Summary
The FAA proposes to supersede an existing airworthiness directive (AD) that applies to all Boeing Model 737-300, -400, and -500 series airplanes. The existing AD currently requires repetitive inspections for discrepancies of the fuselage skin under the dorsal fin assembly, and repairing if necessary. This proposed AD would require an inspection for any chafing or crack in the fuselage skin and abrasion resistant coating at the dorsal fin landing, an inspection for damage to the dorsal fin seals, attach clip, and seal retainer, and other specified and corrective actions as necessary. The new proposed requirements would end the need for the existing repetitive inspections. This proposed AD results from a report of an 18-inch crack found in the fuselage skin area under the blade seals of the nose cap of the dorsal fin due to previous wear damage, and additional reports of fuselage skin wear. We are proposing this AD to prevent discrepancies of the fuselage skin, which could result in fatigue cracking due to cabin pressurization and consequent rapid in-flight decompression of the airplane fuselage.