Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Aerospatiale Model ATR42 series airplanes. This proposal would require modification of the electrical power supply for the standby horizon indicator. This proposal is prompted by issuance of mandatory continuing airworthiness information by a foreign civil airworthiness authority. The actions specified by the proposed AD are intended to prevent loss of the standby horizon indicator in the event of failure of emergency direct current (DC) power, which could result in reduced controllability of the airplane during instrument flight rules conditions.