Apparent operational error causes less than standard separation or near midair collision.

Attributes
ACN	302298
Time
Date	199504
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : msp
State Reference	MN
Altitude	msl bound lower : 9600 msl bound upper : 10000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : msp
Operator	common carrier : air carrier
Make Model Name	B727-200
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	arrival other arrival star : star
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	other : unknown
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : flight engineer pilot : commercial pilot : atp
Experience	flight time last 90 days : 180 flight time total : 12000 flight time type : 5000
ASRS Report	302298
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : atp pilot : instrument
Experience	flight time last 90 days : 210 flight time total : 10000 flight time type : 210
ASRS Report	302297
Events
Anomaly	altitude deviation : undershoot conflict : nmac non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	vertical : 400
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

TCASII commanded a climb resolution at 9600 ft MSL, no visual was obtained on target, but TCASII showed a climbing target 400 ft below my aircraft. Approach control had given us clearance to 9000 ft and had given no advisory of oncoming traffic. Needless to say, the resolution was complied with and I believe TCASII prevented a midair collision. Callback conversation with reporter acn #302671 revealed the following information: the reporting so believes that this incident was not a false alarm as the TRACON approach controller said something like 'thanks for the help' after the intruder aircraft had passed. None of the crewmen saw the intruder.

Original NASA ASRS Text

Title: APPARENT OPERROR CAUSES LTSS OR NMAC.

Narrative: TCASII COMMANDED A CLB RESOLUTION AT 9600 FT MSL, NO VISUAL WAS OBTAINED ON TARGET, BUT TCASII SHOWED A CLBING TARGET 400 FT BELOW MY ACFT. APCH CTL HAD GIVEN US CLRNC TO 9000 FT AND HAD GIVEN NO ADVISORY OF ONCOMING TFC. NEEDLESS TO SAY, THE RESOLUTION WAS COMPLIED WITH AND I BELIEVE TCASII PREVENTED A MIDAIR COLLISION. CALLBACK CONVERSATION WITH RPTR ACN #302671 REVEALED THE FOLLOWING INFO: THE RPTING SO BELIEVES THAT THIS INCIDENT WAS NOT A FALSE ALARM AS THE TRACON APCH CTLR SAID SOMETHING LIKE 'THANKS FOR THE HELP' AFTER THE INTRUDER ACFT HAD PASSED. NONE OF THE CREWMEN SAW THE INTRUDER.

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.