ZHU controller experienced operational error at FL290 during sequencing vectors to iah.

Attributes
ACN	692726
Time
Date	200603
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : sbi.vor
State Reference	TX
Altitude	msl single value : 29000
Environment
Flight Conditions	Mixed
Weather Elements	Turbulence Thunderstorm
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zhu.artcc
Operator	common carrier : air carrier
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zhu.artcc
Operator	common carrier : air carrier
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller time certified in position1 : 20
ASRS Report	692726
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	atc equipment : conflict alert
Resolutory Action	controller : issued new clearance
Consequence	faa : investigated
Miss Distance	horizontal : 20700 vertical : 800
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

WX was impacting houston terminal area. Stros; gland; and lisse arrs were closed. Aircraft from psx were assigned headings from crp hi. In addition to the WX at houston; there was WX south of sbi. The arrival route to houston was direct mhf direct the airport. I was sequencing psx; oac; and normal arrs from the east. Air carrier X was assigned; when able; fly heading 030 degrees; maintain 280 KTS. Air carrier Y (behind air carrier X) declared minimum fuel and was assigned a 030 degree heading. Air carrier X was then assigned a 345 degree heading. I noticed the 2 aircraft converging. I cleared air carrier X to descend and maintain FL270; expedite through FL280. I then cleared air carrier Y to fly heading 100 degrees. After re-establishing separation; I continued to sequence arrs and departures until I was relieved. I clearly did not take action in time; although our data shows that air carrier X did not commence his descent for 20 seconds.

Original NASA ASRS Text

Title: ZHU CTLR EXPERIENCED OPERROR AT FL290 DURING SEQUENCING VECTORS TO IAH.

Narrative: WX WAS IMPACTING HOUSTON TERMINAL AREA. STROS; GLAND; AND LISSE ARRS WERE CLOSED. ACFT FROM PSX WERE ASSIGNED HDGS FROM CRP HI. IN ADDITION TO THE WX AT HOUSTON; THERE WAS WX S OF SBI. THE ARR RTE TO HOUSTON WAS DIRECT MHF DIRECT THE ARPT. I WAS SEQUENCING PSX; OAC; AND NORMAL ARRS FROM THE E. ACR X WAS ASSIGNED; WHEN ABLE; FLY HDG 030 DEGS; MAINTAIN 280 KTS. ACR Y (BEHIND ACR X) DECLARED MINIMUM FUEL AND WAS ASSIGNED A 030 DEG HDG. ACR X WAS THEN ASSIGNED A 345 DEG HDG. I NOTICED THE 2 ACFT CONVERGING. I CLRED ACR X TO DSND AND MAINTAIN FL270; EXPEDITE THROUGH FL280. I THEN CLRED ACR Y TO FLY HDG 100 DEGS. AFTER RE-ESTABLISHING SEPARATION; I CONTINUED TO SEQUENCE ARRS AND DEPS UNTIL I WAS RELIEVED. I CLRLY DID NOT TAKE ACTION IN TIME; ALTHOUGH OUR DATA SHOWS THAT ACR X DID NOT COMMENCE HIS DSCNT FOR 20 SECONDS.

Data retrieved from NASA's ASRS site as of January 2009 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.