TCAS RA. Flight crew descends.

Attributes
ACN	183960
Time
Date	199107
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : pxv
State Reference	IN
Altitude	msl bound lower : 34800 msl bound upper : 35000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zme
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Flight Plan	IFR
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 : 10500 flight time type : 7000
ASRS Report	183960
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	Other
Supplementary
Air Traffic Incident	Pilot Deviation other

Narrative:

While cruising at FL350, received a TCAS resolution advisory directing us to descend at 1500 FPM or faster. Initiated descent and notified memphis center. Resolution advisory was cancelled almost immediately. Returned to FL350. Lowest altitude reached was 34800. The aircraft that caused the TCAS RA appeared to be level at FL370, which indicated to me that the RA was not a valid warning. However, since we did not have a visual fix on the traffic, we felt obligated to initiate the descent. Documented the event in the aircraft logbook for company study. Hopefully, this event will not prove typical of all TCAS operation.

Original NASA ASRS Text

Title: TCAS RA. FLC DSNDS.

Narrative: WHILE CRUISING AT FL350, RECEIVED A TCAS RESOLUTION ADVISORY DIRECTING US TO DSND AT 1500 FPM OR FASTER. INITIATED DSCNT AND NOTIFIED MEMPHIS CENTER. RESOLUTION ADVISORY WAS CANCELLED ALMOST IMMEDIATELY. RETURNED TO FL350. LOWEST ALT REACHED WAS 34800. THE ACFT THAT CAUSED THE TCAS RA APPEARED TO BE LEVEL AT FL370, WHICH INDICATED TO ME THAT THE RA WAS NOT A VALID WARNING. HOWEVER, SINCE WE DID NOT HAVE A VISUAL FIX ON THE TFC, WE FELT OBLIGATED TO INITIATE THE DSCNT. DOCUMENTED THE EVENT IN THE ACFT LOGBOOK FOR COMPANY STUDY. HOPEFULLY, THIS EVENT WILL NOT PROVE TYPICAL OF ALL TCAS OP.

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.