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ZFW controller explains snowballing events that ended in issuing a 360 degree turn at a handoff fix to D10.
| Attributes | |
| ACN | 545829 |
| Time | |
| Date | 200204 |
| Day | Sun |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : dfw.airport |
| State Reference | TX |
| Altitude | msl single value : 14000 |
| Environment | |
| Flight Conditions | Mixed |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tower : lbb.tower |
| Operator | common carrier : air carrier |
| Make Model Name | MD-80 Series (DC-9-80) Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent : intermediate altitude |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | government : faa |
| Function | controller : radar |
| Experience | controller limited radar : 11 controller radar : 9 |
| ASRS Report | 545829 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Events | |
| Anomaly | inflight encounter : weather inflight encounter other non adherence : published procedure non adherence : clearance |
| Independent Detector | other controllera |
| Resolutory Action | controller : issued new clearance |
| Supplementary | |
| Problem Areas | Airspace Structure Weather ATC Human Performance |
| Primary Problem | Flight Crew Human Performance |
Narrative:
MD80 arrived in the middle of a complex rush of aircraft being vectored in line to be handed off to dfw TRACON. This MD80 was assigned FL240 by the high altitude controller and switched to my frequency. The pilot did not check on frequency, but did answer when I called to see if they were on frequency. I then gave the MD80 the crossing restr required. Because the aircraft got a late start down for their crossing restr, they were much higher than the aircraft in front of them and getting more tailwind. This gave the back aircraft more ground speed and required an assigned speed reduction in the vicinity of the crossing restr. The speed reduction caused the aircraft to be too high for the altitude crossing restr. Little things like forgetting to check on can snowball into larger things like having to make a 360 degree turn to make a crossing restr.
Original NASA ASRS Text
Title: ZFW CTLR EXPLAINS SNOWBALLING EVENTS THAT ENDED IN ISSUING A 360 DEG TURN AT A HDOF FIX TO D10.
Narrative: MD80 ARRIVED IN THE MIDDLE OF A COMPLEX RUSH OF ACFT BEING VECTORED IN LINE TO BE HANDED OFF TO DFW TRACON. THIS MD80 WAS ASSIGNED FL240 BY THE HIGH ALT CTLR AND SWITCHED TO MY FREQ. THE PLT DID NOT CHK ON FREQ, BUT DID ANSWER WHEN I CALLED TO SEE IF THEY WERE ON FREQ. I THEN GAVE THE MD80 THE XING RESTR REQUIRED. BECAUSE THE ACFT GOT A LATE START DOWN FOR THEIR XING RESTR, THEY WERE MUCH HIGHER THAN THE ACFT IN FRONT OF THEM AND GETTING MORE TAILWIND. THIS GAVE THE BACK ACFT MORE GND SPD AND REQUIRED AN ASSIGNED SPD REDUCTION IN THE VICINITY OF THE XING RESTR. THE SPD REDUCTION CAUSED THE ACFT TO BE TOO HIGH FOR THE ALT XING RESTR. LITTLE THINGS LIKE FORGETTING TO CHK ON CAN SNOWBALL INTO LARGER THINGS LIKE HAVING TO MAKE A 360 DEG TURN TO MAKE A XING RESTR.
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.