MD80 crew had TCASII RA in dfw class B airspace.

Attributes
ACN	448976
Time
Date	199909
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : dfw.airport
State Reference	TX
Altitude	msl bound lower : 2500 msl bound upper : 3000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : d10.tracon
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 17c
Route In Use	approach : visual
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : d10.tracon
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 18r
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	448976
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : multi engine
Events
Anomaly	conflict : airborne critical non adherence : required legal separation non adherence : clearance other spatial deviation
Independent Detector	aircraft equipment : tcas
Resolutory Action	flight crew : took evasive action
Supplementary
Problem Areas	ATC Human Performance Airport Airspace Structure Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation
Situations
ATC Facility	procedure or policy : d10.tracon

Narrative:

We were being vectored for a left base to final visual for runway 17C. We had a TA on TCASII, followed shortly after with a 'descend' RA in excess of 1500 FPM. We saw visually an aircraft heading directly for us. He appeared to be on a right base for the same runway. We were on the left base at the same altitude. We responded to the RA with a descent to below 2500 ft. We advised the controller, who told us that the offending aircraft had overshot final. We presume he was to be on runway 18R. While the TCASII system worked, in the interest of safety, I do not believe aircraft should be on opposing bases at the same altitude with conflicting flight paths. Had TCASII been on MEL on both aircraft, only a lucky look ahead as both aircraft were looking for the runway would have averted at minimum a near miss.

Original NASA ASRS Text

Title: MD80 CREW HAD TCASII RA IN DFW CLASS B AIRSPACE.

Narrative: WE WERE BEING VECTORED FOR A L BASE TO FINAL VISUAL FOR RWY 17C. WE HAD A TA ON TCASII, FOLLOWED SHORTLY AFTER WITH A 'DSND' RA IN EXCESS OF 1500 FPM. WE SAW VISUALLY AN ACFT HDG DIRECTLY FOR US. HE APPEARED TO BE ON A R BASE FOR THE SAME RWY. WE WERE ON THE L BASE AT THE SAME ALT. WE RESPONDED TO THE RA WITH A DSCNT TO BELOW 2500 FT. WE ADVISED THE CTLR, WHO TOLD US THAT THE OFFENDING ACFT HAD OVERSHOT FINAL. WE PRESUME HE WAS TO BE ON RWY 18R. WHILE THE TCASII SYS WORKED, IN THE INTEREST OF SAFETY, I DO NOT BELIEVE ACFT SHOULD BE ON OPPOSING BASES AT THE SAME ALT WITH CONFLICTING FLT PATHS. HAD TCASII BEEN ON MEL ON BOTH ACFT, ONLY A LUCKY LOOK AHEAD AS BOTH ACFT WERE LOOKING FOR THE RWY WOULD HAVE AVERTED AT MINIMUM A NEAR MISS.

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.