Air carrier X TCASII TA RA had less than standard separation from air carrier Y assigned same altitude. Evasive action descent. System error.

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Attributes
ACN	291764
Time
Date	199412
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : aba
State Reference	FO
Altitude	msl bound lower : 33000 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : tncf tower : msp
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	DC-10 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	291764
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
ASRS Report	291763
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance non adherence : published procedure non adherence : required legal separation
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 3000 vertical : 500
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

In cruise at FL330 approaching aruba we noticed on TCASII a target at 1 O'clock, constant bearing, closing range. We received a TA and then an RA to descend. As I commenced the descent the TCASII showed the traffic beginning to climb. We obtained visual contact with the dc-10 when it was at 12 O'clock and 1/2 mi or less. We advised curacao control of our action and were told to maintain FL330. We told curacao about the traffic again and they called the other aircraft to confirm they were climbing to FL370. We were unable to understand the call sign and repeated requests to obtain the assigned flight level or aircraft identify from curacao were met with instructions for us to climb to FL370 which we repeatedly advised we were unable to do. Once that was understood, our requests were met with silence. The target aircraft had been level at FL330 until we received our RA.

Original NASA ASRS Text

Title: ACR X TCASII TA RA HAD LTSS FROM ACR Y ASSIGNED SAME ALT. EVASIVE ACTION DSCNT. SYS ERROR.

Narrative: IN CRUISE AT FL330 APCHING ARUBA WE NOTICED ON TCASII A TARGET AT 1 O'CLOCK, CONSTANT BEARING, CLOSING RANGE. WE RECEIVED A TA AND THEN AN RA TO DSND. AS I COMMENCED THE DSCNT THE TCASII SHOWED THE TFC BEGINNING TO CLB. WE OBTAINED VISUAL CONTACT WITH THE DC-10 WHEN IT WAS AT 12 O'CLOCK AND 1/2 MI OR LESS. WE ADVISED CURACAO CTL OF OUR ACTION AND WERE TOLD TO MAINTAIN FL330. WE TOLD CURACAO ABOUT THE TFC AGAIN AND THEY CALLED THE OTHER ACFT TO CONFIRM THEY WERE CLBING TO FL370. WE WERE UNABLE TO UNDERSTAND THE CALL SIGN AND REPEATED REQUESTS TO OBTAIN THE ASSIGNED FLT LEVEL OR ACFT IDENT FROM CURACAO WERE MET WITH INSTRUCTIONS FOR US TO CLB TO FL370 WHICH WE REPEATEDLY ADVISED WE WERE UNABLE TO DO. ONCE THAT WAS UNDERSTOOD, OUR REQUESTS WERE MET WITH SILENCE. THE TARGET ACFT HAD BEEN LEVEL AT FL330 UNTIL WE RECEIVED OUR 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.