Air carrier large transport reversed descent in response to TCAS ii RA.

Attributes
ACN	172785
Time
Date	199103
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : atl
State Reference	GA
Altitude	msl bound lower : 11000 msl bound upper : 11500
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : atl
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent other
Route In Use	arrival star : star
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	climbout : intermediate altitude
Route In Use	departure sid : sid
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 84 flight time total : 10670 flight time type : 4600
ASRS Report	172785
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	altitude deviation : undershoot altitude deviation : excursion from assigned altitude conflict : airborne less severe
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : took evasive action flight crew : returned to intended course or assigned course
Consequence	Other
Miss Distance	vertical : 1300
Supplementary
Air Traffic Incident	Pilot Deviation

Narrative:

While descending to assigned altitude of 11000' and deviating slightly north of arrival radial (for cumulus buildup), TCAS ii RA went off at approximately 11500' MSL, and PF immediately followed TCAS advisory to climb at over 1200 FPM. As climb was established, TCAS issued 'monitor vertical speed' immediately followed by 'clear of conflict.' ATC then issued instruction for a right turn to 090 degrees and as turn was initiated and altitude returned to 11000', first officer and F/east reported traffic passing below approximately 1000'. The traffic in question was departing atl and climbing to 10000'. Our crew felt that the other aircraft's climb rate and our descent rate (approximately 1000 FPM) was enough closure rate to activate the warning, even though adequate sep existed at all times.

Original NASA ASRS Text

Title: ACR LGT REVERSED DESCENT IN RESPONSE TO TCAS II RA.

Narrative: WHILE DSNDING TO ASSIGNED ALT OF 11000' AND DEVIATING SLIGHTLY N OF ARR RADIAL (FOR CUMULUS BUILDUP), TCAS II RA WENT OFF AT APPROX 11500' MSL, AND PF IMMEDIATELY FOLLOWED TCAS ADVISORY TO CLB AT OVER 1200 FPM. AS CLB WAS ESTABLISHED, TCAS ISSUED 'MONITOR VERT SPD' IMMEDIATELY FOLLOWED BY 'CLR OF CONFLICT.' ATC THEN ISSUED INSTRUCTION FOR A RIGHT TURN TO 090 DEGS AND AS TURN WAS INITIATED AND ALT RETURNED TO 11000', F/O AND F/E RPTED TFC PASSING BELOW APPROX 1000'. THE TFC IN QUESTION WAS DEPARTING ATL AND CLBING TO 10000'. OUR CREW FELT THAT THE OTHER ACFT'S CLB RATE AND OUR DSNT RATE (APPROX 1000 FPM) WAS ENOUGH CLOSURE RATE TO ACTIVATE THE WARNING, EVEN THOUGH ADEQUATE SEP EXISTED AT ALL TIMES.

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.