TCASII RA results in an altitude excursion for an air carrier aircraft.

Attributes
ACN	178959
Time
Date	199105
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : ard airport : lga
State Reference	PA
Altitude	msl bound lower : 11000 msl bound upper : 12000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent : approach descent other
Route In Use	arrival other arrival star : star
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 18000
ASRS Report	178959
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	vertical : 300
Supplementary
Primary Problem	Ambiguous
Air Traffic Incident	other

Narrative:

Level at 11000' on nanci 4 arrival to lga, we got a TCAS TA at 12 O'clock, then ATC (ZDC) called traffic Y 11-12 O'clock as we got a climb instruction (RA) from our TCAS system. We pulled up and climbed to 12000' and advised ATC. TCAS showed aircraft Y 300' below. We did not see it. A more timely call from ATC or a heading change may have prevented us from getting an RA and having to take evasive action. TCAS worked as advertised.

Original NASA ASRS Text

Title: TCASII RA RESULTS IN AN ALT EXCURSION FOR AN ACR ACFT.

Narrative: LEVEL AT 11000' ON NANCI 4 ARR TO LGA, WE GOT A TCAS TA AT 12 O'CLOCK, THEN ATC (ZDC) CALLED TFC Y 11-12 O'CLOCK AS WE GOT A CLB INSTRUCTION (RA) FROM OUR TCAS SYS. WE PULLED UP AND CLBED TO 12000' AND ADVISED ATC. TCAS SHOWED ACFT Y 300' BELOW. WE DID NOT SEE IT. A MORE TIMELY CALL FROM ATC OR A HDG CHANGE MAY HAVE PREVENTED US FROM GETTING AN RA AND HAVING TO TAKE EVASIVE ACTION. TCAS WORKED AS ADVERTISED.

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.