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Technical Paper

The 2nd-generation Audi Space Frame of the A2: A trendsetting all-aluminium car body concept in a compact class car

2000-06-12
2000-05-0260
Vehicle concepts of the future will have to satisfy such contradictory requirements as high body rigidity and maximum safety in all driving situations, coupled with minimum weight. With this in mind, at the 1997 Frankfurt Motor Show Audi presented the A12 study vehicle, a car which makes ultra-low fuel consumption possible thanks to its new overall technical concept based on extremely low-weight ASF techniques and innovative engines, but is a multi-purpose four-door vehicle despite its compact exterior dimensions. This study model was developed into a production-ready vehicle within a very short space of time: the Audi A2, which made its début at the Frankfurt Motor Show in September 1999. Only with the aid of simulation techniques was it possible to bring such a novel body concept to production maturity within such a short space of time. The following article describes the technical highlights of the ASF body on the Audi A2.
Technical Paper

Technology Impact Forecasting for a High Speed Civil Transport

1998-09-28
985547
This paper outlines a comprehensive, structured, and robust methodology for decision making in the early phases ofaircraft design. The proposed approach is referred to as the Technology Identification, Evaluation, and Selection (TIES) method. The seven-step process provides the decision maker/designer with an ability to easily assess and trade-off the impact of various technologies in the absence of sophisticated, time-consuming mathematical formulations. The method also provides a framework where technically feasible alternatives can be identified with accuracy and speed. This goal is achieved through the use of various probabilistic methods, such as Response Surface Methodology and Monte Carlo Simulations. Furthermore, structured and systematic techniques are utilized to identify possible concepts and evaluation criteria by which comparisons could be made.
Technical Paper

Optimization of Wave Rotors for Use as Gas Turbine Engine Topping Cycles

1995-05-01
951411
Use of a wave rotor as a topping cycle for a gas turbine engine can improve specific power and reduce specific fuel consumption. Maximum improvement requires the wave rotor to be optimized for best performance at the mass flow of the engine. The optimization is a trade-off between losses due to friction and passage opening time, and rotational effects. An experimentally validated, one-dimensional CFD code, which includes these effects, has been used to calculate wave rotor performance, and find the optimum configuration. The technique is described, and results given for wave rotors sized for engines with sea level mass flows of 4,26, and 400 lb/sec.
Technical Paper

A Stepped-Piston Two-Stroke Engine for High Altitude Applications

1994-03-01
940400
The crankcase-scavenged two-stroke-cycle engine is preferred in cases where low weight and high power output are paramount requirements. These qualities are most important in small pilotless aircraft. It was found that the main problem in the use of two-stroke cycle engines for this purpose, is a sharp decrease in the engine power with the increase in altitude. This is attributed not only to the low density of the ambient air, but also to the deterioration of the efficiency of the gas exchange process. In order to improve the engine performance at high altitude, it is proposed here to employ a stepped-piston engine. The engine is constructed of a stepped piston and a single stepped cylinder thus forming three compartments; a power, a compression and a crankcase compartment. In this arrangement, the fresh charge is compressed in the compression compartment before it enters the crankcase compartment.
Technical Paper

Natural and Hybrid Laminar Flow Control for Aero-Engine Nacelles

1995-09-01
952016
In the search for methods of reducing aircraft drag, much attention has been devoted to the problems of maintaining large areas of laminar flow on wings. However, the operational requirement of high subsonic cruising speeds implies the use of wing sweep. This complicates the design since wing flows are fully three-dimensional and additional mechanisms for boundary layer transition e.g. attachment line contamination and cross-flow instability are present. In this research programme, an alternative component, the engine nacelle, is considered as a candidate for the application of laminar flow. The achievement of large areas of laminar flow over aircraft engine nacelles offers significant savings in aircraft fuel consumption.
Technical Paper

A Generic Model Concept for Optimisation in Preliminary Design

1996-10-01
965519
The design process is an interactive feedback process where the performance of the design is compared with the performance specification. In aircraft design it is very important that the system is optimised with respect to different aspects such as performance and weight. Traditionally, and by necessity, the design procedure has began with some kind of performance specification followed by a conceptual design, and after that the system has been optimised (usually implicitly) with respect to the performance specification. Typically, aircraft design optimisation is characterised by a multitude of objectives that can be difficult to compare to each other, such as low fuel consumption, high speed and passenger comfort. Usually this is where the engineering judgement of the designer comes in. In traditional design it is often difficult to establish what was the result of design decisions and what was the result of pure optimisation.
Standard

Cryogenically Fueled Dynamic Power Systems

2011-08-03
CURRENT
AIR999A
In this report, "Cryogenically Fueled Dynamic Power Systems" include all open cycle, chemically fueled, dynamic engine power systems which utilize cryogenic fuels and oxidizers. For nearly all practical present day systems, this category is limited to cryogenic hydrogen or hydrogen-oxygen fueled cycles with potential in future, more advanced systems for replacement of oxygen by fluorine. Excluded from the category are static cryogenic systems (e.g., fuel cells) and chemical dynamic power systems which utilize earth storable propellants.
Standard

CRYOGENICALLY FUELED DYNAMIC POWER SYSTEMS

1968-10-01
HISTORICAL
AIR999
In this report, "Cryogenically Fueled Dynamic Power Systems" include all open cycle, chemically fueled, dynamic engine power systems which utilize cryogenic fuels and oxidizers. For nearly all practical present day systems, this category is limited to cryogenic hydrogen or hydrogen-oxygen fueled cycles with potential in future, more advanced systems for replacement of oxygen by fluorine. Excluded from the category are static cryogenic systems (e.g., fuel cells) and chemical dynamic power systems which utilize earth storable propellants.
Technical Paper

Flight 2000 Program

1997-10-13
975638
Recognizing that modernization of the National airspace system must be accelerated to accommodate aviation growth, the Federal Aviation Administration, in partnership with the aviation industry, has initiated Flight 2000, a real-world implementation of advanced communications, navigation, surveillance, and air traffic management capabilities. Flight 2000 is a precursor of Free Flight, an evolutionary air traffic management concept that will greatly increase user flexibility to plan and fly their preferred routes. Flight 2000 transfers the Free Flight concept to a real operational setting and gives the FAA an opportunity to conduct a complete operational system evaluation prior to NAS-wide deployment.
Standard

Aircraft Fuel Weight Penalty Due to Air Conditioning

1989-09-01
HISTORICAL
AIR1168/8
The purpose of this section is to provide methods and a set of convenient working charts to estimate penalty values in terms of take-off fuel weight for any given airplane mission. The curves are for a range of specific fuel consumption (SFC) and lift/drag ratio (L/D) compatible with the jet engines and supersonic aircraft currently being developed. A typical example showing use of the charts for an air conditioning system is given. Evaluation of the penalty imposed on aircraft performance characteristics by the installation of an air conditioning system is important for two reasons: 1 It provides a common denominator for comparing systems in the preliminary design stage, thus aiding in the choice of system to be used. 2 It aids in pinpointing portions of existing systems where design improvements can be most readily achieved.
Standard

Aircraft Fuel Weight Penalty Due to Air Conditioning

2011-07-25
CURRENT
AIR1168/8A
The purpose of this section is to provide methods and a set of convenient working charts to estimate penalty values in terms of take-off fuel weight for any given airplane mission. The curves are for a range of specific fuel consumption (SFC) and lift/drag ratio (L/D) compatible with the jet engines and supersonic aircraft currently being developed. A typical example showing use of the charts for an air conditioning system is given. Evaluation of the penalty imposed on aircraft performance characteristics by the installation of an air conditioning system is important for two reasons: 1 It provides a common denominator for comparing systems in the preliminary design stage, thus aiding in the choice of system to be used. 2 It aids in pinpointing portions of existing systems where design improvements can be most readily achieved.
Standard

RECOMMENDED RMS TERMS AND PARAMETERS

1995-12-01
CURRENT
AIR4896
The terms used in most engineering technologies tend to be physical characteristics such as speed, rate of turn, and fuel consumption. While they may require very careful definition and control of the way in which they are measured, the terms themselves are not subject to different interpretations. Reliability, maintainability and supportability (RMS) however, use terms that are mathematically defined. As a result, there are more than 2000 terms defined in just the documents reviewed so far, many of which have multiple interpretations. This proliferation of definitions of the terms leads to problems when one attempts to compare the performance of one system to another. For example, the RMS performance of a transport aircraft from the commercial arena is measured using metrics that are not the same as those for a fighter or attack aircraft from a military service.
Standard

Maintenance Life Cycle Cost Model

2010-03-22
CURRENT
AIR5416
This document describes a life cycle cost model for commercial aircraft composite structure. The term life cycle cost used herein, refers to the airline costs for maintenance, spares support, fuel, repair material and labor associated with composites after introduction into service and throughout its useful life. This document contains the equations that can be programmed into software which is used to estimate the total cost of ownership aircraft, including structure. Modification costs and operating costs are estimated over a specified life (any period up to 30 years). Modification costs include spares holding, training, support equipment, and other system related costs. Annual operating costs include: Schedule interruption, fuel, spares, insurance, and maintenance. Maintenance costs are separated by scheduled maintenance or unscheduled damage, or can by grouped into the typical organizations of line, shop, and hangar maintenance.
Standard

HELICOPTER TURBINE ENGINE WASH

1995-05-01
CURRENT
AIR4416
Engines subject to dust, industrial pollution, saltwater contamination or other chemically laden atmosphere (including pesticides and herbicides) lose performance due to deposits of contaminants on surfaces in the aidgas flow path. Engine wash and engine rinse procedures are utilized to restore turbine engine performance. These procedures are generated by the engine manufacturer and are included in the Engine Maintenance/Service Manuals. For most turbine engines these procedures are similar in concept and practice; however, application details, choice of solvents and many other service features can vary from engine manufacturer to engine manufacturer and may even vary within the range of engine models produced by any manufacturer.
Standard

Environmental Control Systems Life Cycle Cost

2017-02-07
CURRENT
AIR1812B
This report contains background information on life cycle cost elements and key ECS cost factors. Elements of life cycle costs are defined from initial design phases through operational use. Information on how ECS designs affect overall aircraft cost and information on primary factors affecting ECS costs are discussed. Key steps or efforts for comparing ECS designs on the basis of LCC are outlined. Brief descriptions of two computer programs for estimating LCC of total aircraft programs and their use to estimate ECS LCC, are included.
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