Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Aerospatiale Model ATR42- 200, -300, and -320 series airplanes. This proposal would require modifying the wiring of the starting rotary switch. This action is necessary to prevent the loss of electrical power supply of the DC emergency and standby buses, which could result in the loss of some electrical loads and the consequent display of erroneous information to the flight crew. This action is intended to address the identified unsafe condition.