Narrative:

I was called by a colleague who had a engine 1 reverser log item. He was accomplishing a fim test and I had to open the fan cowls and exercise the maintenance switch on the outside fan area. The message remained latched so after ensuring the area was clear of equipment and personnel he exercised the reverse from stow to reverse while I activated the maintenance switch. When the reverser stowed I spotted splinters of wood falling from the cascade vane area from the inboard side. When we then deployed the reverser I found that there was a length of 4x2 inch wood approximately 2 feet long broken into pieces sitting on top of the 5:30 position cascade vane. It had caused damage to the cascade vane and an l duct section. The aircraft remained overnight and departed with the reverser on MEL and a missing cascade on cdl.as the wood did not enter through the fan then I believe that it was either placed behind the fan blades or in the reverser cascade area as part of a mm process at a previous station. Maybe used as an unapproved tool and undocumented. The least likely idea is that it was a malicious act and placed there on purpose.

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Original NASA ASRS Text

Title: A Maintenance Technician reported finding a piece of 2x4 in a B787 reverser that caused damage to a cascade vane and an L Duct section.

Narrative: I was called by a colleague who had a Engine 1 Reverser log item. He was accomplishing a FIM test and I had to open the fan cowls and exercise the maintenance switch on the outside fan area. The message remained latched so after ensuring the area was clear of equipment and personnel he exercised the reverse from stow to reverse while I activated the maintenance switch. When the reverser stowed I spotted splinters of wood falling from the cascade vane area from the inboard side. When we then deployed the reverser I found that there was a length of 4x2 inch wood approximately 2 feet long broken into pieces sitting on top of the 5:30 position cascade vane. It had caused damage to the cascade vane and an l duct section. The aircraft remained overnight and departed with the reverser on MEL and a missing cascade on cdl.As the wood did not enter through the fan then I believe that it was either placed behind the fan blades or in the reverser cascade area as part of a mm process at a previous station. Maybe used as an unapproved tool and undocumented. The least likely idea is that it was a malicious act and placed there on purpose.

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.