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A failed microphone contributes to a misunderstanding between the controller and pilot as to a descent clearance.
| Attributes | |
| ACN | 521410 |
| Time | |
| Date | 200108 |
| Day | Mon |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | atc facility : czyz.artcc |
| State Reference | ON |
| Altitude | msl bound lower : 37600 msl bound upper : 39000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Night |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | B757 Undifferentiated or Other Model |
| Flight Phase | cruise : enroute altitude change |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 80 flight time total : 7000 flight time type : 80 |
| ASRS Report | 521410 |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : published procedure |
| Resolutory Action | controller : issued advisory controller : issued new clearance |
| Supplementary | |
| Problem Areas | ATC Human Performance Aircraft Flight Crew Human Performance |
| Primary Problem | Aircraft |
Narrative:
Toronto center cleared us to descend from FL390 to FL370. Both the first officer and myself heard the clearance. He reset the altitude control window, while I acknowledged the change to center. As we were descending through FL376 the controller said 'your mode C shows FL376 and descending check altitude.' when we said 'yes, descending to FL370 as directed,' he seemed surprised and said, 'negative, maintain FL390.' we climbed back to FL390. During this exchange of radio calls it was determined that my microphone had failed. My acknowledgement of the descent clearance may not have transmitted.
Original NASA ASRS Text
Title: A FAILED MIKE CONTRIBUTES TO A MISUNDERSTANDING BTWN THE CTLR AND PLT AS TO A DSCNT CLRNC.
Narrative: TORONTO CTR CLRED US TO DSND FROM FL390 TO FL370. BOTH THE FO AND MYSELF HEARD THE CLRNC. HE RESET THE ALT CTL WINDOW, WHILE I ACKNOWLEDGED THE CHANGE TO CTR. AS WE WERE DSNDING THROUGH FL376 THE CTLR SAID 'YOUR MODE C SHOWS FL376 AND DSNDING CHK ALT.' WHEN WE SAID 'YES, DSNDING TO FL370 AS DIRECTED,' HE SEEMED SURPRISED AND SAID, 'NEGATIVE, MAINTAIN FL390.' WE CLBED BACK TO FL390. DURING THIS EXCHANGE OF RADIO CALLS IT WAS DETERMINED THAT MY MIKE HAD FAILED. MY ACKNOWLEDGEMENT OF THE DSCNT CLRNC MAY NOT HAVE XMITTED.
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.