Narrative:

Approach was vectoring aircraft X toward final for runway 18L and asked if we had the preceding 'bac jet' Y in sight. Still on base, we decided not to call the traffic in sight due to the haze. Approach then vectored us onto the runway 18L localizer and, as we joined, the bac jet was clearly in sight both visually and on TCASII showing 3 mi ahead. We told approach that the bac jet was in sight. Approach then cleared us for the runway 18L visual approach and told us to both follow the bac jet and maintain 170 KIAS until fraze, the IFR FAF. Prior to our reaching fraze, we were indicating 170 KIAS but the separation with the bac jet began to decrease rapidly as evidenced by TCASII. As the lateral decreased to 2 mi, the captain and I decided that in order to maintain a safe in trail distance we would have to begin slowing from 170 KIAS. So we configured and slowed enough to maintain the 2 mi separation. However, the aircraft Z behind us, who was initially only 3 mi behind us, was maintaining the assigned speed and had closed to approximately 1 1/2 mi behind us. ATC then asked the aircraft behind us if they would be able to continue. There was some discussion of making s-turns for spacing. Meanwhile we asked what the bac jet's ground speed was. ATC's response was 100 KTS, so we configured to match that speed over the ground. The aircraft behind us elected to go around. We maintained the 2 mi separation and landed without incident. The bottom line is that by accepting the visual approach to follow preceding traffic that we had called in sight, the responsibility for maintaining safe in trail and wake turbulence separation became our responsibility. And, as it turned out, the clearance instructions to both follow the traffic and maintain 170 KIAS to fraze were incompatible once the bac jet began to slow. At least we slowed to maintain safe separation by matching the ground speed of the preceding traffic. At that point we could have been more helpful/correct by specifically notifying ATC that we were unable to maintain 170 KIAS due to decreasing separation and that we were specifically 'requesting an amended clearance.' but, the situation would have been evident on radar in the tower cabin attendant, and ATC was involved in plenty of discussion with the parties involved as the event unfolded. In the future, I'll keep my distance and notify ATC of the need to slow/request an amended clearance.

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Original NASA ASRS Text

Title: DUE TO CVG SPACING CTL ACTIONS, CL65 INITIATES SPD REDUCTION TO FOLLOW LNDG TFC AHEAD WHILE SUBSEQUENT ACFT EXECUTES A GAR.

Narrative: APCH WAS VECTORING ACFT X TOWARD FINAL FOR RWY 18L AND ASKED IF WE HAD THE PRECEDING 'BAC JET' Y IN SIGHT. STILL ON BASE, WE DECIDED NOT TO CALL THE TFC IN SIGHT DUE TO THE HAZE. APCH THEN VECTORED US ONTO THE RWY 18L LOC AND, AS WE JOINED, THE BAC JET WAS CLRLY IN SIGHT BOTH VISUALLY AND ON TCASII SHOWING 3 MI AHEAD. WE TOLD APCH THAT THE BAC JET WAS IN SIGHT. APCH THEN CLRED US FOR THE RWY 18L VISUAL APCH AND TOLD US TO BOTH FOLLOW THE BAC JET AND MAINTAIN 170 KIAS UNTIL FRAZE, THE IFR FAF. PRIOR TO OUR REACHING FRAZE, WE WERE INDICATING 170 KIAS BUT THE SEPARATION WITH THE BAC JET BEGAN TO DECREASE RAPIDLY AS EVIDENCED BY TCASII. AS THE LATERAL DECREASED TO 2 MI, THE CAPT AND I DECIDED THAT IN ORDER TO MAINTAIN A SAFE IN TRAIL DISTANCE WE WOULD HAVE TO BEGIN SLOWING FROM 170 KIAS. SO WE CONFIGURED AND SLOWED ENOUGH TO MAINTAIN THE 2 MI SEPARATION. HOWEVER, THE ACFT Z BEHIND US, WHO WAS INITIALLY ONLY 3 MI BEHIND US, WAS MAINTAINING THE ASSIGNED SPD AND HAD CLOSED TO APPROX 1 1/2 MI BEHIND US. ATC THEN ASKED THE ACFT BEHIND US IF THEY WOULD BE ABLE TO CONTINUE. THERE WAS SOME DISCUSSION OF MAKING S-TURNS FOR SPACING. MEANWHILE WE ASKED WHAT THE BAC JET'S GND SPD WAS. ATC'S RESPONSE WAS 100 KTS, SO WE CONFIGURED TO MATCH THAT SPD OVER THE GND. THE ACFT BEHIND US ELECTED TO GO AROUND. WE MAINTAINED THE 2 MI SEPARATION AND LANDED WITHOUT INCIDENT. THE BOTTOM LINE IS THAT BY ACCEPTING THE VISUAL APCH TO FOLLOW PRECEDING TFC THAT WE HAD CALLED IN SIGHT, THE RESPONSIBILITY FOR MAINTAINING SAFE IN TRAIL AND WAKE TURB SEPARATION BECAME OUR RESPONSIBILITY. AND, AS IT TURNED OUT, THE CLRNC INSTRUCTIONS TO BOTH FOLLOW THE TFC AND MAINTAIN 170 KIAS TO FRAZE WERE INCOMPATIBLE ONCE THE BAC JET BEGAN TO SLOW. AT LEAST WE SLOWED TO MAINTAIN SAFE SEPARATION BY MATCHING THE GND SPD OF THE PRECEDING TFC. AT THAT POINT WE COULD HAVE BEEN MORE HELPFUL/CORRECT BY SPECIFICALLY NOTIFYING ATC THAT WE WERE UNABLE TO MAINTAIN 170 KIAS DUE TO DECREASING SEPARATION AND THAT WE WERE SPECIFICALLY 'REQUESTING AN AMENDED CLRNC.' BUT, THE SIT WOULD HAVE BEEN EVIDENT ON RADAR IN THE TWR CAB, AND ATC WAS INVOLVED IN PLENTY OF DISCUSSION WITH THE PARTIES INVOLVED AS THE EVENT UNFOLDED. IN THE FUTURE, I'LL KEEP MY DISTANCE AND NOTIFY ATC OF THE NEED TO SLOW/REQUEST AN AMENDED CLRNC.

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.