Ensip4 englPhases of the development and the proof of a component/part repair. 1. Understanding of the problem respectively failure: Problem analysis/ failure investigation: Identification of the failure mechanism. Identification of the primary and secondary innfluences/causes. Analysis of Failure investigations and statistics. Overhaul manuals. Analytical considerations/calculations.2. Problem relevant component test: The suitability will be shown with the reproduction of the service/operation failure. Comparative component tests between new parts, used parts and if necessary several repair versions.4. Proof at the operator: Fleetleader principle. Sampling investigations. Monitoring in the assembled condition (e.g., with borescope)3. Proof with aeroengine tests at the test rig.