Narrative:

After being assigned FL180; as pilot flying I was beginning to level off at FL180 with the standard pressure setting of 29.92 in my altimeter. After the altitude caps message had been displayed my captain hinted that I should use the local pressure setting of 30.39 in the altimeter which I hastily rolled in and then he reselected vs and we descended to FL180 once again with 30.39 in the altimeter. The workload was high during this time given multiple step down altitude assignments; crossing restrictions; speed reductions and even a vector for sequencing. After the aircraft captured FL180 with the local pressure setting I admitted to the captain that I was unsure whether I should use the local setting or the standard setting in an effort to subtly verify the situation at which time he acknowledged we should use the standard setting. Upon rolling the standard setting into the altimeter we realized we were almost 400 ft below our assigned altitude and initiated a climb back up to FL180 and recaptured FL180 with the standard pressure setting set. No further issues were realized with this error and no contact was made to ATC or by ATC to us regarding the error. This was the first continuous duty over night I had done this reserve period and the 3rd for my captain in a row. I attribute this error to both a high workload and to fatigue from the continuous duty over night; especially from the 3 consecutive my captain had flown. Threat of an altitude deviation can be severe in certain circumstances of course but in this scenario there was no perceived threat. I cannot think of any procedural changes that could be made which could have prevented this. As mentioned above I believe this can be contributed to both a high workload during the time the error occurred and also the crew being tired.

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Original NASA ASRS Text

Title: A CRJ200 First Officer reported leveling a FL180 using the standard altimeter when the local altimeter was 30.39 which made the aircraft 400 FT low; an error which was corrected.

Narrative: After being assigned FL180; as pilot flying I was beginning to level off at FL180 with the standard pressure setting of 29.92 in my altimeter. After the ALT CAPS message had been displayed my Captain hinted that I should use the local pressure setting of 30.39 in the altimeter which I hastily rolled in and then he reselected VS and we descended to FL180 once again with 30.39 in the altimeter. The workload was high during this time given multiple step down altitude assignments; crossing restrictions; speed reductions and even a vector for sequencing. After the aircraft captured FL180 with the local pressure setting I admitted to the Captain that I was unsure whether I should use the local setting or the standard setting in an effort to subtly verify the situation at which time he acknowledged we should use the standard setting. Upon rolling the standard setting into the altimeter we realized we were almost 400 FT below our assigned altitude and initiated a climb back up to FL180 and recaptured FL180 with the standard pressure setting set. No further issues were realized with this error and no contact was made to ATC or by ATC to us regarding the error. This was the first continuous duty over night I had done this reserve period and the 3rd for my Captain in a row. I attribute this error to both a high workload and to fatigue from the continuous duty over night; especially from the 3 consecutive my Captain had flown. Threat of an altitude deviation can be severe in certain circumstances of course but in this scenario there was no perceived threat. I cannot think of any procedural changes that could be made which could have prevented this. As mentioned above I believe this can be contributed to both a high workload during the time the error occurred and also the crew being tired.

Data retrieved from NASA's ASRS site as of April 2012 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.