*These are a few suggested uses of AVDS to help students better understand how flight dynamics are modeled and how changes in the modeling parameters affect the models.*

### Aircraft Orientation

One of the most difficult concepts to demonstrate is how Euler angles relate aircraft body axes to earth axes. Since AVDS can display an aircraft at any altitude and from any vantage point, it is ideal for demonstrating the different axis systems, and describing how Euler angles relate to them.

Combining AVDS's ability to display an aircraft while interactively rotating it about the body axes, with the capabilility to display earth fixed and aircraft fixed axes, you can easily demonstrate how Euler angles relate an aircraft's altitude to the earth. In addition, by displaying and manipulating stability (wind) axes along with the other axes, you can demonstrate how the stability axes relate the aircraft's motion--through the air--to the earth. In this manner, you can use AVDS to display aircraft orientation measurements such as angle of attack, sideslip angle, flight path angle, and pitch, roll and yaw angles.

### Aircraft Motion

Using AVDS to animate prerecorded data showing an aircraft performing maneuvers, you can demonstrate phenomena such as flight path, linear velocities, and angular velocities. In addition to animating the data in forward motion, AVDS lets you stop the action, slow the action down, and reverse directions. During data animation, AVDS can display a heads-up display, velocity vector, flight path indicator, and strip charts. (Strip charts track any of the model parameters selected by the user.) Whether inside or outside the aircraft, the viewing perspective is completely user-definable, allowing you to display the best vantage point for the phenomena being demonstrated.

### Aerodynamic Coefficients and Stability Derivatives

With AVDS, you can explain and then demonstrate the effects of aerodynamic coefficients and stability derivatives. To demonstrate the effect of variation in an aerodynamic coefficient or stability derivative, first use one of the predefined aircraft models in AVDS. Then set the appropriate parameters in the model's configuration file to baseline values. Next, run the interactive simulation to demonstrate the baseline aircraft. Finally, vary the parameter file and run the interactive simulation to demonstrate the effect of the variation.

For example, to demonstrate the effect on lift due to an elevator deflection, choose a baseline value of _________, such as the default in the AVDS fighter model, initializing the aircraft at a steady state flight condition, and then commanding a step elevator deflection. By monitoring the aircraft's altitude and other related measurements, you can record the effect of a step elevator deflection at this flight condition. Repetitions of this experiment with various values of __________ will demonstrate how variations in this parameter affect the aircraft's response to elevator deflection.

### Flying Qualities

AVDS lets you demonstrate longitudinal and lateral flying qualities by flying a specially prepared aircraft model in AVDS's interacive simulation mode and recording the flight data. You can then animate the recorded data for your students by using the visual vantage points most appropriate to highlight the flying qualities. To interactively simulate flying qualities, you can either use the full aircraft model in AVDS and manipulate the appropriate stability derivatives, or insert transfer functions that contain the appropriate modes into AVDS, and then manipulate their damping ratios and natural frequencies directly.

AVDS helps your students gain a better understanding of aircraft dymanic modes, short period, phugoid, roll, dutch roll, and spiral. Use AVDS in the interactive simulation mode to develop data files that demonstrate the modes. Then use AVDS to animate this data for your students. For example, the effects of the phugoid can be exaggerated during interactive simulation and recorded. When the data is animated, your students will be able to see the phugoid effects on the aircraft. By monitoring the aircraft's altitude and velocity on the strip charts, your students can watch the exchange of altitude and velocity.

The degree of stability or instability of modes, time to double for unstable modes, is a phenomenon that is easily understood, but must be experienced to be appreciated. Interactive simulation is an ideal environment to give your students an appreciation for these effects. As an example, you can ask your students to control an aircraft with variable stability in pitch response to elevator input. By varying the degree of stability, students can experience firsthand what it is like to have an aircraft that is too stable and unresponsive, mildly unstable but controllable and responsive, or totally uncontrollable.