Narrative:

An access panel departed from the underside of a falcon 900B aircraft in flight; near the ZZZ VOR over a desolate area. Five days prior; I had opened the panel to evaluate a slow fuel seep (within falconjet allowable limits) at a component in that bay. I had only tacked the panel in place; as I had to open it several times over a two day period. I was trying to isolate the exact location of this slow seep; and having phone consultations with falconjet technical support and the component repair facility discussing repair options. I neglected to fully close the panel at the end of this process when I moved on to other items. The panel is on the underside; between the main landing gear (medium large transport).I had not made a maintenance log entry; thinking that I was not opening it with the intent to do any work; but to evaluate a situation for future repair. An 'open' entry would have alerted me to the loose panel. To prevent a recurrence in the future; I will make a maintenance entry for any panel opening; and will put a warning flag on any open panel not readily visible.

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Original NASA ASRS Text

Title: A Mechanic with an Inspection Authority (IA) rating reports a lower fuselage access panel between the Main Landing Gears (MLG) departed a Dassault Falcon 900B aircraft after take-off. He had only 'tacked the panel' in place; while trouble shooting the location of a slow fuel seepage over a five day period.

Narrative: An access panel departed from the underside of a Falcon 900B aircraft in flight; near the ZZZ VOR over a desolate area. Five days prior; I had opened the panel to evaluate a slow fuel seep (within Falconjet allowable limits) at a component in that bay. I had only tacked the panel in place; as I had to open it several times over a two day period. I was trying to isolate the exact location of this slow seep; and having phone consultations with Falconjet Technical Support and the Component Repair facility discussing repair options. I neglected to fully close the panel at the end of this process when I moved on to other items. The panel is on the underside; between the Main Landing Gear (MLG).I had not made a Maintenance Log entry; thinking that I was not opening it with the intent to do any work; but to evaluate a situation for future repair. An 'Open' entry would have alerted me to the loose panel. To prevent a recurrence in the future; I will make a Maintenance entry for any panel opening; and will put a warning flag on any open panel not readily visible.

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.