Recent aerospace industry interest in developing subsonic commercial transport airplanes with at least 50% greater passenger capacity than the largest existing aircraft in this category (e.g. the Boeing 747-400 with approximately 400-450 seats) has generated a number of proposals based primarily on the configuration paradigm established 50 years ago with the Boeing B-47 bomber. While this classic configuration has come to dominate subsonic commercial airplane development since the advent of the Boeing 707/Douglas DC-8 in the mid-1950s, its extrapolation to the size required to carry more than 600-700 passengers raises a number of questions, including: - How large can an airplane of 707/747 configuration be built and still remain economically and operationally viable? - What configuration alternatives might allow circumvention of practical size limitations inherent in the basic 707/747 configuration? - What new and/or dormant technology elements might be brought together in synergistic ways to resolve or ameliorate very large subsonic airplane problems? To explore these and a number of related issues, a team of Boeing, university and NASA engineers was formed under the auspices of the NASA Advanced Concepts Program during 1994. The results of a Research Analysis contract (NAS1-20269) focused on a large, unconventional (C-wing) transport configuration for which Boeing and the authors were granted a design patent in 1995 is the subject of this paper which is based on information contained in McMasters et al. (NASA CR 198351, October 1996).
A large database of currently manufactured turbofan engines with a bypass ratio of at least 2.0 was compiled in 1996. Key parameters (dry weight, length, fan diameter, nacelle diameter, cruise thrust, air mass flow, bypass ratio, total pressure ratio, take-off specific fuel consumption, and cruise specific fuel consumption) were plotted, most as a function of take-off thrust. The resulting plots are a rich source of basic information, which can be used to quickly define an engine for use in a preliminary airplane design. The database is sorted by take-off thrust and can also be used to determine if an existing engine can be used in the proposed airplane. Relationships are suggested for use in preliminary design.
This paper describes the nature and development of an undergraduate aircraft design course involving students in US and UK universities working in an integrated team that models the international collaboration commonplace in the aerospace industry. The reasoning that led to this collaboration is outlined and details of the organisation and management of the programme described. Observations from the three years of experience with running the programme are made and some overall conclusions given. Some of the design projects are illustrated including the roadable aircraft design which won the 1999/2000 NASA/FAA AGATE National General Aviation Design Competition. The collaboration has been successful from an educational standpoint and would serve as an effective model that could be adopted by other pairs of universities.
Aerodynamic optimisation of wings in multi-engined tractor propeller arrangements is discussed and analysed with a fast calculation based on a Trefftz-plane analysis where the conservation laws of mass, momentum and energy are fulfilled in a control volume surrounding the configuration. The paper discusses the formulation of the optimisation algorithm based on augmented Lagrange integrals. The effect of viscous effects is incorporated in the calculation process. The method was implemented in a computer program which enables the user to find the optimum lift distribution for minimum drag for any tractor propeller/wing arrangement of arbitrary shape. As input for the slipstream data the user can either select input of experimental data or generate artificial data using a simple slipstream model based on the well-known blade element theory with Prandtl tip loss factor. Some numerical studies show that optimisation of a modern medium speed turboprop aircraft leads to performance increase by adapting the wing shape.
This paper presents a conceptual project of a high-altitude long-endurance unmanned aerial vehicle. It describes a number of historical, current and prospective HALE aircraft and considers existing four serious obstacles, to overcome them can mean the successful building of HALE aircraft. Among these obstacles there are very special aerodynamic (low Reynolds numbers together with transonic speeds), very light structures usually of high aspect ratio, propulsion technology (usually propeller driven by turbocharged piston engines) and flight control system (usually combining the best features of preprogrammed and hand-flown modes). Four aerodynamic design concepts are presented and their performances are compared. Among them is a biplane, considered mainly because of its moderate wing span, which can be obtained for a relatively big wing area and a high effective wing aspect ratio, a relatively stiff wing structure, and lower induced drag being possible to be obtained at the same lift and wing area as for the equivalent monoplane. It is shown that an attentively designed biplane can be efficient aerodynamically for high altitude patrol missions having almost the same endurance, using the same fuel to reach a service ceiling and having the take-off mass (and the payload) considerably bigger than a corresponding, equivalent monoplane. The paper is completed with selected considerations about dynamic stability.
The Concurrent Subspace Design (CSD) framework has been used to conduct a preliminary design optimization of an electric-powered, unmanned air vehicle operating at low Reynolds number. A multidisciplinary system analysis has been developed for this class of vehicles and includes aerodynamics, weights, propulsion, performance and stability and control. The CSD framework employs artificial neural network-based response surfaces to provide approximations to the design space. This approach was applied to a number of conceptual aircraft design studies. In each case the CSD framework was able to identify feasible designs with significant weight reductions relative to any previously considered (i.e. initial database) designs. This was accomplished with a reasonable number of system analyses. The results also demonstrate the adaptive nature of this design framework to changes in design requirements.
This paper discusses the application of simulated annealing in the conceptual design and optimization of twin-turboprop Commuter & Regional aircraft to obtain the optimum configuration and flight profile of such aircraft for operation over a given stage length. Generalized cost of travel incurred by a passenger for air travel between two cities is considered as the objective function to be minimized. Generalized cost is assumed to consist of four cost terms, viz., access cost, flight cost, time cost and airport cost. A computational methodology was developed for the estimation of these cost terms for short-haul air travel, as a function of 17 design variables and nine constraints. A simulated annealing optimization method was coupled to this methodology and a case study for short-haul business travel in India was carried out. A modified optimization strategy was adopted to reduce the overall computation time required. The results obtained in this case study are discussed in the paper.