Narrative:

An ATR 72 left main gear door separated in flight. No damage was found to the gear door or to any part of the aircraft during the preflight inspection. The conditions of the flight were clear skies and no turbulence. Air traffic control center instructed the flight to cross zzzzz intersection at 8;000 ft MSL. The plane was on autopilot and the captain was the pilot flying. The most likely time for the gear door separating in flight was when the crew heard a loud bang and felt a thump through the floor of the aircraft. This event occurred after leveling off in the vicinity of zzzzz intersection at 8;000 ft. The crew discussed what might have happened but could not determine the cause of the noise. ATC was not notified and no action was taken by the crew at that time since there was no known cause for the thump. No cautions or warnings appeared and all systems operated normally so it was decided that a thorough post flight inspection was all that was necessary. The flight continued to destination with a visual approach and landing. After landing; a mechanic notified the crew that the left main gear door was completely missing. During the post flight inspection by the flight crew the left main gear door was identified to be missing and an entry was made into the aircraft logbook. Operations; maintenance control and the manager on duty were all notified. No actions were taken in flight because it was not determined until after engine shut down that the gear door had separated from the aircraft. While in flight all systems operated normally and no indication of any problem existed. Once on the ground and parked the full extent of the damage was determined by a post flight inspection and an entry was made into the aircraft logbook saying the left main gear door was missing.

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Original NASA ASRS Text

Title: An ATR72's left main gear door separated in level flight with no warning or flight deck indications.

Narrative: An ATR 72 left main gear door separated in flight. No damage was found to the gear door or to any part of the aircraft during the preflight inspection. The conditions of the flight were clear skies and no turbulence. Air traffic control Center instructed the flight to cross ZZZZZ intersection at 8;000 FT MSL. The plane was on autopilot and the Captain was the pilot flying. The most likely time for the gear door separating in flight was when the crew heard a loud bang and felt a thump through the floor of the aircraft. This event occurred after leveling off in the vicinity of ZZZZZ intersection at 8;000 FT. The crew discussed what might have happened but could not determine the cause of the noise. ATC was not notified and no action was taken by the crew at that time since there was no known cause for the thump. No cautions or warnings appeared and all systems operated normally so it was decided that a thorough post flight inspection was all that was necessary. The flight continued to destination with a visual approach and landing. After landing; a mechanic notified the crew that the left main gear door was completely missing. During the post flight inspection by the flight crew the left main gear door was identified to be missing and an entry was made into the aircraft logbook. Operations; Maintenance Control and the manager on duty were all notified. No actions were taken in flight because it was not determined until after engine shut down that the gear door had separated from the aircraft. While in flight all systems operated normally and no indication of any problem existed. Once on the ground and parked the full extent of the damage was determined by a post flight inspection and an entry was made into the aircraft logbook saying the left main gear door was missing.

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.