Fixed-base Simulator Research Articles

A Study of Parameters Affecting a Display for Aircraft Instrument Landings

A fixed-base simulator study has been conducted to evaluate the effects of varying several parameters of a cathode ray tube (CRT) presentation of an advanced display for instrument landing of transport aircraft. This research was conducted in support of NASA's Terminal Configured Vehicle (TCV) program which was established to develop and evaluate advanced aircraft systems that will benefit conventional takeoff and landing operation in the terminal area.

The influence of low frequency vibration on pilot performance (as measured in a fixed base simulator).

This report describes a study on the effects of low frequency vibration on pilot performance. Army pilots acted as subjects and flew simulated helicopter missions in a realistic fixed base simulator environment. While flying the two-hour missions pilots were exposed to vibration stimuli varying in frequency from 6 to 12 Hz and in amplitude from ±0·1 to ±0·3g (measured at the floor). Measurements were taken of the vibration tramsmissibility of the pilot's seat so that the vibration actually felt by the subject could be determined. Missions involved transporting external loads in a simulated logistics environment. Performance was evaluated by measuring flight path deviations from prescribed en route, approach, and hover parameters. The vibration stimuli used did not degrade performance. In fact, performance tended to improve with increased stress. It is hypothesized that this trend was due to motivation, i.e. as subjects felt the onset of fatigue they compensated by working harder and thus tended to improve...

Effect of Radar Disturbances on Ground-Controlled Precision-Landing Delivery

This study examined the effect of radar disturbances on time-controlled precision-landing delivery. A simulation was developed and tested which models an aircraft on a four-dimensional navigation terminal approach. Trained pilots flew a nominal approach in a fixed-base cockpit simulator following timed delivery commands from an initial fix to a final approach fix. During the flight, position information was estimated from noisy radar observations. Three phases of testing were conducted to quantify the accuracy of a timed delivery algorithm with modifications in the flight commands. In all cases, timed delivery was performed with great accuracy, while keeping pilot workload at a low level.

Feasibility Demonstration of the Earth-Referenced Maneuvering Flight-Path Display

A feasibility demonstration of integrated cockpit guidance and control display concept, the maneuvering flight-path display, is reported. The display provides attitude, altitude, direction, and speed director information to the pilot in the form of an electronically generated, graphical representation of the real-world flight path that should be flown. There are two types of moving elements constituting the display: the flight-path and the speedindex elements. The flight-path elements are analogous to tar strips on a highway. The speed-index element, immediately to the left of the flight-path elements, moves perspectively to denote deviation from proper speed by either moving away from or toward the aircraft to signal too slow or too fast, respectively. The feasibility demonstration was carried out on a fixed-base simulator. The practicability of using an Earth-referenced flightpath display as the principal source of pilot guidance and control information during representative flight modes was investigated. The flights demonstrated the feasibility and desirability of the concept, and its development is continuing.

Display Analysis with the Optimal Control Model of the Human Operator

Application of the optimal control model of the human operator to problems in display analysis is discussed. Those aspects of the model pertaining to the operator-display interface and to operator information processing are reviewed and discussed. The techniques are then applied to the analysis of advanced display/control systems for a Terminal Configured Vehicle. Model results are compared with those obtained in a large, fixed-base simulation.

Application of Active Controls Technology to Aircraft Ride Smoothing

Prototype ride smoothing systems (RSS's) were synthesized for flight testing aboard the NASA general purpose airborne simulator (GPAS). The systems were designed to meet comprehensive criteria, including passenger comfort and aircraft handling qualities considerations. System performance estimates based on analytic expressions were compared to estimates derived from digital calculations. The effects of RSS's on pilot workload during instrument landing system (ILS) approach in turbulence was examined in a fixed-base simulator. A limited number of flights were conducted to verify predicted RSS performance. Results of these experiments indicate that the RSS's reduce pilot workload and increase passenger comfort, while maintaining handling qualities.

Failure detection by pilots during automatic landing - Models and experiments

A model is proposed to describe the pilot as a monitor of automatic landing systems. The failures treated are equivalent to the addition of a dynamic change in the mean of the observation process. The failure detection model of the pilot consists of two stages: a linear estimator (Kalman filter) and a decision mechanism based on sequential analysis. The filter equations are derived from a simplified version of the linearized dynamics of the airplane and the control loop. The perceptual observation noise is modified to include the effects of allocation of attention among the several instruments. The final result is a simple model consisting of a high-pass filter to produce the observation residuals and a decision function which is a pure integration of the residuals minus a bias term. The dynamics of a Boeing 707 were used to simulate the fully coupled final approach in a fixed-base simulator. Observers monitored the approaches and detected the failures; their performance was compared with the predictions of the model.

Vehicular Control by Visual Field Cues-analytical Model and Experimental Validation

The development and experimental validation of an analytical model for manual visual field control (VFC) of aircraft is presented. A basic model for control-oriented visual field information (VFI) is proposed and formulated in an optimal control framework. A special case of VFC is studied, namely, the manual lateral control of a TV guided remotely piloted vehicle (RPV) along a straight reference trajectory in the presence of side gusts. For experimental validation, a five-degree-of-freedom fixed-base simulator has been constructed to simulate a RPV flight along a nominally straight reference trajectory. The starting point in the validation program was a VFI model based on error detection at a single looking distance, which is proved to be correct for fixed distance viewing but not for the complete VFC task. The analytical model is then reformulated to allow VFI detection at two looking distances. This two-distance VFI model was found to be an adequate representation for the complete VFC task and to match the experimental results closely, thus enabling the determination of the human operator (HO) parameters within narrow limits.

YF-17 Ground Testing and Simulation

The flight control test stand (FCTS) is one of the engineering tools used in the flight control system development of the Northrop YF-17 airplane. The FCTS is a functional simulator of the airplane involving mechanical, hydraulic, electrical, and electronic systems. The systems are the same as those used on the airplane. In its fundamental mode, the FCTS is used to qualify and life-test the flight control system. In its ancillary mode, it is used as a fixed-base simulator to investigate flight control system performance and as a tes.t bed for control system modifications. This paper describes the FCTS and its use in the testing and qualification of the YF-17 flight control system. The application of the FCTS in the system development of the Control Augmentation System and, in particular, the failure management system is discussed. Examples are presented of the supporting role played by the FCTS during the flight test development of the YF-17 prototype airplane.

A Model-Based Analysis of a Display for Helicopter Landing Approach

A control theoretic model of the human pilot was used to analyze a baseline electronic cockpit display in a helicopter landing approach task. The head down display was created on a stroke written cathode ray tube and the vehicle was a UH-1H helicopter. The landing approach task consisted of maintaining prescribed groundspeed and glideslope in the presence of random vertical and horizontal turbulence. The pilot model was also used to generate and evaluate display quickening laws designed to improve pilot vehicle performance. A simple fixed base simulation provided comparative tracking data.

Touchdown Performance with a Computer Graphics Night Visual Attachment

A computer graphics system was programmed to display to the pilot a dynamic perspective view of an airport terminal area comprised of 1200 points of light. The advantages of this system are that it has high resolution and it eliminates the camera optics and electromechanical servos of TV-model systems. The disadvantages are that it lacks fine ground texture and has a small computational delay. A brief experimental evaluation was conducted in which eight airline pilots made 50 landings each in a fixed-based simulation of a DC-8 transport. They were instructed to touch down at 0.6 m/sec. The vertical velocity of the aircraft at touchdown was displayed to the pilot at the completion of each run. Their average vertical velocity at touchdown for the last 10 landings was about 0.8 m/sec. This performance was similar to that obtained on current TV-model systems.

Evaluating a CRT Map Predictor for Airborne Use

Six airline pilots participated in a fixed-base simulator experiment designed to study the advantages and disadvantages of incorporating a simple horizontal flight path predictor on both fixed and rotating electronic CRT map displays. The pilots were asked to fly a modified ``figure eight'' ground track (similar to right and left procedure turns in sequence) while attempting to maintain constant altitude. The dynamics were representative of a transport aircraft. All flight information was displayed on one 17-in (43-cm) CRT monitor. The controlled variables were 1) map orientation, 2) pilots, 3) presence or absence of crosswinds, 4) presence or absence of wind gusts, and 5) presence or absence of predictor. Error scores were recorded as deviations from the commanded ground track and altitude. Pilot comments and ratings were also obtained. No interaction in performance scores was found between the predictor and the two different map display orientations. It was found that the predictor reduced deviations from the commanded ground track, narrowed performance differences among pilots, narrowed the error differences found with and without crosswinds, and decreased pilot workload.

Alcohol Effects on Driving Behavior and Performance in a Car Simulator

A fixed-base simulation has been developed to test the effect of alcohol on driving performance. The simulation includes both lateral steering control and a discrete visual detection, recognition, and response task set up to provide the workload and division of attention typical of real world driving. Measurements of both driver control behavior and driver-vehicle performance were obtained for the steering task, and detection and recognition indexes and reaction time were measured on the discrete task. Preliminary results on scanning behavior as measured with an eye-point-of-regard monitor are also presented. Data are given for eighteen drivers, ranging in age from 21-65, at blood alcohol concentrations (BAC) of 0, 0.06, and 0.11. Alcohol causes larger lane and heading deviations, and increases detection and reaction times on the discrete task. Control-behavior measures show that the driver's control gain decreases, but stability margins are maintained under alcohol, while driver remnant increases. Such effects could be due to indifference thresholds and/or intermittent attention in the control task. Both continuous steering control and discrete peripheral ``sign'' response tasks were performed, singly and combined, to investigate the effects of divided attention. Performance on the steering control task was decreased when both tasks were done concurrently, but the sensitivity to alcohol effects was similar. The driving simulation has proven an efficient tool for alcohol research. It has gained acceptance from subjects as a valid approximation of driving, and the various related measurements have proven to be reliable and sensitive to levels of intoxication.

A Study on Aircraft Map Display Location and Orientation

Six airline pilots participated in a fixed-base simulator study to determine the effects of two Horizontal Situation Display (HSD/map) panel locations relative to the Vertical Situation Display (VSD), and of three map orientations on manual piloting performance. Pilot comments and opinions were formally obtained. Significant performance differences were found between wind conditions, and among pilots, but not between map locations and orientations. The results also illustrate the potential tracking accuracy of such a display. Recommendations concerning display location and map orientation are made.

Recent Experience with Techniques for Prediction of Spin Characteristics of Fighter Aircraft

Spin-tunnel tests and radio-controlled model tests have proven to be useful for prediction of spin characteristics, but these specialized techniques may not be available in early design phases. The present paper discusses other techniques that are more generally available, specifically: 1) conventional wind-tunnel tests, 2) analytical studies, and 3) fixed-base simulation. The techniques and hardware used are described, but the emphasis is placed on the application of the techniques and examples of the type of results that have been obtained. Recent research has indicated that some spin problems (in particular, dangerous flat spins) can be readily analyzed using conventional wind-tunnel equipment and techniques normally employed during routine stability and control investigations. Recent experience with analytical spin prediction methods is discussed using results obtained for a variable-sweep fighter with a long pointed nose. Correlation between theoretical calculations and actual spin characteristics exhibited by a free-flight model of the configuration was quite poor due to large nonrepeatable asymmetric yawing moments created by flow separation on the long pointed nose at high angles of attack. Development and preliminary evaluations of a fixedbase simulator with limited visual and buffet cues for stall/spin studies are also discussed.

Summary and Interpretation of Recent Longitudinal Flying Qualities Results

10 Chalk, C. R., Evaluation of Various Short Period Dynamics at Four Drag Configurations for the Landing Approach Task, FDL-TDR-64-60, 1964. 11 Hall, W. G., In Flight Investigation of Longitudinal Short Period Handling Characteristics of Wheel Controlled Airplanes, AFFDL-TR-68-91, 1968. 12 Parrag, M. L., Evaluation in a Ground Simulator of the Effects of Elevator Control System Dynamics in Fighter AFFDL-TR-67-19, 1967. 13 Montgomery, R. C. and Hatch, H. G., Application of Differential Synthesis to Design of Multiaxis Stability Augmentation Systems, Journal of Aircraft, Vol. 6, No. 4, July-Aug. 1969, pp. 336-343. 14 Chalk, C. R., Fixed Base Simulator Investigation of the Effects of La and True Airspeed on Pilot Opinion of Longitudinal Qualities, ASD-TDR-63-399, 1963. 15 Berry, D. T. and Powers, B. G., Flying Qualities of a Large, Supersonic Aircraft in Cruise and Landing Approach, AIAA Paper 70-566, Tullahoma, Tenn., 1970.

Experimental Evaluation of a Visual Detection Model

A fixed-base simulation experiment was performed to gather visual air-to-ground target recognition performance data for comparison with predictions from the Autonetics Detection Model. Color motion picture imagery obtained during a low-altitude flight was used to simulate the observer's forward view. Observer performance was measured in terms of probability and range of correct target recognition. The Autonetics Detection Model incorporates parameters related to the target, the environment, and the observer. In generating theoretical predictions from the model, values of all parameters were specified independently of the data obtained in the experiment. No curve fitting techniques were used to improve the fit between the empirical and theoretical curves. Results indicated a close relationship between the obtained performance data and the model predictions. A product-moment correlation of +0.53, significant at the 0.001 level, was obtained between the empirical and theoretical 50% recognition ranges.

Initial military flight tests of the X-22A VSTOL research aircraft

The X-22A aircraft was evaluated to establish the status of its development and its potential usefulness for conducting flight research using a variable stability system. The more significant aspects and results of the tests are covered in this paper. Ground familiarization and planning conducted prior to the flight tests included the use of a fixed-based simulator programmed with X-22A design data. Test techniques were developed and/or refined during both ground simulator work and actual flight tests as necessary to adapt to the unique characteristics of the aircraft. Quantitative and qualitative evaluation of the stability and control characteristics in terms of their effect on the aircraft to perform its intended mission of flight research have shown that it is acceptable in all respects considered. Unusually high sideforce, with no means of variation, was the most detrimental characteristic of the aircraft noted relative to its potential use as a variable stability flight research vehicle.

Flying qualities - An integral part of a stability augmentation system

During the conception, development, and flight testing of a stability augmentation system designed to improve the structural response characteristics of the B-52, it was necessary to provide flying qualities criteria and to conduct piloted simulator studies to assure that the B-52 flying qualities were improved or maintained. The fixed-base simulator studies utilized a point light projection display system and a B-52 cockpit display and included the effect of random turbulence. The results of the studies conducted for the lateral-directional axis are presented. In the piloted simulation study the Dutch roll frequency and damping were varied while other pertinent lateral-directional parameters were maintained constant. It was found that the Dutch roll damping required to provide satisfactory flying qualities in turbulence was significantly greater than the damping required in essentially calm air. Improvements in the handling qualities as verified by flight test are also presented.

Pilot's response to stability augmentation system failures and implications for design

The degree to which a pilot can successfully and reliably retain control following a stability augmentation system failure is a key factor in the system design philosophy. Results of a fixed-base simulation of multiple-loop lateral/directional control of a conventional airframe with an abrupt yaw damper failure are presented. They indicate that the postfailure performance is improved if the difference in controlled element dynamics at failure is reduced. One way to achieve this is to utilize a less than optimum prefailure augmentation system so the pilot is required to be in the loop at all times, rather than to merely monitor system activity prior to failure. A model for the pilot's dynamic response is presented which accounts for his behavior during and following failure.