Flight Segments Research Articles

Pilot Oriented Performance Measurement

Flight simulators provide a complete quantitative record of a pilot's flying performance. Evaluating this record is complicated by the volume of data and by its fine detail, dozens of flight parameters, sampled many times per second. Automated performance measurement systems (APMS) reduce the volume of data to an amount which is manageable and understandable. The usual APMS is aircraft state oriented. The APMS keys on aircraft state (e.g., X-Y position, bank angle) to define intervals over which performance data are integrated. This APMS is relatively insensitive to pilots' intentions and so may average performances which had differing objectives, based only on their having occurred at the same point during the task sequence. An alternative APMS has been developed which is pilot oriented. This APMS defines measurement intervals based on control inputs. Control inputs are identified by discrete changes in flight path. These intervals are psychologically relevant in that they begin with a goal-directed control input and end with a countervailing input. By relating performance in the pilot defined intervals to state defined intervals, it is possible to quantify performance on given flight segments (e.g., a level turn), and to specify factors which lead to a given level of performance.

The Reliability and Validity of Flight Task Workload Ratings

Twelve instrument-rated general aviation pilots each flew two scenarios in a motion-base simulator. During each flight, the pilots verbally estimated their workload every three minutes. Following each flight, they again estimated workload for each flight segment and also rated their overall workload, perceived performance, and 13 specific factors on a bipolar scale. The results indicate that time (a priori, inflight, or postflight) of eliciting ratings, period to be covered by the ratings (a specific moment in time or a longer period), type of rating scale, and rating method (verbal, written, or other) may be important variables. Overall workload ratings appear to be predicted by different specific scales depending upon the situation, with activity level the best predictor. Perceived performance seems to bear little relationship to observer-rated performance when pilots rate their overall performance and an observer rates specific behaviors. Perceived workload and performance also seem unrelated.

The Passenger-Mix Problem in the Scheduled Airlines

Deregulation has opened up many opportunities and challenges in the transportation industry—opportunities to increase profits and challenges to keep from being outflanked by competition. A goal of particular interest to the scheduled airlines is to set prices more adaptively and to change them more rapidly. A difficult problem arises when many passengers with different itineraries compete for a limited number of seats on a single-flight segment. The problem is complicated by the existence of different fare classes, many flight segments, and different demands across time. For any given set of prices, flight-segment capacities, and passenger-carrying demand, there is some number of passengers at each fare class on each flight segment that will optimize revenue. Knowledge of such an optimum can be used not only in pricing analysis but also in setting policies to influence the passenger fare-class mix so that the optimum will be more nearly achieved in actual practice. We describe a method for identifying the optimum fare-class mix and the design of a system for that purpose which we built and implemented for Frontier Airlines. The recognition and formulation of the problem has become even more important as the number of aircraft in the sky has been reduced and the competition for a limited number of seats has become more intense.

An Overview of Progress in the Design And Implementation of Landsat-D Systems

Landsat-D will be launched in late 1981 or early 1982 into a Sun-synchronous orbit near 700 km. Landsat-D systems and the principal observing instrument, the Thematic Mapper, are being designed and implemented to provide a significantly improved Earth-resources monitoring capability. The Thematic Mapper will have seven spectral bands (0.45-0.52, 0.52-0.60, 0.63-0.69, 0.76-0.90, 1.55-1.75, 2.08-2.35, and 10.5-12.5 μm), with an instantaneous field of view at nadir of 30 m except for the thermal band (120 m). The data from the Thematic Mapper and other Landsat-D flight segment systems will be relayed to the Landsat-D ground data processing system using a direct readout capability or the Tracking and Data Relay Satellite System and communications satellites. The ground systems will process the data as it arrives at rates up to 100 Mbit/s and a total volume of 2.6 × 1011 bit/day into standard digital and photographic products within 48 hours of data acquisition. This includes 200 Multispectral Scanner Subsystem and 100 Thematic Mapper scenes per day. The Thematic Mapper increased spatial, spectral, and radiometric resolution should be of primary benefit in agricultural and vegetation surveys, but substantial improvements in resource and land cover observations for geology, land use, and water resources applications are also to be anticipated.

Effects of Aircraft Motion on Passengers' Comfort Ratings and Response Times

Comfort ratings and response times for changes in the experienced level of comfort were examined in 20 subjects using the NASA Flight Research Center's Jetstar aircraft modified to carry the GPAS system (General Purpose Airborne Simulator). Data were obtained for each of the subjects during two runs of 10 1-min. flight segments. In general, as the magnitude of aircraft motion increased in either the vertical or transverse (lateral) directions, there was an increase in feelings of discomfort and a decrease in response times to those changes. These results suggest parallels between the large body of laboratory data on human reaction time and that collected in this field study on response times to changes in ride comfort.

MATS - The mission analysis and trajectory simulation program

T Mission Analysis and Trajectory Simulation Program (MATS) is a general-purpose digital computer pragram written in FORTRAN IV.' It either has simulated or is potentially capable of simulating such diverse missions as Apollo, Mariner, Surveyor, Tiros, Comsat, Minuteman, and Sentinel. Key points of philosophy underlying the MATS design concept are: a phase-oriented sequencer controls the occurrence of events; the input parameters control the simulation; a bucket concept generalizes and minimizes data storage; and a modularized integrated systems approach permits planned evolution. The phase concept provides the mechanism whereby occurrence of events can be sequenced logically as in real-time situations. A phase is defined as a time interval corresponding to one of a continuous sequence of flight segments. A phase may be of zero duration to simulate an instantaneous inflight or logical event. Phase changes are treated as trajectory discrete points at which variables that affect the vehicle, environment or simulation may be introduced or varied. Examples of phase-oriented trajectory parameters are engine ignition and cutoff, attitude maneuvers or steering algorithms, and environment modifications; phase-oriented simulation parameters include integration method and stepsize control, output requests, logical phase manipulations, and iteration processes. The bucket concept minimizes the input storage requirements by identifying the data by phase, and storing it en masse; as each phase is initiated, the associated data are brought into active memory. The data are stored contiguously, so that no preassigned limits determine the type and volume active during any phase. Figure 1 schematically represents the program structure, which is based on a modular design concept.

CLEAR AIR TURBULENCE FREQUENCY AS A FUNCTION OF WIND SHEAR AND DEFORMATION1

The probability is determined that an aircraft will encounter moderate or severe high-level turbulence during a 100-mi. flight segment when particular values of certain meteorological quantities exist in that locality. The turbulence data used are pilot reports collected by the U.S. Weather Bureau Clear Air Turbulence Project, for March 12–24, 1962 and February 4–9, 1963. The meteorological quantities which were computed from standard data include vertical vector wind shear, vertical wind direction shear, temperature lapse rate, horizontal wind shear, vorticity, and resultant deformation. A correlation of 0.45 was found between turbulence frequency and the product of vertical vector wind shear and deformation. This value is the highest correlation found so far with data of this type. The product of wind shear and deformation is an important factor in the development of fronts. One might expect that a tendency for frontogenesis would correlate better with turbulence than would frontolysis. The data however, indicate that both processes are equally important. Temperature lapse rate appeared to have little influence on the turbulence frequency except for a few occasions when conditions were nearly dry adiabatic. The regression equations between turbulence frequency and meteorological quantities that have been derived appear useful in estimating the risk of encountering turbulence in a given locality. Such turbulence estimates can be made at a particular time from the concurrent upper-air data, or on a climatological basis from the climatology of the pertinent meteorological factors.