Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 757-200 and -300 series airplanes. This proposed AD would require installing clamps on certain end caps of the overhead distribution ducts, and doing other specified and related investigative actions as necessary. This proposed AD results from finding that the end caps of the overhead distribution ducts for the air conditioning system were not bonded to the ducts with an adhesive. We are proposing this AD to detect and correct loosened end caps, which could change the air flow balance in the airplane. During a smoke event in the cargo or main electronics compartments, the incorrect balance of air flow could change the smoke clearance air capacity and result in smoke and toxic fumes penetrating the flight deck and main cabin.