MDT ACFT AND 2 C130 MIL ACFT HAD NMAC.

Narrative

OUR FLT WAS WBOUND ABOUT 6 NM SSW OF PIT; AND ON RADAR VECTORS FOR AN ILS/VISUAL APCH TO RWY 10R. THIS PUTS US ON A R DOWNWIND; S OF THE ARPT. WE EXPECTED TO CONTINUE A FEW MI FURTHER; THEN BE TURNED R TO THE N; AND FINALLY R AGAIN TO AN EBOUND HDG FOR RWY 10R FINAL APCH. THE WX WAS GOOD VFR AND IT WAS NIGHTTIME. WE HAD BEEN GIVEN A DSCNT TO 3000 FT. I NOTICED AN INDICATION OF 'PROXIMATE TFC' ON THE TCASII AT ABOUT OUR 10 O'CLOCK POS AND ABOUT 4 MI AWAY; WHICH I SCANNED VISUALLY FOR BUT WAS UNABLE TO SEE AT THIS TIME. THIS TFC SHOWED ABOUT 700 FT BELOW OUR CURRENT ALT; WHICH WAS 4200 FT AT THE TIME; AS WE WERE STILL DSNDING AT 1000 FPM. THIS WOULD PUT THE TFC AT ABOUT 3500 FT AND I WONDERED IF IT MIGHT BECOME A PROB FOR US. THERE WAS NO PLUS OR MINUS INDICATION ON THE TCASII ASSOCIATED WITH THE TFC; SO I HAD NO TIMELY WAY TO TELL IF IT WAS LEVEL OR CHANGING ALT SLOWLY. AS WE DSNDED THROUGH ABOUT 4000 FT; THE TCASII MADE THE TFC A TA AND AGAIN I BEGAN TO SCAN VISUALLY FOR IT. AT ABOUT THE SAME TIME THE CTLR ISSUED US A TA STATING THAT 'THE TFC HAS YOU IN SIGHT AND WILL MAINTAIN VISUAL SEPARATION;' BUT NEVER GAVE ANY DETAILS AS TO WHAT TYPE IT WAS. IT WAS AT THIS TIME THAT I FIRST SAW THE TFC; NOW IN OUR 8:30 POS LOW AND PRETTY MUCH NBOUND. IT WAS EXACTLY WHERE THE TCASII SAID IT WAS. I COULD ONLY SEE NAV LIGHTS AND ANTI- COLLISION BEACONS BUT COULD TELL IT WAS A LARGE ACFT THAT I ESTIMATED TO BE ABOUT THE SIZE OF A B737. I TOLD MY FO; WHO WAS THE PF; THAT I HAD THE TFC IN SIGHT AND THAT IT WOULD PASS BELOW AND BEHIND US ON ITS NBOUND COURSE. THEN 2 THINGS HAPPENED AT ONCE. FIRST; ATC ISSUED US A R TURN TO 340 DEGS; WHICH WE BEGAN TO COMPLY WITH. SECOND; AS WE STARTED THE TURN; DSNDING OUT OF ABOUT 3800 FT; THE TCASII MADE THE TARGET AN RA; AND ASKED FOR A DSCNT RATE REDUCTION TO NOT GREATER THAN -500 FPM. WE COMPLIED WITH THIS; SLOWING OUR DSCNT TO A VIRTUAL LEVELOFF AT 3500 FT. SINCE WE WERE NOW IN A R TURN; I HAD LOST VISUAL CONTACT WITH THE TFC; AND WAS WATCHING IT ON THE TCASII. I EXPECTED THAT SINCE THE CTLR OBVIOUSLY KNEW ABOUT IT; AND HAD TOLD US THAT IT WOULD MAINTAIN VISUAL SEPARATION; THAT IT WOULD DSND FURTHER OR DIVERGE AWAY FROM US ON A MORE NE HDG. THIS WAS NOT TO BE THE CASE. OVER A PERIOD OF JUST A FEW SECONDS; I WATCHED WITH GROWING APPREHENSION AS THE TARGET MERGED WITH OUR AIRLINE SYMBOL AND STAYED TUCKED NEATLY IN BENEATH OUR R WING ON THE DISPLAY. I IMMEDIATELY ASKED THE FO TO SEE IF HE COULD SEE THE TFC OUT HIS WINDOW (HE WAS ALREADY LOOKING); AND IN ABOUT 1 SECOND HE ANSWERED IN THE AFFIRMATIVE; SWEARING IN THE PROCESS. TURNS OUT THAT HE WAS LOOKING AT 2 (THAT HE SAW) MIL C130'S AT ABOUT 4 O'CLOCK; OUR ALT; AND ONLY AN ESTIMATED 1000 FT AWAY LATERALLY HEADED STRAIGHT FOR US. IT SHOULD BE NOTED HERE THAT TO THE BEST OF MY RECOLLECTION; NO FURTHER TCASII RA'S WERE GIVEN AFTER THE INITIAL 'REDUCE DSCNT' ALERT; AND THE TCASII HAD; AT THIS POINT BEEN SILENT FOR SOME TIME. WE SAT THERE FOR ABOUT 1 SECOND JUST ABSORBING AND EVALUATING THE SIT; WE HAD NO IDEA WHAT THE OTHER ACFT WERE GOING TO DO; THEN WE CLBED TO GET OUT OF THEIR PATH. AT THE SAME MOMENT ATC CALLED AND ASKED OUR ALT; TO WHICH I RESPONDED '3500 FT; WE WERE DSNDING TO 3000 FT AS ASSIGNED BUT NOW WE'RE CLBING.' THE CTLR PAUSED AND THEN ASKED US TO MAINTAIN 4000 FT. FROM THIS POINT ON; THE CTLR'S XMISSION WERE OF A MANNER AND IN A TONE THAT SUGGESTED TO ME THAT HE HAD REALIZED THE MISTAKE HE MADE AND HAD BEEN SHAKEN BY THIS EVENT; AS HAD WE ALL. WHEN HE HANDED US OFF TO THE TWR HE THANKED US FOR OUR 'HELP WITH THE ALT BACK THERE.' THERE IS NO QUESTION IN MY OR THE FO'S MIND THAT WE HAD INDEED BEEN GIVEN A DSCNT TO 3000 FT. WE DISCUSSED IT AT LENGTH ON THE GND AS WE WENT THROUGH A NATURAL VENTING PROCESS. THERE IS ALSO NO QUESTION THAT IT WAS GIVEN IN ERROR. I ALSO BELIEVE; BASED ON HIS TONE AND COMMENTS; THAT THE CTLR REALIZED THIS AS WELL. WE WERE GIVEN THAT DSCNT IN ERROR; BUT LUCKILY WE WERE ABLE TO AVOID A TRAGEDY. I BELIEVE THAT SEVERAL OTHER FACTORS; SIMILAR TO AN 'ERROR CHAIN;' PLAYED A KEY ROLE IN HEIGHTENING THE DANGER OF THIS SIT; AND MAYBE HAD ANY ONE OF THEM BEEN ABSENT; THIS NEAR COLLISION MIGHT NOT HAVE OCCURRED. THEY ARE: 1) WHEN GIVEN THE INITIAL TA BY ATC; NO SPEC WAS GIVEN AS TO THE TYPE OF ACFT; OR THAT IT WAS A FORMATION FLT INVOLVING MORE THAN 1 ACFT. 2) AS IS COMMON PRACTICE IN MIL FORMATION FLTS; ONLY 1 ACFT HAD ITS XPONDER ON; SO WE HAD NO INDEPENDENT MEANS VIA THE TCASII TO SEE FOR OURSELVES THAT THERE WAS MORE THAN ONE. 3) THE C130'S WERE COMMUNICATING WITH THE CTLR ON UHF FREQS; SO WE COULD NOT HEAR THEIR XMISSIONS AND GLEAN ANY INFO WE MIGHT HAVE FROM THAT. IN THIS INSTANCE; WE COULD NOT EVEN HEAR THE CTLR'S XMISSIONS TO THE C130'S AS IS SOMETIMES THE CASE. 4) OUR TCASII NEVER GAVE US A MORE URGENT RA AFTER THE FIRST ALERT; I DON'T KNOW WHETHER THIS IS DUE TO A MALFUNCTION OR SYS LIMITATION RELATED TO OUR PROX TO THE C130'S. THE LATTER; IF TRUE; WOULD SEEM TO MOOT THE WHOLE INTENT OF TCASII. 5) I DON'T KNOW WHAT THE C130'S WERE DOING; WHETHER IT WAS A ROUTINE TRAINING OP OR SOME MORE CRITICAL MISSION; BUT IT IF WAS JUST TRAINING; I QUESTION THE WISDOM OF DOING IT DURING A PEAK TIME AT AN ARPT WITH SUCH DENSE TFC. I ESPECIALLY QUESTION THE WISDOM OF THEM FLYING THROUGH THIS PACKED TFC PATTERN LEVEL AT A VFR ALT ALLOWING ONLY 500 FT OF VERT SEPARATION BTWN THEM AND MANY OTHER ACFT CLBING AND DSNDING ALL AROUND THEM.