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An air carrier medium large transport got below its assigned altitude when it misunderstood the very low altimeter setting.
| Attributes | |
| ACN | 265217 |
| Time | |
| Date | 199403 |
| Day | Wed |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | airport : anc |
| State Reference | AK |
| Altitude | msl bound lower : 1600 msl bound upper : 2000 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : anc |
| Operator | common carrier : air carrier |
| Make Model Name | Commercial Fixed Wing |
| Operating Under FAR Part | Part 121 |
| Navigation In Use | Other Other |
| Flight Phase | cruise other descent other |
| Route In Use | enroute : on vectors |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 150 flight time total : 19000 flight time type : 1000 |
| ASRS Report | 265217 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : cfi pilot : atp pilot : flight engineer |
| Experience | flight time last 90 days : 95 flight time total : 5200 flight time type : 90 |
| ASRS Report | 264911 |
| Events | |
| Anomaly | altitude deviation : overshoot inflight encounter : weather non adherence : clearance other spatial deviation |
| Independent Detector | other controllera |
| Resolutory Action | flight crew : returned to intended course or assigned course other |
| Consequence | Other |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation Operational Deviation |
| Situations | |
| ATC Facility | procedure or policy : unspecified |
Narrative:
During vectors for approach to anc ILS runway 6R, ATC gave altimeter setting 29.87 (sounded like and was read back). We had 28.97 set but, thinking we had copied wrong data in ATIS report, we changed to 29.87. Approach controller asked our altitude and we verified it was 2000 ft (cleared to 1600 ft). He stated his readout was more than 300 ft different than our reported altitude and advised altitude 'low 28.87' and to turn off our altitude encoder as it was in error. We crosschecked the radar altitude and reset the altimeters to this setting and adjusted our altitude. Rest of flight was normal.
Original NASA ASRS Text
Title: AN ACR MLG GOT BELOW ITS ASSIGNED ALT WHEN IT MISUNDERSTOOD THE VERY LOW ALTIMETER SETTING.
Narrative: DURING VECTORS FOR APCH TO ANC ILS RWY 6R, ATC GAVE ALTIMETER SETTING 29.87 (SOUNDED LIKE AND WAS READ BACK). WE HAD 28.97 SET BUT, THINKING WE HAD COPIED WRONG DATA IN ATIS RPT, WE CHANGED TO 29.87. APCH CTLR ASKED OUR ALT AND WE VERIFIED IT WAS 2000 FT (CLRED TO 1600 FT). HE STATED HIS READOUT WAS MORE THAN 300 FT DIFFERENT THAN OUR RPTED ALT AND ADVISED ALT 'LOW 28.87' AND TO TURN OFF OUR ALT ENCODER AS IT WAS IN ERROR. WE XCHKED THE RADAR ALT AND RESET THE ALTIMETERS TO THIS SETTING AND ADJUSTED OUR ALT. REST OF FLT WAS NORMAL.
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.