A B757 crew reported mis-set Captain and standby altimeters that were not noticed until after ATC questioned the aircraft's cleared altitude.
Synopsis
A B757 crew reported mis-set Captain and standby altimeters that were not noticed until after ATC questioned the aircraft's cleared altitude.
Narrative
In the descent to 8;000 FT; around FL180 I inadvertently set 29.20 instead of 30.20 on both my altimeter and the standby altimeter. I think we spoke the correct altimeter when discussing the ATIS; I don't know why I made this dumb mistake. I think I knew the correct altimeter in my mind and dialed up 29.20 and then subsequently thought I'd dialed up 30.20. I do not know if the First Officer set 29.20 or 30.20; unfortunately; it is now clear that I only crosschecked and saw the last two numbers of his altimeter. We were vectored west of the final approach intersection; planning a visual approach; and although one of us called out of 9 for 8; I did not effectively crosscheck his or my altimeter again at this point as is my habit after reading past reports. We checked in with a new approach frequency and were immediately cleared for 4;000 FT; however she asked 'What altitude did you say you were leaving?' in a tone of voice that got our attention. At this point both the First Officer and I realized that my altimeters were mis-set and I immediately corrected my settings. ATC did not indicate that there was a problem and we were not aware of any traffic conflicts. I find a mistake of this magnitude totally unacceptable. My personal corrective action includes being very careful to set the correct altimeters on my side; not rushing this step or performing it mindlessly and also looking at the entire altimeter setting; not just the last two numbers.
Second reporter narrative
We were in a descent when we reported in to Approach Control. Our outside scan for traffic was greater than normal because the TCAS was placarded as inoperative. When I called in to Approach; my outside scan for traffic just happened to be covering the area to the left so I naturally read the altitude from the Captain's Altimeter. Shortly after; Approach Control asked us to confirm the altitude that we were passing. It then became clear that our altimeters were showing different readings. We then noticed that we had 2 different altimeter settings after which the Captain corrected his altimeter settings. I then corrected the reported altitude passing with Approach Control.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.