The Role Of Aircraft Simulation In Improving Flight Safety .
NASA/TM-2002-210731The Role of Aircraft Simulation inImproving Flight Safety ThroughControl TrainingKarla S. Shy, Jacob J. Hageman, and Jeantette H. LeNASA Dryden Flight Research CenterEdwards, CaliforniaAugust 2002
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NASA/TM-2002-210731The Role of Aircraft Simulation inImproving Flight Safety ThroughControl TrainingKarla S. Shy, Jacob J. Hageman, and Jeantette H. LeNASA Dryden Flight Research CenterEdwards, CaliforniaNational Aeronautics andSpace AdministrationDryden Flight Research CenterEdwards, California 93523-0273August 2002
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THE AIRCRAFT SIMULATION ROLE IN IMPROVING FLIGHTSAFETY THROUGH CONTROL ROOM TRAININGKarla S. Shy*, Jacob J. Hageman† and Jeanette H. Le‡NASA Dryden Flight Research CenterEdwards, CaliforniaAbstractNomenclatureNASA Dryden Flight Research Center uses itssix-degrees-of-freedom (6-DOF) fixed-base simulationsfor mission control room training to improve flightsafety and operations. This concept is applied tonumerous flight projects such as the F-18 High AlphaResearch Vehicle (HARV), the F-15 Intelligent FlightControl System (IFCS), the X-38 Actuator Control Test(XACT), and X-43A (Hyper-X). The Dryden 6-DOFsimulations are typically used through various stages ofa project, from design to ground tests. The roles of thesesimulations have expanded to support control roomtraining, reinforcing flight safety by building controlroom staff proficiency. Real-time telemetry, radar, andvideo data are generated from flight vehicle simulationmodels. These data are used to drive the control roomdisplays. Nominal static values are used to completeinformation where appropriate. Audio communication isalso an integral part of training sessions. This simulationcapability is used to train control room personnel andflight crew for nominal missions and emergencysituations. Such training sessions are also opportunitiesto refine flight cards and control room display pages,exercise emergency procedures, and practice controlroom setup for the day of flight. This paper describesthis technology as it is used in the X-43A and F-15 IFCSand XACT projects.*Simulation Engineer†Simulation Engineer, Member‡Simulation EngineerCopyright 2002 by the American Institute of Aeronautics andAstronautics, Inc. No copyright is asserted in the United States underTitle 17, U.S. Code. The U.S. Government has a royalty-free licenseto exercise all rights under the copyright claimed herein forGovernmental purposes. All other rights are reserved by the copyrightowner.Notice: The use of trade names or names of manufacturers in thisdocument does not constitute an official endorsement of suchproducts or manufacturers, either expressed or implied, by theNational Aeronautics and Space Administration.CVTcurrent value tableDOFdegrees-of-freedomGRIMGlobal Real-Time Interactive MapGUIgraphical user interfaceHARVHigh Alpha Research VehicleIFCSIntelligent Flight Control SystemIFPCIntegrated Flight Propulsion ControlSystemMCCMission Control CenterNToperating system, Microsoft Corp.Redmond, WashingtonOTWout-the-windowPAGEProject Application Graphics ExecutablePCMpulse code modulationPDFParameter Description FilePDSParameter Display SoftwareRESReal-Time Ethernet ServerRS 232asynchronous serial data stream, ITU-Tinternational standardSIDsimulation interface deviceTMFtest maneuver featureTRAPSTelemetry and Radar AcquisitionProcessing SystemUNIXoperating system, The Open Group, SanFrancisco, CaliforniaXACTX-38 Actuator Control TestVMEVersa Module Eurocard1American Institute of Aeronautics and Astronautics
IntroductionControl room training using flight simulation is also achance to refine the flight cards for the mission. For anominal piloted mission, time is critical, emphasizingthe necessity for a well thought out, efficientprogression through the flight test. During a simulatedmission, various sequencing combinations can easily beperformed to find the optimum order for maneuvers tomaximize the amount of important data gathered whileminimizing fuel usage. In the realm of flight safety, thesmooth and timely execution of emergency proceduresis even more vital. Safety demands emergencyprocedures be in place for all imaginable off-nominalsituations. It also requires that the project procedureswork effectively and efficiently as intended. Withsimulation, failures can be introduced, to test thatappropriate and effective emergency procedures are inplace.Flight safety and mission success are two primaryobjectives in flight-test programs at NASA DrydenFlight Research Center (Edwards, California). Manyprocesses are exercised through the duration of a flightprogram to ensure that both objectives are met by allresearch disciplines and support facilities. The Drydensix-degrees-of-freedom (6-DOF) simulation has longbeen a valuable tool for achieving mission success. Itplays a role during vehicle design and development,ground testing, mission planning, and postflight dataanalysis. In the last decade, simulation capabilities wereexpanded to contribute towards flight safety bysupporting control room training.One way to ensure flight safety is to gather the controlroom staff with the flight crew, connected through audiocommunication, to simulate a day of flight. With thesimulation driving the Mission Control Center (MCC),the control room personnel and flight crew can exercisenominal missions, emergency situations, andcommunications protocol. Such simulated flight provesespecially beneficial for projects with few flights, orprojects with new engineers who have little or noprevious control room experience. These sessions giveboth primary and backup personnel the opportunities todevelop familiarity with the control room setup, thedisplays, the flight cards, emergency procedures, and theoverall dynamics in the control room on the day offlight. The training also benefits people behind thescenes who are setting up the control room forday-of-flight operations. The MCC support staff canexecute many of their control room procedures andevaluate their readiness and efficiency during thesetraining exercises.This paper describes how control room training thatuses Dryden simulations is applied in the X-43A(Hyper-X) project and the Intelligent Flight ControlSystem (IFCS) and X-38 Actuator Control Test (XACT)projects. The IFCS and XACT are both flown on theF-15 research aircraft. These programs demonstrate howDryden consolidates resources between the controlroom and simulation facilities to provide a valuablecapability that meets project objectives. In addition,these efforts reduce both cost and time spent forresource development of tools that can be usedcenter-wide, and expand capabilities of Drydensimulation, from vehicle design to preparation for flight.BackgroundThis section discusses the simulation environmentand the Mission Control Center, and provides anoverview of the capabilities and uses of these facilities.This information broadens understanding and informsreaders regarding Hyper-X and F-15 control roomtraining configurations.These training sessions are also opportunities toimprove control room displays. Prior to formal controlroom training, the simulation can be used to drive thedisplay pages, both statically and dynamically, to checkfor both aesthetics and function. This can be done eitherwith the displays running in the simulation laboratory,or with the data connection between the simulation andthe actual control room. The final test is to use thesedisplays during a day-of-flight training scenario in orderto evaluate their effectiveness during an actual mission.Engineers can then verify that the data displayed arepertinent, easy to analyze, and function well with theprocedures in the flight cards. Refinements to better suitcontrol room displays to flight objectives, can then bemade, contributing to both the safety and success of themission.Simulation EnvironmentThe Dryden 6-DOF simulation varies in complexityto reflect the requirements of the flight researchprogram. Simulations are designed to be operable by asingle user, whether it be a batch version running on aworkstation, or a full pilot-in-the-loop configuration.Simulations can also integrate with the actual flighthardware, or software in the hardware-in-the-loopconfiguration, or both. The fullest use of a simulation isin the aircraft-in-the-loop configuration, where thesimulation is integrated with the aircraft itself.2American Institute of Aeronautics and Astronautics
calculated in the simulation and control of the variousfunctions.Each project may require any or all of these levels ofsimulation complexity. The hardware configurations canbe designed specifically for a project, using a dedicatedlaboratory and simulator cockpit (such as the case forthe F-15 simulation), or the project may choose to use ageneric glass cockpit and heads-up displays such as inthe case for Hyper-X. Regardless of the level ofcomplexity, data monitoring tools are available in thereal-time simulation environment, including mechanicalstrip charts, simulated heads-up graphics, and controlroom displays, as well as a variety of data analysissoftware.The real-time mode supports configurations thatinvolve a pilot-in-the-loop, hardware-in-the-loop, oraircraft-in-the-loop. The key differences between batchand real-time modes are the addition of a scheduler andthe ability to communicate with the desired hardware. Inmost cases the same program executable is used for bothmodes, with flags provided at the start determining thedesired configuration. Figure 1 shows an illustration ofthe typical simulation hardware setup.The pilot-in-the-loop simulation is used to evaluateaircraft performance and stability, test experimentalobjectives, conduct mission planning and rehearsals,perform overall pilot system assessment, and conductcontrol room training and checkout of control roomdisplays. This simulation can also be used during theearly stages of simulation development, to design theguidance and controls for autonomous vehicles. In thepilot-in-the-loop configuration, the simulation interfacesto a cockpit that uses the Dryden simulation electricstick for pilot inputs and a control panel for push-buttoncontrol of the simulation.The simplest configuration of a typical simulation isthe batch mode, also referred to as either an “allsoftware” mode or a “non-real-time” mode. The onlyhardware required for the batch simulation is a UNIXworkstation. The applications for a batch simulationinclude development and testing of aircraft models,evaluation of aircraft performance, Monte Carloanalysis, and development of new simulation features tofacilitate certain applications, if necessary. The batchsimulation can also be used to develop procedures forground tests that use the simulation. The simulation canalso serve as a tool to evaluate the test data. Engineerscan run a simulation in batch mode at their desk for anyof these applications. A graphical user interface (GUI) isprovided, allowing easy access to informationVisual cues in the pilot-in-the-loop configurationinclude heads-up graphics and a heads-down instrumentpanel. The heads-up graphics, projected onto aFigure 1. Simulation environment (hardware configuration).13American Institute of Aeronautics and Astronautics
The hardware-in-the-loop simulation configurationsupports (1) functional checks for both flight hardwareand flight software; (2) closed-loop performance; and(3) preparations for aircraft-in-the-loop testing. In thisconfiguration, the simulation interfaces with actualflight hardware or software. The simulation can monitordata output from these elements and provide inputs todrive these flight articles. The controlled environmentprovided by the simulation is often used for failuremodes and effects testing and validation of newhardware before it is installed in the aircraft. In theaircraft-in-the-loop configuration, the simulationinterfaces to the vehicle in a similar manner to supportfull mission, integrated closed-loop testing.2.5-meter diagonal projection screen, includes theterrain, roads, and several base facilities (such asrunways, tower, and hangars). The graphics also containa three-dimensional model of the vehicle witharticulated flight controls surfaces and a heads-updisplay. From the simulation, the user can choose fromseveral viewpoints including an out-the-window (OTW)view, a ground fixed view (such as from the tower orrunway), an aircraft fixed view from a chase aircraft, ora view from some other fixed point in space. Thecockpit heads-down instrument panel can vary from afull analog replication of the actual aircraft cockpit to aglass-cockpit display with an 8-ball and genericinstruments.All Dryden simulations use the same basic softwareskeleton (fig 2).2 The aircraft models vary in eachsimulation to reflect the corresponding research vehicle.The basic models include the flight control system,actuator model, aerodynamics model, and enginemodel. In the real-time configurations, the simulationhas routines to interpret inputs from the simulationcockpit or flight hardware. Outputs from the simulationare also sent to drive cockpit instruments and displays,and flight hardware and software. Simulations featurestypically include the ability to produce linear models,automated maneuvers, data recording and use of scripts,as well as many project-specific tools.Control room displays can also be run in thesimulation real-time environment for additional datamonitoring capability, either in the laboratoryenvironment or during ground tests. Engineers can usethis environment to design and evaluate theeffectiveness and functionality of control room displays.This environment also gives the users an additionalopportunity to familiarize themselves with thesedisplays in preparation for the day of flight.Strip charts, driven by simulation data, allow theengineers to monitor data and evaluate various dataconfigurations for use in the control room. In the case ofthe F-15 simulation laboratory, the same model of stripcharts are used as in the control room, allowing users tosave the desired configuration to a disk for use at eitherlocation.Mission Control Center (MCC)A Mission Control Center (MCC) is composed of acontrol room, and Telemetry and Radar AcquisitionProcessing System (TRAPS) facility with input fromFigure 2. Simulation software structure.4American Institute of Aeronautics and Astronautics
pulse code modulation (PCM), radar, and video streams,as shown in figure 3.room. The system can process multiple PCM streamssupporting data rates up to 20 Mbits/sec, providing thecapacity of a maximum of 64,000 downlink parametersfor display in the control room. The front-end computersare responsible for data processing of the telemetry andradar streams. This processing includes decommutationof the PCM streams and conversion of PCM data fromtelemetry count values to engineering units. Thefront-end computers are also responsible for parameterderivations, data storage in reflective memory, at-ratedata delivery to the strip charts, and data archiving forpostflight analysis. The Real-time Ethernet Server(RES) gathers the data from the reflective memory anddistributes it to the control room through Ethernet. Theraw PCM and radar data, as well as time-stamps arestored on the data recorders in the TRAPS.The control room includes numerous flight testengineer and research stations supporting manydifferent functions such as range safety and control,mission control, flight operations, and research. Thecontrol room is configured with overhead videomonitors, communication panels, strip chart recorders,weather and timing displays, and graphics workstations.Video monitors are used for the display of aircraftdownlink and tracking video. Fixed and mobile camerasystems acquire operational video data for monitoring,control, and safety purposes. Communication panels areavailable at every workstation in the control room,providing voice links between the TRAPS area, thecontrol room, the simulation laboratory, and theresearch aircraft. Graphics workstations are availablethroughout the control room, while strip chart recordersare located at the research stations only.Two types of data are available in the control room:at-rate and RES. At-rate data consists of the downlinkparameters only and is supplied to the strip chartrecorders. The RES provides a current value table(CVT) to the graphics workstations in the control roomfor special purpose displays. The CVT contains allparameters; PCM, radar, system, and derived—at agiven instance in time.The TRAPS processes data for the control room andis composed of several front-end computers, a dataserver, and data recorders. The TRAPS performs thedata processing and delivery service for the controlFigure 3. Mission Control Room configuration.5American Institute of Aeronautics and Astronautics
The special purpose displays consist of the GlobalReal-Time Interactive Map (GRIM), Parameter DisplaySoftware (PDS), and Project Application GraphicsExecutable (PAGE). The GRIM application (fig 4)allows range safety personnel the ability to trackmultiple targets anywhere in the world by providing agraphical representation of vehicle position on asimplified map with range information. The PDSapplication (fig 5) is a re-configurable display tool, withfeatures such as alphanumeric displays, light panels, bargraphs, and discrete messages. Where limitations inPDS occur, the PAGE application (fig 6) can be used toprovide custom graphical displays. The page applicationis most commonly used to display vehicle stick, rudder,and control surface positions. Logic can be built intothese displays for fault-error detection, either throughthe derivations in the front-end or through theapplications themselves.information is generated to drive the mission controlroom facilities, simulating day-of-flight operations.Hyper-X Training ConfigurationsControl room training is accomplished on theHyper-X project using the simulation in two ways. Thefirst method is to combine training with a ground testthat uses the simulation in the aircraft-in-the-loopconfiguration, shown in Figure 7. The data is typicallytransmitted to the control room through the downlinksystem for data recording and provides an opportunityfor additional control room display checkout. The testcan be conducted from the vehicle location or thecontrol room, allowing engineers the ability to walkthrough various parts of a simulated mission and gaincontrol room familiarization.The more common configuration used on Hyper-Xhas the real-time simulation residing on a UNIXworkstation installed in the TRAPS facility (fig 8). Adirect connection from the control room to thesimulation lab is not required, since the Hyper-X projectinvolves an autonomous vehicle and no pilot-in-the-loopcapability is needed. All one needs is a simulationcomputer that broadcasts data to whomever wants tolisten, in this case the control room.Control Room Training ConfigurationsSeveral current projects demonstrate how thesimulation drives the MCC to support control roomtraining, such as the X-43A (Hyper-X) and two F-15(IFCS, XACT) projects. These projects were selected todemonstrate the different configurations for which thesimulation environment can be adapted. For eachproject, this section will outline how the simulationfacility interfaces with the control room and howThe control room displays get their data through anEthernet broadcast from the RES. Since the Hyper-XFigure 4. F-15 Global Real-Time Interactive Map (GRIM) example.6American Institute of Aeronautics and Astronautics
Figure 5. F-15 Parameter Display Software (PDS) example.Figure 6. F-15 Project Application Graphics Executable (PAGE) example.7American Institute of Aeronautics and Astronautics
Figure 7. Hyper-X ground test using the simulation in the aircraft-in-the-loop configuration.Figure 8. Hyper-X control room training configuration using real-time simulation to simulate flight data and theReal-Time Ethernet Server function.8American Institute of Aeronautics and Astronautics
simulation already includes the ability to mimic RES, itis used as the interface to the control room, drivingeverything downstream of this junction. The softwareused by the control room to compute the derivedparameters is also run in this simulation since many ofthese parameters appear on the displays.project the RES process was synchronized with thesimulation.Hyper-X Training Objectives and ScenariosThe primary objectives of the control room trainingsessions for the Hyper-X project are to prepare thecontrol room staff for nominal and off-nominalmissions, improve the quality of the flight cards, andoptimize the effectiveness of the control room displays.Simulated Real-Time Ethernet ServerThe simulated RES function does basically twothings: maps simulation parameters to the CVT, andsends the CVT data to the applications that need it. First,it creates and writes a CVT using the simulation datawith the aid of two input files. The initial file is the CVTitself that is provided by the MCC. Both the simulationand the MCC must use the same CVT file or theparameter mapping will be incorrect. Second is aparameter description file (PDF) that may contain all, orjust a subset of, the CVT parameters. It also contains theassociated simulation parameter name that will be usedto drive that CVT parameter. The parameters in the PDFfile are PCM, radar, system, and derived parameters.Once the simulated RES has built the CVT, the data isbroadcast on Ethernet. The CVT data then becomesavailable to the graphics workstations in the controlroom.Building control room proficiency improves flightsafety and mission success. The opportunities to walkthrough a day-of-flight training scenario are critical forprojects like Hyper-X, where there are few missions andlarge time gaps between flights. These also prove to bebeneficial for personnel who have little to no experiencebeing in the control room to support a flight.The project also used control room training sessionsto improve the quality of flight cards and emergencyprocedures. These training sessions ensure thatprocedures are in place for all anticipated scenarios andthat they function correctly. Engineers check to see thatprocedures are sequenced properly and serve theirintended purpose. They also check that the control roomdisplays allow them to make their decisions in a correctand timely manner.The software that simulates the RES runs as ly with the simulation. This process isstarted by the simulation software and can also bestopped and restarted at any time through the simulationGUI. The user then has the ability to update the inputfiles for the data mapping and restart RES withoutbringing down the entire simulation. For the Hyper-XFor Hyper-X, there were a total of three nominaltraining sessions and three emergency procedurestraining sessions within a five-month period before firstflight. The flight scenario usually begins at or before taxiand continues until the end of the flight experiment orsplashdown. Figure 9 shows the Hyper-X flight profile.During all sessions, the control room is fully staffedFigure 9. Hyper-X flight profile.9American Institute of Aeronautics and Astronautics
with either primary or back-up personnel. The B-52flight crew is also present on audio communication toperform duties specified by the flight cards.who need to make these calls have to rely on the displaypage information to make their decisions correctly andin the time allowed. Thus, the emergency training alsohelps them design the displays to provide them with thedata they need, when they need it. If an abort is called,the simulation can take the project through thatsequence and end the training session. Alternatively, thereactions to the failure are noted, then the simulationreturns to a nominal state and the training proceeds tothe next scenario. Failures may not be modeled exactly,but the first-order effects are included for trainingpurposes.For each session, engineers have access to allavailable control room displays designed for the project;mechanical strip charts; and the GRIM display showingthe ground track for the B-52, launch vehicle, andresearch vehicle. The simulation provides all datarequired to drive the control room displays during themission, which is usually a subset of the entire downlinkparameter set. For Hyper-X, approximately 25 percentof the CVT data (or close to 1200 parameters) weredriven for the training sessions, either statically ordynamically.As in the day of flight, there is a briefing before eachtraining session, but more importantly there is a debriefimmediately afterwards to evaluate the training. In thedebrief, the project reviews the results of the training,the quality of the flight cards, how well peoplecommunicated in the control room, the quality of thecontrol room displays, the setup and stationassignments, and any other issues that came up duringthe training. Feedback from people is also used to helpformulate or improve future training sessions.Communication in the control room during the day offlight is also a critical element factored into thesetraining sessions. Various audio communication linesare set up to reflect the day of flight. One line connectsthe test conductor, flight crew, and the mission lead.Another communication line allows all the disciplineleads to communicate with each other. Then a separateline is available to allow members of each discipline totalk amongst themselves. For these training sessions, anisolated line is also set up between the simulationengineer (sitting in the TRAPS area) and the safetyrepresentative (in the control room) who calls to thesimulation engineer to initiate the various scenarios.During emergency procedures training, only these twoindividuals know what the off-nominal scenarios are inorder to maintain the element of surprise for theremaining control room staff.Hyper-X Training Data ManipulationFigure 10 shows data can be manipulated in severalways. The simulation has a feature called “Autotest”that allows the user to force a profile on a desiredparameter. The user can superimpose steps, squarewaves, doublets, ramps, sine waves, or frequencysweeps to create the desired parameter profile. The userspecifies the parameter name, location in the real-timeloop where this profile is injected, and characteristicsabout the profile, such as times, amplitudes, andfrequencies. Up to 512 parameters with four test legsper parameter can be manipulated through this feature.For off-nominal training scenarios, the simulation caninject a failure on any control room parameter driven bythe simulation, to provide opportunities to exercisego-no-go criteria and emergency procedures. EngineersFigure 10. Simulation data manipulation to drive control room displays.10American Insti
procedures in the flight cards. Refinements to better suit control room displays to flight objectives, can then be made, contributing to both the safety and success of the mission. Control room training using flight simulation is also a chance to refine the flight cards for the mis
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