frequency change. We did not ever get an RA, and we never changed course or altitude. The traffic went by so fast (approximately 900 KTS closure rate) that we didn't have time to make out the aircraft type.

Original NASA ASRS Text

Title: A B737 FLT CREW RECEIVE A TCASII TA WHILE CRUISING AT FL310 UNDER ZTL CTL.

Narrative: WE WERE ENRTE IN LNAV AT FL310, 30 MI N OF ATL. AS CTR WAS GIVING US A FREQ CHANGE, WE GOT A TA ON THE TCASII. BOTH MY FO AND I HAD TO TURN OUR MAP RANGE DOWN TO 10 MI BECAUSE THE TA TARGET WAS SO CLOSE. I TOLD ZTL TO 'STAND BY, WE HAVE A TA ON THE TCASII.' THE TARGET WAS AT 12 O'CLOCK POS AND 5 MI. APPROX 1 SECOND LATER, THE TARGET WAS AT 12:30 O'CLOCK POS AND 4 MI. THE TARGET PASSED LESS THAN 2 MI OFF OUR R AT OUR ALT. OUR HDG WAS 210 DEGS, THE TARGET HDG WAS APPROX 340 DEGS. I RPTED TO CTR THAT THE TFC PASSED LESS THAN 2 MI OFF OUR R AND THE OTHER ACFT AGREED, LESS THAN 2 MI. I THEN ASKED CTR WHAT THAT WAS ALL ABOUT, AND THEY SAID THAT THEY WERE TAKING CARE OF IT. WE THEN RECEIVED A FREQ CHANGE. WE DID NOT EVER GET AN RA, AND WE NEVER CHANGED COURSE OR ALT. THE TFC WENT BY SO FAST (APPROX 900 KTS CLOSURE RATE) THAT WE DIDN'T HAVE TIME TO MAKE OUT THE ACFT TYPE.

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.