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An air carrier medium large transport crew misinterpreted a pilot's discretion clearance and deviated from its assigned altitude.
| Attributes | |
| ACN | 236915 |
| Time | |
| Date | 199303 |
| Day | Thu |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : buf |
| State Reference | NY |
| Altitude | msl bound lower : 11000 msl bound upper : 29000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zob |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Flight Phase | cruise other descent other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp pilot : flight engineer |
| Experience | flight time last 90 days : 150 flight time total : 13000 flight time type : 105 |
| ASRS Report | 236915 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : flight engineer pilot : instrument pilot : cfi pilot : commercial |
| Experience | flight time last 90 days : 150 flight time total : 1570 flight time type : 570 |
| ASRS Report | 236669 |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other |
| Independent Detector | other controllera |
| Resolutory Action | controller : issued new clearance other |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
After being cleared direct buf at FL290 we were given clearance to cross buf at 11000 ft, pilot's discretion, by ZOB. Shortly after, we were told to descend to FL280 for traffic. Again, after level off descend to FL270. The first officer was now off ATC to copy the roc ATIS. About this time, cleveland said we were cleared to FL240. Again, descent was started and a level off at FL240 was made. Approximately 42 DME southwest of buf I started a descent to cross buf at 11000 ft. A call to center on leaving FL240 was not made due to frequency congestion. As we were approaching FL230, center asked if we were maintaining FL240. We replied we were descending to cross buf at 11000 ft. Center said our cleared altitude was FL240 and we were now cleared to maintain FL230. Of course, to us, center was not clear in telling us pilot's discretion to cross buf at 11000 ft was cancelled. We incorrectly assumed the buf crossing was still valid and interim dscnts to FL280, FL270, and FL240 were to get us below other traffic. It was not evident to us FL240 was a hard altitude. Perhaps a comment by center that 'pilot's discretion' to cross buf was cancelled and maintain FL240 would have not caused the confusion. Also were we able to promptly report leaving FL240 that would have averted the misunderstanding.
Original NASA ASRS Text
Title: AN ACR MLG CREW MISINTERPRETED A PLT'S DISCRETION CLRNC AND DEVIATED FROM ITS ASSIGNED ALT.
Narrative: AFTER BEING CLRED DIRECT BUF AT FL290 WE WERE GIVEN CLRNC TO CROSS BUF AT 11000 FT, PLT'S DISCRETION, BY ZOB. SHORTLY AFTER, WE WERE TOLD TO DSND TO FL280 FOR TFC. AGAIN, AFTER LEVEL OFF DSND TO FL270. THE FO WAS NOW OFF ATC TO COPY THE ROC ATIS. ABOUT THIS TIME, CLEVELAND SAID WE WERE CLRED TO FL240. AGAIN, DSCNT WAS STARTED AND A LEVEL OFF AT FL240 WAS MADE. APPROX 42 DME SW OF BUF I STARTED A DSCNT TO CROSS BUF AT 11000 FT. A CALL TO CTR ON LEAVING FL240 WAS NOT MADE DUE TO FREQ CONGESTION. AS WE WERE APCHING FL230, CTR ASKED IF WE WERE MAINTAINING FL240. WE REPLIED WE WERE DSNDING TO CROSS BUF AT 11000 FT. CTR SAID OUR CLRED ALT WAS FL240 AND WE WERE NOW CLRED TO MAINTAIN FL230. OF COURSE, TO US, CTR WAS NOT CLR IN TELLING US PLT'S DISCRETION TO CROSS BUF AT 11000 FT WAS CANCELLED. WE INCORRECTLY ASSUMED THE BUF XING WAS STILL VALID AND INTERIM DSCNTS TO FL280, FL270, AND FL240 WERE TO GET US BELOW OTHER TFC. IT WAS NOT EVIDENT TO US FL240 WAS A HARD ALT. PERHAPS A COMMENT BY CTR THAT 'PLT'S DISCRETION' TO CROSS BUF WAS CANCELLED AND MAINTAIN FL240 WOULD HAVE NOT CAUSED THE CONFUSION. ALSO WERE WE ABLE TO PROMPTLY RPT LEAVING FL240 THAT WOULD HAVE AVERTED THE MISUNDERSTANDING.
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.