Home Engineering Small Unmanned Fixed-Wing Aircraft Design. A Practical Approach
To go beyond a simple XFLR5 stability analysis, yet without resorting to a full Navier-Stokes solver, it is possible to gain further insights into the controllability of a new design by using one of the better aircraft flight simulator packages. These necessarily allow for the behavior of all lifting and control surface actions, and the more powerful systems will give highly realistic simulations of aircraft flight characteristics. The main difficulties in using such an approach to evaluate a new design are (a) installing all the required geometric information into the simulator and (b) having sufficient piloting skills to be able to evaluate the resulting design in a controlled manner. We have used the X-Plane system to assess aircraft designs for
Figure 13.27 Time-domain simulation for XFLR5-generated eigenvalues at 30m/s taken from Table 13.2 showing tR for the roll mode and T2 for the spiral mode.
a number of years, employing professional test pilots to give us reports on the behavior of our aircraft. We have access to a large-scale aircraft simulator environment in which to do this, see Figure 13.28. X-Plane works with a blade element momentum model and actuator disks to predict the behavior of the aircraft as it flies in an animated 3D world. It is also capable of capturing large amounts of flight data from its simulations. To install a new aircraft into X-Plane, a separate tool called Plane Maker is provided, see http://developer.x-plane.com/?article=creating- a-basic-aircraft-in-plane-maker together with the example provided at http://wiki.x-plane .com/File:A36.zip. Whether or not it is worth the expense and effort of building an accurate simulator model will depend on the project in hand; for most conventional designs, provided the XFLR5 stability analysis is acceptable and reasonable size control surfaces are planned, it is probably not necessary.
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