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An medium large transport crew misinterped a heading change to be an altitude change and deviated from assigned altitude by 800 ft.
| Attributes | |
| ACN | 525992 |
| Time | |
| Date | 200110 |
| Day | Mon |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : zjx.artcc |
| State Reference | FL |
| Altitude | msl bound lower : 31000 msl bound upper : 33000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zjx.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | Medium Large Transport, Low Wing, 2 Turbojet Eng |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : enroute altitude change |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : multi engine pilot : atp |
| Experience | flight time last 90 days : 150 flight time total : 7000 flight time type : 2000 |
| ASRS Report | 525992 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude non adherence : published procedure other anomaly other |
| Independent Detector | atc equipment : conflict alert atc equipment other atc equipment : 2 aircraft equipment : tcas aircraft equipment other aircraft equipment : 1 other controllera other controllerb |
| Supplementary | |
| Problem Areas | Flight Crew Human Performance ATC Human Performance |
| Primary Problem | ATC Human Performance |
Narrative:
During cruise flight at FL310, center cleared aircraft to maintain FL330 for traffic. Flight crew began climb to FL330. At FL315, captain asked center how long they expected aircraft to remain at FL330. Captain made inquiry due to change in flight plan altitude of FL310 to FL330. During captain's inquiry, ATC advised flight they were actually cleared on heading 330 degrees and not FL330. Captain expeditiously returned flight to FL310. I believe the following factors contributed to this altitude deviation of approximately 600-800 ft MSL: 1) original ATC phraseology of 'maintain 330 for traffic' was not properly understood by flight crew. 2) PNF responding back to ATC with same clearance of 'maintain 330' instead of stating 'leaving FL310 for FL330.' controller assumed the flight crew understood original ambiguous clearance. 3) captain beginning climb without first rechking an obvious ambiguous clearance that did not make sense at present position.
Original NASA ASRS Text
Title: AN MLG CREW MISINTERPED A HDG CHANGE TO BE AN ALT CHANGE AND DEVIATED FROM ASSIGNED ALT BY 800 FT.
Narrative: DURING CRUISE FLT AT FL310, CTR CLRED ACFT TO MAINTAIN FL330 FOR TFC. FLC BEGAN CLB TO FL330. AT FL315, CAPT ASKED CTR HOW LONG THEY EXPECTED ACFT TO REMAIN AT FL330. CAPT MADE INQUIRY DUE TO CHANGE IN FLT PLAN ALT OF FL310 TO FL330. DURING CAPT'S INQUIRY, ATC ADVISED FLT THEY WERE ACTUALLY CLRED ON HDG 330 DEGS AND NOT FL330. CAPT EXPEDITIOUSLY RETURNED FLT TO FL310. I BELIEVE THE FOLLOWING FACTORS CONTRIBUTED TO THIS ALTDEV OF APPROX 600-800 FT MSL: 1) ORIGINAL ATC PHRASEOLOGY OF 'MAINTAIN 330 FOR TFC' WAS NOT PROPERLY UNDERSTOOD BY FLC. 2) PNF RESPONDING BACK TO ATC WITH SAME CLRNC OF 'MAINTAIN 330' INSTEAD OF STATING 'LEAVING FL310 FOR FL330.' CTLR ASSUMED THE FLC UNDERSTOOD ORIGINAL AMBIGUOUS CLRNC. 3) CAPT BEGINNING CLB WITHOUT FIRST RECHKING AN OBVIOUS AMBIGUOUS CLRNC THAT DID NOT MAKE SENSE AT PRESENT POS.
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.