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37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
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An air carrier flight crew reports having followed a pilot's discretion clearance after receiving an amended clearance to descend from FL390 to FL370. The crew even read back the clearance including the earlier pilot's discretion to FL240. At FL340, the controller intervened.
| Attributes | |
| ACN | 341978 |
| Time | |
| Date | 199607 |
| Day | Mon |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : dlh |
| State Reference | MN |
| Altitude | msl bound lower : 34000 msl bound upper : 37000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zmp |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Flight Phase | descent other |
| Route In Use | arrival other arrival star : star enroute airway : zmp |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 123 flight time total : 18875 flight time type : 6480 |
| ASRS Report | 341978 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : second officer |
| Qualification | pilot : atp pilot : flight engineer pilot : instrument |
| Experience | flight time last 90 days : 150 flight time total : 11000 flight time type : 150 |
| ASRS Report | 342000 |
| Events | |
| Anomaly | altitude deviation : overshoot non adherence : clearance |
| 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:
At FL390 approaching msp for landing we were cleared down to FL240 at our discretion. Before we started down, the controller said that the next sector requested we leave FL390 for FL370 at that time. The discretionary descent to FL240 was not modified to the knowledge of any of the cockpit crew. When we reached the proper point for the beginning of a normal descent we reported out of FL370 and began a descent for FL240. The controller did not respond until approximately FL340, when he gave us a 30 degree turn to the right and told us that we had not been cleared any further down than FL370. I feel this was a classic communications problem. Our interpretation of the clearance out of FL390 was simply that ATC needed that altitude and that we would be allowed to remain as high as possible (FL370) until we were ready to continue our discretionary descent. If the controller had used words like 'cancel your descent to FL240,' or 'traffic at both FL390 and FL350, remain at FL370 until further advised,' the incident would have never occurred.
Original NASA ASRS Text
Title: AN ACR FLC RPTS HAVING FOLLOWED A PLT'S DISCRETION CLRNC AFTER RECEIVING AN AMENDED CLRNC TO DSND FROM FL390 TO FL370. THE CREW EVEN READ BACK THE CLRNC INCLUDING THE EARLIER PLT'S DISCRETION TO FL240. AT FL340, THE CTLR INTERVENED.
Narrative: AT FL390 APCHING MSP FOR LNDG WE WERE CLRED DOWN TO FL240 AT OUR DISCRETION. BEFORE WE STARTED DOWN, THE CTLR SAID THAT THE NEXT SECTOR REQUESTED WE LEAVE FL390 FOR FL370 AT THAT TIME. THE DISCRETIONARY DSCNT TO FL240 WAS NOT MODIFIED TO THE KNOWLEDGE OF ANY OF THE COCKPIT CREW. WHEN WE REACHED THE PROPER POINT FOR THE BEGINNING OF A NORMAL DSCNT WE RPTED OUT OF FL370 AND BEGAN A DSCNT FOR FL240. THE CTLR DID NOT RESPOND UNTIL APPROX FL340, WHEN HE GAVE US A 30 DEG TURN TO THE R AND TOLD US THAT WE HAD NOT BEEN CLRED ANY FURTHER DOWN THAN FL370. I FEEL THIS WAS A CLASSIC COMS PROB. OUR INTERP OF THE CLRNC OUT OF FL390 WAS SIMPLY THAT ATC NEEDED THAT ALT AND THAT WE WOULD BE ALLOWED TO REMAIN AS HIGH AS POSSIBLE (FL370) UNTIL WE WERE READY TO CONTINUE OUR DISCRETIONARY DSCNT. IF THE CTLR HAD USED WORDS LIKE 'CANCEL YOUR DSCNT TO FL240,' OR 'TFC AT BOTH FL390 AND FL350, REMAIN AT FL370 UNTIL FURTHER ADVISED,' THE INCIDENT WOULD HAVE NEVER OCCURRED.
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.