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A320. ARTCC radar controller was surprised by the FMC asymptotic capture mode to track a new course in ZOB class a airspace.
| Attributes | |
| ACN | 543885 |
| Time | |
| Date | 200204 |
| Day | Wed |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | navaid : djb.vortac |
| State Reference | OH |
| Altitude | msl single value : 24000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zob.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | A320 |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | other other vortac |
| Route In Use | arrival star : cetus enroute : on vectors |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp pilot : commercial pilot : flight engineer pilot : instrument pilot : private pilot : multi engine |
| Experience | flight time last 90 days : 180 flight time total : 20500 flight time type : 600 |
| ASRS Report | 543885 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Events | |
| Anomaly | conflict : airborne less severe other anomaly other |
| Independent Detector | other controllera |
| Resolutory Action | controller : issued alert none taken : detected after the fact |
| Consequence | faa : reviewed incident with flight crew |
| Supplementary | |
| Problem Areas | Aircraft ATC Human Performance FAA |
| Primary Problem | FAA |
Narrative:
En route from pbi to dtw, we were filed over djb and the cetus arrival. South of djb at FL290, and after off-course vectoring, we were cleared direct djb and the cetus arrival. We tracked inbound to djb on the 186 degree radial and about 20 NM south of djb were cleared to FL230. The turn to intercept the djb 310 degree radial outbound was almost 60 degrees, so the A320 FMS led the turn and cut the corner as it is programmed to do. This caused ATC to query us about whether we were cleared direct to djb and the cetus arrival, and if we were intercepting course. We answered in the affirmative. He then had us stop descent at FL240. He later asked us about it again and I told him that's how the airbus FMS does over-station intercepts, and that I was surprised he hadn't seen this before. Before he handed us off to the next controller, he made a comment about the situation almost causing a conflict. We probably missed a direct overfly by 4 NM. Speed 320 KIAS assigned, ATC frequency 127.9 MHZ.
Original NASA ASRS Text
Title: A320. ARTCC RADAR CTLR WAS SURPRISED BY THE FMC ASYMPTOTIC CAPTURE MODE TO TRACK A NEW COURSE IN ZOB CLASS A AIRSPACE.
Narrative: ENRTE FROM PBI TO DTW, WE WERE FILED OVER DJB AND THE CETUS ARR. S OF DJB AT FL290, AND AFTER OFF-COURSE VECTORING, WE WERE CLRED DIRECT DJB AND THE CETUS ARR. WE TRACKED INBOUND TO DJB ON THE 186 DEG RADIAL AND ABOUT 20 NM S OF DJB WERE CLRED TO FL230. THE TURN TO INTERCEPT THE DJB 310 DEG RADIAL OUTBOUND WAS ALMOST 60 DEGS, SO THE A320 FMS LED THE TURN AND CUT THE CORNER AS IT IS PROGRAMMED TO DO. THIS CAUSED ATC TO QUERY US ABOUT WHETHER WE WERE CLRED DIRECT TO DJB AND THE CETUS ARR, AND IF WE WERE INTERCEPTING COURSE. WE ANSWERED IN THE AFFIRMATIVE. HE THEN HAD US STOP DSCNT AT FL240. HE LATER ASKED US ABOUT IT AGAIN AND I TOLD HIM THAT'S HOW THE AIRBUS FMS DOES OVER-STATION INTERCEPTS, AND THAT I WAS SURPRISED HE HADN'T SEEN THIS BEFORE. BEFORE HE HANDED US OFF TO THE NEXT CTLR, HE MADE A COMMENT ABOUT THE SIT ALMOST CAUSING A CONFLICT. WE PROBABLY MISSED A DIRECT OVERFLY BY 4 NM. SPD 320 KIAS ASSIGNED, ATC FREQ 127.9 MHZ.
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.