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ZFW controller experienced operational error at 11000 ft when failing to note a speed reduction by leading aircraft resulting in less than required separation.
| Attributes | |
| ACN | 801529 |
| Time | |
| Date | 200808 |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | navaid : byp.vortac |
| State Reference | TX |
| Altitude | msl single value : 11000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zfw.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | EMB ERJ 145 ER&LR |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : approach |
| Route In Use | arrival star : byp |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | artcc : zfw.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | EMB ERJ 135 ER&LR |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : approach |
| Route In Use | arrival star : byp |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Qualification | controller : radar |
| Experience | controller radar : 20.50 controller time certified in position1 : 15 |
| ASRS Report | 801529 |
| Events | |
| Anomaly | conflict : airborne less severe non adherence : required legal separation |
| Independent Detector | other controllera |
| Resolutory Action | none taken : detected after the fact |
| Consequence | faa : investigated |
| Miss Distance | horizontal : 24000 vertical : 100 |
| Supplementary | |
| Problem Areas | ATC Human Performance |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | Operational Error |
Narrative:
I was stepping down an E135 above B737; while keeping in trail behind E145. At approximately XA44:39Z; I gave E145 'resume normal speed; contact approach.' at approximately XA44:49Z; I turned E135 15 degrees right (spacing) and descended to 11000 ft. At this time; B737 was no longer a factor; E135 was about 7 mi; 5 O'clock position and diverging to E145. Speeds appeared compatible. At approximately XB45:46Z; I issued another E135 'reduce speed to 250 KTS; cleared direct karla; cross karla at 11000 ft.' I then measured the distance between targets; and I recall 5.8 mi. Taking into account the turn and speed reduction of E135; I felt proper spacing was present (with speeds showing 364 KTS overtaking 381 KTS; both slowing; and the rear aircraft needing to complete a 30-ish degree turn) and switched E135 to approach at approximately XC46:25. I got caught short when I did not realize E145 slowed by 60 KTS over the next 45 seconds; and E135 did not slow as fast.
Original NASA ASRS Text
Title: ZFW CTLR EXPERIENCED OPERROR AT 11000 FT WHEN FAILING TO NOTE A SPEED REDUCTION BY LEADING ACFT RESULTING IN LESS THAN REQUIRED SEPARATION.
Narrative: I WAS STEPPING DOWN AN E135 ABOVE B737; WHILE KEEPING IN TRAIL BEHIND E145. AT APPROX XA44:39Z; I GAVE E145 'RESUME NORMAL SPD; CONTACT APCH.' AT APPROX XA44:49Z; I TURNED E135 15 DEGS R (SPACING) AND DSNDED TO 11000 FT. AT THIS TIME; B737 WAS NO LONGER A FACTOR; E135 WAS ABOUT 7 MI; 5 O'CLOCK POS AND DIVERGING TO E145. SPDS APPEARED COMPATIBLE. AT APPROX XB45:46Z; I ISSUED ANOTHER E135 'REDUCE SPD TO 250 KTS; CLRED DIRECT KARLA; CROSS KARLA AT 11000 FT.' I THEN MEASURED THE DISTANCE BTWN TARGETS; AND I RECALL 5.8 MI. TAKING INTO ACCOUNT THE TURN AND SPD REDUCTION OF E135; I FELT PROPER SPACING WAS PRESENT (WITH SPDS SHOWING 364 KTS OVERTAKING 381 KTS; BOTH SLOWING; AND THE REAR ACFT NEEDING TO COMPLETE A 30-ISH DEG TURN) AND SWITCHED E135 TO APCH AT APPROX XC46:25. I GOT CAUGHT SHORT WHEN I DID NOT REALIZE E145 SLOWED BY 60 KTS OVER THE NEXT 45 SECONDS; AND E135 DID NOT SLOW AS FAST.
Data retrieved from NASA's ASRS site as of May 2009 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.