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ATC flight crew miscom on altitude clearance. New controller cleared reporter flight crew for a rapid descent while the supervisor was working a flight of F4's. Flight crew read back FL210 and controller had said FL310, but controller failed to hear the incorrect altitude readback. Controller supervisor intervened when noticing aircraft at FL250. B737.
| Attributes | |
| ACN | 340370 |
| Time | |
| Date | 199606 |
| Day | Thu |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : elp |
| State Reference | TX |
| Altitude | msl bound lower : 24000 msl bound upper : 35000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zab |
| Operator | common carrier : air carrier |
| Make Model Name | B737 Undifferentiated or Other Model |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise other descent other |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 180 flight time total : 7500 flight time type : 2000 |
| ASRS Report | 340370 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp pilot : flight engineer |
| Experience | flight time last 90 days : 120 flight time total : 17500 flight time type : 16000 |
| ASRS Report | 340199 |
| Events | |
| Anomaly | altitude deviation : overshoot non adherence : clearance other anomaly other |
| Independent Detector | other controllera |
| Resolutory Action | controller : issued new clearance other |
| Consequence | faa : reviewed incident with flight crew |
| Supplementary | |
| Primary Problem | ATC Human Performance |
| Air Traffic Incident | other |
Narrative:
While cruising FL350 ATC called and ask if we could make a rapid descent if cleared lower. The captain was flying and said he could if we could deviate north for some thunderstorms, a deviation was started. At this time the captain gave me the aircraft while he made a PA to the cabin to get them ready for landing. I was given FL210 which I read back. The captain finished his PA and took the aircraft at FL310. Passing FL250, descending, ZAB called and asked our altitude, and what we were descending to. We said passing FL250 on the way to FL210. At that time she said we had been cleared to FL310. We leveled at FL240 and asked for instructions. We were then cleared to lower altitude. There were no conflicts. Captain called ZAB supervisor upon landing elp. The supervisor had been working some F4's in the area. They had stayed at 17000 ft and no conflict existed. It would appear my readback of FL210 was missed and caused the confusion.
Original NASA ASRS Text
Title: ATC FLC MISCOM ON ALT CLRNC. NEW CTLR CLRED RPTR FLC FOR A RAPID DSCNT WHILE THE SUPVR WAS WORKING A FLT OF F4'S. FLC READ BACK FL210 AND CTLR HAD SAID FL310, BUT CTLR FAILED TO HEAR THE INCORRECT ALT READBACK. CTLR SUPVR INTERVENED WHEN NOTICING ACFT AT FL250. B737.
Narrative: WHILE CRUISING FL350 ATC CALLED AND ASK IF WE COULD MAKE A RAPID DSCNT IF CLRED LOWER. THE CAPT WAS FLYING AND SAID HE COULD IF WE COULD DEVIATE N FOR SOME TSTMS, A DEV WAS STARTED. AT THIS TIME THE CAPT GAVE ME THE ACFT WHILE HE MADE A PA TO THE CABIN TO GET THEM READY FOR LNDG. I WAS GIVEN FL210 WHICH I READ BACK. THE CAPT FINISHED HIS PA AND TOOK THE ACFT AT FL310. PASSING FL250, DSNDING, ZAB CALLED AND ASKED OUR ALT, AND WHAT WE WERE DSNDING TO. WE SAID PASSING FL250 ON THE WAY TO FL210. AT THAT TIME SHE SAID WE HAD BEEN CLRED TO FL310. WE LEVELED AT FL240 AND ASKED FOR INSTRUCTIONS. WE WERE THEN CLRED TO LOWER ALT. THERE WERE NO CONFLICTS. CAPT CALLED ZAB SUPVR UPON LNDG ELP. THE SUPVR HAD BEEN WORKING SOME F4'S IN THE AREA. THEY HAD STAYED AT 17000 FT AND NO CONFLICT EXISTED. IT WOULD APPEAR MY READBACK OF FL210 WAS MISSED AND CAUSED THE CONFUSION.
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.