<< >> NASA ASRS Report 439994, June 1999

Less than legal separation between aircraft at FL310 results in reporter's aircraft receiving RA from TCASII.

Attributes
ACN	439994
Time
Date	199906
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : bna.vortac
State Reference	TN
Altitude	msl bound lower : 29000 msl bound upper : 31000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zme.artcc
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	cruise : enroute altitude change
Route In Use	enroute airway : j45.airway
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zme.artcc
Make Model Name	Commercial Fixed Wing
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	439994
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : multi engine pilot : commercial
ASRS Report	439995
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance flight crew : took precautionary avoidance action
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I was flying. Level FL310. Center gave us 10 degrees left for traffic. Complied. Center told us to descend to FL290. Started descent. About 5 seconds later center said to disregard the descent and maintain FL310. At this time our altitude was FL307. Acknowledged returning to FL310. Received TCASII TA. Center then told us to descend to FL290. Complied. Received TCASII RA. Complied with RA and advised center of RA. The RA commanded a descent which just happened to correspond with what we were doing anyway so no special maneuvering was required. We had a visual on the conflict throughout the whole event.

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Original NASA ASRS Text

Title: LESS THAN LEGAL SEPARATION BTWN ACFT AT FL310 RESULTS IN RPTR'S ACFT RECEIVING RA FROM TCASII.

Narrative: I WAS FLYING. LEVEL FL310. CTR GAVE US 10 DEGS L FOR TFC. COMPLIED. CTR TOLD US TO DSND TO FL290. STARTED DSCNT. ABOUT 5 SECONDS LATER CTR SAID TO DISREGARD THE DSCNT AND MAINTAIN FL310. AT THIS TIME OUR ALT WAS FL307. ACKNOWLEDGED RETURNING TO FL310. RECEIVED TCASII TA. CTR THEN TOLD US TO DSND TO FL290. COMPLIED. RECEIVED TCASII RA. COMPLIED WITH RA AND ADVISED CTR OF RA. THE RA COMMANDED A DSCNT WHICH JUST HAPPENED TO CORRESPOND WITH WHAT WE WERE DOING ANYWAY SO NO SPECIAL MANEUVERING WAS REQUIRED. WE HAD A VISUAL ON THE CONFLICT THROUGHOUT THE WHOLE EVENT.

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.