Identification of multiloop pilot describing functions obtained from simulated approaches to an aircraft carrier

Predicted results of a simulation of the pilot's approach control strategy in the presence of pilot remnant are presented. The aircraft dynamics and the turbulence environment are representative of a trainer-type aircraft. The non-intrusive pilot identification program (NIPIP) was used to identify the pilot's control strategy required by this highly-coupled, multiloop control task. The results are presented in terms of frequency responses of the individual elements of the pilot's control strategy and indicate that NIPIP can identify the pilot's describing functions even in the presence of significant amounts of pilot remnant

Review of: Thomas Szasz, Fatal Freedom: The Ethics and Politics of Suicide

A review of the book Fatal Freedom: The Ethics and Politics of Suicide by Thomas Szasz (Praeger Publishers 1999). Preface, acknowledgments, appendix, notes, selected bibliography, indexes. ISBN 0-275-96646-1 [178 pp. $25.95. Hardbound, 88 Post Road West, Westport, CT 06881]

A Method for Measuring the Effective Throughput Time Delay in Simulated Displays Involving Manual Control

The advent and widespread use of the computer-generated image (CGI) device to simulate visual cues has a mixed impact on the realism and fidelity of flight simulators. On the plus side, CGIs provide greater flexibility in scene content than terrain boards and closed circuit television based visual systems, and they have the potential for a greater field of view. However, on the minus side, CGIs introduce into the visual simulation relatively long time delays. In many CGIs, this delay is as much as 200 ms, which is comparable to the inherent delay time of the pilot. Because most GCIs use multiloop processing and smoothing algorithms and are linked to a multiloop host computer, it is seldom possible to identify a unique throughput time delay, and it is therefore difficult to quantify the performance of the closed loop pilot simulator system relative to the real world task. A method to address these issues using the critical task tester is described. Some empirical results from applying the method are presented, and a novel technique for improving the performance of GCIs is discussed

Quantification of Cross-coupling and Motion Feedthrough for Multiaxis Controllers Used in an Air Combat Flying Task

A real-time piloted simulation of an air-to-air combat flying task using a wings-level-turn aircraft and various novel controllers was conducted. One objective is to quantify how the pilot interacts with the controllers and control modes, including: (1) controller versus aircraft response; (2) proprioceptive cross-coupling among axes of the controllers; and (3) biodynamic cross-coupling between the aircraft motions and the controllers. In order to aid in identifying the items listed above, both the target aircraft and the large amplitude multimode aerospace research simulator (LAMARS) motion system were distributed with quasi-random sums-of-sinusoids. Since the disturbances were separated in frequency, spectral analysis techniques were used to identify the three items listed. The results of the spectral analysis of controller motions from the two-axis side stick, a twist grip mounted on the side stick, a thumb button mounted on the side stick, and conventional rudder pedals are presented. Conclusions and recommendations for further research are also presented

Study of a safety margin system for powered-lift STOL aircraft

A study was conducted to explore the feasibility of a safety margin system for powered-lift aircraft which require a backside piloting technique. The objective of the safety margin system was to present multiple safety margin criteria as a single variable which could be tracked manually or automatically and which could be monitored for the purpose of deriving safety margin status. The study involved a pilot-in-the-loop analysis of several safety margin system concepts and a simulation experiment to evaluate those concepts which showed promise of providing a good solution. A system was ultimately configured which offered reasonable compromises in controllability, status information content, and the ability to regulate the safety margin at some expense of the allowable low speed flight path envelope

Non-intrusive parameter identification procedure user's guide

Written in standard FORTRAN, NAS is capable of identifying linear as well as nonlinear relations between input and output parameters; the only restriction is that the input/output relation be linear with respect to the unknown coefficients of the estimation equations. The output of the identification algorithm can be specified to be in either the time domain (i.e., the estimation equation coefficients) or in the frequency domain (i.e., a frequency response of the estimation equation). The frame length ("window") over which the identification procedure is to take place can be specified to be any portion of the input time history, thereby allowing the freedom to start and stop the identification procedure within a time history. There also is an option which allows a sliding window, which gives a moving average over the time history. The NAS software also includes the ability to identify several assumed solutions simultaneously for the same or different input data

Flow Visualization of a Turbulent Shear Flow using an Optical Wavefront Sensor

The research reported here investigated the use of a shearing interferometer (SI) wavefront sensor to determine the effects of shear-layer turbulence on an optical wavefront. A collimated helium-neon laser beam was propagated through a plane shear-layer produced by mixing helium and nitrogen at different velocities. Since the gases have different indices of refraction, the optical wavefront was distorted by different amounts by each gas. The SI measured the wavefront slope across the sampled area of the wavefront. The shear-layer was viewed from two orthogonal directions. This document contains shadow graphs, interference patterns imaged by each of the SI\u27s six cameras, interferograms containing fringes with separation proportional to the wavefront slope, and phase maps showing the shape of the perturbed optical wavefronts. The side view showed an area of steep slope along the mixing area of the two gases. The slope gradually changed as the distance from the mixing layer region increased. For the top view, the peaks and valleys grew as they propagated away from the shear-layer turbulence generator. The results also indicated that the interference patterns recorded by the SI cameras provide a simple way to visualize turbulence in a manner that provides phase information about the wavefront

Does Footfall Pattern in Forefoot Runners Change Over a Prolonged Run?

There has been much debate on the benefits of a forefoot versus rearfoot strike pattern in distance running in terms of performance and injury prevalence. Shock attenuation occurs more prominently in soft tissues at impact in forefoot runners compared to the passive skeletal loading in rearfoot runners. Recent studies indicate that a forefoot strike pattern may not be maintainable over long distance efforts. Therefore, this study tested the hypothesis that habitual forefoot runners could not maintain their strike pattern throughout a prolonged, intensive run. Fourteen forefoot runners ran to voluntary exhaustion on an instrumented force treadmill (average run duration: 15.4±2.2 minutes). Kinematic and kinetic data were sampled each minute at 200Hz and 1000Hz, respectively. Ankle plantar-flexor torque was measured during pre- and post-run isometric contractions, during which electromyographic activity was measured in the soleus, lateral, and medial gastrocnemius. Loading rate (49.95±14.83 to 57.40±22.53 BW*s-1, p=0.0311) and impact peak (1.35±0.43 to 1.50±0.51, p=0.0207) increased significantly throughout the run. Both peak knee flexion (-33.93±3.67º to -36.21±3.48º, p=\u3c0.0000) and sagittal ankle angle at touchdown (-11.83±5.33º to -9.33±6.29º, p =0.0202) increased significantly. Ankle torque decreased significantly from pre- to post-run (120.57±33.57 to 110.76±32.91 Nm, p = 0.0154). This was accompanied by a decrease in medial and lateral gastrocnemius integrated electromyographic activity (iEMG) (p=0.0387 and 0.0186, respectively). The results indicated that there were significant changes in landing mechanics in the habitual forefoot runners with increased levels of exertion, as they shifted towards strike patterns more similar to rearfoot runners throughout the run. These changes are in line with metabolic findings of other studies. There is increased eccentric loading of the ankle plantar-flexor muscles at touchdown in forefoot runners that may contribute to a decreased torque output by the end of the run. The decline in iEMG may indicate altered central drive of the system and a decline in the impact attenuation ability of the triceps surae, leading to the changes exhibited up the kinematic chain. These findings suggest that while forefoot strike patterns are good for speed, the onset of fatigue may affect the ability to maintain this pattern during a prolonged, intensive effort

Technical approaches for measurement of human errors

Human error is a significant contributing factor in a very high proportion of civil transport, general aviation, and rotorcraft accidents. The technical details of a variety of proven approaches for the measurement of human errors in the context of the national airspace system are presented. Unobtrusive measurements suitable for cockpit operations and procedures in part of full mission simulation are emphasized. Procedure, system performance, and human operator centered measurements are discussed as they apply to the manual control, communication, supervisory, and monitoring tasks which are relevant to aviation operations