26

Testing Relevant to Aeroelasticity and Loads

26.1 INTRODUCTION

The clearance process relating to aeroelastic and loads issues during the design and certification phase of a new aircraft is a combination of numerical modelling backed up by testing. An outline of the main tests used to validate various elements of the aircraft mathematical model for aeroelastic issues is shown in Figure 26.1. Note how there is an opportunity to update the numerical models of each element based upon the test results. A similar series of tests are undertaken to certify aircraft for ground and flight loads. In this chapter, only a very brief outline of the methods will be given.

It must be emphasized is that no one test is capable of providing the information for full validation of the mathematical models used for certification. That must inevitably come by building up a range of test results on different aspects (e.g. structural stiffness, mass, mass distribution, centre of mass, wind tunnel tests, systems tests, etc). The ground tests can be quite accurate and are backed up by checks that show, when assembled together, that the structural dynamic and the flight response properties are both reasonable. However, tests performed in-flight to demonstrate aeroelastic stability and validate flight loads are subject to a number of uncertainties. The test set up for flight flutter testing is much less ideal (e.g. noisy environment, inadequate excitation) than that for ground vibration testing, whereas ...

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