Medium large transport TCASII RA at mdw.

Attributes
ACN	427887
Time
Date	199902
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : mdw.airport
State Reference	IL
Altitude	agl single value : 1500
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tower : mdw.tower
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 31c
Flight Phase	descent : approach descent other landing other
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tower : mdw.tower
Make Model Name	Helicopter
Flight Phase	descent : approach
Route In Use	approach : visual approach : circling approach other
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 240 flight time total : 20000
ASRS Report	427887
Person 2
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine
Events
Anomaly	conflict : nmac
Independent Detector	aircraft equipment : tcas other flight crewa other flight crewb
Resolutory Action	flight crew : exited adverse environment flight crew : took precautionary avoidance action
Miss Distance	vertical : 200
Supplementary
Problem Areas	FAA Environmental Factor Airspace Structure Airport
Primary Problem	FAA
Air Traffic Incident	other

Narrative:

With the winds out of the southwest, I was cleared for the ILS runway 31C circle to land runway 22L. On the downwind, mdw tower pointed out our traffic on short final and cleared my aircraft to land on runway 22L. As we descended on the base leg for our landing, our TCASII issued the aural TA 'traffic, traffic' followed immediately by the TCASII RA 'monitor vertical speed.' at that time a data tag was presented on the TCASII showing an aircraft 200 ft directly below my aircraft. The descent was immediately stopped and the traffic passed under my aircraft. I told mdw tower that we had a TCASII advisory on traffic that was now just behind my aircraft. Mdw tower stated that the traffic was a helicopter. I replied that I would sure have appreciated knowing about the traffic earlier. Mdw tower responded that the 'traffic had just appeared on their radar.' a normal landing was accomplished on runway 22L.

Original NASA ASRS Text

Title: MLG TCASII RA AT MDW.

Narrative: WITH THE WINDS OUT OF THE SW, I WAS CLRED FOR THE ILS RWY 31C CIRCLE TO LAND RWY 22L. ON THE DOWNWIND, MDW TWR POINTED OUT OUR TFC ON SHORT FINAL AND CLRED MY ACFT TO LAND ON RWY 22L. AS WE DSNDED ON THE BASE LEG FOR OUR LNDG, OUR TCASII ISSUED THE AURAL TA 'TFC, TFC' FOLLOWED IMMEDIATELY BY THE TCASII RA 'MONITOR VERT SPD.' AT THAT TIME A DATA TAG WAS PRESENTED ON THE TCASII SHOWING AN ACFT 200 FT DIRECTLY BELOW MY ACFT. THE DSCNT WAS IMMEDIATELY STOPPED AND THE TFC PASSED UNDER MY ACFT. I TOLD MDW TWR THAT WE HAD A TCASII ADVISORY ON TFC THAT WAS NOW JUST BEHIND MY ACFT. MDW TWR STATED THAT THE TFC WAS A HELI. I REPLIED THAT I WOULD SURE HAVE APPRECIATED KNOWING ABOUT THE TFC EARLIER. MDW TWR RESPONDED THAT THE 'TFC HAD JUST APPEARED ON THEIR RADAR.' A NORMAL LNDG WAS ACCOMPLISHED ON RWY 22L.

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.