An air carrier large transport descended in response to a TCASII command.

Attributes
ACN	233624
Time
Date	199301
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : pbi
State Reference	FL
Altitude	msl bound lower : 3500 msl bound upper : 4000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : pbi artcc : zfw
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Aircraft
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 230 flight time total : 12000
ASRS Report	233624
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 6000 vertical : 500
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation other

Narrative:

During approach to pbi, 8-10 mi north of field, while at 4000 ft, TCASII gave TA followed by RA (descend). Traffic spotted was small aircraft. We advised ATC of our deviation below 4000 ft and then returned to 4000 ft when clear of traffic.

Original NASA ASRS Text

Title: AN ACR LGT DSNDED IN RESPONSE TO A TCASII COMMAND.

Narrative: DURING APCH TO PBI, 8-10 MI N OF FIELD, WHILE AT 4000 FT, TCASII GAVE TA FOLLOWED BY RA (DSND). TFC SPOTTED WAS SMALL ACFT. WE ADVISED ATC OF OUR DEV BELOW 4000 FT AND THEN RETURNED TO 4000 FT WHEN CLR OF TFC.

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.