Summary
The FAA is revising an earlier NPRM for an airworthiness directive (AD) that applies to certain Aerospatiale Model ATR42-200, - 300, and -320 airplanes. The original NPRM would have required doing repetitive inspections of the upper arms of the main landing gear (MLG) side braces for missing or inadequately bonded identification plates; replacing the upper arm if necessary; and replacing the side brace assembly with a modified part. The original NPRM resulted from an operator who reported experiencing an unlock warning for the MLG on the right side of the airplane. This action revises the original NPRM by proposing to require doing an ultrasonic inspection of the upper arm of the MLG side brace for any defects and related investigative/corrective actions if necessary, instead of replacing the upper arm if necessary. This action also adds airplanes to the applicability. We are proposing this supplemental NPRM to prevent cracking of the upper arms of the side braces of the MLG,which could result in failure of the MLG during landing and possible damage to the airplane and injury to the flightcrew and passengers.