The Federal Aviation Administration (FAA) has filed a new airworthiness directive (AD) that requires operators to replace next generation Boeing 737 drain tubes assemblies and support clamps at an estimated total cost of $14.8 million.
The new airworthiness directive (AD), which supersedes a previous directive, requires US operators of Boeing 737-600, -700, -700C, -800 and -900 models to replace the drain tube assembly on the left and right engine strut aft fairings. The FAA estimates the directive will affect 1,098 US-registered aircraft. This part includes a support clamp made from nickel alloy 625 material.
Reports of broken drain tube assemblies on the left engine strut where the clamp support resides and tube wear in additional aircraft prompted the AD. The FAA says the directive will prevent failure of the drain tube assemblies on the engine strut aft fairings, which could eventually cause an "undetected and uncontrollable" fire if flammable fluids leak into the drain system and make contact with the fairings' heat shields.
Operators will have to replace the equipment within five years after the AD becomes effective.