AD FAA-2007-29063

We are adopting a new airworthiness directive (AD) for all Boeing Model 767 airplanes. This AD requires a one-time inspection to determine the material of the forward and aft gray water drain masts. For airplanes having composite gray water drain masts, this AD also requires installation of a ground bracket and a bonding jumper between a ground bracket and the clamp on the tube of the forward and aft gray water composite drain masts. This AD results from a report of charred insulation blankets and burned wires around the forward gray water composite drain mast found during an inspection of the forward cargo compartment. We are issuing this AD to prevent a fire near a composite drain mast and possible disruption of the electrical power system caused by a lightning strike on a composite drain mast, which could result in the loss of several functions essential for safe flight.