Fuel Benefit from Optimal Trajectory Assignment on the North Atlantic Tracks

The North Atlantic Tracks represent one of the highest density international traffic regions in the world. Due to the lack of high-resolution radar coverage over this region, the tracks are subject to more restrictive operational constraints than flights over the continental U.S. Recent initiatives to increase surveillance over the North Atlantic has motivated studies on the total benefit potential for increased surveillance over the tracks. One of the benefits of increased surveillance is increased accessibility of optimal altitude and speed operations over the track system. For a sample of 4033 flights over 12 days from 2014-2015, a fuel burn analysis was performed that calculates the fuel burn from optimal altitude, optimal speed and optimal track trajectories over the North Atlantic Tracks. These results were compared with calculated as-flown fuel burn in order to determine the benefit potential from optimal trajectories. Operation at optimal altitude and speed increased this benefit to 2.83% reduction potential in average fuel burn. Operation at optimal altitude alone, however, reduces the benefit potential to 1.24% reduction in average fuel burn. Optimal track assignment allows for a 3.20% reduction in average fuel burn. For the sample data, 45.1% of flights were unable to access their optimal altitude and speed due to separation requirements. Reduced separation up to 5 nautical miles can decrease the number of conflicts to 14.0%. Reducing the separation requirements both longitudinally and laterally can allow for increased accessibility of optimal altitudes, speeds and track configurations. Pilot decision support tools that increase awareness of aircraft fuel performance by integrating optimal altitude and speed configurations can also reduce aircraft fuel burn. The utility of such a tool is evaluated through a survey on pilot-decision making.This work was funded by the US Federal Aviation Administration (FAA) Office of Environment and Energy as a part of ASCENT Project 15 under Air Force Contract FA8721-05-C-0002. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the FAA or other ASCENT Sponsors

Heat Transfer Variation on Protuberances and Surface Roughness Elements

In order to determine the effect of surface irregularities on local convective heat transfer, the variation in heat transfer coefficients on small (2-6 mm diam) hemispherical roughness elements on a flat plate has been studied in a wind funnel using IR techniques. Heat transfer enhancement was observed to vary over the roughness elements with the maximum heat transfer on the upstream face. This heat transfer enhancement increased strongly with roughness size and velocity when there was a laminar boundary layer on the plate. For a turbulent boundary layer, the heat transfer enhancement was relatively constant with velocity, but did increase with element size. When multiple roughness elements were studied, no influence of adjacent roughness elements on heat transfer was observed if the roughness separation was greater than approximately one roughness element radius. As roughness separation was reduced, less variation in heat transfer was observed on the downstream elements. Implications of the observed roughness enhanced heat transfer on ice accretion modeling are discussed

Cruise Fuel Reduction Potential from Altitude and Speed Optimization in Global Airline Operations

This paper examines the potential fuel efficiency benefits of cruise altitude and speed optimization using historical fight path records. Results are presented for a subset of domestic US flights in 2012 as well as for long haul flights tracked by the European IAGOS atmospheric research program between 2010 and 2013. For a given lateral flight route, there exists an optimal combination of altitude and speed. Analysis of 217,000 flights in domestic US airspace has shown average potential savings of up to 1.96% for altitude optimization or 1.93% for speed optimization. International flights may be subject to different airline and/or air traffic management procedures and constraints. Examination of 3,478 long-haul flights, representing three airlines and a single aircraft type over a four-year period, indicates average potential savings of up to 0.87% for altitude optimization or 1.81% for speed optimization. This is equivalent to a mean fuel savings of 905 pounds and 1981 pounds per flight, respectively. Due to the limited sample set for long haul flight records, conclusions from this stage of the international study are limited to the specific airlines and aircraft types included in the IAGOS measurement program. I. BACKGROUND Environmental and economic concerns provide motivation for fuel consumption reduction in air transportation. There are various techniques to control fuel-related environmental impact with varying implementation timelines and potential benefits. These include new aircraft technology (decade-scale implementation, high cost), retrofits to existing aircraft (multi-year implementation, medium cost), alternative jet fuel and propulsion technology (decade-scale implementation, high cost), and operational mitigation (rapid implementation, low cost) [1]. Operational mitigations are useful due to the potential for rapid implementation and low capital expenditure, although the long-term benefit is generally less than other technology-driven solutions. Prior research in academia and industry has identified potential operational mitigations. For example, Marais et al. proposed 61 specific operational mitigations with implementation timelines in the 5-10 year range [2]. Of these, eight mitigations dealt with opportunities in cruise altitude and speed optimization (CASO). The fuel efficiency of an aircraft at any point along its flight path is a function of weight, altitude, speed, wind, temperature, and other second-order effects. At a fixed weight, there exists a combination of speed and altitude at which instantaneous fuel efficiency is maximized, as shown in Figure 1 for a typical widebody long-range airliner. For a full flight, this becomes an optimal sequence of speeds and altitudes to minimize fuel consumption [3]. The speed and altitude at which aircraft are actually flown may differ from this optimal point for a variety of operational and practical reasons. Integrated fuel consumption depends on effective trajectory planning in speed and altitude as well as in lateral flight path. There are many examples in the literature demonstrating techniques and potential applications for single-flight trajectory optimization in lateral, vertical, and temporal dimensions (e.g. [4]–[11]). However, no research has demonstrated the systemwide benefits pool of such optimization concepts compared to current operating practices. The degree to which flights may operate at optimal altitudes and speeds depends on a variety of system characteristics, including prevailing weather conditions, congestion, airline schedules, operating costs, and Air Traffic Management (ATM) technologies available on the ground and in the cockpit of participating aircraft. In domestic US operations, the suite of communication, navigation, and surveillance (CNS) technologies allows for continuous very-high frequency (VHF) radio communication, and radio-based navigation, and radar tracking. However, traffic volumes prevent unconstrained altitude selection in most areas of the country. Speed selection is driven by a combination of ATM constraints and airline operational priorities. Figure 1. Instantaneous fuel efficiency of a typical long-haul aircraft at a fixed weight (calm winds, standard atmosphere)

Caracterisation hydrodynamique des sols deformables partiellement satures. Etude experimentale a l'aide de la spectrometrie gamma double-sources

SIGLEINIST T 75313 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Measurement of heat transfer variation on surface roughness elements using infrared techniques

Communication to : 32nd Aerospace Sciences Meeting and Exhibit, Reno, NV (USA), january 10-13, 1994Available at INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1994 n.145 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc