Ageing airplane repair assessment program for Airbus A300

Summary as a result of a commitment between the FAA and ATA the Airworthiness Assurance Task Force (AATF) steering committee requested the transport aircraft manufacturers to develop a program to assess the repairs on in-service aircraft since recent Supplemental Structural Inspection Programs (SSIP) had not been addressed to assessing repairs. The intent of the assessment program is to remove all existing ambiguities and to achieve a sufficient level of safety across the fleet by applying actual fatigue and damage tolerance criteria defined by FAR 25.571 to repaired structures. A general three stage program has been developed with major aircraft manufacturers and airlines cooperation including area/component classification, repair categorization and inspection/removal requirement establishment which is the basis for model specific repair assessment programs.

This paper describes the current status of the repair categorization activities and includes all details about the methodologies developed for determination of the inspection program for the skin on pressurized fuselages. For inspection threshold determination two methods are defined based on fatigue life approach, i.e. a simplified and a detailed method. The detailed method considers 15 different parameters to assess the influences of material, geometry, size, location, aircraft usage and workmanship on the fatigue life of the repair and the original structure. For definition of the inspection intervals a general method is developed which applies to all concerned repairs. For this the initial flaw concept is used by considering 6 parameters and the detectable flaw sizes depending on proposed nondestructive inspection methods. An alternative method is provided for small repairs allowing visual inspection with shorter intervals.