RA on TCAS ii commanded a dive. Flight crew responded with same.

Attributes
ACN	167768
Time
Date	199101
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ewc
State Reference	PA
Altitude	msl bound lower : 22500 msl bound upper : 23000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other 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 : 70 flight time total : 8200 flight time type : 900
ASRS Report	167768
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : instrument pilot : commercial
Experience	flight time last 90 days : 200 flight time total : 10000 flight time type : 2000
ASRS Report	168386
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance non adherence : far other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 0 vertical : 900
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation other

Narrative:

At FL230 the TCAS resolution alert commanded a dive of at least 1000 FPM. Previously noted traffic above us and descending. No visibility contact was established, and at approximately 22500' TCAS advised there was no longer a conflict. I noted traffic above was level 900' above (level at FL240). Although I felt the RA was in error (probably because of closure rate of descending traffic), we descended (no traffic was in close proximity below us). ZOB concurred that traffic above was level at FL240.

Original NASA ASRS Text

Title: RA ON TCAS II COMMANDED A DIVE. FLT CREW RESPONDED WITH SAME.

Narrative: AT FL230 THE TCAS RESOLUTION ALERT COMMANDED A DIVE OF AT LEAST 1000 FPM. PREVIOUSLY NOTED TFC ABOVE US AND DSNDING. NO VIS CONTACT WAS ESTABLISHED, AND AT APPROX 22500' TCAS ADVISED THERE WAS NO LONGER A CONFLICT. I NOTED TFC ABOVE WAS LEVEL 900' ABOVE (LEVEL AT FL240). ALTHOUGH I FELT THE RA WAS IN ERROR (PROBABLY BECAUSE OF CLOSURE RATE OF DSNDING TFC), WE DSNDED (NO TFC WAS IN CLOSE PROX BELOW US). ZOB CONCURRED THAT TFC ABOVE WAS LEVEL AT FL240.

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.