Narrative:

After initial climb we were on an assigned heading and told to contact departure. When we did they gave us a climb to a higher altitude and direct to pmpkn intersection. I was hand flying and my captain selected the fix and moved it in the FMS I confirmed it and said confirmed execute; nav mode please. We began a turn to the course following the flight director. Both of us thought that this looked like a drastic course change and was not what we expected as the first several fixes on the cleared course should have made a fairly straight south to north line; however this was showing us going directly west practically then returning to a point to our north. I started to range out my mfd to find where the software was trying to take us and as soon as I got one click out (which still wasn't far enough to see the fix on my screen) ATC said 'aircraft X turn right immediately to a heading of 360.' my captain spun the heading bug to 360 and I made an immediate turn to that heading. ATC queried us as to the fix we were going to and it was discovered that the fix had been incorrectly entered in the FMS as pumkn instead of pmpkn; when my captain entered it in the FMS off of the pre departure clearance. We both reviewed the clearance as entered in the FMS prior to closing the door; but I let my captain down when he was reading the clearance and I was looking at the fixes in the FMS they all looked correct as far as what I was hearing; but I failed to remember the correct spelling of this fix and did not cross check it vs the printed pre departure clearance.thus a breakdown in my CRM and monitoring skills. ATC-confirmed the correct spelling and its location in relation to our heading and once we entered it correctly and confirmed the correct spelling; location; etc. Then we were once again cleared direct to pmpkn and then handed off to the next controller. At no time was there a TCAS proximal traffic; alert; or warning. I am not sure how close that we were to any other traffic; but it didn't appear that we had gotten very close or closed on anyone at a very high rate; no traffic was observable ahead of us when we were issued the turn to the north.we both reviewed the clearance as entered in the FMS prior to closing the door; but I let my captain down when he was reading the clearance and I was looking at the fixes in the FMS they all looked correct as far as what I was hearing; but I failed to remember the correct spelling of this fix and did not cross check it vs the printed pre departure clearance. Thus a breakdown in my CRM and monitoring skills. Contributing factors were definitely overconfidence in the familiarity that my captain and I have with this routing. I know the order of the fixes by heart; thus when he was confirming them their order sounded exactly as I was expecting; and unfortunately I did not apply enough scrutiny or attention to detail when confirming this or actually reading the spelling more purposefully and confirming the spelling was correct.application of more scrutiny etc. As mentioned in the contributing factors section. Also I asked my captain after this occurred if he had confirmed the mfd data and he said that it showed us landing with about 2200 pounds of fuel so he thought that it looked ok. I did not get this done; however I think it would be a good idea to do this as well as confirming the mileage vs the release planned mileage as the incorrect fix was nearly to the western side of iowa. These things are things I failed to notice as well and even after we turned toward the fix I did not think to look at how far it was to that fix; if I had it would have probably been a strong sign that it was the incorrect fix.

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Original NASA ASRS Text

Title: Air carrier flight crew reported of a mistake with similar spelled intersections. Pilots entered incorrect intersection into FMS and did not check with the PDC for correct spelling. Aircraft turned away from intended route when it went to the misspelled intersection.

Narrative: After initial climb we were on an assigned heading and told to contact departure. When we did they gave us a climb to a higher altitude and direct to PMPKN intersection. I was hand flying and my captain selected the fix and moved it in the FMS I confirmed it and said confirmed execute; nav mode please. We began a turn to the course following the flight director. Both of us thought that this looked like a drastic course change and was not what we expected as the first several fixes on the cleared course should have made a fairly straight south to north line; however this was showing us going directly west practically then returning to a point to our north. I started to range out my MFD to find where the software was trying to take us and as soon as I got one click out (which still wasn't far enough to see the fix on my screen) ATC said 'Aircraft X turn right immediately to a heading of 360.' My captain spun the heading bug to 360 and I made an immediate turn to that heading. ATC queried us as to the fix we were going to and it was discovered that the fix had been incorrectly entered in the FMS as PUMKN instead of PMPKN; when my Captain entered it in the FMS off of the PDC. We both reviewed the clearance as entered in the FMS prior to closing the door; but I let my captain down when he was reading the clearance and I was looking at the fixes in the FMS they all looked correct as far as what I was hearing; but I failed to remember the correct spelling of this fix and did not cross check it vs the printed PDC.Thus a breakdown in my CRM and monitoring skills. ATC-confirmed the correct spelling and its location in relation to our heading and once we entered it correctly and confirmed the correct spelling; location; etc. then we were once again cleared direct to PMPKN and then handed off to the next controller. At no time was there a TCAS proximal traffic; alert; or warning. I am not sure how close that we were to any other traffic; but it didn't appear that we had gotten very close or closed on anyone at a very high rate; no traffic was observable ahead of us when we were issued the turn to the north.We both reviewed the clearance as entered in the FMS prior to closing the door; but I let my Captain down when he was reading the clearance and I was looking at the fixes in the FMS they all looked correct as far as what I was hearing; but I failed to remember the correct spelling of this fix and did not cross check it vs the printed PDC. Thus a breakdown in my CRM and monitoring skills. Contributing factors were definitely overconfidence in the familiarity that my Captain and I have with this routing. I know the order of the fixes by heart; thus when he was confirming them their order sounded exactly as I was expecting; and unfortunately I did not apply enough scrutiny or attention to detail when confirming this or actually reading the spelling more purposefully and confirming the spelling was correct.Application of more scrutiny etc. as mentioned in the contributing factors section. Also I asked my captain after this occurred if he had confirmed the MFD data and he said that it showed us landing with about 2200 pounds of fuel so he thought that it looked ok. I did not get this done; however I think it would be a good idea to do this as well as confirming the mileage vs the release planned mileage as the incorrect fix was nearly to the western side of Iowa. These things are things I failed to notice as well and even after we turned toward the fix I did not think to look at how far it was to that fix; if I had it would have probably been a strong sign that it was the incorrect fix.

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.