Narrative:

On a routine flight we received an RA alert from TCAS. We departed normally from mcw and were advised in 'radar contact' by ZMP. Around 20 NM southwest of mcw VOR; established on the airway; at 6000 ft MSL and in cruise; we had been tracking 1 TCAS target indicating 7500 ft MSL; and between 15-20 NM south of our track. Suddenly; a new target appeared at 5500 ft MSL and within only 1 mi of our position; and closing; immediately causing the TCAS alert to sound. We were given the aural alerts 'traffic! Climb; climb; climb; climb!' with full visual indications on the mfd TCAS display as well as the TCAS command led's on the vsi's to execute a climbing escape maneuver. I called to the captain (PF); 'let's go!' and the captain disengaged the autoplt and executed an escape climb. Once we were established in the climb; I looked out the windscreen at our 12:30 - 1 O'clock position; and spotted the intruding aircraft; identing a single engine cessna type. Had we not executed the escape; this would have been a near miss event; as I estimated the range of the aircraft track to have been less than 1/4 NM; and in fact; the aircraft paths nearly intersected. Since we had climbed to about 6700 ft; the conflict looked visually clear; and the TCAS also confirmed aurally and visually 'clear of conflict.' the captain re-established the aircraft to cruise flight at 6000 ft. I radioed the ZMP controller and reported the TCAS RA. She queried me as to aircraft type and suspected altitude; and I reported back. She then stated; 'aircraft X you are not in radar there.' I responded; 'ok that's good to know.' 2 mins later; the controller asked me to copy down the phone number of the supervisor and for us to contact them when we arrived. This event happened due to a VFR traffic conflict coming in close proximity to our flight without early warning from either radar services from ATC or from our TCAS equipment. Had we been alerted to: 1) the fact that we were no longer in radar contact; or 2) that there was closing traffic in our area; we may have been able to avoid the TCAS RA and conflict. Once we idented the TCAS RA the crew coordination to execute the evasive maneuver to become clear of the traffic conflict. Once we arrived at our destination; we debriefed the event in preparation for the captain's requested phone call to ATC; as well as to better prepare this report. Suggestions: 1) ATC should advise IFR traffic of the loss of radar contact; per established FAA-order ATC procedures. This then cues pilots to heighten their awareness of VMC traffic avoidance responsibility. 2) my experience with the TCAS system installed in the SF340 has been that many GA aircraft xponders do not transmit enough mode-south interrogation reply signal to incur a reliable target on our TCAS displays. Put another way; it seems that private GA light aircraft do not show as readily on TCAS as heavier; more robustly equipped aircraft do. I don't know; but would suggest looking at improved TCAS technology. 3) as a part of training for TCAS/collision avoidance in the curriculum; I would suggest reviewing 'hot spots' as idented by our pilots; as we all know where they are; and they should be shared with crews from across the system.

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Original NASA ASRS Text

Title: SF340 CREW REPORTS TCAS RA 20 NM SW OF MCW AT 6000 FEET.

Narrative: ON A ROUTINE FLT WE RECEIVED AN RA ALERT FROM TCAS. WE DEPARTED NORMALLY FROM MCW AND WERE ADVISED IN 'RADAR CONTACT' BY ZMP. AROUND 20 NM SW OF MCW VOR; ESTABLISHED ON THE AIRWAY; AT 6000 FT MSL AND IN CRUISE; WE HAD BEEN TRACKING 1 TCAS TARGET INDICATING 7500 FT MSL; AND BTWN 15-20 NM S OF OUR TRACK. SUDDENLY; A NEW TARGET APPEARED AT 5500 FT MSL AND WITHIN ONLY 1 MI OF OUR POS; AND CLOSING; IMMEDIATELY CAUSING THE TCAS ALERT TO SOUND. WE WERE GIVEN THE AURAL ALERTS 'TFC! CLB; CLB; CLB; CLB!' WITH FULL VISUAL INDICATIONS ON THE MFD TCAS DISPLAY AS WELL AS THE TCAS COMMAND LED'S ON THE VSI'S TO EXECUTE A CLBING ESCAPE MANEUVER. I CALLED TO THE CAPT (PF); 'LET'S GO!' AND THE CAPT DISENGAGED THE AUTOPLT AND EXECUTED AN ESCAPE CLB. ONCE WE WERE ESTABLISHED IN THE CLB; I LOOKED OUT THE WINDSCREEN AT OUR 12:30 - 1 O'CLOCK POS; AND SPOTTED THE INTRUDING ACFT; IDENTING A SINGLE ENG CESSNA TYPE. HAD WE NOT EXECUTED THE ESCAPE; THIS WOULD HAVE BEEN A NEAR MISS EVENT; AS I ESTIMATED THE RANGE OF THE ACFT TRACK TO HAVE BEEN LESS THAN 1/4 NM; AND IN FACT; THE ACFT PATHS NEARLY INTERSECTED. SINCE WE HAD CLBED TO ABOUT 6700 FT; THE CONFLICT LOOKED VISUALLY CLR; AND THE TCAS ALSO CONFIRMED AURALLY AND VISUALLY 'CLR OF CONFLICT.' THE CAPT RE-ESTABLISHED THE ACFT TO CRUISE FLT AT 6000 FT. I RADIOED THE ZMP CTLR AND RPTED THE TCAS RA. SHE QUERIED ME AS TO ACFT TYPE AND SUSPECTED ALT; AND I RPTED BACK. SHE THEN STATED; 'ACFT X YOU ARE NOT IN RADAR THERE.' I RESPONDED; 'OK THAT'S GOOD TO KNOW.' 2 MINS LATER; THE CTLR ASKED ME TO COPY DOWN THE PHONE NUMBER OF THE SUPVR AND FOR US TO CONTACT THEM WHEN WE ARRIVED. THIS EVENT HAPPENED DUE TO A VFR TFC CONFLICT COMING IN CLOSE PROX TO OUR FLT WITHOUT EARLY WARNING FROM EITHER RADAR SVCS FROM ATC OR FROM OUR TCAS EQUIP. HAD WE BEEN ALERTED TO: 1) THE FACT THAT WE WERE NO LONGER IN RADAR CONTACT; OR 2) THAT THERE WAS CLOSING TFC IN OUR AREA; WE MAY HAVE BEEN ABLE TO AVOID THE TCAS RA AND CONFLICT. ONCE WE IDENTED THE TCAS RA THE CREW COORD TO EXECUTE THE EVASIVE MANEUVER TO BECOME CLR OF THE TFC CONFLICT. ONCE WE ARRIVED AT OUR DEST; WE DEBRIEFED THE EVENT IN PREPARATION FOR THE CAPT'S REQUESTED PHONE CALL TO ATC; AS WELL AS TO BETTER PREPARE THIS RPT. SUGGESTIONS: 1) ATC SHOULD ADVISE IFR TFC OF THE LOSS OF RADAR CONTACT; PER ESTABLISHED FAA-ORDER ATC PROCS. THIS THEN CUES PLTS TO HEIGHTEN THEIR AWARENESS OF VMC TFC AVOIDANCE RESPONSIBILITY. 2) MY EXPERIENCE WITH THE TCAS SYS INSTALLED IN THE SF340 HAS BEEN THAT MANY GA ACFT XPONDERS DO NOT XMIT ENOUGH MODE-S INTERROGATION REPLY SIGNAL TO INCUR A RELIABLE TARGET ON OUR TCAS DISPLAYS. PUT ANOTHER WAY; IT SEEMS THAT PVT GA LIGHT ACFT DO NOT SHOW AS READILY ON TCAS AS HEAVIER; MORE ROBUSTLY EQUIPPED ACFT DO. I DON'T KNOW; BUT WOULD SUGGEST LOOKING AT IMPROVED TCAS TECHNOLOGY. 3) AS A PART OF TRAINING FOR TCAS/COLLISION AVOIDANCE IN THE CURRICULUM; I WOULD SUGGEST REVIEWING 'HOT SPOTS' AS IDENTED BY OUR PLTS; AS WE ALL KNOW WHERE THEY ARE; AND THEY SHOULD BE SHARED WITH CREWS FROM ACROSS THE SYS.

Data retrieved from NASA's ASRS site as of January 2009 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.