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After spending about an hour in the holding pattern, a flight crew finds themselves 250 ft off their assigned altitude due to the issuance of a new altimeter setting that has changed with the rapidly passing WX front.
| Attributes | |
| ACN | 507700 |
| Time | |
| Date | 200104 |
| Day | Wed |
| Local Time Of Day | 0601 To 1200 |
| Place | |
| Locale Reference | atc facility : zau.artcc |
| State Reference | IL |
| Altitude | msl bound lower : 10750 msl bound upper : 11000 |
| Environment | |
| Light | Daylight |
| Aircraft 1 | |
| Operator | common carrier : air carrier |
| Make Model Name | Fokker 100 |
| Flight Phase | descent : approach |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp |
| ASRS Report | 507700 |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude inflight encounter other non adherence : far non adherence : published procedure |
| Resolutory Action | flight crew : returned to assigned altitude |
| Consequence | other |
| Supplementary | |
| Problem Areas | Flight Crew Human Performance Weather ATC Human Performance |
| Primary Problem | Weather |
Narrative:
Upon initial descent from FL240 to 13000 ft, ZAU gave us the altimeter of 30.15 for the area. Through FL180 we reset our altimeters to 30.15 and leveled at 13000 ft. We subsequently went into a 45-60 min hold. After we were released from holding we were given a descent to 11000 ft. Upon leveling at 11000 ft ZAU asked us our altitude and we reported 11000 ft. The controller then read us the current ZAU altimeter of 29.75. This, of course, changed our MSL altitude to approximately 10750 ft MSL. We immediately corrected back to 11000 ft. A rapidly moving front caused the altimeter to change for the area we were initially descending over versus the ZAU altimeter some 60 mins later. There appeared to be no traffic conflicts as a result of this descent and ZAU made no further comments.
Original NASA ASRS Text
Title: AFTER SPENDING ABOUT AN HR IN THE HOLDING PATTERN, A FLT CREW FINDS THEMSELVES 250 FT OFF THEIR ASSIGNED ALT DUE TO THE ISSUANCE OF A NEW ALTIMETER SETTING THAT HAS CHANGED WITH THE RAPIDLY PASSING WX FRONT.
Narrative: UPON INITIAL DSCNT FROM FL240 TO 13000 FT, ZAU GAVE US THE ALTIMETER OF 30.15 FOR THE AREA. THROUGH FL180 WE RESET OUR ALTIMETERS TO 30.15 AND LEVELED AT 13000 FT. WE SUBSEQUENTLY WENT INTO A 45-60 MIN HOLD. AFTER WE WERE RELEASED FROM HOLDING WE WERE GIVEN A DSCNT TO 11000 FT. UPON LEVELING AT 11000 FT ZAU ASKED US OUR ALT AND WE REPORTED 11000 FT. THE CTLR THEN READ US THE CURRENT ZAU ALTIMETER OF 29.75. THIS, OF COURSE, CHANGED OUR MSL ALT TO APPROX 10750 FT MSL. WE IMMEDIATELY CORRECTED BACK TO 11000 FT. A RAPIDLY MOVING FRONT CAUSED THE ALTIMETER TO CHANGE FOR THE AREA WE WERE INITIALLY DSNDING OVER VERSUS THE ZAU ALTIMETER SOME 60 MINS LATER. THERE APPEARED TO BE NO TFC CONFLICTS AS A RESULT OF THIS DSCNT AND ZAU MADE NO FURTHER COMMENTS.
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.