Summary
We propose to adopt a new airworthiness directive (AD) for all Boeing Model 737-300, -400, and -500 series airplanes. This proposed AD would require repetitive inspections for discrepancies of the fuse pins of the inboard and outboard midspar fittings of the nacelle strut, and corrective actions if necessary. This proposed AD results from a report of corrosion damage of the chrome runout on the head side found on all four midspar fuse pins of the nacelle strut. Additionally, a large portion of the chrome plate was missing from the corroded area of the shank. We are proposing this AD to detect and correct discrepancies of the fuse pins of the inboard and outboard midspar fittings of the nacelle strut, which could result in reduced structural integrity of the fuse pins and consequent loss of the strut and separation of the engine from the airplane.