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TRACON atcs reported a loss of separation on final due to compression. Reporter stated a blocked frequency precluded timely alternate instructions.
| Attributes | |
| ACN | 869951 |
| Time | |
| Date | 201001 |
| Local Time Of Day | 1201-1800 |
| Place | |
| Locale Reference | ZZZ.Airport |
| State Reference | US |
| Aircraft 1 | |
| Make Model Name | Regional Jet 900 (CRJ900) |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Final Approach |
| Flight Plan | IFR |
| Aircraft 2 | |
| Make Model Name | Large Transport Low Wing 2 Turbojet Eng |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Final Approach |
| Person 1 | |
| Function | Approach |
| Qualification | Air Traffic Control Fully Certified |
| Events | |
| Anomaly | ATC Issue All Types Deviation - Procedural Published Material / Policy |
Narrative:
Aircraft X was catching aircraft Y on final due to the fact that the aircraft Y slowed to 100 KTS inside the FAF. His was the first aircraft to slow that much in this rush. This caused a greater than usual amount of compression in this sequence. I slowed aircraft X to 160 KTS and then moments later slowed him to 'slowest practical speed'. I then canceled the approach clearance and issued pull-out instructions - after waiting for a pilot to stop talking on frequency. This delay caused a critical loss of time which contributed to the loss of separation. It is possible that had I been able to talk to aircraft X when I wanted/needed to; separation would have been preserved.give controllers some kind of software tool that 'projects' the compression between all aircraft on final and alarms when the software determines that a loss of separation may/will occur due to compression. Compression is never the same twice depending on crews and aircraft types and changing wind and weather conditions. Also; develop a system where we can communicate to pilots without interruptions; blocks; etc. Until then; we really don't have control. The idea that a controller's critical transmission to a pilot in harm's way may not get to the pilot or may be blocked is unacceptable in this safety industry. Until such time; we don't have control - only the illusion of control.
Original NASA ASRS Text
Title: TRACON ATCS reported a loss of separation on final due to compression. Reporter stated a blocked frequency precluded timely alternate instructions.
Narrative: Aircraft X was catching Aircraft Y on final due to the fact that the Aircraft Y slowed to 100 KTS inside the FAF. His was the first aircraft to slow that much in this rush. This caused a greater than usual amount of compression in this sequence. I slowed Aircraft X to 160 KTS and then moments later slowed him to 'slowest practical speed'. I then canceled the approach clearance and issued pull-out instructions - AFTER waiting for a pilot to stop talking on frequency. This delay caused a critical loss of time which contributed to the loss of separation. It is possible that had I been able to talk to Aircraft X when I wanted/needed to; separation would have been preserved.Give controllers some kind of software tool that 'projects' the compression between all aircraft on final and alarms when the software determines that a loss of separation may/will occur due to compression. Compression is never the same twice depending on crews and aircraft types and changing wind and weather conditions. Also; develop a system where we can communicate to pilots without interruptions; blocks; etc. Until then; we really don't have control. The idea that a controller's critical transmission to a pilot in harm's way may not get to the pilot or may be blocked is unacceptable in this safety industry. Until such time; we don't have control - only the illusion of control.
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.