Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 767-300F series airplanes. This proposed AD would require replacing the rotomolded duct(s) of the mix manifold system with new duct(s). This proposed AD results from a report of failures of the duct joint seal of the mix manifold system. We are proposing this AD to prevent air conditioning leakage into the mix manifold bay. Such leakage could decrease the air flow to the flight compartment and main cabin or could allow smoke into the flight compartment in the event of a fire in the main cabin or forward cargo compartment.