Narrative:

After arriving at the airport at xa:10 and multiple delays from ATC; we departed at xd:00. On climb out; I the ca and PF; asked for gear retraction and as I did we received a left main down gear disagree on the EICAS. After transferring the controls to my first officer; I ran the QRH procedure and determined that a gear pin and been left in the left main by maintenance after being in the hangar overnight. My first officer did not notice the gear pin in the left main during his walk-around and we both missed that one was not present during the originating check. We returned to ZZZ; contacted maintenance; dispatch; and my assistant chief pilot for further instruction. Maintenance came out; removed the pin; and signed the aircraft back to an airworthy status. We departed about an hour later.the failure of ZZZ line maintenance to remove the gear pin; the failure of the first officer to see that a gear pin had still be inserted; and the failure of the PIC to verify that all 4 were on board during the originating check. As the PIC and a new captain; I was distracted by the two separate flow delays we received from ATC due to poor weather and high winds [at our destination]. I was focused on accommodating passengers; ensuring we had enough fuel; and trying to do my best to manage what was in front of me. Although I glanced at the pin holder as I always do during the originating check; I failed to notice that one was missing. The pins themselves are very small; but the flags that are attached are quite large and sometimes create the illusion that they are all in place. Specifically counting 4 pins as opposed to simply stating 'removed' during the originating check would help me as the PIC ensure that; indeed; all of the pins were removed.

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Original NASA ASRS Text

Title: CRJ-200 flight crew reported they had to return to the airport because the left main gear pin was not removed after Maintenance was performed the previous night.

Narrative: After arriving at the airport at XA:10 and multiple delays from ATC; we departed at XD:00. On climb out; I the CA and PF; asked for gear retraction and as I did we received a left main down gear disagree on the EICAS. After transferring the controls to my FO; I ran the QRH procedure and determined that a gear pin and been left in the left main by Maintenance after being in the hangar overnight. My FO did not notice the gear pin in the left main during his walk-around and we both missed that one was not present during the originating check. We returned to ZZZ; contacted Maintenance; Dispatch; and my assistant chief pilot for further instruction. Maintenance came out; removed the pin; and signed the aircraft back to an airworthy status. We departed about an hour later.The failure of ZZZ line maintenance to remove the gear pin; the failure of the first officer to see that a gear pin had still be inserted; and the failure of the PIC to verify that all 4 were on board during the originating check. As the PIC and a new Captain; I was distracted by the two separate flow delays we received from ATC due to poor weather and high winds [at our destination]. I was focused on accommodating passengers; ensuring we had enough fuel; and trying to do my best to manage what was in front of me. Although I glanced at the pin holder as I always do during the originating check; I failed to notice that one was missing. The pins themselves are very small; but the flags that are attached are quite large and sometimes create the illusion that they are all in place. Specifically counting 4 pins as opposed to simply stating 'removed' during the originating check would help me as the PIC ensure that; indeed; all of the pins were removed.

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.