KEASLEXMATVMDANACANASAOBESPGMERAVRFCSSRCSTEMSTVCSVISTA0High-Alpha Technology Programknots equivalent airspeedleading-edge extensionMulti-Axis Thrust VectoringMcDonnell Douglas AerospaceNational Advisory Committee on AeronauticsNational Aeronautics and Space Administrationon-board excitation systempropylene glycol monomethyl etherremotely augmented vehicleresearch flight control systemspin recovery chutestandard test evaluation maneuvers setthrust-vectoring control systemVariable-Stability In-Flight Simulator Test Aircraftangle of attack, degradial nose angle, degINTRODUCTIONInterest in high-angle-of-attack flight has increased in recent years. High-angle-of-attackresearch has progressed from stall characteristics to spin resistance and is now in the area ofpoststall agility. To support this recent interest, NASA has developed the High-Alpha TechnologyProgram (HATP). One of the objectives of this program is flight validation of ground-based designmethodologies, and a modified F-18 aircraft was used to this end. This aircraft is called the NASAF-18 High Alpha Research Vehicle (HARV).History: Missile Platforms to Departures to Air Combat Maneuvering and AgilityResearch into high-angle-of-attack flight has waned and revived over the history of aviation(fig. 1).t,2 High-angle-of-attack research has also changed over the years. Initially, high-angle-of-attack research was only concerned with stall characteristics. Research then evolved to departureand spin characteristics, and now concentrates on exploring the poststall region of the high-angle-of-attack envelope. Early jet aircraft emphasized high performance with classical metrics,2

An Overview of the NASA F- 18 High Alpha Research

This paper gives an overview of the NASA F-18 High Alpha Research Vehicle. The three flight phases of the program are introduced, along with the specific goals and data examples taken during each phase. The aircraft configuration and systems needed to perform the disciplinary and inter-disciplinary research are discussed. The specific disciplines involved with the flight research are introduced, including aerodynamics, controls, propulsion, systems, and structures. Decisions that were made early in the planning of the aircraft project and the results of those decisions are briefly discussed. Each of the three flight phases corresponds to a particular aircraft configuration, and the research dictated the configuration to be flown. The first phase gathered data with the baseline F-18 configuration. The second phase was the thrust-vectoring phase. The third phase used a modified forebody with deployable nose strakes. Aircraft systems supporting these flights included extensive instrumentation systems, integrated research flight controls using flight control hardware and corresponding software, analog interface boxes to control forebody strakes, a thrust-vectoring system using external post-exit vanes around axisymmetric nozzles, a forebody vortex control system with strakes, and backup systems using battery-powered emergency systems and a spin recovery parachute.

/pdf/an-overview-of-the-nasa-f-18-high-alpha-research-vehicle-zdt1d7x8mf.pdf

An Overview of the NASA F-18 High Alpha Research Vehicle

The NASA F/A-18 High Alpha Research Vehicle (HARV) has been the flight test bed of a focused technology effort to significantly increase maneuvering capability at high angles of attack. Development and flight test of control law design methodologies, handling qualities metrics, performance guidelines, and flight evaluation maneuvers are described. The HARV has been modified to include two research control effectors, thrust vectoring, and actuated forebody strakes in order to provide increased control power at high angles of attack. A research flight control system has been used to provide a flexible, easily modified capability for high-angle-of-attack research controls. Different control law design techniques have been implemented and flight-tested, including eigenstructure assignment, variable gain output feedback, pseudo controls, and model-following. Extensive piloted simulation has been used to develop nonlinear performance guide-lines and handling qualities criteria for high angles of attack. This paper reviews the development and evaluation of technologies useful for high-angle-of-attack control. Design, development, and flight test of the research flight control system, control laws, flying qualities specifications, and flight test maneuvers are described. Flight test results are used to illustrate some of the lessons learned during flight test and handling qualities evaluations.

/pdf/an-overview-of-controls-and-flying-qualities-technology-on-3ip72t05tz.pdf

An Overview of Controls and Flying Qualities Technology on the F/A-18 High Alpha Research Vehicle

This paper describes a study that is being done as part of the Methods for Affordable Design (MAD) program within the National Aeronautics and Space Administration (NASA), for which the goal is to develop design methods and information that contribute to reductions in the aircraft development cycle time while increasing design confidence throughout the design cycle. The product of the study will be a database of information that relates key stability and control parameters to affordability considerations such as air combat exchange ratio, safety of flight, and probability of loss of the aircraft or pilot. The overall background and methodology are described, and preliminary results are shown for the first phase of the study to evaluate characteristics in the longitudinal axis. For these preliminary results a simplified analytical model of the aircraft response to uncommanded nose-up pitching moments was developed and used to characterize the requirements for recoveries to controlled flight conditions and to evaluate some parameters that affect the survivability of the aircraft and the pilot.

/pdf/preliminary-study-of-relationships-between-stability-and-4ptv18s670.pdf

Preliminary Study of Relationships between Stability and Control Characteristics and Affordability for High-Performance Aircraft

This paper presents a review of an ongoing NASA/U.S. Navy study to determine control power requirements at high angles of attack for the next-generation high-performance aircraft. This paper will focus on recent flight test activities using the NASA High Alpha Research Vehicle (HARV), which are intended to validate reaults of previous ground-based simulation studies. The purpose of this study will be discussed, and the overall program structure, approach, and objectives will be described. Results from two areas of investigation will be presented: (1) nose-down control power requirements and (2) lateral-directional control power requirements. Selected results which illustrate issues and challenges that are being addressed in the study will be discussed including test methodology, comparisons between simulation and flight, and general lessons learned.

https://ntrs.nasa.gov/api/citations/19950007832/downloads/19950007832.pdf

Flight Validation of Ground-Based Assessment for Control Power Requirements at High Angles of Attack

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Flight Validation of Ground-Based Assessment for Control Power Requirements at High Angles of Attack