Rodrigo Martinez-Val

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.

Assessment of Narrow-Body Transport Airplane Evacuation by Numerical Simulation

This paper presents the results obtained with a new agent-based computermodel that can simulate the evacuation of narrow-body transport airplanes in the conditions prescribed by the airworthiness regulations for certification. The model, described in detail in a former paper, has been verified with real data of narrow-body certification demonstrations. Numerical simulations of around 20 narrow-body aircraft, representative of current designs in various market segments, show the capabilities of the model and provide relevant information on the relationship between cabin features and emergency evacuation. The longitudinal location of emergency exits seems to be even more important than their size or the overallmarginwith respect to theprescribed number and type of exits indicated by the airworthiness requirements.

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.

Visual measurement of streamwise vorticity in the mixing layer

The analysis of the film of a turbulent mixing layer shows evidence of highly bent spanwise vorticity filaments within the large coherent structures (bending that produces streamwise vorticity and thence three‐dimensionality), likely becaue of a certain type of columnar instability of those structures.

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

Debating Aeronautics from History. A Doctorate Experience

*† ‡ § The paper summarizes the evolution of aeronautical engineering s tudies in Spain, including the Doctor degree. Following important changes in the programs occurred after 1995 new optional matters have appeared both at undergrad and graduate level. History of aviation is one of the novel topics introduced in the undergra d curriculum. At graduate level a new Doctorate course on technological evolution of airplanes has been set up. The experience of quantifying this evolution has been very fruitful and pedagogical.

Vorticity distribution in the mixing layer

The experimental analysis of a turbulent mixing layer shows, by means of a simple algorithm, that the vorticity is concentrated in individual cores of (a) half the strength corresponding to the initial instability and (b) dimensions appreciably smaller than the vorticity thickness of the mixing layer.

Uncommon exit arrangement effects in airplane emergency evacuation

This paper presents the effects of uncommon exit size and location arrangement in the emergency evacuation of transport airplanes. The analysis is carried out by means of an agent-based computer model conceived to simulate the evacuation of narrow-body aircraft as required in the certification process, as well as for design purposes. The simulation model provides full evacuation data of all occupants: escape route followed, distance to exit, time to reach the ground, etc., as well as those of the whole cabin: exit utilization patterns, evacuation histograms, chronolines and total evacuation time. The present research concentrates on the effect of uncommon exit size and location arrangements, such as large longitudinal shifting and/or suppression of some of the exits in the evacuation performance.