Simulation to Flight Test for a UAV Controls Testbed

The United States Air Force Test Pilot School (TPS) performs six to eight flight test management projects (TMP) annually. The TMPs cover all aspects of flight test including performance, flying qualities, avionic systems, and human factors. The flight tests are performed for a wide variety of government agencies and commercial sector companies. Test teams are composed of TPS students with a broad base of aviation and research flight experience. Student teams consist of four to six students made up of a 50/50 percent pilot/engineer mix. The test projects address all phases of testing from program introduction, through test plan working groups, technical/safety review boards, and test execution, to final oral and written reports. The test execution occurs over a period of 3 to 4 weeks and generally encompasses 4 to 20 flight test sorties. This paper provides the background of the USAF Test Pilot School program in general and the test management projects in particular. An overview of TPS technical capabilities and resources is provided. Examples of recent TMPs are detailed. These examples include efforts with Air Force research laboratories, Air Force major commands, and Technology Transfer programs using Cooperative Research and Development Agreements between the government and private companies INTRODUCTION The United States Air Force Test Pilot School (TPS) is the premier institute for training test pilots, test navigators, and flight test engineers in the conduct of flight test and evaluation of research, prototype, and production aerospace vehicles, systems, and weapons. The capstone event of the TPS curriculum is the test management program (TMP) in which student teams perform an extensive flight test project in support of a broad base of outside agencies. The TMP provides comprehensive end-to-end training in all phases of test management and execution. These programs provide students with practical hands-on test experience from program introduction to writing the final report and providing oral presentations of test results, conclusions, and recommendations to the customer and Air Force Flight Test Center (AFFTQ leadership and technical personnel. The program presents students the opportunity to apply the technical, management, and leadership concepts taught during the course. Emphasis is placed on understanding customer technical requirements within the constraints of cost and schedule demands. To date, TPS has been exceptionally successful in meeting customer requirements and providing real world training for its students. The purpose of this paper is to highlight our recent programs, and to inform outside agencies of our capabilities to perform low cost, quick-reaction flight test programs. USAF TEST PILOT SCHOOL COURSE OVERVIEW The USAF Test Pilot School provides training in three courses: the Experimental Test Pilot Course, Test Navigator Course, and Flight Test Engineer Course. The courses are integrated to instill cooperation and understanding between test team members which is essential for successful flight test operations. Data group teams plan, fly, evaluate, and report on selected test projects throughout the course. The flying program for the pilots develops the knowledge, flying precision, and powers of observation necessary for successful flight evaluations. The flying program for navigators and engineers leads to an understanding of problems pilots encounter and familiarizes them with airborne test tasks needed to accomplish precise flight test techniques. Navigators and engineers perform extensive evaluations of airborne avionics and weapons systems to determine suitability under operational conditions. The course is divided into four phases: (1) Performance, (2) Flying Qualities, (3) Systems Test, and (4) Test Management The Performance Phase develops the theory and methods of evaluating aircraft takeoff, climb, cruise, descent, turn, acceleration, propulsion, and landing performance. The Flying Qualities Phase examines the stability and control characteristics which influence the ease of safely flying the aircraft during steady and maneuvering flight in execution of the total mission. During this phase, aircraft are tested to determine static and dynamic characteristics, estimate stability parameters, evaluate flight control system effectiveness, and measure engine-out handling quality characteristics. The Systems Test Phase evaluates aircraft avionics and their system integration. The Performance, Flying Qualities, and System Test Phases all have integrated academic and flying programs to maximize student training effectiveness. The Test Management Phase academics are integrated throughout the program with the actual test management project execution occurring during the latter part of the course. USAF TEST PILOT SCHOOL TECHNICAL RESOURCES The curriculum is supported with state-of-the-art instrumented aircraft and contemporary data acquisition and analysis systems. TPS serves as a self-contained Combined Test Force (CTF) providing extensive technical capabilities for complete flight test engineering. TPS instructs basic flight test techniques with four instrumented T-38A aircraft. The T-38A aircraft are instrumented with sensitive cockpit instrumentation (airspeed, altimeter, mach, g, angle of attack, and sideslip gauges) and a programmable data acquisition system. All four aircraft possess onboard data recorders and telemetry

: The development of system identification technology was undertaken to provide for more effective aircraft flight testing by reducing the time required to conduct specific tests and/or to provide for a more comprehensive data analysis. F-14A and TA-4J flight test results presented demonstrate that the flight time required to obtain stability and control data can be significantly reduced without loss in accuracy of conventional flight test derived parameters. Presentation of S-3A and EA-6B system identification results demonstrate that this technology can be successfully used to update the aerodynamic data bases of modern jet aircraft from flight test data. These system identification results are compared with wind tunnel data and flight test derived parameters to demonstrate the accuracy of this new technology. Applications of this technology to integrate several areas of aircraft flight testing are discussed. (Author)

As part of the COUNTER program, cooperative control algorithms have been designed, implemented, and tested. This paper describes challenges, and their solutions, that were encountered during the program. The cooperative control challenges include: system configuration, suitability of the algorithms, and algorithm implementation into the system. During flight tests challenges arose such as: selection of autopilot, generation of flyable trajectories, and ability to image targets. In order to advance the state-of-the-art of Intelligence Surveillance and Reconnaissance (ISR) using Unmanned Aerial Vehicles (UAVs) over urban areas, researchers from the Air Force Research Laboratory conducted a project called Cooperative Operations in UrbaN TERrain (COUNTER). COUNTER consists of basic research, algorithm and ground station development, and flight tests. The concept employed in COUNTER is operator-on-the-loop control of Small unmanned Aerial Vehicles (SAVs) and Micro unmanned Aerial Vehicles (MAVs) performing cooperative multilevel ISR. In this concept, a single ground operator controls a single SAV, that flies high enough to view large portions of the urban area, and a team of four MAVs, that fly low enough to get good resolution images of objects selected from the SAV video. For an overview of the COUNTER program, see Jodeh 2008. 1 Since this program has included everything from concept to flight test, there were many conceptual and practical challenges to overcome. These challenges can be separated into two categories: those involving the cooperative control algorithms, and those involving vehicle control. The remainder of this paper provides an overview of the challenges that were encountered, explains how they were resolved, and discusses the lessons learned during the project.

The Landing and Impact Research Facility (LandIR) at NASA Langley Research Center is a 240 ft. high A-frame structure which is used for full-scale crash testing of aircraft and rotorcraft vehicles. Because the LandIR provides a unique capability to introduce impact velocities in the forward and vertical directions, it is also serving as the facility for landing tests on full-scale and sub-scale Orion spacecraft mass simulators. Recently, a threedimensional photogrammetry system was acquired to assist with the gathering of vehicle flight data before, throughout and after the impact. This data provides the basis for the post-test analysis and data reduction. Experimental setups for pendulum swing tests on vehicles having both forward and vertical velocities can extend to 50 × 50 × 50 foot cubes, while weather, vehicle geometry, and other constraints make each experimental setup unique to each test. This paper will discuss the specific calibration techniques for large fields of views, camera and lens selection, data processing, as well as best practice techniques learned from using the large field of view photogrammetry on a multitude of crash and landing test scenarios unique to the LandIR.

In support of NASA's Fly-By-Light/Power-By-Wire (FBL/PBW) program, a series of flight tests were conducted by NASA Langley Research Center in February, 1995. The NASA Boeing 757 was flown past known RF transmitters to measure both external and internal radiated fields. The aircraft was instrumented with strategically located sensors for acquiring data on shielding effectiveness and internal coupling. The data are intended to support computational and statistical modeling codes used to predict internal field levels of an electromagnetic environment (EME) on aircraft. The software was an integral part of the flight tests, as well as the data reduction process. The software, which provided flight test instrument control, data acquisition, and a user interface, executes on a Hewlett Packard (HP) 300 series workstation and uses HP VEEtest development software and the C programming language. Software tools were developed for data processing and analysis, and to provide a database organized by frequency bands, test runs, and sensors. This paper describes the data acquisition system on board the aircraft and concentrates on the software portion. Hardware and software interfaces are illustrated and discussed. Particular attention is given to data acquisition and data format. The data reduction process is discussed in detail to provide insight into the characteristics, quality, and limitations of the data. An analysis of obstacles encountered during the data reduction process is presented.

An airborne differential absorption lidar (DIAL) system has been developed at the NASA Langley Research Center for the remote measurement of water vapor (H2O) and aerosols in the lower troposphere. Significant modifications to the laser transmitters and other major subsystems have been implemented during the past two years to improve the system's performance and field reliability. The previous configuration of the airborne H2O DIAL system and the associated atmospheric data collected during flight tests at Wallops Flight Facility are described in detail in two recently published papers (Higdon et al., 1994 and Ponsardin et al., 1994). The modified system is to be flight tested in late 1994, and the system performance characteristics and preliminary atmospheric H2O and aerosol data from these flights are discussed in this paper.

Loiter Attack Munition Flight Test Program

This paper describes the latest efforts to develop an Automated UAV Mission System (AUMS) for small vertical takeoff and landing (VTOL) unmanned air vehicles (UAVs). In certain applications such as force protection, perimeter security, and urban surveillance a VTOL UAV can provide far greater utility than fixed-wing UAVs or ground-based sensors. The VTOL UAV can operate much closer to an object of interest and can provide a hover-and-stare capability to keep its sensors trained on an object, while the fixed wing UAV would be forced into a higher altitude loitering pattern where its sensors would be subject to intermittent blockage by obstacles and terrain. The most significant disadvantage of a VTOL UAV when compared to a fixed-wing UAV is its reduced flight endurance. AUMS addresses this disadvantage by providing forward staging, refueling, and recovery capabilities for the VTOL UAV through a host unmanned ground vehicle (UGV), which serves as a launch/recovery platform and service station. The UGV has sufficient payload capacity to carry UAV fuel for multiple launch, recovery, and refuel iterations. The UGV also provides a highly mobile means of forward deploying a small UAV into hazardous areas unsafe for personnel, such as chemically or biologically contaminated areas. Teaming small UAVs with large UGVs can decrease risk to personnel and expand mission capabilities and effectiveness. There are numerous technical challenges being addressed by these development efforts. Among the challenges is the development and integration of a precision landing system compact and light enough to allow it to be mounted on a small VTOL UAV while providing repeatable landing accuracy to safely land on the AUMS. Another challenge is the design of a UGV-transportable, expandable, self-centering landing pad that contains hardware and safety devices for automatically refueling the UAV. A third challenge is making the design flexible enough to accommodate different types of VTOL UAVs, such as the AAI iSTAR ducted-fan vehicle and small helicopter UAVs. Finally, a common command-and-control architecture which supports the UAV, UGV, and AUMS must be developed and interfaced with these systems to allow fully autonomous collaborative behaviors. Funded by the Joint Robotics Program, AUMS is part of a joint effort with the Air Force Research Laboratory and the Army Missile Research Development and Engineering Command. The objective is to develop and demonstrate UGV-UAV teaming concepts and work with the warfighter to ensure that future upgrades are focused on operational requirements. This paper describes the latest achievements in AUMS development and some of the military program and first responder situations that could benefit from this system.

Beech 1900D flight test to characterize propeller noise on the fuselage exterior

NASA Langley Research Center (LaRC) and The MITRE Corporation (MITRE) have developed - and successfully demonstrated - an integrated simulation-to-flight capability for evaluating sense and avoid (SAA) system elements. This integrated capability consists of a MITRE developed fast-time computer simulation for evaluating SAA algorithms, and a NASA LaRC surrogate unmanned aircraft system (UAS) equipped to support hardware and software in-the-loop evaluation of SAA system elements (e.g., algorithms, sensors, architecture, communications, autonomous systems), concepts, and procedures. The fast-time computer simulation subjects algorithms to simulated flight encounters/ conditions and generates a fitness report that records strengths, weaknesses, and overall performance. Reviewed algorithms (and their fitness report) are then transferred to NASA LaRC where additional (joint) airworthiness evaluations are performed on the candidate SAA system-element configurations, concepts, and/or procedures of interest; software and hardware components are integrated into the Surrogate UAS' research systems; and flight safety and mission planning activities are completed. Onboard the Surrogate UAS, candidate SAA system element configurations, concepts, and/or procedures are subjected to flight evaluations and in-flight performance is monitored. The Surrogate UAS, which can be controlled remotely via generic Ground Station uplink or automatically via onboard systems, operates with a NASA Safety Pilot/Pilot in Command onboard to permit safe operations in mixed airspace with manned aircraft. An end-to-end demonstration of a typical application of the capability was performed in non-exclusionary airspace in October 2011; additional research, development, flight testing, and evaluation efforts using this integrated capability are planned throughout fiscal year 2012 and 2013.

A real-time method for estimating time-varying aircraft frequency responses from input and output measurements was demonstrated. The Bat-4 subscale airplane was used with NASA Langley Research Center's AirSTAR unmanned aerial flight test facility to conduct flight tests and collect data for dynamic modeling. Orthogonal phase-optimized multisine inputs, summed with pilot stick and pedal inputs, were used to excite the responses. The aircraft was tested in its normal configuration and with emulated failures, which included a stuck left ruddervator and an increased command path latency. No prior knowledge of a dynamic model was used or available for the estimation. The longitudinal short period dynamics were investigated in this work. Time-varying frequency responses and stability margins were tracked well using a 20 second sliding window of data, as compared to a post-flight analysis using output error parameter estimation and a low-order equivalent system model. This method could be used in a real-time fault detection system, or for other applications of dynamic modeling such as real-time verification of stability margins during envelope expansion tests.

Liquid propellant makes up a significant portion of the total weight for large launch vehicles such as Saturn V, Space Shuttle, and the Space Launch System. Careful attention must be given to the influence of fuel slosh motion on the stability of the vehicle in the design of the Flight Control System (FCS). Historically, there have been instances where a poorly designed FCS in addition to a lack of passive damping have caused the slosh mass to drive the launch vehicle unstable. The dynamics behind controlling a quadcopter/hanging mass configuration is analogous to that of controlling the attitude of a rocket with a single propellant tank. The quadcopter/hanging mass configuration offers a reasonably accurate platform for assessing the real-time effectiveness of the SLS Adaptive Augmenting Controller in suppressing slosh instability. Flight test experiments were carried out at the NASA Langley Research Center's Autonomy Incubator. During both simulation and flight test, the hanging mass was intentionally made unstable and the adaptive algorithm successfully suppressed the instability as expected.

NASA has a technology program in place to enable the development of a next generation Reusable Launch Vehicle that will carry our future payloads into orbit at a much-reduced cost. The VentureStar, Lifting Body (LB) flight vehicle, is one of the potential reusable launch vehicle configurations being studied. A LB vehicle has no wings and derives its lift solely from the shape of its body, and has the unique advantages of superior volumetric efficiency, better aerodynamic efficiency at high angles-of-attack and hypersonic speeds, and reduced thermal protection system weight. Classically, in a ballistic vehicle, drag has been employed to control the level of deceleration in reentry. In the LB, lift enables the vehicle to decelerate at higher altitudes for the same velocity and defines the reentry corridor which includes a greater cross range. This paper outlines the flight stability and control aspects of our LB heritage which was utilized in the design of the VentureStar LB and its test version, the X-33. NASA and the U.S. Air Force have a rich heritage of LB vehicle design and flight experience. In the initial LB Program, eight LB's were built and over 225 LB test flights were conducted through 1975. Three LB series were most significant in the advancement of today's LB technolocy: the M2-F; the HL-10; and the X-24 series. The M2-F series was designed by NASA Ames Research Center, the HL-10 series by NASA Langley Research Center, and the X-24 series by the U. S. Air Force. LB vehicles are alive again today with the X- 33, X-38, and VentureStar.

Tailless Unmanned Aerial Vehicles (UAVs) offer several advantages over their conventional counterparts, including enhanced maneuverability, higher durability, and better stealth. However, they are challenging in their stability and control due to the absence of stabilizing and control surfaces that typically exist in conventional empennage. A crucial process for analyzing the tailless UAVs’ stability/performance characteristics and determining/validating their flight control parameters is done via the modeling and simulation of flight dynamics. This paper presents a comprehensive and systematic procedure for investigating the flight dynamics of a tailless UAV, including modeling, simulation, analytical verification, and flight testing, while also explaining the interconnections among these elements. It also addresses the common challenge of limited accessibility of UAV essential data through using diverse analytical, empirical, and experimental methods. First, a rapid and effective first-principles modeling approach is introduced to simulate the nonlinear six-degree-of-freedom flight dynamics of a small tailless UAV case study. The modeling process follows a modular framework where well-defined experiments and commercial of-the-shelf software, tools, and sensors are employed to build the necessary sub-models, including geometric, mass–inertia, aerodynamic, propulsion, and actuator models. Then, all sub-models are integrated into a simulation environment to allow the prediction of the UAV dynamic response obtained from the given control inputs. The developed flight dynamic model is subjected to a thorough verification process to ensure its integrity and proper functionality by comparing the simulated trim and natural flight modes with the calculated analytical results. Finally, a set of specific flight tests are performed to validate the developed simulation model and verify relevant performance characteristics for the case-study UAV. The results show that the proposed approach provides a systematic and straightforward method for examining the flight dynamics of small tailless UAVs with reasonable accuracy.

Airbus and Boeing are cooperatively presenting this topic dealing with transport aircraft stalls. The paper will begin by defining a stall, followed by a review of requirements, predictive validation and flight testing. There are various ways of designing modern jet transports for the stall regime such as aerodynamic approaches, flight deck indications, and augmentation control laws to deal with the high angle-of-attack (α) arena. The goal of augmented control laws for high α is common – no full aerodynamic stall or loss of climb performance should occur in the operational flight envelope, in Normal flight control modes. The validation techniques employed in preparation for a flight test campaign will follow. These include flight characteristic predictions based on wind-tunnel data as well as pilot-in-the-loop simulation rehearsals. The preparation for flight testing will be reviewed from both the engineer and pilot viewpoints. This will be followed by a review of various flight testing that has been conducted. The paper will close with a brief foray into what the future of transport stalls could be – perhaps protection features in degraded flight control modes? What are the benefits as well as drawbacks to increased augmentation for high α?