Abstract:
The V-22 SAFE (Structural Appraisal of Fatigue Effects) is a software program for the V-22 Osprey tiltrotor aircraft that calculates fatigue damage for serialized components based on the aircraft's actual usage instead of a pre-defined design spectrum. SAFE allows life limited aircraft components to remain on the aircraft beyond the initially defined fatigue life if the aircraft was flown less aggressively than the design spectrum. Although fatigue lives for the various components are determined with the same design usage spectrum for the aircraft, different maneuvers within that design spectrum will drive the fatigue damage assessment for different components. For example, a component in the rotor system may be sensitive to high g maneuvers in helicopter mode, while the airframe is more sensitive to hard landings and taxi conditions. Aircraft that fly a milder usage will incur a lower operating cost since components are not replaced as often. With SAFE in operation, a few components will be replaced early if severe loadings are encountered. Trending, however, indicates that fleet aircraft generally operate below the loading thresholds of the design usage spectrum. Only flight test aircraft that are often flown at the edge of the envelope see high loadings more frequently than the design usage spectrum. With current fleet usage trends, a cost assessment of individual components by SAFE analysis shows that savings can be significant.