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Flight crew of a DHC7 expecting FL190 leaves their assigned altitude of 11000 ft when they misunderstand a strangely issued clearance to 'maintain 180.'
| Attributes | |
| ACN | 458138 |
| Time | |
| Date | 199912 |
| Day | Sun |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | navaid : sli.vortac |
| State Reference | CA |
| Altitude | msl bound lower : 11000 msl bound upper : 11600 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : sct.tracon |
| Operator | common carrier : air carrier |
| Make Model Name | DHC-7 |
| Navigation In Use | other vortac |
| Flight Phase | cruise : level |
| Route In Use | enroute airway : v64.airway |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : instrument pilot : multi engine pilot : commercial pilot : cfi |
| Experience | flight time last 90 days : 60 flight time total : 1400 flight time type : 80 |
| ASRS Report | 458138 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude non adherence : published procedure non adherence : clearance |
| Independent Detector | atc equipment other atc equipment : radar, mode c other controllera |
| Resolutory Action | controller : issued advisory |
| Supplementary | |
| Problem Areas | Environmental Factor Flight Crew Human Performance ATC Human Performance |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
Our filed altitude was FL190. The clearance we received was 'expect FL190, 10 mins after departure.' we were approximately 50 mi east of the sli VOR on V64, at an intermediate altitude of 11000 ft. Departure called and told us to 'maintain one-eight-oh.' we interpreted this as FL180. However, the communication was not delivered in the usual 'climb and maintain, flight level, etc.' one-eight-oh could mean heading, speed, or altitude. We started a climb to FL180, and at 11600 ft the controller told us we were assigned 11000 ft. We immediately went back to 11000 ft and do not know why the communication was given the way that it was. To avoid this in the future we will clarify any instructions that could be interpreted incorrectly.
Original NASA ASRS Text
Title: FLC OF A DHC7 EXPECTING FL190 LEAVES THEIR ASSIGNED ALT OF 11000 FT WHEN THEY MISUNDERSTAND A STRANGELY ISSUED CLRNC TO 'MAINTAIN 180.'
Narrative: OUR FILED ALT WAS FL190. THE CLRNC WE RECEIVED WAS 'EXPECT FL190, 10 MINS AFTER DEP.' WE WERE APPROX 50 MI E OF THE SLI VOR ON V64, AT AN INTERMEDIATE ALT OF 11000 FT. DEP CALLED AND TOLD US TO 'MAINTAIN ONE-EIGHT-OH.' WE INTERPED THIS AS FL180. HOWEVER, THE COM WAS NOT DELIVERED IN THE USUAL 'CLB AND MAINTAIN, FLT LEVEL, ETC.' ONE-EIGHT-OH COULD MEAN HDG, SPD, OR ALT. WE STARTED A CLB TO FL180, AND AT 11600 FT THE CTLR TOLD US WE WERE ASSIGNED 11000 FT. WE IMMEDIATELY WENT BACK TO 11000 FT AND DO NOT KNOW WHY THE COM WAS GIVEN THE WAY THAT IT WAS. TO AVOID THIS IN THE FUTURE WE WILL CLARIFY ANY INSTRUCTIONS THAT COULD BE INTERPED INCORRECTLY.
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.