Effects of aircraft flexure on transfer alignment performance

Transfer alignment (TA) is the alignment of an air-launched weapon inertial navigation system (INS) by using the aircraft INS before the weapon is released. By TA, both velocity and attitude errors can be estimated and sensor calibration can be made by estimating the weapon inertial sensor errors. Flexure, which occurs during the carriage of the weapon under the aircraft wing, has an important effect on the TA performance. The aim of this study is to improve the TA performance by determining the in-flight aircraft flexure. In the content of the study, velocity match (VM) method which uses velocity differences and velocity and attitude match (VAM) method which uses velocity and attitude differences between aircraft and weapon as measurements are used and the indicated measurements are processed in a Kalman Filter (KF) in which weapon velocity, attitude and inertial sensor errors are modeled as states. Cases with and without the real flight data are considered during the calculations. Accordingly, by using the simulated or real data of the coordinated turn and wing rock maneuvers made by the aircraft in the horizontal plane at various altitudes, speeds and with different durations, VM and VAM results are compared for cases which the deterministic flexures are known or modeled as noise by assuming that they are unknown. Standard deviation variations of error states calculated by the KF are used for the comparison.