An SF34 crew, departing dfw, responded to a descend RA from TCASII.

Attributes
ACN	536374
Time
Date	200201
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : dfw.airport
State Reference	TX
Altitude	msl single value : 3000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : d10.tracon
Operator	common carrier : air carrier
Make Model Name	SF 340A
Operating Under FAR Part	Part 121
Flight Phase	climbout : vacating altitude
Route In Use	departure : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 15200 flight time type : 9200
ASRS Report	536374
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude conflict : nmac other anomaly other
Independent Detector	aircraft equipment : gpws aircraft equipment : tcas other flight crewa other flight crewb
Resolutory Action	controller : provided flight assist flight crew : diverted to another airport flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew other
Miss Distance	horizontal : 100 vertical : 100
Supplementary
Problem Areas	Aircraft ATC Human Performance Flight Crew Human Performance
Primary Problem	Aircraft

Narrative:

As we were approaching 3000 ft, climbing out of dfw, we received a TCASII RA to descend. I asked first officer to respond to RA, as I tried to ask departure control if he showed any conflicting traffic. This RA was very unusual, in that ATC said there was no conflicting traffic (once I was able to communicate on congested frequency). Also, the RA continued even though we had descended about 800 ft. So, I asked first officer to abandon responding to RA and resume climb. I recycled TCASII switch to stand-by and back to automatic, this discontinued the RA command. Apparently, this was a spurious TCASII RA. Since we are trained to respond to RA's and not try to second-guess the veracity of every RA, we responded. In retrospect, this maneuver turned out to be a harrowing experience for the passenger. However, the alternative of not responding to this RA, at all, then finding out that it was a genuine RA, may have been even more harrowing, if not worse! A few mins later into our climb, we noticed a transient anomaly in the backup channel of the aircraft's warning electronic unit. Immediately, we contacted company maintenance. Consensus was reached to return back to dfw airport. The rest of the flight was uneventful. Also, the warning electronic unit redundancy light never reilluminated. After parking at the gate, I entered 2 discrepancy items in aircraft maintenance logbook. One reporting TCASII problem. The other warning electronic unit light illuminating for a split second.

Original NASA ASRS Text

Title: AN SF34 CREW, DEPARTING DFW, RESPONDED TO A DSND RA FROM TCASII.

Narrative: AS WE WERE APCHING 3000 FT, CLBING OUT OF DFW, WE RECEIVED A TCASII RA TO DSND. I ASKED FO TO RESPOND TO RA, AS I TRIED TO ASK DEP CTL IF HE SHOWED ANY CONFLICTING TFC. THIS RA WAS VERY UNUSUAL, IN THAT ATC SAID THERE WAS NO CONFLICTING TFC (ONCE I WAS ABLE TO COMMUNICATE ON CONGESTED FREQ). ALSO, THE RA CONTINUED EVEN THOUGH WE HAD DSNDED ABOUT 800 FT. SO, I ASKED FO TO ABANDON RESPONDING TO RA AND RESUME CLB. I RECYCLED TCASII SWITCH TO STAND-BY AND BACK TO AUTO, THIS DISCONTINUED THE RA COMMAND. APPARENTLY, THIS WAS A SPURIOUS TCASII RA. SINCE WE ARE TRAINED TO RESPOND TO RA'S AND NOT TRY TO SECOND-GUESS THE VERACITY OF EVERY RA, WE RESPONDED. IN RETROSPECT, THIS MANEUVER TURNED OUT TO BE A HARROWING EXPERIENCE FOR THE PAX. HOWEVER, THE ALTERNATIVE OF NOT RESPONDING TO THIS RA, AT ALL, THEN FINDING OUT THAT IT WAS A GENUINE RA, MAY HAVE BEEN EVEN MORE HARROWING, IF NOT WORSE! A FEW MINS LATER INTO OUR CLB, WE NOTICED A TRANSIENT ANOMALY IN THE BACKUP CHANNEL OF THE ACFT'S WARNING ELECTRONIC UNIT. IMMEDIATELY, WE CONTACTED COMPANY MAINT. CONSENSUS WAS REACHED TO RETURN BACK TO DFW ARPT. THE REST OF THE FLT WAS UNEVENTFUL. ALSO, THE WARNING ELECTRONIC UNIT REDUNDANCY LIGHT NEVER REILLUMINATED. AFTER PARKING AT THE GATE, I ENTERED 2 DISCREPANCY ITEMS IN ACFT MAINT LOGBOOK. ONE RPTING TCASII PROB. THE OTHER WARNING ELECTRONIC UNIT LIGHT ILLUMINATING FOR A SPLIT SECOND.

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.