THIS PAPER DESCRIBES THE DESIGN PHILOSOPHY, AND DESIGN DETAILS, STRUCTURAL TESTS (INCLUDING STATIC AND FATIGUE OF ULTRASONIC SPOT-WELDS), AND FINAL MANUFACTURE AND ASSEMBLY OF LOWER ENGINE ACCESS DOORS. TWO DOORS WERE INSTALLED ON OPERATIONAL AIRCRAFT FOR AN EXTENDED FLIGHT EVALUATION. A THIRD DOOR WAS FABRICATED FOR TESTING TO VERIFY THE STRUCTURAL DESIGN WITH PROCESS CHARACTERISTICS.
