Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 737-700 and 737-800 series airplanes. This proposed AD would require performing a one-time high frequency eddy current inspection for cracking of the backup intercostals located above the cutout for the forward airstair door; doing related investigative and corrective actions if any crack is found; and doing other specified corrective actions if no crack is found. This proposed AD results from a report of fatigue cracks discovered during a full- scale fatigue test conducted by the manufacturer. We are proposing this AD to detect and correct such cracking, which could result in more extensive fatigue cracking and lead to possible loss of cabin pressure.