Summary
The FAA proposes to adopt a new airworthiness directive (AD) for all Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. This proposed AD would require 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 proposed AD would also require installation of a copper bonding jumper between a ground and the clamp on the tube of the forward and aft gray water composite drain masts. This proposed 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 on a Model 767-300F airplane. We are proposing 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.