Stick-to-Stress Dynamic Flight Simulation for Predicting Fatigue Life and Scheduling Inspections of Aircraft

ABSTRACT:Both commercial and military aircraft are being flown/utilized for extended operational time; a more accurate prediction of residual life and the inspection interval for an individual aircraft is required, as these aging aircraft are kept in operational status. A technique for converting actual aircraft measured flight usage data into accurate calculated stresses/strains on the structural "hot spots" via physics-based, real-time aeroservoelastic simulations will be extremely useful to the Air Force to continue the operational readiness of its aging fleet. In Phase I, ZONA Technology, Inc. successfully demonstrated distributed loads calculations using the Stick-to-Stress Dynamic Flight Simulation (StS-DFS) framework and F-15 Saudi (F-15SA) flight test data, taking into account changing fuel mass. The overall objective of the Phase II effort is to establish a broad simulation capability for loads generation using StS-DFS, including store mass variation. We will use the F-15SA as a demonstration case to validate StS-DFS predicted loads with flight test data, account for variation of mass and pilot from aircraft to aircraft, generate stress time history due to various maneuvers, and perform fatigue analysis for estimation of residual fatigue life. The outcome of this effort shall be a crucial step towards the Airframe Digital Twin vision, leading to an updated life prediction and inspection interval of individual aircraft.BENEFIT:The technology developed during this Phase II effort will result in a technique for converting actual aircraft measured flight usage data into accurate calculated stresses/strains on the structural hot spots via physics-based, real-time aeroservoelastic simulations; this resultant technology is called the StS-DFS Framework. The StS-DFS Framework will have the capability to simulate the key aeroelastic coupling mechanism between structural dynamics and nonlinear unsteady aerodynamics with classical rigid body dynamics to generate a broad range of loads including the store ejection loads, maneuver loads, gust loads, buffet loads with the consideration of the effect of uncertainty associated with aircraft-to-aircraft variability, leading to an estimation of residual fatigue life of the airframe. This capability is a crucial early step towards the Airframe Digital Twin vision. The StS-DFS Framework will promote physical understanding of observed in-flight dynamic behavior by virtual flight test simulations. Since the StS-DFS Framework is able to accurately predict the fatigue life and damage of individual aircraft, it will be highly desirable to both military and commercial aircraft companies. The target customers for the StS-DFS Framework include all aircraft manufacturers, owners, and maintenance organizations, most of which are current ZONA customers. Potential customers include Edwards AFB, Eglin AFB, AFRL, NASA, NAVAIR/NAWC/Navy, US Army, Lockheed Martin, Boeing, Northrop-Grumman, Raytheon, General Atomics Aeronautical Systems, Cessna Aircraft, Pilatus, Airbus, and others.