Air carrier X TCASII RA with VFR small aircraft. Evasive action taken.

Attributes
ACN	248384
Time
Date	199308
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : stl
State Reference	MO
Altitude	msl bound lower : 10500 msl bound upper : 11500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 4 Turbojet Eng
Navigation In Use	Other
Flight Phase	descent other
Route In Use	enroute : direct enroute airway : zkc
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	VFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller military : 5 controller radar : 7
ASRS Report	248384
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : developmental
Events
Anomaly	conflict : airborne less severe
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	controller : issued new clearance flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 1500 vertical : 300
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	other

Narrative:

Air carrier X descending into stl to 11000 ft. VFR traffic angling across the approach course. Traffic was issued to air carrier X when targets were 15 mi apart. Air carrier X was through 12400 ft descending to 11000 ft. Air carrier X asked for a vector and was given permission to deviate north, a right turn. After a short discussion with the developmental we issued a turn to a heading of 230 degrees, a left turn to air carrier X. TCASII RA descended him to 10500 ft. Pilot later reported on the phone the aircraft were 300 ft and 1/4 of a mi apart. Once my trainee allowed the pilot to deviate north he began a 30 degree right turn. I should have issued either an additional turn to the north or suggested a 230 degree heading to the pilot giving him the option of turning to the south based on what he saw displayed on his TCASII scope. The VFR target was indicating 11500 ft.

Original NASA ASRS Text

Title: ACR X TCASII RA WITH VFR SMA. EVASIVE ACTION TAKEN.

Narrative: ACR X DSNDING INTO STL TO 11000 FT. VFR TFC ANGLING ACROSS THE APCH COURSE. TFC WAS ISSUED TO ACR X WHEN TARGETS WERE 15 MI APART. ACR X WAS THROUGH 12400 FT DSNDING TO 11000 FT. ACR X ASKED FOR A VECTOR AND WAS GIVEN PERMISSION TO DEVIATE N, A R TURN. AFTER A SHORT DISCUSSION WITH THE DEVELOPMENTAL WE ISSUED A TURN TO A HDG OF 230 DEGS, A L TURN TO ACR X. TCASII RA DSNDED HIM TO 10500 FT. PLT LATER RPTED ON THE PHONE THE ACFT WERE 300 FT AND 1/4 OF A MI APART. ONCE MY TRAINEE ALLOWED THE PLT TO DEVIATE N HE BEGAN A 30 DEG R TURN. I SHOULD HAVE ISSUED EITHER AN ADDITIONAL TURN TO THE N OR SUGGESTED A 230 DEG HDG TO THE PLT GIVING HIM THE OPTION OF TURNING TO THE S BASED ON WHAT HE SAW DISPLAYED ON HIS TCASII SCOPE. THE VFR TARGET WAS INDICATING 11500 FT.

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.