Airworthiness Directives; The Boeing Company Model 757-200 Series Airplanes Modified by Supplemental Type Certificate (STC) ST01529SE or STC ST02278SE

We propose to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 757-200 series airplanes modified by particular STCs. This proposed AD was prompted by reports of a main cargo door being blown past its full open position while on the ground during gusty wind conditions, which resulted in uncontrolled fall down to its closed position. This proposed AD would require installing a new placard and bracket, replacement of an existing placard, and replacement of the main cargo door control panel. We are proposing this AD to prevent damage to the main cargo door, which could result in rapid decompression, leading to in-flight breakup.