Narrative:

We were on leg six of a 13.5 plus hour duty day. After departure and during climb out; I noticed a check position message on the pfd and FMS. Also; due to the nature of the departure; I noticed the FMS was in inhibit mode and so; having taught all the right classes on the threats associated with inhibited FMS on; I briefed that just in case they gave us a heading to join the SID down track. After this; we became busy with ATC and were given on course. I do not remember if the check position message disappeared or not. As we continued; I was feeling tired. Then; as we progressed enroute; I noticed again that the check position message was present. So I mentioned to the first officer that the message was appearing. He hadn't noticed it until then. So; I said it may have been on since takeoff; but we may have been tired to notice it. So; I said we can correct that. I looked at the set position line on page 1 of position init; and noticed dashed lines. So; I told the first officer; we can update that by going to the 2nd page and dropping the GPS position into the scratch pad and put it in the set position line on page 1. But as I put the GPS position into the set position line select; for some reason; the FMS position shifted. All of a sudden; the previous intersection was behind us and the map on the mfd shifted as well. The airplane went toward the next fix. I was looking at the FMS when the first officer said; the FMS shifted and the airplane was turning. There was a moment of confusion at that time. I thought I'd done something wrong and immediately I centered the heading bug and asked the first officer to ask ATC for a heading. He stated to ATC that we were having some issues with our FMS and requested a heading. They put us on a heading to the south east; I believe. Then within a few seconds of all this happening; the FMS returned to proper position. Again; I do not remember how many seconds it was; but we weren't on the heading for much time when the FMS regained proper positioning. So; we told ATC that it looked as if the FMS was working normally; and we were given direct to cypress. I made sure that as we came over a fix that ATC verified our position on radar as accurate prior to continuing on the arrival. Then; I requested a second position check over deeds from ATC; which they confirmed as accurate. We continued to our destination for a visual approach. After landing; we contacted maintenance. In hindsight; there should have been some issues that we may not have been prepared for. It was only in cruise that I noticed how tired I was. Perhaps; I should have stated that a little earlier and cautioned my first officer that we need to be extra careful. The only reason I updated that position was because; unaware; I thought it may have been on all the time after takeoff and we may not have noticed after my initial awareness. Also; though I noticed this message after takeoff; I realized later that I didn't mention that to the first officer; but I did mention the FMS was in inhibit on departure. It is very difficult during these long days to decipher between tiredness and fatigue. My experience has taught me that in critical phases of flight I tend to pay detailed attention and brief thoroughly during these long days. But when that phase is over; there's a tendency to settle down from that peak awareness of possible threats and enter into a more relaxed state to identify threats. So; to prevent errors and improve recognition of them; conversation of flying duties needs to take place. For example; though I do not know why the map shifted; perhaps I should have talked to the first officer earlier when I saw that after takeoff the check position message was on. Then perhaps; if he said he hadn't seen it all the while after takeoff; then maybe I would have left it alone and eventually it would have corrected itself. Also; before I push or reset any more positions; I will be asking if we accurately show on course. Invariably it always does; but I didn't think of all these points in flight at the 13th hour of six legs. I'll definitely be briefing my first officer on these issues in the future.

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Original NASA ASRS Text

Title: A fatigued CRJ200 Captain noticed the FMS CHK POSITION alert on after takeoff but failed to take action or notify the First Officer until well into the flight when the GPS position was used to update the FMS.

Narrative: We were on leg six of a 13.5 plus hour duty day. After departure and during climb out; I noticed a CHK POSITION message on the PFD and FMS. Also; due to the nature of the departure; I noticed the FMS was in INHIBIT mode and so; having taught all the right classes on the threats associated with inhibited FMS ON; I briefed that just in case they gave us a heading to join the SID down track. After this; we became busy with ATC and were given on course. I do not remember if the CHK POSITION message disappeared or not. As we continued; I was feeling tired. Then; as we progressed enroute; I noticed again that the CHK POSITION message was present. So I mentioned to the First Officer that the message was appearing. He hadn't noticed it until then. So; I said it may have been on since takeoff; but we may have been tired to notice it. So; I said we can correct that. I looked at the set position line on page 1 of POS INIT; and noticed dashed lines. So; I told the First Officer; we can update that by going to the 2nd page and dropping the GPS position into the scratch pad and put it in the set position line on page 1. But as I put the GPS position into the set position line select; for some reason; the FMS position shifted. All of a sudden; the previous intersection was behind us and the map on the MFD shifted as well. The airplane went toward the next fix. I was looking at the FMS when the First Officer said; the FMS shifted and the airplane was turning. There was a moment of confusion at that time. I thought I'd done something wrong and immediately I centered the heading bug and asked the First Officer to ask ATC for a heading. He stated to ATC that we were having some issues with our FMS and requested a heading. They put us on a heading to the south east; I believe. Then within a few seconds of all this happening; the FMS returned to proper position. Again; I do not remember how many seconds it was; but we weren't on the heading for much time when the FMS regained proper positioning. So; we told ATC that it looked as if the FMS was working normally; and we were given direct to cypress. I made sure that as we came over a fix that ATC verified our position on radar as accurate prior to continuing on the arrival. Then; I requested a second position check over deeds from ATC; which they confirmed as accurate. We continued to our destination for a visual approach. After landing; we contacted Maintenance. In hindsight; there should have been some issues that we may not have been prepared for. It was only in cruise that I noticed how tired I was. Perhaps; I should have stated that a little earlier and cautioned my First Officer that we need to be extra careful. The only reason I updated that position was because; unaware; I thought it may have been on all the time after takeoff and we may not have noticed after my initial awareness. Also; though I noticed this message after takeoff; I realized later that I didn't mention that to the First Officer; but I did mention the FMS was in inhibit on departure. It is very difficult during these long days to decipher between tiredness and fatigue. My experience has taught me that in critical phases of flight I tend to pay detailed attention and brief thoroughly during these long days. But when that phase is over; there's a tendency to settle down from that peak awareness of possible threats and enter into a more relaxed state to identify threats. So; to prevent errors and improve recognition of them; conversation of flying duties needs to take place. For example; though I do not know why the map shifted; perhaps I should have talked to the First Officer earlier when I saw that after takeoff the CHK POSITION message was on. Then perhaps; if he said he hadn't seen it all the while after takeoff; then maybe I would have left it alone and eventually it would have corrected itself. Also; before I push or reset any more positions; I will be asking if we accurately show on course. Invariably it always does; but I didn't think of all these points in flight at the 13th hour of six legs. I'll definitely be briefing my First Officer on these issues in the future.

Data retrieved from NASA's ASRS site as of July 2013 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.