FAA Airworthiness Directive for Boeing 737 Max Sheds Light on Factory Errors

Boeing 737 Max AD Sheds Light on Factory Errors

Improper torquing of fasteners by Boeing factory mechanics in Max jets’ engine anti-ice exhaust ducts results in FAA airworthiness directive.

Boeing 737 Max line in Renton, Washington — Improper torquing of fasteners in engine anti-ice exhaust ducts at Boeing's 737 assembly line in Renton has led to an FAA airworthiness directive. (Photo: Gregory Polek)

By Gregory Polek • Senior Editor

March 24, 2023

An FAA airworthiness directive (AD) scheduled for publication in the Federal Register on Monday highlights improper torquing of engine anti-ice (EAI) exhaust ducts in Boeing 737 Max jets by factory mechanics. The AD calls for some 737 Max operators to inspect EAIs to determine whether all fasteners remain in place and to check their gap spacing. The directive affects 330 U.S.-registered airplanes.

The order stems from a finding during a preflight inspection of a bolt protruding through a drain hole at the bottom of the engine inlet near the EAI exhaust vent. Boeing determined that factory personnel installed some of the fasteners for EAI exhaust ducts with inadequate torque due to the use of a prohibited yoke-style torque wrench adapter at a significant angle. When used at a sufficiently large angle due to the restricted access in the area of the EAI exhaust duct, the adapter will cause what the FAA calls a significant under-torque of the installed fasteners. Inadequately torqued fasteners can loosen over time due to engine vibration, eventually causing the fastener to drop into the inlet inner barrel.

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