Originally Posted by
tdracer
If metal foil external to the carbon fiber structure is so important, why isn't it needed on the A350? According to what Less Hair posted, they embed copper mesh - just like Boeing - no mention of external foil in the fuel tanks...
RE external foil and embedded copper/composite issues in the fuel tank(s). The problem is that to ensure non spark the copper foil/plate must be electrically continuous between inside to outside AND the internal mesh. ONE way to do that involves copper plating of the composite around the penetrations such that it is similar to a internal-external " gasket " AND electrically continuous to the ' embedded " mesh or foil. A bit of searching on patents assigned to Boeing in the mid to late 80's can explain the details. June 14, 1988 # 4,750,981 is a start.