A319 responds to TCAS RA while flying parallel approach to runway 27L at ord.

Attributes
ACN	815585
Time
Date	200812
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : ord.airport
State Reference	IL
Altitude	msl single value : 1500
Environment
Flight Conditions	IMC
Aircraft 1
Controlling Facilities	tower : ord.tower
Operator	common carrier : air carrier
Make Model Name	A319
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 27l
Flight Phase	descent : approach
Route In Use	approach : instrument precision
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tower : ord.tower
Make Model Name	B737 Undifferentiated or Other Model
Navigation In Use	ils localizer & glide slope : 27r
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 160 flight time total : 13000 flight time type : 500
ASRS Report	815585
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 240 flight time total : 8000 flight time type : 3000
ASRS Report	815317
Events
Anomaly	conflict : airborne critical
Independent Detector	aircraft equipment : tcas
Resolutory Action	flight crew : took evasive action other
Supplementary
Problem Areas	Airspace Structure Environmental Factor
Primary Problem	Ambiguous

Narrative:

We were cleared for the ILS runway 27L at ord and established on the GS and localizer outside of the OM when we received a TCAS TA for traffic to the right of us approximately 1 mile (at about the 2 O'clock position) and at the same altitude. This soon turned into a 'descend' RA. We followed the RA with a steeper descent of about 1500 FPM and held this from approximately 1500 ft AGL down to approximately 1200 ft AGL where we broke out and visually acquired the traffic; a B737; established on the ILS runway 27R. The RA stopped about this point; but we were never given a 'clear of conflict.' the RA was reported to tower and we corrected back to the GS by shallowing out the descent. At about 700 ft on the GS; we received another TA; which quickly became an RA of 'adjust vertical speed' based on the same traffic. Again the traffic was abeam to slightly ahead of us about 1 mile and now again roughly at our altitude in VMC. We disregarded this RA; which only lasted for approximately 10 seconds; and continued on the ILS to an uneventful landing. We never received a 'clear of conflict' after either RA.

Original NASA ASRS Text

Title: A319 responds to TCAS RA while flying parallel approach to Runway 27L at ORD.

Narrative: We were cleared for the ILS Runway 27L at ORD and established on the GS and LOC outside of the OM when we received a TCAS TA for traffic to the right of us approximately 1 mile (at about the 2 O'clock position) and at the same altitude. This soon turned into a 'descend' RA. We followed the RA with a steeper descent of about 1500 FPM and held this from approximately 1500 ft AGL down to approximately 1200 ft AGL where we broke out and visually acquired the traffic; a B737; established on the ILS Runway 27R. The RA stopped about this point; but we were never given a 'clear of conflict.' The RA was reported to Tower and we corrected back to the GS by shallowing out the descent. At about 700 ft on the GS; we received another TA; which quickly became an RA of 'adjust vertical speed' based on the same traffic. Again the traffic was abeam to slightly ahead of us about 1 mile and now again roughly at our altitude in VMC. We disregarded this RA; which only lasted for approximately 10 seconds; and continued on the ILS to an uneventful landing. We never received a 'clear of conflict' after either RA.

Data retrieved from NASA's ASRS site as of May 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.