Airworthiness Directives; Boeing Model 737-100, -200, -300, -400, and -500 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to all Boeing Model 737-100, -200, -300, -400, and - 500 series airplanes, that currently requires, for certain airplanes, repetitive replacements of the airplane battery with a new or reconditioned battery and replacement of the battery charger with a new or serviceable battery charger; performing repetitive tests to determine the condition of a certain diode of the Generator Control Units (GCU); and corrective actions, if necessary. This amendment adds, for certain other airplanes, a requirement for repetitive replacements of the airplane battery with a new or reconditioned battery, and clarifies a diode test requirement. This amendment is prompted by an incident during which all electrical power was lost due to a combination of a weak or depleted battery and the failure of a certain diode of the GCU. The actions specified in this AD are intended to prevent failure of all electrically powered airplane systems, which could result in the inability to continue safe flight and landing.