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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

During the last decades a great number of new technologies have been developed to increase the efficiency and safety of new aircraft. Many of these technologies demand, however, a completely different design philosophy, design approach and organization of the design process. At the same time the fast growing capacity of modern computer systems has opened up the possibility of more accurate design and analysis, interactive design, design optimization and strategic design management. In many cases this has led to a complete reconsideration and reorganization of the entire design process. In order to keep pace with these developments and to be able to make a contribution to future developments in this field the ICADS Interactive Computerized Aircraft Design System was set up. This system must enable us to make students and designers familiar with advanced design methods and the logic behind it.

This paper discusses a top-down analysis methodology for the design, development and evaluation of advanced technological systems like those being considered for Free Flight, the Advanced General Aviation Transport Experiment (AGATE), or the High Speed Civil Transport (HSCT) program. In order to ensure a safe and efficient introduction and integration of those technologies, it is generally accepted that human factors engineering concerns must be raised and addressed from the beginning and throughout the research and development cycle. History indicates that human factors engineering concerns were normally addressed too late, contributing significantly to the well known “automation problem” in commercial aviation. In response to the potential for negative side effects advanced technology design guidelines have been developed. This paper focuses on one such guideline concerning sound systems engineering principles.

A numerical model has been developed to predict the formation of NOx and formaldehyde in the combustion and post-combustion zones of a methanol DI engine. For this purpose, a methanol-air mixture model combined with a full kinetics model has been introduced, taking into account 39 species with their 157 related elementary reactions. Through these kinetic simulations, a concept is proposed for optimizing methanol combustion and reducing exhaust emissions.

A number of practical applications where dual fuel systems are used, such as in gas fuelled diesel engines, involve the combustion in air of a gaseous fuel, such as methane in the presence of a higher hydrocarbon vapour. There is a need to examine and understand the nature and extent of any chemical interaction that may take place between the gaseous and higher hydrocarbon fuel components and how this interaction influences the combustion processes and hence the performance of dual fuel engines. Detailed chemical kinetics for the oxidation of the typical higher hydrocarbon fuel n-heptane, representing the behaviour of diesel vapours, in the presence of methane, are examined while using a comprehensive kinetic scheme (1966 reaction steps and 380 species) at different conditions relevant to engine applications, including constant temperature, constant pressure and constant volume processes.

Variable composition of natural gas depending on the gas source causes variable ignition and combustion properties when used as fuel in internal combustion engines. Ignition and combustion problems lead to reduced efficiency, increased levels of emissions, as well as increased mechanical and thermal loads on engine components. The main objective of this study is to investigate the influence of natural gas composition on ignition properties in a direct injection hot surface assisted compression ignition engine. Previous investigations have shown that ignition of methane require hot surface temperature in the range of 1200-1400 K in order to obtain an ignition delay within 2 milliseconds. Pure methane and several natural gas mixtures have been tested under various conditions in a constant volume combustion bomb and in a test engine. Ignition delay and cycle to cycle variations are used to compare the combustion qualities of the different gas.

The ignition and combustion of natural gas directly injected into a multi-cylinder two-stroke diesel engine and ignited by a pilot liquid diesel injection has been investigated experimentally and with the aid of numerical simulation. Measurements of cylinder pressure and thermal efficiency were supplemented by endoscopic observation of flame development and three-dimensional numerical simulation of the ignition and combustion process. With gas/diesel fueling and appropriate injection timing, ignition delay and combustion duration can be about the same as with 100% diesel liquid fueling. Flame photography indicates that, for the same liquid diesel flow rate, subsequent injection of natural gas has a negligible effect on the ignition delay of the liquid fuel. Relative ignition timing is of major importance in obtaining successful combustion.

Two-dimensional images of fuel distributions have been recorded in the intake of a fired 6-cylinder-4-valve spark ignition engine. As markers for the fuel a new exciplex-seed combination of triethylamine (TEA) and benzene was developed. Mixture formation and fuel evaporation of two different types of fuel injectors were compared inside the intake. The images were coupled with measurements of unburnt hydrocarbons (UHC) emissions of the two injectors in the exhaust gas. The behaviour of the fuel vapour distribution was examined at different times during the engine cycle. Instantaneous and averaged fuel distributions are shown and discussed in their influence on mixture formation.

The mixture formation process in a stratified-charge spark-ignition engine under moderate load conditions has been determined from fuel concentration measurements obtained from planar laser-induced fluorescence (PLIF) of a fluorescence fuel marker, 3-pentanone. A one-cylinder 4-valve engine, specifically designed to provided optical access through the walls of the combustion chamber and through a piston window, was used. In order to gain insight into the processes influencing the fuel motion and mixing, average fuel concentrations were recorded in four different planes between 0.7 mm to 15 mm below the spark plug for various crank-angle positions during the inlet and compression stroke and for two different injection timings. These measurements give a mean 3-dimensional picture of the time history of the fuel distribution.

In order to separate the HC-emissions from two-stroke engines into short-circuit losses and emissions due to incomplete combustion, Laser Induced Fluorescence (LIF) measurements were performed on the exhaust gases just outside the exhaust ports of two engines of different designs. The difference between the two engines was the design of the transfer channels. One engine had “finger” transfer channels and one had “cup handle” transfer channels. Apart from that they were similar. The engine with “finger” transfer channels was earlier known to give more short-circuiting losses than the other engine, and that behavior was confirmed by these measurements. Generally, the results show that the emission of hydrocarbons has two peaks, one just after exhaust port opening and one late in the scavenging phase. The spectral information shows differences between the two peaks and it can be concluded that the latter peak is due to short-circuiting and the earlier due to incomplete combustion.

An indirect method to map the burned gases in SI engine has been developed. It is based on visualisation by Laser Induced Fluorescence of the unburned mixture seeded with biacetyl. Both internally and externally recirculated burned gases are monitored. This diagnostic is complementary to the LIF technique applied to measure the gasoline distribution. These LIF gasoline and burned gases measurements are applied in a 4-valve optical access SI engine for a large range of operating conditions. These include variations of both fuel injection and burned gas recirculation modes causing different types of stratification leading to very distinct heat release and exhaust emissions characteristics. Tumble level and spark location are also modified. The observation of the actual stratification in the engine forms a sound basis explanation of the engine performance.

The durability and performance of diesel fuel injection equipment in actual use continues to be a concern for the manufacturers of diesel powered equipment, diesel fuel injection equipment suppliers and diesel fuel suppliers This concern has been caused by recent changes to both the equipment and the diesel fuel driven by environmental legislation The term “lubricity” has become commonly used to describe the ability of a diesel fuel to prevent or minimise wear in diesel fuel injection equipment Of particular interest are distributor and rotary type fuel injection pumps that rely totally on the fuel for lubrication These pump types are commonly used in light and medium duty diesel engines Earlier work has shown that fuels with good low temperature properties have inherently poorer lubricity performance than summer quality diesel fuels (1, 2)* Due to the need for such fuels in Canada we have been investigating the lubricity performance of winter diesel fuels for a number of years Most recently we have studied the lubricity performance of various fuels and additives in rotary type pumps and related these results to the test fuel properties, including lubricity as measured in a number of current lab bench tests

Almost all published work involving injector nozzle cleanliness has been performed by means of keep-clean tests. Another area of interest in the performance of detergents is that of clean-up, which is the ability of a detergent to remove excessive deposits built up in previous service. A study is now reported in which the degree of clean-up is established for a modern commercial detergent used in a low-sulphur diesel fuel. Measurements are presented from a bench engine and also from road vehicles operated under controlled urban driving conditions. Substantial clean-up is demonstrated using detergent treat-rates representative of modern formulation technology, regaining the state of cleanliness that provides optimum performance of the injection equipment. The fouling levels after clean-up are comparable with the results of keep-clean tests, run under identical conditions. Accumulated driving distance and fuel usage to provide this clean-up effect are also discussed.