Dan D. Vicroy

SACCON Static Wind Tunnel Tests at DNW-NWB and 14'x22' NASA LaRC

Static force and pressure measurement results obtained from test campaigns in two different wind tunnels are presented. The model investigated was the generic UCAV configuration SACCON. Model design, build as well as three wind tunnel entries have been performed within the NATO/RTO AVT-161 Task Group “Assessment of Stability and Control Prediction Methods for NATO Air and Sea Vehicles”. The model has undergone static as well as dynamic tests as an international co-operation; the tests have been accompanied by corresponding numerical investigations. This paper covers the static part of the wind tunnel experiments.

UCAV model design and static experimental investigations to estimate control device effectiveness and S&C capabilities

The experimental investigations of two generic UCAV configurations with control surfaces are presented. The current paper is covering the design of the model, layout of the control surfaces as well as the static wind tunnel tests. The low speed static wind tunnel tests have been undertaken to evaluate the effectiveness of different control surfaces and control surface settings. Finally, the experimental results are used to establish a common CFD test matrix for the NATO STO Task Group AVT-201 for computer code validation and to assess the capability to predict the complex vortical flow and aerodynamic Stability and Control (S&C) characteristics of configurations with highly swept leading edges and vortex dominated flow field.

Static and Forced-Oscillation Tests of a Generic Unmanned Combat Air Vehicle

A series of three wind-tunnel static and forced-oscillation tests were conducted on a model of a generic unmanned combat air vehicle. These tests are part of an international research effort to assess the state of the art of computational fluid dynamics methods to predict the static and dynamic stability and control characteristics. The experimental data set includes not only force and moment time histories, but also surface pressure and offbody particle image velocimetry measurements. The extent of the data precludes a full examination within the scope of this paper. This paper provides a general description and selected examples of the available static and dynamic data, as well as some of the observed trends.

Low-speed Dynamic Wind Tunnel Test Analysis of a Generic 53° Swept UCAV Configuration

Several static and dynamic forced-motion wind tunnel tests have been conducted on a generic unmanned combat air vehicle (UCAV) configuration with a 53° swept leading edge. These tests are part of an international research effort to assess and advance the state-of-art of computational fluid dynamics (CFD) methods to predict the static and dynamic stability and control characteristics for this type of configuration. This paper describes the dynamic forced motion data collected from two different models of this UCAV configuration as well as analysis of the control surface deflections on the dynamic forces and moments.

Effect of spatial wind gradients on airplane aerodynamics

Wind shear is considered by many to be one of the major safety issues facing the aviation industry. The flight simulator is an important tool used to address the airborne aspects of wind-shear research. The fidelity of the analytical models that represent the airplane and the atmosphere within the flight simulation environment is, therefore, of critical importance. This paper summarizes the results of recent studies investigating the effect of a spatially sheared wind field on airplane aerodynamics. The wind-shear effect was computed using a modified vortex-lattice computer program and characterized through the formulation of wind-shear aerodynamic coefficients. The magnitude of the aerodynamic effect was demonstrated by computing the resultant change in the aerodynamics of a conventional wing and stabilizer combination on a fixed flight path through a simulated microburst. In addition, a lateral dynamics analysis is presented that exemplifies the impact of derived windshear aerodynamic coefficients on aircraft stability. The results of this research indicate that a significant amount of the control authority of the airplane may be required to counteract the wind-shear-induced forces and moments in the microburst environment. The lateral dynamics analysis revealed new shear-dependent dynamic modes that may produce both aperiodic and oscillatory unstable motions.

Development of an aerodynamic simulation model of a generic configuration for S&C analyses

The development of an aerodynamic simulation model for the inclusion in an open-loop Stability & Control model is presented. The model, based on a generic UCAV configuration, is derived from data gathered during a number of experimental campaigns conducted using various test models and facilities, and covers the full subsonic flight regime. The model includes uncertainties in key model parameters to yield an expected range of model outputs for any given condition.

A Preliminary Study of the Basic Display/Guidance Requirements for Flying Near Optimal Trajectories

The NASA has responded to the increased emphases on cost efficient operation of todays airline fleet with an ongoing research program to investigate the requirements and benefits of using new airborne guidance and pilot procedures, which result in cost optimal flight profiles that are compatible with advanced air traffic control system concepts. A trajectory optimization algorithm has been incorporated into one of NASA Langleys fixed-based simulators to investigate the pilot/cockpit interface requirements. The trajectories that are generated by this algorithm differ from conventional profiles in that they are constantly varying in both flight path angle and airspeed. Considering the dynamic nature of these profiles, conventional guidance may be insufficient for practical use. This paper summarizes the results of an initial set of piloted simulation tests to investigate the basic guidance requirements for flying the near optimal trajectories.

Experimental and Numerical Investigation of Dynamic Derivatives of an UCAV Configuration

Within the AVT-161 Task Group ,,Assessment of Stability and Control Predictions for NATO Air and Sea Vehicles“ a generic UCAV configuration with rounded leading edges was examined. This configuration is also considered in the DLR internal project UCAV-2010 and is still a challenge in the successor DLR project FaUSST. This paper will give an overview of the main objectives and responsibilities of these projects. Focus is the ability to accurately predict both static and dynamic stability characteristics of UCAV configurations using experimental and computational fluid dynamics (CFD) methods. In order to create a S&C databases for such a configuration it is also necessary to have information about the deflection of control surfaces and its impact on the flight dynamic behaviour. Therefore different wind tunnel models for several wind tunnels and flight conditions are considered and should also be part of the future RTO/AVT-201 activities. In case of slender configurations, incorporating vortical flow and high angles of attack, linear mathematical models for the data evaluation may be insufficient to describe the effects properly and non-linear mathematical models should be employed. Preliminary investigations are done to asses the accuracy of the linear models and the range of application.