Browse Topic: Terrain
Army rotorcraft operations demand precision and adaptability to navigate challenging terrain, respond to real-time mission requirements, and ensure time-to-target arrival. Navigating complex terrain, making real-time trajectory adjustments, and ensuring timely arrival at designated objectives while considering other problems are challenging. This paper focuses on the concept of 4D conformal pilot cueing that can facilitate a significant reduction in pilot workload. To enhance the rotorcraft operations with Army scenarios, a visual cueing method based on Tau Theory for obstacle avoidance is proposed so that the pilot can make a coordinated turn away from the obstacle and safely change the helicopter's trajectory to avoid the collision. To demonstrate the visual cueing method, desktop simulations are performed in Matlab/Simulink environment using simulated pilots.
ABSTRACT
The command inputs selected for system identification (SYSID) are dictated by numerous factors, some of which include: 1) The frequency range of interest; 2) The capability of the system to sustain the inputs; 3) The capability of the system to remain ‘agnostic’ to future inputs. When the elements comprising, the system being identified are all electro-mechanical, frequency sweeps, sum-of-sines, and impulsive inputs are standard identification techniques. However, when human manual control becomes an element of the system, the second and third factors are key considerations. Sum-of-sines (SOS) has been used extensively for identifying human control dynamics as it provides an input that is perceived by the pilot as random and focuses power at discrete frequencies. A disadvantage of SOS is the attentional demand it requires from the human operator, which limits the duration of an identification run to typically around one minute. This in turn constrains the lowest frequencies that can be
This paper presents flight test results from a research investigation into the effect of sloping terrain on hover power required. The investigation involved flight test data that were collected for a UH-72A Lakota helicopter while hovering inside ground effect above sloped terrain of varied gradients, in several aircraft orientations and multiple heights above the ground. Performance data were collected over a range of thrust coefficients by varying aircraft weight, rotor speed and environmental conditions over two sorties. The data are compared and contrasted to provide specific insight into the effects of slope magnitude, slope orientation, and rotor hub height. The results demonstrate that hovering over sloping terrain yields performance effects that are both non-intuitive and operationally significant. In particular, the effect of the sloping terrain was seen, in some conditions, to cause power requirements that exceed those for hover out-of-ground-effect, a traditional worst-case
ABSTRACT Low-level flight missions can be complex, at times requiring any or all of the following: maneuvering and navigating over challenging terrain, scanning for hostile or friendly units, operation in degraded visibility, radio communications, and decision-making in uncertain and dynamics environments. These conditions, and time, will affect mental workload (MWL) and performance. While direct performance measurements are normally available, information on pilot workload must either be obtained through (intrusive) subjective measures directly from the pilot, or inferred using indirect measurements. Performance can affect MWL, and MWL can affect performance - as the pilot generally perceives and responds to task performance through display interfaces, these displays can be used to manage and balance the tradeoff between MWL and performance. This paper presents the work of a collaborative project between US and Israel whose objectives are to develop a multimodal integrated cueing
ABSTRACT A new computational technique, Wave Confinement (WC), is extended here to account for sound diffraction around arbitrary terrain. While diffraction around elementary scattering objects, such as a knife edge, single slit, disc, sphere, etc. has been studied for several decades, realistic environments still pose significant problems. This new technique is first validated against Sommerfeld's classical problem of diffraction due to a knife edge. This is followed by comparisons with diffraction over three-dimensional smooth obstacles, such as a disc and Gaussian hill. Finally, comparisons with flight test acoustics data measured behind a hill are also shown. Comparison between experiment and Wave Confinement prediction demonstrates that a Poisson spot occurred behind the isolated hill, resulting in significantly increased sound intensity near the center of the shadowed region.
ABSTRACT The original abstract was titled "Degraded Visual Environment Categories" and in the process of performing the work, it was determined that "Operational Level" was a more relevant term than "category", hence the title change. Degraded Visual Environment (DVE) is a complex topic and not all aircraft or rotorcraft have the same mission or same DVE requirements. While this paper is not assuming a clean sheet of paper approach to defining the problem, it attempts to provide a different view of the problem in the context of Army Attack and Reconnaissance aircraft. The intent is to create a frame work in which the problem can be broken up into smaller pieces using operational contexts that are defined within this paper as operational levels based on visibility and terrain flight levels for Attack aircraft operations under DVE conditions. The objective is to define the problem so that a worst-case problem does not have to be solved first. This is important, because for the near-term
Modern wind farms are subjected to significant aerodynamic interference due to unsteady wakes of individual turbines as well as the complex terrains on which they are erected. The present study uses a new mixed basis formulation of the Navier-Stokes equations for accurate numerical simulation of convection-dominated flows on a complex terrain. The turbines are modeled using a distribution of momentum sources and the incompressible, turbulent flow-field is solved using the Reynolds Averaged Navier-Stokes (RANS) equations. A finite-volume procedure is used on body fitted grids and the SIMPLER algorithm is used to obtain the flow-field. Three different turbulence models including the standard, RNG, and realizable K - ε are implemented and compared. Results validating the ability of the numerical procedure to simulate flows over complex terrains and wind turbines are presented. Applications providing insights into the performance and loading on wind turbines subjected to turbine-terrain
Collision with obstacles (typically wires and towers) and with terrain during low level helicopter flight under low visibility conditions has been a documented problem for the US military. Degraded visual environments (DVE) due to night operations and/or poor weather prevent adequate visibility of terrain and obstacles ahead of the aircraft and contribute to many of the accidents. This paper documents the results of twelve pilots in a simulation evaluating four types of visual conformal symbology sets in a low-visibility condition contour terrain flight: a scene-linked condition, a conformal line condition, a guidance line condition, and the combination of the two in a conformal + guidance condition. The results of combined quantitative and qualitative analyses strongly support the superiority of the contour lines over the scene-linked to ensure the safest flying behavior and the greatest situation awareness. However, the interindividual variability was very high, suggesting that a
North Atlantic Industries (NAI) recently received an initial contract from L-3 Maritime Systems for Custom-on-Standard Architecture™ (COSA™) COTS rugged systems for the Ship to Shore Connector (SSC) Data Acquisition Unit. The advanced, rugged intelligent I/O and communications subsystem delivers significant advantages for data acquisition and control solutions for the U.S. Navy’s new SSC program. The SSC is the successor to the Navy’s versatile Landing Craft Air Cushion (LCAC) vehicle, which is nearing its expected service life. Prime contractor for the detail design and construction of the Ship to Shore Connector, awarded under Naval Sea Systems Command (NAVSEA) Contract N00024-12-C-2401, is Textron Systems.
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