Narrative:

Both aircraft were IFR inbounds to bwi. On frequency 119.7 air carrier X had been given several vectors for sequencing to visual approach for runway 33R. On a heading of 040 degree at 4000 ft MSL we were given to frequency 119.0. We were on this frequency for approximately 1 min 30 seconds without being able to establish contact due to frequency congestion. The first officer was hand flying and looking toward the left at the airport. I was scanning back and forth and had just seen an small aircraft pass below us going in the opposite direction that had not been called. I turned to tell the first officer 'this guy is busy,' but all of a sudden I saw air carrier Y in the first officer's windscreen moving right to left at the same altitude -- approximately 1/4 to 1/2 mi in front of us. I immediately grabbed the control wheel and pitched down without saying a word to the first officer. We passed less than 100 ft apart and went through the air carrier Y wake and propeller wash. The air carrier Y must have seen us about the same moment I saw him and he began a pitch up maneuver. On the ground I spoke with the captain of air carrier Y. He said his first officer was flying and he (the captain) saw me first and pitched up. (Neither aircraft had TCASII). He had been on frequency 124.55 and had been switched to 119.0 on a heading of 280 degree at 3000 ft. He too had been unable to establish contact due to frequency congestion. We both spoke to the approach control supervisor via landline. He admitted to me that there had been a controller procedural error and he was 'reviewing.' neither one of us had a chance to talk on 119.0 and for that controller to resolve the conflict, if he had seen it, time was minimal, considering his workload at the moment. This was a very close incident and traumatic for the passengers in air carrier Y who could see it coming before either aircraft's pilots. Both pilots stated the near miss to the controller on frequency 119.0. His comment was 'I wasn't talking to either of you.' he told us to file our reports as necessary. Supplemental information from acn 212896. Sector was extremely busy. Air carrier X was on a 040 heading, sequence for runway 33R at 3000 ft. Air carrier Y on a 280 degree heading at 3000 ft also for 33R. Aircraft came from different sectors. Pilot of air carrier Y had not checked on the frequency. Air carrier X, checked on, and I descended air carrier X to 2000 ft, however the near midair collision occurred simultaneously. I believe this incident was caused by too heavy a volume in the sector, and not talking to either pilot until immediately before the incident. Pilot of air carrier Y said after the incident, that he had tried to call but the frequency was too busy.

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Original NASA ASRS Text

Title: ACR X HAD NMAC LTSS FROM ACR Y. EVASIVE ACTION TAKEN. SEE AND AVOID. SYS ERROR.

Narrative: BOTH ACFT WERE IFR INBOUNDS TO BWI. ON FREQ 119.7 ACR X HAD BEEN GIVEN SEVERAL VECTORS FOR SEQUENCING TO VISUAL APCH FOR RWY 33R. ON A HDG OF 040 DEG AT 4000 FT MSL WE WERE GIVEN TO FREQ 119.0. WE WERE ON THIS FREQ FOR APPROX 1 MIN 30 SECONDS WITHOUT BEING ABLE TO ESTABLISH CONTACT DUE TO FREQ CONGESTION. THE FO WAS HAND FLYING AND LOOKING TOWARD THE L AT THE ARPT. I WAS SCANNING BACK AND FORTH AND HAD JUST SEEN AN SMA PASS BELOW US GOING IN THE OPPOSITE DIRECTION THAT HAD NOT BEEN CALLED. I TURNED TO TELL THE FO 'THIS GUY IS BUSY,' BUT ALL OF A SUDDEN I SAW ACR Y IN THE FO'S WINDSCREEN MOVING R TO L AT THE SAME ALT -- APPROX 1/4 TO 1/2 MI IN FRONT OF US. I IMMEDIATELY GRABBED THE CTL WHEEL AND PITCHED DOWN WITHOUT SAYING A WORD TO THE FO. WE PASSED LESS THAN 100 FT APART AND WENT THROUGH THE ACR Y WAKE AND PROP WASH. THE ACR Y MUST HAVE SEEN US ABOUT THE SAME MOMENT I SAW HIM AND HE BEGAN A PITCH UP MANEUVER. ON THE GND I SPOKE WITH THE CAPT OF ACR Y. HE SAID HIS FO WAS FLYING AND HE (THE CAPT) SAW ME FIRST AND PITCHED UP. (NEITHER ACFT HAD TCASII). HE HAD BEEN ON FREQ 124.55 AND HAD BEEN SWITCHED TO 119.0 ON A HDG OF 280 DEG AT 3000 FT. HE TOO HAD BEEN UNABLE TO ESTABLISH CONTACT DUE TO FREQ CONGESTION. WE BOTH SPOKE TO THE APCH CTL SUPVR VIA LANDLINE. HE ADMITTED TO ME THAT THERE HAD BEEN A CTLR PROCEDURAL ERROR AND HE WAS 'REVIEWING.' NEITHER ONE OF US HAD A CHANCE TO TALK ON 119.0 AND FOR THAT CTLR TO RESOLVE THE CONFLICT, IF HE HAD SEEN IT, TIME WAS MINIMAL, CONSIDERING HIS WORKLOAD AT THE MOMENT. THIS WAS A VERY CLOSE INCIDENT AND TRAUMATIC FOR THE PAXS IN ACR Y WHO COULD SEE IT COMING BEFORE EITHER ACFT'S PLTS. BOTH PLTS STATED THE NEAR MISS TO THE CTLR ON FREQ 119.0. HIS COMMENT WAS 'I WASN'T TALKING TO EITHER OF YOU.' HE TOLD US TO FILE OUR RPTS AS NECESSARY. SUPPLEMENTAL INFO FROM ACN 212896. SECTOR WAS EXTREMELY BUSY. ACR X WAS ON A 040 HDG, SEQUENCE FOR RWY 33R AT 3000 FT. ACR Y ON A 280 DEG HDG AT 3000 FT ALSO FOR 33R. ACFT CAME FROM DIFFERENT SECTORS. PLT OF ACR Y HAD NOT CHKED ON THE FREQ. ACR X, CHKED ON, AND I DSNDED ACR X TO 2000 FT, HOWEVER THE NMAC OCCURRED SIMULTANEOUSLY. I BELIEVE THIS INCIDENT WAS CAUSED BY TOO HVY A VOLUME IN THE SECTOR, AND NOT TALKING TO EITHER PLT UNTIL IMMEDIATELY BEFORE THE INCIDENT. PLT OF ACR Y SAID AFTER THE INCIDENT, THAT HE HAD TRIED TO CALL BUT THE FREQ WAS TOO BUSY.

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.