Search Results

The process of entrance of a pair of laminar rectilinear vortices into an atmospheric layer with stable stratification is modeled by solving numerically the two-dimensional time-dependent Navier-Stokes equations in Boussinesq's approximation. The solution is obtained on an 200x200 uniform grid using an explicit finite-difference scheme at a flow Reynolds number of Re=106 and a temperature anomaly gradient of 2K per 100m height increment. The computations have shown that at the initial phase of the immersion of the vortex pair into the stratified layer, a retardation of their descent is observed, then vortices bring together and the rate of their descent become higher.

Although there are many commonalties between fixed-wing and rotary-wing aircraft, both in terms of their performance and the missions they fly, their extensive differences demand that we recognize the training requirements that are unique to rotary-wing vehicles. In addition, the rotary-wing industry is made up of many widely distributed small operators whose training needs and logistics vary widely from those of the well-ordered, capital intensive, air carriers. The relative absence of large operators in the rotary-wing industry is a source of challenge to training-equipment manufactures and to the federal agencies responsible for supporting and regulating the development of aviation. In anticipation of growth in the rotary-wing industry, the Federal Aviation Administration (FAA) has proposed new rules, Part 142 Title 14 CFR, which will authorize and regulate certified training centers.

The work deals with the problem on aircraft vortex wake behavior in steady-flow formulation. Further approximations of slender-body theory are constructed with the aid of asymptotic methods. The mathematical approach proposed performs to calculate the aircraft wake up to breakdown. The nontrivial analytic solutions for the problem of motion of one and two vortex filaments with circular cross-section are obtained.

The possibility of visualization of an aircraft jet-and-vortex wake above a landing strip is investigated. The processes of water vapor heterogeneous condensation and droplets coalescence due to turbulent pulsation are taken into account. Numerical examples for the case of B-747-type flyer take-off are presented.

To help reduce operating costs of a High Speed Civil Transport aircraft, our External Vision System Technology Development Team at Honeywell, along with teams at NASA, Boeing and McDonnell Douglas, is investigating the feasibility of replacing forward windows with a synthetic version. The synthetic window will capture the greatest part of information normally visible to pilots. Ideally, it would capture the “look, feel, and functionality” of traditional windows. This paper discusses optical characteristics of certified windows. Measurements were taken from commercial aircraft windows at various stages of service up to and beyond 20,000 hours. Fundamental system attributes, relating to visual performance, were measured and evaluated. Measurement techniques are described. The resultant data provide the synthetic window systems designers a foundation on which to base their work and design goals.

Boeing is participating in a research program to study the feasibility of building a High Speed Civil Transport (HSCT). A program assumption is that the aircraft will not have a droop nose capability, requiring that the forward facing windows be replaced by large format displays showing the outside scene. We refer to this display as the External Vision System (XVS). The issues being addressed in this paper involve the integration of primary flight symbology into the XVS display. We point out how this integrated display is unique, falling someplace between a standard head-down primary flight display and a head-up display. We describe potential advantages of an integrated display as well as point out a number of possible problem areas. High level goals driving the display design are presented. We finish by describing a number of research and development issues, that if resolved, would contribute to the design effort.

An integrated cockpit display suite, the T-NASA (Taxiway Navigation and Situation Awareness) system, is under development for NASA's Terminal Area Productivity (TAP) Low-Visibility Landing and Surface Operations (LVLASO) program. This system has three integrated components: Moving Map -- track-up airport surface display with ownship, traffic and graphical route guidance; Scene-Linked Symbology -- route/taxi information virtually projected via a Head-up Display (HUD) onto the forward scene; and, 3-D Audio Ground Collision Avoidance Warning (GCAW) system -- spatially-localized auditory traffic alerts. In this paper, surface operations in low-visibility conditions, the design philosophy of the T-NASA system, and the T-NASA system display components are described.

Increased demand for machining with higher material removal rates necessitates the use of higher rotational speeds and higher side loads during the cutting process. These new machining parameters manifest themselves as chronic degenerative problems with spindles and tool holder taper interfaces. Regenerative vibrations serve to complicate this condition and greatly contribute to the severity of this degenerative process. This paper describes solutions for these recent machining process problems to manufacturing engineers and machine tool builders. An overview of the complicated processes that cause vibration induced damage to machine tools is presented in simple terms. The objective is to give the reader a basic understanding of vibration induced machine damage, and several ways to combat this problem.

We report the results of a part-task simulation evaluating the separate and combined effects of an electronic moving map display and newly developed HUD symbology on ground taxi performance, under moderate- and low-visibility conditions. Twenty-four commercial airline pilots carried out a series of 28 gate-to-runway taxi trials at Chicago O'Hare. Half of the trials were conducted under moderate visibility (RVR 1400 ft), and half under low visibility (RVR 700 ft). In the baseline condition, where navigation support was limited to surface features and a Jeppesen paper map, navigation errors were committed on almost half of the trials. These errors were virtually abolished when the electronic moving map or the HUD symbology was available; in addition, compared to the baseline condition, both forms of navigation aid yielded an increase in forward taxi speed.

This purpose of this research is to identify the information requirements and interaction issues associated with pilot use of an autoflight system for the high-speed civil transport (HSCT). The approach taken was to survey and evaluate existing research tools and methods for representing and understanding human interaction with complex engineering systems, to model a current-generation autoflight system representative of the capability required in the HSCT using the techniques found to be most appropriate, and then to use this model and other proposed HSCT guidance and control concepts to identify the necessary information requirements and interaction issues. The modeling representation chosen was the Operator Function Model (OFM).

During the commercial aircraft assembly process, many interrelated installations require alignment to a common reference centerline or location to a common reference plane. A rotational laser can be used to establish a vertical, horizontal, or other desired plane orientation to serve as a common installation reference for multiple assemblies. The cargo floor installation in the lower lobe of the 777 forward section requires that three physically separate cargo floor sections be aligned to a common centerline and lie in the same horizontal plane. Two rotational lasers are used in conjunction with laser positioning equipment, digital laser targets, and conventional tooling hardware to meet the installation criteria and provide a reliable, repeatable process.

During the mid-1970s, the US embarked on a modest but highly focused effort to demonstrate an aircraft possessing a very low radar signature and sufficient performance to have operational utility. Known as Have Blue, the project was highly successful and led to the F-117 A. This paper discusses issues associated with reducing radar signature to very low levels (levels that are “tactically meaningful,” e.g., capable of defeating realistic threat systems). Radar phenomena and the concept of radar cross section (RCS) are briefly summarized and RCS reduction techniques as they were applied to Have Blue are described. RCS reduction considerations and techniques pioneered by Have Blue have become an integral component of the combat aircraft design process over the past two decades.

In the last twenty years, radar cross section (RCS) reduction has emerged as an important and achievable way to improve the survivability of military aircraft. Specifically, the first manned aircraft to achieve a tactically significant reduction in RCS was the Lockheed Have Blue technology demonstrator, which was designed starting in 1975 and first flew in 1977. This was followed by a true military aircraft, the F-117 A, which became operational in 1983. Several very low observable (VLO) aircraft have been designed since then. All of them benefit from significant advances in the ability to predict and improve the RCS of an aircraft in its early design stages. The present paper describes these advances and their impact on aircraft design, using examples of reduced RCS aircraft designed before and after the techniques were evolved.

The reduction or other control of an aircraft's radar, infrared, visual and acoustic signatures can greatly improve its survival, resulting in improved weapons' effectiveness. Although radar stealth is important, it is pointless without low observability in the other regions of the electromagnetic spectrum. However, this paper, for reasons of brevity will concentrate on methods to control radar signature only. The topics of: benefits of signature control; contributions of an aircraft to its radar cross section (RCS); methods to reduce RCS; penalties/costs of RCS-reduction, in terms of performance, volume, weight and maintenance; use of radar absorbing and structural composite materials are addressed. The conclusion is that while signature control is important, there are penalties to be paid. RCS-reduction has become merely another factor to be considered in the series of compromises made during aircraft design trade-offs.

Embry-Riddle Aeronautical University (ERAU), the world's leader in aviation and aerospace education, has developed an aggressive program to help students succeed. ERAU students are typically very focused because of a strong interest in the aviation and aerospace fields. However, they experience many of the same problems as other college students. With the assistance of a Strengthening Institutions Grant from the Department of Education, ERAU is developing programs designed to help students succeed. After describing the composition of ERAU, these programs and others targeted at student success will be described.

One of the innovative methods of engineering education today is teaching students at several distant sites simultaneously and interactively using two-way audio and video teleconferencing (VTC) equipment. This method of teaching is referred to as Distance Learning (DL). Teaching in the DL mode offers several advantages to the teacher, to the student, and to the university over the traditional classroom lecture to on-campus students. It also presents several challenges to the teacher, the student, and the university. This paper presents the experience of the author in modifying a graduate level course in aircraft combat survivability (ACS) for presentation in the DL mode. The VTC equipment and the course preparation, delivery, and administration for the DL mode are presented and compared to these same activities when teaching using the classroom lecture mode.

In the TsAGI T-103 wind tunnel, an effective method has been tested for simulating the impact of the vortex wake forming behind a heavy aircraft during take-off and landing operations on aerodynamic characteristics of the following aircraft flying along a trajectory close to the vortex wake axis. For simulation an airfoil lattice with a differential deflection of the sections along the span is used. The lattice is mounted at the wind tunnel nozzle exit. Investigations of flow structure and tests of a general-aviation aircraft model has shown that the airfoil lattice creates in the test section flow deflections which are equivalent of wake influence formed by the B-747 airplane in landing configuration on distance from 500m and more.

The ever increasing complexity of aerospace design has seen the emergence of Aerospace Design Automation, the study of design of aircraft/aerospace vehicle design systems. Our previous publications have dealt with its foundation, the Aerospace Design Representation Programming Interface (AERO-DRPI). To model the design, process and status data the AERO-DRPI uses data schemas appropriate for a tool and data combination. A data schema enables the definition of semantics and syntax of design, status, and process data. For generic design management, a data schema is required on which all the generic operations are possible. It should also meet all the requirements for generic design management. The generic design management schema should be extendible with minimum data redundancy. A specific design management data schema uses the generic design management schema as its foundation. For a specific design sub-discipline there are specific schemas.

The Analytical Design Package (ADP) has been developed as a part of the Air Force Frameless Transparency Program. ADP is an integrated design tool consisting of existing analysis codes and Computer Aided Engineering (CAE) software. The objective of the ADP is to develop and confirm an integrated design methodology for frameless transparencies, related aircraft interfaces, and their corresponding tooling. The application of this methodology is intended to generate a high confidence for achieving a qualified part prior to mold fabrication. ADP is a customized integration of analysis codes, CAE software and material information databases. The primary CAE integration tool for the ADP is MSC/PATRAN, a commercial-off-the-shelf (COTS) software tool. The open architecture of MSC/PATRAN allows customized installations with different application modules for specific site requirements.

This paper describes an Introduction to Flight Performance short course taught at the USAF Academy designed for aeronautical engineering faculty. This course provides an in-flight experience related to the material in a core course on the fundamentals of aeronautics. Its objective is to improve faculty understanding and appreciation of flight and thereby enhance teaching. It consists of five sessions (lectures/preflight briefings/flights) which cover the principles of stability and control, straight and level flight, turning and maneuvering flight, climbs and descents, and takeoffs and landings. To the maximum extent possible the flying is done by the participants