Narrative:

Altimeter was off by 310 feet at FL410. We landed; ca was going to write it up; but discussed it with duty manager and said that it isn't off and that you can apply a correction. Even with that chart; it doesn't explain why the altimeter is all over the place.so at FL410 it's 310 feet low; at FL350 160 feet at FL320 it's almost dead on and at 10k it's 140 feet high. That just doesn't make sense. When do you apply correction? Sometimes? How do I know that while I'm doing my approach at 10k feet the plane is really 140 feet low? Or is it really high but showing low? Something is off here; seems like an unreliable standby altimeter to me. If I apply the correction on the chart for each altitude; then at least some of those altitudes are still off.I also discussed the 'altitude readings on standby altimeters (general check)' chart from the amm. I was told this chart has no application as I am not a mechanic. As a pilot I am concerned with knowing if my standby altimeter is providing reliable information. The amm page and the correction chart are the only items I've seen to help me make a decision as to when a mechanic needs to look at it.bottom line is duty manager and chief pilot felt this is not a write up. I need help understanding why not. Some airplanes are not off. After a few write ups on this in the last year; I spoke with the mechanics; they said the culprit is water in the line; dirt in the lines and in some cases the lines are getting cracked. Why would they say all that if this isn't really a problem? When do I know it is a problem and how do I use that chart and when?also; the images provided all flight level altimeter pictures represent 29.92 on all altimeters; the 10;000 altimeter represents the same local altimeter setting across all altimeters. Provide us with a procedure that we can use to ascertain the quality and reliability of information being provided by the standby altimeter.

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Original NASA ASRS Text

Title: DA2000 First Officer experienced a standby altimeter that was off by varying amounts at different altitudes. The Captain discussed the write up with the Duty Manager who believed that it should not be written up since a correction could be applied.

Narrative: Altimeter was off by 310 feet at FL410. We landed; CA was going to write it up; but discussed it with duty manager and said that it isn't off and that you can apply a correction. Even with that chart; it doesn't explain why the altimeter is all over the place.So at FL410 it's 310 feet low; at FL350 160 feet at FL320 it's almost dead on and at 10k it's 140 feet high. That just doesn't make sense. When do you apply correction? Sometimes? How do I know that while I'm doing my approach at 10k feet the plane is really 140 feet low? Or is it really high but showing low? Something is off here; seems like an unreliable standby altimeter to me. If I apply the correction on the chart for each altitude; then at least some of those altitudes are still off.I also discussed the 'Altitude readings on standby altimeters (general check)' chart from the AMM. I was told this chart has no application as I am not a mechanic. As a pilot I am concerned with knowing if my standby altimeter is providing reliable information. The AMM page and the correction chart are the only items I've seen to help me make a decision as to when a mechanic needs to look at it.Bottom line is Duty Manager and Chief Pilot felt this is not a write up. I need help understanding why not. Some airplanes are not off. After a few write ups on this in the last year; I spoke with the mechanics; they said the culprit is water in the line; dirt in the lines and in some cases the lines are getting cracked. Why would they say all that if this isn't really a problem? When do I know it is a problem and how do I use that chart and when?Also; the images provided all flight level altimeter pictures represent 29.92 on all altimeters; the 10;000 altimeter represents the same local altimeter setting across all altimeters. Provide us with a procedure that we can use to ascertain the quality and reliability of information being provided by the standby altimeter.

Data retrieved from NASA's ASRS site 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.