Narrative:

My first officer and I arrived at the aircraft and upon an inspection of the logbook I noticed that the aircraft had just received an airworthiness inspection. Before the first officer went to do the walk around I informed him to please make sure there are no gear pins in the aircraft as there has been an issue lately with them not being removed. He came back from the inspection and continued his normal duties.the flight operated normally to our first destination. After arrival I informed the first officer that I would conduct the preflight walk around for the return flight. Upon arrival at the left main gear well I noticed the inspection lights were left on. I did a normal look over and noticed something red I had never seen before in the very center of the top of the gear well and out of reach. I got as close to the object as possible and I realized it was some sort of pin. The flag attached to the pin was red but did not say anything on it.I then asked the first officer what it was and asked if he had seen it on his initial preflight. We determined it was some sort of pin and should not be there. We then asked the ramp agent for a stool or steps to take a closer look. I then pulled the flag down from its position and noticed on the backside it said 'remove before flight'.I called the maintenance controller and informed him of what I had found and asked him what it could be? He stated; 'I don't know.' I said; 'what do you mean you don't know. It's in the center of the main gear well and it says remove before flight.' he said he would need to call contract maintenance to remove it. The contract maintenance technician had no idea what the item was either. He went inside; called maintenance control and came back out to the plane. He said they told him it was the 'bypass solenoid lockout pin'. He spent the next 15 minutes or so removing the pin. He then came back with a signed off logbook. I again asked him what was the pin supposed to be locking out? He said it was something for the leading edge slats. I recalled actually looking at the leading edge position lights on approach and everything was in the normal range. We finally left about 40 minutes late.how to keep this event from happening again is difficult to determine; but what I will say is if the captain of an aircraft asks maintenance control to explain what an item is and what it does or affects I expect a response. If the flag had been installed with the flag hanging down in line of sight it might have been more visible to the first officer on his initial walk around.

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Original NASA ASRS Text

Title: A B737-700 flight crew; during an enroute walkaround; discovered a flagged pin of undetermined function in the left main gear well. The aircraft had undergone an intensive maintenance inspection prior to their initial departure.

Narrative: My First Officer and I arrived at the aircraft and upon an inspection of the logbook I noticed that the aircraft had just received an Airworthiness Inspection. Before the First Officer went to do the walk around I informed him to please make sure there are no gear pins in the aircraft as there has been an issue lately with them not being removed. He came back from the inspection and continued his normal duties.The flight operated normally to our first destination. After arrival I informed the First Officer that I would conduct the preflight walk around for the return flight. Upon arrival at the left main gear well I noticed the inspection lights were left on. I did a normal look over and noticed something red I had never seen before in the very center of the top of the gear well and out of reach. I got as close to the object as possible and I realized it was some sort of pin. The flag attached to the pin was red but did not say anything on it.I then asked the First Officer what it was and asked if he had seen it on his initial preflight. We determined it was some sort of pin and should not be there. We then asked the ramp agent for a stool or steps to take a closer look. I then pulled the flag down from its position and noticed on the backside it said 'REMOVE BEFORE FLIGHT'.I called the Maintenance Controller and informed him of what I had found and asked him what it could be? He stated; 'I don't know.' I said; 'what do you mean you don't know. It's in the center of the main gear well and it says Remove Before Flight.' He said he would need to call Contract Maintenance to remove it. The Contract Maintenance Technician had no idea what the item was either. He went inside; called Maintenance Control and came back out to the plane. He said they told him it was the 'bypass solenoid lockout pin'. He spent the next 15 minutes or so removing the pin. He then came back with a signed off logbook. I again asked him what was the pin supposed to be locking out? He said it was something for the leading edge slats. I recalled actually looking at the leading edge position lights on approach and everything was in the normal range. We finally left about 40 minutes late.How to keep this event from happening again is difficult to determine; but what I will say is if the Captain of an aircraft asks Maintenance Control to explain what an item is and what it does or affects I expect a response. If the flag had been installed with the flag hanging down in line of sight it might have been more visible to the First Officer on his initial walk around.

Data retrieved from NASA's ASRS site as of April 2012 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.