Narrative:

During post flight; the pilot in command (PIC) qualified first officer (first officer) was conducting his post flight inspection of the exterior of the aircraft when he discovered a mechanics vise grip tool wedged in between the right main landing gear door and its attach point. The landing gear door itself was bent when the door closed on the tool following gear extension for landing.during the previous evening layover; maintenance had attempted to trouble-shoot a previously recorded and deferred maintenance discrepancy involving the fuel crossflow valve which is located in the main landing gear wheel well. Even though the second in command (sic) (who holds an a&P certificate) conducted an extra thorough pre-flight of the fuel system components in the wheel well due to the maintenance having been performed; he did not see the tool which apparently was left behind in the wheel well by a maintenance technician. Soot; grease; and dirt in the wheel well have rendered the area very dark and the tool in question is a very dark gray providing no contrast against the background of the wheel well compartment making detection extremely difficult.as PIC; I arrived to the aircraft after the preflight had been conducted due to a later show time than the sic following minimum rest the night prior. Since the PIC qualified sic had already performed a thorough preflight; I performed a more cursory exterior inspection as required by policy in the more limited preparation time available. Regardless; it is unlikely that I would have detected the tool either. There was a fair amount of moderate turbulence during the 5 hour flight and we speculate that the turbulence dislodged the tool from its original hidden location and moved it to a place where it could interfere with the door during landing gear extension.there was no indication in the cockpit of any issue and there was no impact on the passengers or the completion of the flight.maintenance technicians are subject to the same demanding scheduling and potentially fatiguing issues as pilots. Given the maintenance techs were working in the very early morning hours; it is possible fatigue may have played a role in a tool being left behind in the work area. Consequently; perhaps closer monitoring of maintenance scheduling and fatigue levels could have prevented the issue.also; the tool was obviously very difficult to see due to its color and the area where it may have been left behind providing no contrast. Better aircraft cleaning standards in the more remote areas of the airframe might have helped as well as high visibility reflective paint or tape being applied to a portion of the tool.finally; surgical staffs are required to count every instrument and sponge before closing after surgery. I have no idea if mechanics are required to count their tools following maintenance work but it might be a policy to consider.

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Original NASA ASRS Text

Title: A Gulfstream G450 Captain reported that during post flight inspection a mechanic's tool was found in the main landing gear door.

Narrative: During post flight; the Pilot in Command (PIC) qualified First Officer (FO) was conducting his post flight inspection of the exterior of the aircraft when he discovered a mechanics vise grip tool wedged in between the right main landing gear door and its attach point. The landing gear door itself was bent when the door closed on the tool following gear extension for landing.During the previous evening layover; maintenance had attempted to trouble-shoot a previously recorded and deferred maintenance discrepancy involving the fuel crossflow valve which is located in the main landing gear wheel well. Even though the Second in Command (SIC) (who holds an A&P certificate) conducted an extra thorough pre-flight of the fuel system components in the wheel well due to the maintenance having been performed; he did not see the tool which apparently was left behind in the wheel well by a maintenance technician. Soot; grease; and dirt in the wheel well have rendered the area very dark and the tool in question is a very dark gray providing no contrast against the background of the wheel well compartment making detection extremely difficult.As PIC; I arrived to the aircraft after the preflight had been conducted due to a later show time than the SIC following minimum rest the night prior. Since the PIC qualified SIC had already performed a thorough preflight; I performed a more cursory exterior inspection as required by policy in the more limited preparation time available. Regardless; it is unlikely that I would have detected the tool either. There was a fair amount of moderate turbulence during the 5 hour flight and we speculate that the turbulence dislodged the tool from its original hidden location and moved it to a place where it could interfere with the door during landing gear extension.There was no indication in the cockpit of any issue and there was no impact on the passengers or the completion of the flight.Maintenance technicians are subject to the same demanding scheduling and potentially fatiguing issues as pilots. Given the maintenance techs were working in the very early morning hours; it is possible fatigue may have played a role in a tool being left behind in the work area. Consequently; perhaps closer monitoring of maintenance scheduling and fatigue levels could have prevented the issue.Also; the tool was obviously very difficult to see due to its color and the area where it may have been left behind providing no contrast. Better aircraft cleaning standards in the more remote areas of the airframe might have helped as well as high visibility reflective paint or tape being applied to a portion of the tool.Finally; surgical staffs are required to count every instrument and sponge before closing after surgery. I have no idea if mechanics are required to count their tools following maintenance work but it might be a policy to consider.

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.