Emilio Perez

Design constraints in the payload-range diagram of ultrahigh capacity transport airplanes

The economic and productivity potential of ultrahigh capacity airplanes, assessed through the payload-range diagram and the direct operating cost, is considered in the present work from a designers viewpoint. Two different scenarios are envisaged: first, with current requirements and constraints; second, after including some achievable improvements. The design constraints analyzed are maximum takeoff weight-based wing loading, maximum wingspan, minimum aspect ratio, maximum zero fuel weight-based wing loading, and maximum fuel capacity. Furthermore, to account for possible advantages of unconventional concepts, the common wingtailplane and a three-surface arrangement are dealt with in parallel, yielding a total of four cases: two configurations in two scenarios. The payload-range diagrams obtained are compatible with very dense, transatlantic, and transpacific routes; however, the three-surface solution in the second scenario exhibits very poor pay load vs range flexibility. The benefits of the four cases are considered by computing the direct operating cost relative to that of a B747-400, providing clear economic arguments in favor of these ultrahigh capacity aircraft.

Road and railway accessibility atlas of Spain

Abstract Please click here to download the map associated with this article. This article presents accessibility maps for road and railway on the Spanish peninsular for 1990, 1995, 2000, 2005 and 2007. Accessibility is defined as the ability of reaching a particular destination using the transport network. To calculate accessibility, a network efficiency indicator was used to measure the speed with which the distance between the starting point and the destination is actually covered. The process consisted of first configuring the Spanish road and railway networks by establishing their connectivity and identifying their typology, with a precision of 500 metres, for each of the years studied. The current road networks and the various railway networks (high speed, conventional…) were considered separately. Another process involved creating a map showing all the municipal districts in the Spanish part of the Iberian Peninsula (8,176), and then assigning to each one an economic variable to calculate its accessibility. The indicators were calculated by computing the minimum paths, where the cost is the travel time determined according to the type of section of the route. An accessibility value was obtained for each node (urban agglomeration) and was then interpolated in order to provide a graphic representation of the results.

Effects of the Mismatch Between Design Capabilities and Actual Aircraft Utilization

Air routes are mainly determined by the interaction of geographical, political, economic, and social factors. On another side, airlines use their aircraft for a diversity of missions. Because of both factors the actual utilization of transport aircraft is well inside the payload-range envelope, which means that the design features are oversized for most flights. The objective of this paper is to evaluate the savings that could be achieved if transport aircraft were designed for shorter ranges: i.e., closer to the actual utilization pattern. In this design scenario the maximum takeoff weight and the operating empty weight would be remarkably reduced. This would lead to a reduction in aircraft price, trip fuel, maintenance cost, landing and navigation charges, and environmental impact. Direct operating cost is used as the figure of merit of the reduced-range approach.

Wake of Transport Flying Wings

Flying wings are among the most promising concepts regarding the ever-increasing air traffic demand. They could help in improving economic efficiency and would be environmentally friendly, both in terms of emissions and noise. This paper addresses the problem of trailing vortices shed from the flying wing, arranged as a pair of counter-rotating vortex tubes as in conventional aircraft. The turbulence produced by the wake obliges airports to maintain certain time and distance separation between aircraft in takeoff and landing maneuvers, imposing a limit on the number of movements per runway. With the help of a simple model, the present paper provides preliminary estimations of circulation, core size, induced velocities, and other relevant features of the wake of transport flying wings and shows that it is less hazardous than that of conventional aircraft of similar size.

Cost-range trade-off of intermediate stop operations of long-range transport airplanes

The objective of this study is to show the environmental and operating cost savings that could be achieved if long-range transport aircraft were designed for shorter ranges, and long-range flights were operated with an intermediate stop, obviously, with the drawback of longer trip duration and the increase in the number of flight cycles. The maximum take-off weight and operating empty weight, the main design variables of transport airplanes, noticeably diminish. The overall result depends on the length of the route, the extra distance due to the detour, the location of the intermediate airport and the technology level (range factor and operating empty weight fraction with respect to the maximum take-off weight). In all the routes analysed, the uneven splitting between both legs plays a secondary role. It is shown that long routes are well adapted to intermediate stop operations, particularly when the airliner serving the route has been designed for a medium range. However, intermediate stop operations produce a negative impact for medium and short city pair distances, since the reduction in aircraft weight is more than counterbalanced by the extra fuel and time required in the non-cruise phases of the flights.

Potential Effects of Blended Wing Bodies on the Air Transportation System

Flying wings in various layouts (blended wing body, C-wing, tail-less aircraft, etc.) are among the most promising concepts in the foreseeable scenario of air traffic increase and very demanding noise and emission regulations. Published literature shows that these aircraft will exhibit considerable gains in field length and cruise performance with respect to conventional airplanes and could be less harmful in terms of emissions and noise. The objective of this study is to present the beneficial effects that blended wing bodies would have on the air transportation system: specifically, on four relevant aspects of airport capacity, community noise, air space capacity, and emissions.

Extended Range Operations of Two and Three Turbofan Engined Airplanes

The objective of the present work is a comparative analysis of the behavior of two and three turbofan engined airplanes after engine failure. A simple but fairly realistic treatment of the range equation allows study of extended range operations of airplanes after any prescribed decrease in thrust. The approach takes into account the increase in parasite drag, and considers variations of thrust and specific fuel consumption with altitude and Mach number. All peculiarities of the powerplant are translated into a few nondimensional parameters. The model provides the long-range cruise conditions after engine failure, namely altitude and Mach number, and the additional fuel needed to reach the final destination. Results for a typical 5000-km route show the relative disadvantage of twins. Nomenclature A = aspect ratio of wing AF = extra fuel needed to reach destination due to engine failure aQ = speed of sound at sea level of = normalized extra fuel, AF/W* C = specific fuel consumption CDO = parasite drag coefficient CL = lift coefficient C0 = increment factor in parasite drag due to engine

Effects of the design mismatch between aircraft capabilities and actual aircraft utilization

Air routes are largely determined by the interaction of geographical, political, economic and social factors. And airlines use their aircraft for a diversity of missions. Because of both factors the actual utilization of transport aircraft is well inside the payload-range envelope, which means that the designs are oversized for most flights. The objective of this paper is to evaluate the savings that could be achieved if transport aircraft were designed for shorter ranges; i.e., closer to the actual utilization pattern. In this design scenario, the maximum take-off weight and the operating empty weight would be remarkably reduced. This would lead to a reduction in aircraft price, trip fuel, maintenance cost, and landing and navigation charges as well as environmental impact. Direct operating cost as will be used as figure of merit of the reduced range approach.

Reconstructing the features and performances of historic airplanes

The process of modelling the aerodynamics and performances of historic air planes is somehow similar to the conceptual and preliminary design phases of a new project with two major advantages: 1) the configuration is known beforehand and 2) the airplane airworthiness has already been proved. Unlike a new project it is unnecessary to outline and assess many different alternatives. But the drag polar, most key performances, stability features, etc, are frequently unknown or incomplete. In the present research work, two cases are addressed: the Grand Raid of the Spanish “Cuatro Vient os”, and the rivalry between the Supermarine Spitfire and the Messerschmitt Me -109. The legendary Spanish airplane, a Breguet XIX Super TR, flew non -stop from Seville to Cuba (about 7500 km or 4100 nautical miles, mostly over the seas) in around 40 hours, one of the last Grand Raids, before disappearing in a relatively short stage between Havana and Mexico a few days later. On its turn, the legendary English and German aircraft were for many years the protagonists of air fight in the Western European front of Second World War. The modelling considered in this paper takes well known expressions of Aerodynamics and Flight Mechanics to obtain estimations of the drag polar and some relevant performances such as cruise conditions and range for the Grand Raid, and time to climb, radius of gyration, etc for the fighters. This approach, mixed up of historic considerations and quantitative analysis, is very well appreciated by students for its pedagogic and motivating character.

Students' attitudes and performances on airplane design

The paper describes the evolution over the last ten years of attitudes, preferences and performances of the students following the Airplane Design course at the School of Aeronautical Engineering (ETSI Aeronauticos) of Universidad Polit6cnica de Madrid, in Spain. The students’ attitudes and preferences are known through a teaching quality assessment questionnaire prepared and managed at university level and an Airplane Design course questionnaire arranged by the airplane design academic staff. Special consideration is given to the marks obtained by students in the AD course and the content of some outstanding Final Year (Graduation) Projects.