Low-speed stability and control characteristics of a transport model with aft-fuselage-mounted advanced turboprops

A limited experimental investigation was conducted in the Langley 4- by 7-Meter Tunnel to explore the effects of aft-fuselage-mounted advanced turboprop installations on the low-speed stability and control characteristics of a representative transport aircraft in a landing configuration. In general, the experimental results indicate that the longitudinal and lateral-directional stability characteristics for the aft-fuselage-mounted single-rotation tractor and counter-rotation pusher propeller configurations tested during this investigation are acceptable aerodynamically. For the single-rotation tractor configuration, the propeller-induced aerodynamics are significantly influenced by the interaction of the propeller slipstream with the pylon and nacelle. The stability characteristics for the counter-rotation pusher configuration are strongly influenced by propeller normal forces. The longitudinal and directional control effectiveness, engine-out characteristics, and ground effects are also presented. In addition, a tabulated presentation of all aerodynamic data presented in this report is included as an appendix

Experimental and theoretical aerodynamic characteristics of a high-lift semispan wing model

Experimental and theoretical aerodynamic characteristics were compared for a high-lift, semispan wing configuration that incorporated a slightly modified version of the NASA Advanced Laminar Flow Control airfoil section. The experimental investigation was conducted in the Langley 14- by 22-Foot Subsonic Tunnel at chord Reynolds numbers of 2.36 and 3.33 million. A two-dimensional airfoil code and a three-dimensional panel code were used to obtain aerodynamic predictions. Two-dimensional data were corrected for three-dimensional effects. Comparisons between predicted and measured values were made for the cruise configuration and for various high-lift configurations. Both codes predicted lift and pitching moment coefficients that agreed well with experiment for the cruise configuration. These parameters were overpredicted for all high-lift configurations. Drag coefficient was underpredicted for all cases. Corrected two-dimensional pressure distributions typically agreed well with experiment, while the panel code overpredicted the leading-edge suction peak on the wing. One important feature missing from both of these codes was a capability for separated flow analysis. The major cause of disparity between the measured data and predictions presented herein was attributed to separated flow conditions

Low-disturbance wind tunnels

During the past years, there was an extensive program under way at the Langley Research Center to upgrade the flow quality in several of the large wind tunnels. This effort has resulted in significant improvements in flow quality in these tunnels and has also increased the understanding of how and where changes in existing and new wind tunnels are most likely to yield the desired improvements. As part of this ongoing program, flow disturbance levels and spectra were measured in several Langley tunnels before and after modifications were made to reduce acoustic and vorticity fluctuations. A brief description of these disturbance control features is given for the Low-Turbulence Pressure Tunnel, the 4 x 7 Meter Tunnel, and the 8 Foot Transonic Pressure Tunnel. To illustrate typical reductions in disturbance levels obtained in these tunnels, data from hot-wire or acoustic sensors are presented. A concept for a subsonic quiet tunnel designed to study boundary layer stability and transition is also presented. Techniques developed at Langley in recent years to eliminate the high intensity and high-frequency acoustic disturbances present in all previous supersonic wind tunnels are described. In conclusion, the low-disturbance levels present in atmospheric flight can now be simulated in wind tunnels over the speed range from low subsonic through high supersonic

Exploring Cooperation with Social Machines

As humans become more and more immersed in a networked world of connected and mobile devices, cooperation and sociability to achieve valued outcomes within geographic locales appears to be waning in favour of extended personal networks and interaction using semi-automated agents to support communications, transportation and other services. From a messaging structure that is complex, multiplexed and much of the time asynchronous, conditions emerge that disrupt symmetry of information exchange. People thus encounter circumstances that seem unpredictable given the information available to them, resulting in limited or failed cooperation and consequent quality of outcomes. We explore the role of Social Machines to support, change, and enhance human cooperation within a blended reality context

Low-speed aerodynamic characteristics of a twin-engine general aviation configuration with aft-fuselage-mounted pusher propellers

An investigation was conducted to determine the aerodynamic characteristics of an advanced turboprop aircraft model with aft-pylon-mounted pusher propellers. Tests were conducted through an angle-of-attack range of -8 to 28 degrees, and an angle-of-sideslip range of -20 to 20 degrees at free-stream conditions corresponding to Reynolds numbers of 0.55 to 2.14 x 10 to the 6th power based on mean aerodynamic chord. Test results show that for the unpowered configurations the maximum lift coefficients for the cruise, takeoff, and landing configurations are 1.45, 1.90, and 2.10, respectively. Nacelle installation results in a drag coefficient increase of 0.01. Increasing propeller thrust results in a significant increase in lift for angles of attack above stall and improves the longitudinal stability. The cruise configuration remains longitudinally stable to an angle of attack 5 degrees beyond the stall angle, the takeoff configuration is stable 4 degrees beyond stall angle, and the landing configuration is stable 3 degrees beyond stall angle. The predominant effect of symmetric thrust on the lateral-directional aerodynamic characteristics is in the post-stall region, where additional rudder control is available with power on

New Technologies and Mixed-Use Convergence How Humans and Algorithms are Adapting to Each Other

Human experience with technology has shifted from technological contexts requiring occasional intervention by a fraction of people mostly in command of technologies, to technological contexts that require constant ongoing participation from most people to complete tasks. We examine the current state of `mixed-use' new technologies integration with legacy systems, and whether the human assistance required to complete tasks and processes could function as a training ground for future smart systems, or whether increasing `co-dependence with' or `training of' algorithmic systems, enhancing task completion and inadvertently educating systems in human behaviour and intelligence, will simply subsume people into the algorithmic landscape. As the Internet of Things (IoT) arises in conjunction with advancing robotics and drone technology, semi and fully automated algorithmic systems are being developed that intersect with human experience in new and heterogeneous ways. Many new technologies are not yet flexible enough to support the choices people require in their daily lives, due to limitations in the algorithmic `logics' used that restrict options to predetermined pathways conceived of by programmers. This greatly limits human agency, and presently the potential to overcome problems that arise in processes. In this mixed-use period, we have the opportunity to develop new ways to address ethical guidance as knowledge that machines can learn. We explore promoting embedding of ethically-based principles into automated contexts through: (1) developing mutually agreed automated external ethical review systems (human or otherwise) that evaluate conformance across multiple ethical codes and provide feedback to designers, agents, and users on the distribution of conformance; (2) focusing on review systems to drive distributed development of embedded ethical principles in individual services by responding to this feedback to develop ongoing correction through dynamic adaption or incremental releases; and (3) using multi-agent simulation tools to forecast scenarios in real time

A Review of Choice and Preference Assessments to Increase Academic Attainment for Autism Spectrum Disorders

Many schools use choice and preference assessments to decrease and/or increase behaviors of students with disabilities such as Autism Spectrum Disorders or ASD. Although there exists scant evidence from the literature exploring the relationship between utilizing choice and preference assessments as a tool to increase academic achievement, the Council for Exceptional Children’s (CEC ) “ Initial Level Special Educator Preparation Standards” require beginning special education professionals to, “select, adapt, and use a repertoire of evidence-based instructional strategies to advance learning of individuals with exceptionalities,” (CEC, 2012). To contribute to the knowledge base regarding using choice and preference assessment as a tool to increase academic attainment, this article provides a brief examination of the existing literature by reviewing four studies based on the following criteria: (a) participants referred for intervention based upon poor academic performance, (b) participants ranging from primary or elementary-grade students with or without identified disabilities, (c) studies examined the use of preference assessment to increase academic achievement, and (d) studies published in a peer reviewed publication within the past fifteen years. Findings from these studies produced mixed results and left the original purpose and question of the article review unanswered. The mixed results and conclusions drawn highlight the need for future research to be conducted to evaluate the effectiveness of choice and preference assessments as a tool to increase academic achievement for students with ASD

The Langley 14- by 22-Foot Subsonic Tunnel: Description, Flow Characteristics, and Guide for Users

The Langley 14- by 22-foot Subsonic Tunnel is a closed circuit, single-return atmospheric wind tunnel with a test section that can be operated in a variety of configurations (closed, slotted, partially open, and open). The closed test section configuration is 14.5 ft high by 21.75 ft wide and 50 ft long with a maximum speed of about 338 ft/sec. The open test section configuration has a maximum speed of about 270 ft/sec, and is formed by raising the ceiling and walls, to form a floor-only configuration. The tunnel may be configured with a moving-belt ground plane and a floor boundary-layer removal system at the entrance to the test section for ground effect testing. In addition, the tunnel had a two-component laser velocimeter, a frequency modulated (FM) tape system for dynamic data acquisition, flow visualization equipment, and acoustic testing capabilities. Users of the 14- by 22-foot Subsonic Tunnel are provided with information required for planning of experimental investigations including test hardware and model support systems

Spectral properties and geology of bright and dark material on dwarf planet Ceres

Variations and spatial distributions of bright and dark material on dwarf planet Ceres play a key role in understanding the processes that have led to its present surface composition. We define limits for bright and dark material in order to distinguish them consistently, based on the reflectance of the average surface using Dawn Framing Camera data. A systematic classification of four types of bright material is presented based on their spectral properties, composition, spatial distribution, and association with specific geomorphological features. We found obvious correlations of reflectance with spectral shape (slopes) and age; however, this is not unique throughout the bright spots. Although impact features show generally more extreme reflectance variations, several areas can only be understood in terms of inhomogeneous distribution of composition as inferred from Dawn Visible and Infrared Spectrometer data. Additional material with anomalous composition and spectral properties are rare. The identification of the composition and origin of the dark, particularly the darkest material, remains to be explored. The spectral properties and the morphology of the dark sites suggest an endogenic origin, but it is not clear whether they are more or less primitive surficial exposures or excavated subsurface but localized material. The reflectance, spectral properties, inferred composition, and geologic context collectively suggest that the bright and dark material tends to gradually change toward the average surface over time. This could be because of multiple processes, i.e., impact gardening/space weathering, and lateral mixing, including thermal and aqueous alteration, accompanied by changes in composition and physical properties such as grain size, surface temperature, and porosity (compaction).Comment: Meteoritics and Planetary Science; Dawn at Ceres special issu