ZHU ARTCC controller instructed a B757 crew at FL350 to turn immediately then descend to FL330. No explanation was given by ATC and apparently the crew didn't ask any questions. The captain called the center the next day for information and may have been told that they were turned for traffic 12 mi away and 2000 ft vertical.

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Attributes
ACN	426740
Time
Date	199901
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : lev
State Reference	LA
Altitude	msl bound lower : 33000 msl bound upper : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Navigation In Use	Other
Flight Phase	cruise other descent other
Flight Plan	IFR
Aircraft 2
Make Model Name	Commercial Fixed Wing
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 210 flight time total : 18000 flight time type : 7000
ASRS Report	426740
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial
Events
Anomaly	conflict : airborne less severe other anomaly other
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 72000 vertical : 2000
Supplementary
Air Traffic Incident	other

Narrative:

While cruising at FL350, the center controller stated 'turn immediately to heading 170 degrees.' he had an urgent tone in his voice. As we completed the turn, he commanded 'descend immediately to FL330.' after leveling off at FL330, we determined that a near miss had not occurred. A subsequent check with flight attendants revealed that no incident (spilled beverage/passenger falling) had occurred. The seat belt sign had been on due to light turbulence in the area. No TCASII sounded. In a phone call to center the next day, I learned that a conflict went unnoticed until alerts went off at the controller position.

Original NASA ASRS Text

Title: ZHU ARTCC CTLR INSTRUCTED A B757 CREW AT FL350 TO TURN IMMEDIATELY THEN DSND TO FL330. NO EXPLANATION WAS GIVEN BY ATC AND APPARENTLY THE CREW DIDN'T ASK ANY QUESTIONS. THE CAPT CALLED THE CTR THE NEXT DAY FOR INFO AND MAY HAVE BEEN TOLD THAT THEY WERE TURNED FOR TFC 12 MI AWAY AND 2000 FT VERT.

Narrative: WHILE CRUISING AT FL350, THE CTR CTLR STATED 'TURN IMMEDIATELY TO HDG 170 DEGS.' HE HAD AN URGENT TONE IN HIS VOICE. AS WE COMPLETED THE TURN, HE COMMANDED 'DSND IMMEDIATELY TO FL330.' AFTER LEVELING OFF AT FL330, WE DETERMINED THAT A NEAR MISS HAD NOT OCCURRED. A SUBSEQUENT CHK WITH FLT ATTENDANTS REVEALED THAT NO INCIDENT (SPILLED BEVERAGE/PAX FALLING) HAD OCCURRED. THE SEAT BELT SIGN HAD BEEN ON DUE TO LIGHT TURB IN THE AREA. NO TCASII SOUNDED. IN A PHONE CALL TO CTR THE NEXT DAY, I LEARNED THAT A CONFLICT WENT UNNOTICED UNTIL ALERTS WENT OFF AT THE CTLR POS.

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.