Pre-test Analyses for Flight Flutter Test of an EASA CS-23 Aircraft

Small aircraft manufacturers are typically constrained by stringent budget requirements. Among all the cost headings the certification process cost is a non-negligible part, especially as regards the tests. Flight Flutter Test is a crucial means to state flutter clearance. A fundamental issue connected to this test is the choice of good excitation devices or maneuvers in order to excite the flutter mode. Different types of excitation means are available, each one more or less suitable to the aircraft which will be tested. The choice of the best excitation device among the various available solutions basically depends upon the flutter mode frequency to be excited as well as time and budget constraints. If a rational analysis able to predict the reliability of the excitation is available, significant time/cost expenses reduction can be achieved. In this paper a pre-test analysis aimed at correctly exciting the flutter mode during Flight Flutter test on an EASA CS-23 aircraft is presented. The Aeroelastic Dynamic Response under external forces (State Space representation and modal approach) has been investigated to assess the reliability of two different types of excitation devices: the control surface pulse (with zero additional cost) and the pyrotechnical thruster (bonker). Actually no pre-Flight Flutter Test rational analyses are strictly required by Airworthiness Requirements, but it would be desirable if such an approach was followed, especially in the viewpoint of a better addressing of the test and of course the cost reduction.