Airworthiness Directives; Boeing Model 737-600, -700, -700C, -800, and -900 Series Airplanes

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes, that requires replacement of the proximity switch electronics unit with a new, improved unit. This action is necessary to prevent a malfunction of the aural warning for the landing gear, leading the crew to open the circuit breaker for the aural warning horn which stops the operation of other aural warnings of malfunctions in other systems and, thus, could jeopardize a safe flight and landing. This action is intended to address the identified unsafe condition.