Wing Torsional Stiffness Tests Of The Active Aeroelastic Wing F A 18 Airplane

The left wing of the Active Aeroelastic Wing (AAW) F/A-18 airplane has been ground-load-tested to quantify its torsional stiffness. The test has been performed at the NASA Dryden Flight Research Center in November 1996 and again in April 2001 after a wing skin modification was performed. The primary objectives of these tests were to characterize the wing behavior before the first flight, and provide a before-and-after measurement of the torsional stiffness. Two streamwise load couples have been applied. The wing skin modification is shown to have more torsional flexibility than the original configuration has. Additionally, structural hysteresis is shown to be reduced by the skin modification. Data comparisons show good repeatability between the tests.

The Active Aeroelastic Wing research program was a joint program between the U.S. Air Force Research Laboratory and NASA established to investigate the characteristics of an aeroelastic wing and the technique of using wing twist for roll control. The flight test program employed the use of an F/A-18 aircraft modified by reducing the wing torsional stiffness and adding a custom research flight control system. The research flight control system was optimized to maximize roll rate using only wing surfaces to twist the wing while simultaneously maintaining design load limits, stability margins, and handling qualities. NASA Dryden Flight Research Center developed control laws using the software design tool called CONDUIT, which employs a multi-objective function optimization to tune selected control system design parameters. Modifications were made to the Active Aeroelastic Wing implementation in this new software design tool to incorporate the NASA Dryden Flight Research Center nonlinear F/A-18 simulation for time history analysis. This paper describes the design process, including how the control law requirements were incorporated into constraints for the optimization of this specific software design tool. Predicted performance is also compared to results from flight.Dibley, Ryan P. and Allen, Michael J. and Clarke, Robert and Gera, Joseph and Hodgkinson, JohnArmstrong Flight Research CenterAEROELASTIC RESEARCH WINGS; AEROELASTICITY; FLIGHT TESTS; NASA PROGRAMS; F-18 AIRCRAFT; CONTROLLABILITY; LOADS (FORCES); TWISTED WINGS; OPTIMIZATION; DEFLECTION; COMPUTERIZED SIMULATION; ROLL; NONLINEARITY

This report describes strain-gage calibration loading through the application of known loads of the Active Aeroelastic Wing F/A-18 airplane. The primary goal of this test is to produce a database suitable for deriving load equations for left and right wing root and fold shear; bending moment; torque; and all eight wing control-surface hinge moments. A secondary goal is to produce a database of wing deflections mesured by string potentiometers and the onboard flight deflection measurement system. Another goal is to produce strain-gage data through both the laboratory data acquisition system and the onboard aircraft data system as a check of the aircraft system. Thirty-two hydraulic jacks have applied loads through whiffletrees to 104 tension-compression load pads bonded to the lower wing surfaces. The load pads covered approximately 60 percent of the lower wing surface.

Successful flight-testing of the Active Aeroelastic Wing airplane was completed in March 2005. This program, which started in 1996, was a joint activity sponsored by NASA, Air Force Research Laboratory, and industry contractors. The test program contained two flight test phases conducted in early 2003 and early 2005. During the first phase of flight test, aerodynamic models and load models of the wing control surfaces and wing structure were developed. Design teams built new research control laws for the Active Aeroelastic Wing airplane using these flight-validated models; and throughout the final phase of flight test, these new control laws were demonstrated. The control laws were designed to optimize strategies for moving the wing control surfaces to maximize roll rates in the transonic and supersonic flight regimes. Control surface hinge moments and wing loads were constrained to remain within hydraulic and load limits. This paper describes briefly the flight control system architecture as well as the design approach used by Active Aeroelastic Wing project engineers to develop flight control system gains. Additionally, this paper presents flight test techniques and comparison between flight test results and predictions.Clarke, Robert and Allen, Michael J. and Dibley, Ryan P. and Gera, Joseph and Hodgkinson, JohnArmstrong Flight Research CenterAEROELASTICITY; FLIGHT CONTROL; FLIGHT TESTS; AEROELASTIC RESEARCH WINGS; AIRCRAFT CONTROL; FLIGHT CHARACTERISTICS; AIRCRAFT DESIGN; AERODYNAMIC CHARACTERISTICS; WING OSCILLATIONS

Successful flight-testing of the Active Aeroelastic Wing airplane was completed in March 2005. This program, which started in 1996, was a joint activity sponsored by NASA, Air Force Research Laboratory, and industry contractors. The test program contained two flight test phases conducted in early 2003 and early 2005. During the first phase of flight test, aerodynamic models and load models of the wing control surfaces and wing structure were developed. Design teams built new research control laws for the Active Aeroelastic Wing airplane using these flight-validated models; and throughout the final phase of flight test, these new control laws were demonstrated. The control laws were designed to optimize strategies for moving the wing control surfaces to maximize roll rates in the transonic and supersonic flight regimes. Control surface hinge moments and wing loads were constrained to remain within hydraulic and load limits. This paper describes briefly the flight control system architecture as well as the design approach used by Active Aeroelastic Wing project engineers to develop flight control system gains. Additionally, this paper presents flight test techniques and comparison between flight test results and predictions.

This report describes strain-gage calibration loading through the application of known loads of the Active Aeroelastic Wing F/A-18 airplane. The primary goal of this test is to produce a database suitable for deriving load equations for left and right wing root and fold shear; bending moment; torque; and all eight wing control-surface hinge moments. A secondary goal is to produce a database of wing deflections measured by string potentiometers and the onboard flight deflection measurement system. Another goal is to produce strain-gage data through both the laboratory data acquisition system and the onboard aircraft data system as a check of the aircraft system. Thirty-two hydraulic jacks have applied loads through whiffletrees to 104 tension-compression load pads bonded to the lower wing surfaces. The load pads covered approximately 60 percent of the lower wing surface. A series of 72 load cases has been performed, including single-point, double-point, and distributed load cases. Applied loads have reached 70 percent of the flight limit load. Maximum wingtip deflection has reached nearly 16 in. Lokos, William A. and Olney, Candida D. and Chen, Tony and Crawford, Natalie D. and Stauf, Rick and Reichenbach, Eric Y. and Bessette, Denis (Technical Monitor) Armstrong Flight Research Center NASA/TM-2002-210726, NAS 1.15:210726, H-2490

Understanding the wing twist of the active aeroelastic wing F/A-18 aircraft is a fundamental research objective for the program and offers numerous benefits. In order to clearly understand the wing flexibility characteristics, a model was created to predict real-time wing twist. A reliable twist model allows the prediction of twist for flight simulation, provides insight into aircraft performance uncertainties, and assists with computational fluid dynamic and aeroelastic issues. The left wing of the aircraft was heavily instrumented during the first phase of the active aeroelastic wing program allowing deflection data collection. Traditional data processing steps were taken to reduce flight data, and twist predictions were made using linear regression techniques. The model predictions determined a consistent linear relationship between the measured twist and aircraft parameters, such as surface positions and aircraft state variables. Error in the original model was reduced in some cases by using a dynamic pressure-based assumption and by using neural networks. These techniques produced excellent predictions for flight between the standard test points and accounted for nonlinearities in the data. This report discusses data processing techniques and twist prediction validation, and provides illustrative and quantitative results.Lizotte, Andrew and Allen, Michael J.Armstrong Flight Research CenterAEROELASTICITY; WINGS; FLEXIBILITY; FLIGHT SIMULATION; REAL TIME OPERATION; DYNAMIC PRESSURE; FLIGHT TESTS; ERROR ANALYSIS; DATA PROCESSING; DATA ACQUISITION

What Is Active Aeroelastic Wing The X-53 Active Aeroelastic Wing (AAW) development program is an American research project that has been completed. This project was carried out jointly by the Air Force Research Laboratory (AFRL), Boeing Phantom Works, and NASA's Dryden Flight Research Center. At NASA's Dryden Flight Research Center, the technology was flight tested on a modified McDonnell Douglas F/A-18 Hornet. Active Aeroelastic Wing Technology is a technology that blends the aerodynamics, controls, and structure of a wing in order to harness and regulate the aeroelastic twist that a wing experiences under dynamic stresses and high speeds. The use of multiple leading and trailing edge controls, such as "aerodynamic tabs," enables subtle amounts of aeroelastic twist to be controlled to provide large amounts of wing control power, while simultaneously minimizing maneuver air loads under high wing strain conditions or aerodynamic drag under low wing strain conditions. This is accomplished while maintaining a balance between the two extremes of wing strain conditions. This operation served as the very first demonstration of AAW technology on a large scale. How You Will Benefit (I) Insights, and validations about the following topics: Chapter 1: Active Aeroelastic Wing Chapter 2: Aileron Chapter 3: Aeroelasticity Chapter 4: Elevon Chapter 5: NASA X-43 Chapter 6: List of experimental aircraft Chapter 7: Boeing X-45 Chapter 8: Grumman X-29 Chapter 9: Air Force Research Laboratory Chapter 10: Boeing X-48 Chapter 11: Elevator (aeronautics) Chapter 12: Flap (aeronautics) Chapter 13: United States Air Force Stability and Control Digital DATCOM Chapter 14: Leading-edge cuff Chapter 15: Flaperon Chapter 16: Spoileron Chapter 17: McDonnell Douglas F-15 STOL/MTD Chapter 18: Boeing X-51 Waverider Chapter 19: Adaptive compliant wing Chapter 20: Leading-edge slat Chapter 21: General Dynamics-Boeing AFTI/F-111A Aardvark (II) Answering the public top questions about boeing x53 active aeroelastic wing. (III) Real world examples for the usage of boeing x53 active aeroelastic wing in many fields. (IV) 17 appendices to explain, briefly, 266 emerging technologies in each industry to have 360-degree full understanding of boeing x53 active aeroelastic wing' technologies. Who This Book Is For Professionals, undergraduate and graduate students, enthusiasts, hobbyists, and those who want to go beyond basic knowledge or information for any kind of boeing x53 active aeroelastic wing.