Narrative:

I was working ar-O; and got aircraft X from my arrival feeder. I cleared aircraft X for the ILS 27L approach from about 7 miles north of zintu. This approach has a way point that will allow aircraft approaching from the north to join the final from more of an angle. Having a large gap in front of aircraft X; I instructed him to maintain 210 KTS until anval; about a 9 mile final. I saw him slowing prior to the turn from cumra to yabba. I re instructed him to maintain 210 to anval. At yabba I switched him to the tower frequency since we were running monitored approached; and one more time; told him to maintain 210 to anval. They acknowledged all clearances. This created an unexpected condition. Coming down the final; he was 40 KTS slower than other aircraft; including aircraft Y behind him (cleared to maintain 210 to doooh; then 180 to depot). I called my monitor; and he talked to aircraft X; who said he wouldn't be able to do more than 180 KTS on the approach. This was unsafe. I had to slow the next 5 aircraft in a quick fashion (the monitor slowed the trailing aircraft and was a bare 3 miles between aircraft X and aircraft Y). I didn't mind if he didn't want to go fast down the final; but the crew needs to share this important information! They aren't the only airplanes in the sky. It almost created a go-around scenario for the trailing aircraft; and it did cause unnecessary workload for my feeder and me as I had to adjust for the surprise. I hope you can get this to aircraft X and instruct the crew to communicate so they don't cause an operational error by keeping secrets. Advise aircraft X operations to find this crew and remind them to communicate with ATC; or don't accept the clearance three times if they have no intent to do any of it.

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Original NASA ASRS Text

Title: A80 Controller described a near overtake event on final when the leading aircraft failed to comply with an assigned speed after accepting the clearance.

Narrative: I was working AR-O; and got Aircraft X from my Arrival Feeder. I cleared Aircraft X for the ILS 27L Approach from about 7 miles north of ZINTU. This approach has a way point that will allow aircraft approaching from the north to join the final from more of an angle. Having a large gap in front of Aircraft X; I instructed him to maintain 210 KTS until ANVAL; about a 9 mile final. I saw him slowing prior to the turn from CUMRA to YABBA. I re instructed him to maintain 210 to ANVAL. At YABBA I switched him to the Tower frequency since we were running monitored approached; and one more time; told him to maintain 210 to ANVAL. They acknowledged ALL clearances. This created an unexpected condition. Coming down the final; he was 40 KTS slower than other aircraft; including Aircraft Y behind him (cleared to maintain 210 to DOOOH; then 180 to DEPOT). I called my monitor; and he talked to Aircraft X; who said he wouldn't be able to do more than 180 KTS on the approach. This was unsafe. I had to slow the next 5 aircraft in a quick fashion (the monitor slowed the trailing aircraft and was a bare 3 miles between Aircraft X and Aircraft Y). I didn't mind if he didn't want to go fast down the final; but the crew needs to SHARE this IMPORTANT information! They aren't the only airplanes in the sky. It almost created a go-around scenario for the trailing aircraft; and it did cause unnecessary workload for my Feeder and me as I had to adjust for the surprise. I hope you can get this to Aircraft X and instruct the crew to COMMUNICATE so they don't cause an operational error by keeping secrets. Advise Aircraft X operations to find this crew and remind them to communicate with ATC; or DON'T ACCEPT THE CLEARANCE THREE TIMES if they have no intent to do any of it.

Data retrieved from NASA's ASRS site as of April 2012 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.