Dynamic Behavior and Performances Determination of DG400 Sailplane through Flight Tests

Abstract

In recent years several general techniques have been developed for the determination of the characteristics of physical systems, based on their measured responses (time histories of some observed variables). The present paper analyzes one of these techniques, known as Maximum Likelihood Method (MLM), and applies to airplane flight data. Given the equations governing the aircraft flight, the MLM allows the "estimatiorr", or extractiory of the parameters included in the mathematical model directly from flight data. The linearized aircraft equations of motion are discussed, as implemented in the performances and dynamic behavior prediction code MeMaV, developed at DPA. Then, as a validation case study, the application of the proposed approach to an aircraft whose flight characteristics are known is performed. Finally, the MeMaV code is applied to the DG400 sailplane. Details are given on the instrumentation used to acquire flight data. For the prediction of performances and dynamic behavior of the sailplane in flight, specific and detailed maneuvers have been designed and executed in order to excite dynamics modes. Control surfaces deflections, angular rates, accelerations, speed, attitude angles have all been measured and acquired during many test flights performed. All dynamic characteristics and performances of DG400 have been obtained and uncertainty and limits of the applied methods are highlighted and discussed.