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.
Synopsis
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.
NASA callback
Reporter stated the flight crew heard an odd drumming noise after takeoff and than all of a sudden the noise stopped and the aircraft got quiet. During their post flight walk-around; the flight crew found a missing center section lower fuselage access panel between the two Main Landing Gears (MLG). That area was not easy to see because of the low MLGs.Reporter stated the missing panel is secured with screw type fasteners and is approximately three feet by two feet (3'x 2') in size. The exposed area is a box section with fuel manifolds and shut-off valves. No damage to the aircraft or lower antennas occurred other than the missing panel tore away from the few screws that were loosely holding the panel in place. This was his first incident since working on aircraft for over thirty-two years and he just couldn't believe he forgot to secure that panel.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.