Design study of high aspect ratio wings for unmanned air vehicles (UAV's)

<div class="section abstract"> <div class="htmlview paragraph">This Recommended Practice provides a procedure for measuring and documenting the aerodynamic performance in a full-scale wind tunnel of passenger vehicles, i.e., mass-produced cars and light-duty trucks intended primarily for individual consumers. Testing or numerical modeling of pre-production and/or reduced-scale models is outside the scope of this document. Aerodynamic <i>development</i> procedures, i.e., methods to improve or optimize aerodynamic performance, are also excluded.</div> <div class="htmlview paragraph">It is well-known that aerodynamic performance results depend significantly on vehicle content and loading, as well as the wind tunnel itself (type, scale, and simulation qualities of the wind tunnel). Publication of non-standard test results causes unnecessary additional development work and incorrect perception of a vehicle’s anticipated aerodynamic performance by government, academia, and the general public.</div> <div class="htmlview paragraph">The intent of this document is to promote uniformity and traceability of published aerodynamic performance data acquired in a wind tunnel, thereby enhancing the public reputation and credibility of the aerodynamics discipline in the total vehicle development process.</div> <div class="htmlview paragraph">Measurement of the aerodynamic performance according to this Recommended Practice requires a full-scale wind tunnel test on a production-ready, full-scale vehicle according to specifications for vehicle loading, content, and wind tunnel conditions.</div> <div class="htmlview paragraph">The measurement and resulting documentation for a particular vehicle shall be reported only by the company that intends to produce the vehicle. Whenever there is an opportunity for interpretation of the document, a good faith effort shall be made to obtain the vehicle’s typical in-service performance and avoid finding the best possible performance under the best possible circumstances.</div> <div class="htmlview paragraph">Use of and compliance with this Recommended Practice is voluntary; however, it is mandatory for those advertising or otherwise publishing aerodynamic performance as “measured according to SAE J2881.” Conversely, any advertised or otherwise published result carrying this or a substantially similar designation must have the necessary documentation accepted by and on file with the SAE in accordance with the procedures defined in this Recommended Practice.</div> <div class="htmlview paragraph"><span class="xref">Appendices B</span> and <span class="xref">C</span> contain the necessary submittal documents for compliance with this Recommended Practice. When a submittal is made, the chairman of the Road Vehicle Aerodynamics Forum Committee (RVAC) or his/her designee shall review the submittal for proper completion according to the requirements herein, but without consideration of the technical merit of the claimed performance. After the chairman’s review, SAE will maintain an electronic database of all submittals.</div> <div class="htmlview paragraph">The database shall be available only to members and liasion members of the RVAC. Any RVAC member who retrieves information from the database shall do so with the understanding that the information is to be considered confidential within his or her company.</div></div>

<div class="htmlview paragraph">The aim of this paper is to present the Hermes Thermal Control Concept which constitutes the reference baseline for the phase 2 of the Hermes program.</div> <div class="htmlview paragraph">The technical solutions based on active and passive means, are dictated by a variety of requirements including temperature and heat flux limits, mass & power minimization, availability of space for accommodation of TCS devices.</div> <div class="htmlview paragraph">Furthermore thecomplex mission profile (including atmospheric flight and several modes of operation o002d;orbit) and the configuration of the space-vehicle, require the adoption of a particularly flexible thermal control.</div> <div class="htmlview paragraph">The <b>ATCS (Active Thermal Control Section)</b> is based on a dual loop concept, using both water and Freon R114 cooling loops for heat collection from the various sources, heat transportation and heat rejection through dedicated devices.</div> <div class="htmlview paragraph">The main heat sources to be considered are those extracted from the cabin air loop, the electronics, the power generation items (fuel cells and lithium batteries) and the environmental loads during ascent and re-entry.</div> <div class="htmlview paragraph">The major heat rejection devices are the Ground Support Equipment Heat Exchangers (on ground, before launch and after landing), the Ammonia Boilers during ascent or re-entry (low altitude), the Hermes Radiators on orbit, the Water Evaporators during ascent and re-entry (high altitudes) and to complement the radiator rejection capability.</div> <div class="htmlview paragraph">The <b>PTCS (Passive Thermal Control Section)</b> relies on different concepts of insulations together with a system of temperature sensors and heaters, to control the thermal excursions of the space-plane components and structural parts, within the specified limits.</div> <div class="htmlview paragraph">Thermal insulation blankets (foams, thermal control coatings, multi layer insulations) involve an extensive material research and testing activity, since they are subjected to quite different conditions: vacuum, atmospheric, internal, external and very different level of temperatures depending on the location.</div> <div class="htmlview paragraph">The present design of the Thermal Control Subsystem is oriented to the minimization of mass and power budgets and to respect the quantitative and qualitative safety and reliability requirements.</div>

<div class="section abstract"><div class="htmlview paragraph">The VUSIL program has developed a concept for the integration of unmanned aircraft systems (UAS) into non-segregated airspace, which is also used by manned civil aviation. For the integration of UAS it is necessary for the Unmanned Aircraft (UA) pilot to be aware of the surrounding traffic in order to recognise and resolve possible conflicts. Therefore the surrounding traffic was displayed in the pilot ground control station (GCS) based on Radar data provided by DFS Deutsche Flugsicherung GmbH (DFS). The pilot was supported in detecting potential conflicts by means of a “Sense and Avoid” tool provided by ESG GmbH. This tool shows conflicts and possible avoidance manoeuvres on a separate display. To validate the concept, two flight campaigns with two different UAS (LUNA by EMT GmbH and NEO by Swiss UAV) and several intruders were conducted. In the first flight campaign, the intruders for the real flying UAS were simulated. In the second flight campaign the intruder was a manned helicopter supplied and flown by the German Federal Police. The proof of concept has been validated by the results of both flight campaigns.</div><div class="htmlview paragraph">Additionally, a safety analysis was conducted, aiming at demonstration of safe integration of UAS. Especially the equivalent level of safety (ELOS) of “See and Avoid” in manned aviation and “Sense and Avoid” as developed in the VUSIL program was addressed. Based on the results of the flight trials, workshops with aviation experts and relevant literature, under some conditions and assumptions, ELOS of VUSIL's integration concept has been shown.</div><div class="htmlview paragraph">Collecting the ability requirements of unmanned aircraft pilots was also part of the program. To this end, the UA pilots filled in a job analysis questionnaire to gather first information about the required abilities. The results were compared with the results from air traffic controllers and pilots.</div></div>

<div class="htmlview paragraph">Nomographs and an equation (shown below) have been developed for estimating the fuel vapor generation from a vehicle fuel tank as a function of fuel volatility (Read vapor pressure) and fuel tank temperature increase. <div id="FD1" class="formula"> <div class="graphic-wrapper"><img class="article-image equation block" src="892089_fig0001.jpg" alt="No Caption Available"/></div> </div></div> <div class="htmlview paragraph">where A, B, and C are the constants and are equal to 0.00817, 0.2357, and 0.0409, respectively, for gasoline at sea level; T<sub>1</sub> and T<sub>2</sub> are the initial and final tank temperatures, respectively, in °F; and RVP is the Reid vapor pressure of the fuel in psi.</div> <div class="htmlview paragraph">Nomographs were developed for estimating the effects of altitude, oxygenated fuels (<span class="xref">10</span>% ethanol blends), and tank pressure controls on tank vapor generation. The equation constants were also determined for gasolines at high altitude and for 10% ethanol blends both at sea level and high altitude.</div> <div class="htmlview paragraph">Since tank vapor generation is directly proportional to tank vapor space volume, the equation can be used for estimating vapor generation from any fuel tank. Experimentally measured fuel vapor generations with a wide variety of fuels over a wide range of temperatures were compared with those predicted by the equation; the agreement between the measured and predicted results was excellent (R<sup>2</sup>=0.97).</div>

<div class="htmlview paragraph">In order to allow continued production of the AM General Optimizer 6500 during MY 2007 through 2010 this IDI engine (Indirect Injection - swirl chamber) requires sophisticated aftertreatment controls while maintaining its fuel economy and durability.</div> <div class="htmlview paragraph">The main purpose of the development program was to retain the relatively inexpensive and simple base engine with distributor pump and waste-gated turbocharger, while adding hardware and software components that allow achievement of the phase-in emission standards for 2007 through 2010. The aftertreatment system consists of Diesel Oxidation Catalyst (DOC), NOx Adsorber Catalyst (or DeNOx Trap - DNT) and Diesel Particle Filter (DPF). In addition to the base hardware, an intake air throttle valve and an in-exhaust fuel injector were installed.</div> <div class="htmlview paragraph">The presented work will document the development process for a 2004 certified 6.5 l IDI heavy-duty diesel engine to comply with the 2007 heavy-duty emission standards. The system architecture evaluation proved to be one of the key development items that determined the packaging in the projected vehicle platform. Based on the temperature profile, it was found that the DOC-DPF-DNT configuration is mandatory to achieve NOx and NMHC standards. The development of the DPF regeneration, deNOx and deSOx strategy were strongly based on a multi-variable controls approach using temperature or lambda interventions depending on the system request.</div> <div class="htmlview paragraph">Development results for the HD-FTP and SET (13-mode Supplemental Emissions Test) show that the tailpipe emissions and the NTE (not-to-exceed) limits can be met with a considerable safety margin allowing reasonable degradation factors.</div> <div class="htmlview paragraph">The integrated system was installed in a project vehicle and underwent multiple climate testing trips focusing on DPF regeneration under cold ambient, high altitude and hot ambient conditions.</div> <div class="htmlview paragraph">It could be proven that a concept with a comparably cost-effective base engine which does not utilize direct fuel injection, along with an advanced aftertreatment control system, is capable to meet the U.S. 2007-2010 phase-in emission standards.</div>

<div class="htmlview paragraph">A detailed description is presented of the design and fabrication of the Marvel II composite wing. The wing was constructed in a short time using a combination of sailplane and modern prepreg composite structures technologies. The wing design requirements were to minimize the use of metal in the structure, to develop a high performance flap system which would be insensitive to a sand environment, and to explore composite production structural concepts.</div> <div class="htmlview paragraph">The desired high lift capability was achieved through the use of a double slotted flap with a fixed slat. A unique flap support mechanism was developed to give excellent flap positioning over the flap angle range.</div> <div class="htmlview paragraph">The wing was constructed in three major assemblies, the spars, the wing skins, and the flap and ailerons. The wing spar was constructed applying conventional sailplane techniques which uses a wet layup of S-glass rovings.</div> <div class="htmlview paragraph">The fabrication of the wing skins was made in three steps. The original XV-11A wing was extended and used as the male mold. A heat resistant female mold was fabricated using an epoxy-graphite paste with a honeycomb backing. The mold had excellent dimensional stability and was light (300 lbs.). The wing skins were fabricated using Kevlar 250 deg. prepreg, Nomex honeycomb, and some high density foam. The wing skins were cured using a vacuum bag process.</div> <div class="htmlview paragraph">The Marvel II wings were designed and fabricated along with major modifications to the fuselage in an eight month period. The aerodynamic performance was outstanding with an airplane lift coefficient in excess of 3.0. There were no structural problems encountered in the flight test program. The structural weight was much higher than expected. It was found that the weight of secondary structure was difficult to control.</div> <div class="htmlview paragraph">From this development program, a methodology to produce excellent dimensional fidelity, and high structural efficiency wings has evolved. From the lessons learned on this prototype development program it is now possible to produce composite wing and fuselage structures for limited production aircraft at a modest cost and in a relatively short time frame.</div>

<div class="section abstract"><div class="htmlview paragraph">The European Union’s Horizon 2020 programme has funded the SENS4ICE (Sensors for Certifiable Hybrid Architectures for Safer Aviation in Icing Environment) project [<span class="xref">1</span>], an innovative approach for the development and testing of new sensors for the detection of supercooled large droplets (SLD). SLD may impinge behind the protected surfaces of aircraft and therefore represents a threat to aviation safety. The newly developed sensors will be tested in combination with an indirect detection method on two aircraft, in two parallel flight programs: One on the Embraer Phenom 300 in the U.S. and one on the ATR-42 in Europe.</div><div class="htmlview paragraph">In this framework the Deutsches Zentrum für Luft- und Raumfahrt (German Aerospace Center) is in charge of the airborne measurements and data evaluation of the microphysical properties of clouds encountered during the SENS4ICE field campaigns in February, March and April 2023. We present the instrumentation that is used in the flight experiments for the characterization of icing environments and for the validation and performance assessment of new sensors for the detection and discrimination of Appendix O and Appendix C conditions [<span class="xref">2</span>, <span class="xref">3</span>].</div><div class="htmlview paragraph">Further, with partners from Centre Europeen De Recherche Et De Formation Avancee En Calcul Scientifique (CERFACS), the German Weather Service (DWD), the Italian Aerospace Research Center (CIRA) and Leading Edge Atmospherics (LEA), we present the considerations that were undertaken to find the best campaign location with highest frequency of icing occurrence on a climatological basis, taking into account the safety requirements of the aircraft. Four data sets of icing conditions based on various meteorological input data (model and observations) have been analyzed to provide an overview of the occurrence of icing. The data give a good impression on the geographical and vertical distribution of icing conditions above Europe and the Northern U.S. in general and specifically at higher altitudes (> 750 hPa or 8000ft) for the European campaign. We find enhanced icing frequencies between 1 to 5% at altitudes between 2 and 6 km even in the spring, summer and autumn months above Europe.</div><div class="htmlview paragraph">We show highlights from selected individual cases from the North American test campaign performed in February and March 2023. The analysis gives a first impression of the extensive data set of icing conditions made available by the SENS4ICE project for sensor evaluation and for validation of satellite observations and model forecasts.</div></div>

<div class="section abstract"> <div class="htmlview paragraph">The scope of this report is to capture fundamental principles of selecting a wire size for an aerospace application using the method prescribed in the AS50881 standard and additional calculations, not found in AS50881, to ensure the wire selection will adequately perform in the specific physical and environment conditions.</div> <div class="htmlview paragraph">This report covers wire selection and sizing as part of the electrical wire interconnection systems (EWIS) used in aerospace vehicles. Aerospace vehicles include manned and unmanned airplanes, helicopters, lighter-than-air vehicles, missiles, and external pods. This document does not apply to wiring inside of airborne electronic equipment but shall apply to wiring externally attached to such equipment.</div> <div class="htmlview paragraph">Wire selection must consider physical and environmental factors to size wires such that they have sufficient mechanical strength, do not exceed allowable voltage drop levels, are protected by materials or circuit protection devices, and meet circuit current carrying requirements. For electrical power feeders and distribution, or EWIS applications, other information and environmental and installation limitations are also needed to adequately evaluate and select the correct wire size for a specific application and meet design requirements.</div> <div class="htmlview paragraph">The report presents only fundamental principles and guidelines and cannot adequately cover all aspects and complexities associated with wire selection and sizing. Some of the calculations in this report have been simplified to demonstrate the process for validating a wire size selection for a design application. More precise calculations should be investigated and evaluated to ensure proper assessment of each individual calculation in this report.</div></div>

<div class="htmlview paragraph">Combi-Road is a container road transport system with high capacity. The system uses specially designed tracks which can be constructed as separate roads or as extra lanes alongside existing motorways. The containers are pulled on semi-trailers by unmanned automatically controlled electrical vehicles. The system allows to reduce the amount of vertical handlings in the transport chain. On so-called transfer stations containers are exchanged with sea shipping, road, railway and inland shipping.</div> <div class="htmlview paragraph">The Combi-Road project started January 1994. During the process of development the innovative technological nature of the concept has been strongly emphasized. In an early stage the implementation strategy has been paid attention to.</div> <div class="htmlview paragraph">This paper describes the basic technical details of the Combi-Road system, as well as the results of the initial test phase which has been completed by the end of 1996. Furthermore the follow-up phase is discussed which includes a broadening of the logistical concept in a concrete situation of introduction of the system in the Netherlands. Starting from so-called Logistical City Parks at the edge of a city, goods are distributed via tubes with unmanned vehicles to District Distribution Depots with a service area of approximately 500 metres.</div> <div class="htmlview paragraph">The supply of goods to the Logistical City Parks can be via the traditional transport modes road, water and rail or, for example, Combi-Road.</div> <div class="htmlview paragraph">In the concrete situation maritime containers as well as continental unitised cargo are transported between the following origin and destination points:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">on the one hand the container terminal on the Maasvlakte in Rotterdam, and,</div></li> <li class="list-item"><div class="htmlview paragraph">on the other hand the District Distribution depot in a city such as Utrecht,</div></li> <li class="list-item"><div class="htmlview paragraph">utilising the SHIFT-infra (Specific Highway Infrastructure for Freight Transport) as basic network,</div></li> <li class="list-item"><div class="htmlview paragraph">which, in the Logistical City Parks, is linked to the tube network for urban freight transport, and,</div></li> <li class="list-item"><div class="htmlview paragraph">en route at transfer stations such as the Multimodal Transport centre Valburg along the river Rhine exchanges with other modes take place or connections are made to systems such as the Underground Logistical System (ULS) at Amsterdam Airport Schiphol.</div></li> </ul> </div> <div class="htmlview paragraph">This is an ambitious approach which could lead to a break-through in automatic goods transportation in densely populated urban and interurban areas with intense traffic congestion problems.</div>

<div class="section abstract"><div class="htmlview paragraph">The impact of Reynolds number on the aerodynamics and operational performance of commercial vehicles is discussed. All supporting data has been obtained from published experimental and computational studies for complete vehicles and vehicle components.</div><div class="htmlview paragraph">A review of Reynolds number effects on boundary layer state, unsteady and steady flow, time dependent wake structure, interacting shear layer and separated flows is presented. Reynolds number modeling and simulation criteria that impact aerodynamic characteristics and performance of a commercial vehicle are shown. The concepts of dimensional analysis and flow similarity are employed to show that aerodynamics of commercial ground vehicles is only dependent on Reynolds number. The terminology of Roshko is adopted for discussing the variation in drag with Reynolds number in which the subcritical, transitional and transcritical flow regimes are defined for commercial vehicles. Criteria for aerodynamic simulation as well as testing and design of commercial vehicles are defined and show a minimum transcritical Reynolds number value of 3 million is recommended for simulating the aerodynamics of full-scale commercial vehicles.</div><div class="htmlview paragraph">Guidance is provided for aerodynamic design and analysis in the framework of Reynolds number and boundary layer flows as they relate to previous designs, current testing and analysis criteria, and the development of future vehicles. A discussion of aerodynamic tools is presented which call for the continued development of aerodynamic test and analysis tools capable of capturing Reynolds number sensitivities. Of particular importance is the maturation of computational simulation tools with improved friction modeling capability specifically developed for commercial ground vehicles.</div></div>

<div class="section abstract"><div class="htmlview paragraph">In recent years the automotive industry has been using an increasing number of high powered engines with fewer cylinders, with the goal to reduce weight and fuel consumption and hence to achieve lower CO2 emissions. In the following paper, an overview about the currently existing methods and products within the exhaust development is given which follow automotive lightweight trend.</div><div class="htmlview paragraph">Continuous innovations in new materials, structural design and manufacturing process as well as mastering the integration of the components and modules within the system with a thorough understanding and optimization of the system behavior is enabling the reduction of weight in exhaust system.</div><div class="htmlview paragraph">Another possibility to reduce the weight is the use of additional components such as valves. In the following, a discussion about the different types of valves is presented. These valves can be implemented within the exhaust system in order to bring a constraint in the system and consequently additional acoustic damping.</div><div class="htmlview paragraph">Due to engine downsizing, many premium vehicles lost their class-representing sound signature. An active system can be used in order to enhance the sound according to the customer demands. In addition to that, an active system can help reducing muffler volume.</div></div>

<div class="htmlview paragraph">The advent of various structural optimization methods has made the process of deriving efficient lightweight designs for complex structures under multiple load conditions far more attainable than ever before. Three of these methods, namely sizing, topology and topometry optimization have been used extensively in the structural optimization of body-in-white structures. While all these techniques have their unique advantages, they provide different solutions to the posed problem. In this paper, we examine how best these optimization techniques can be used to derive a more efficient design within a linear domain, through a case study. Depending on the starting point of the design, all three techniques can play a vital role in making design decisions.</div>

<div class="section abstract"><div class="htmlview paragraph">OBD (On-Board Diagnostic) test system is applied to research influences of environmental parameters (altitude and environment temperature) on real-world NOx emission and fuel consumption for heavy-duty diesel trucks in this paper. The research results indicate that altitude and environment temperature have great influence on NOx emission rate and fuel consumption. High altitude in range of 3000~4000 m results in NOx emission rate is lower than low and moderate temperature because of air intake amount decreasing. However the fuel consumption rate is higher than lower altitude because altitude influences real-time changes of air inflow and combustion conditions in the cylinder of the engine. NOx emission rate and fuel consumption is more stable at different vehicle speed, VSP and RPM at high altitude, and NOx emission rate fluctuate dramatically at low and moderate altitude. The fuel consumption rate is higher at 10~20 °C than that at lower and higher temperature. The environment temperature of 20~35 °C provides beneficial conditions for NOx production and deteriorates emission, and the environment temperature of −10~10 °C provides oxygen enrichment environment because of low temperature and high air density, so increases in production amount of NOx. Effects of altitude and environment temperature on NOx emission rate and fuel consumption rate show an opposite tendency. Compared with fuel consumption rate, NOx emission rate is more sensitive to vehicle speed, VSP and rotating speed.</div></div>

<div class="section abstract"><div class="htmlview paragraph">The braking safety of heavy-duty vehicles is widely concerned. This paper proposed a new purely mechanical transmitted OHC two-stroke braking device. The rigid–flexible coupled dynamics model of the device and the engine working process simulation model were used for joint simulation. The effects of CR lift, environmental conditions, compression ratio, and braking type on the engine braking performance were comprehensively evaluated. The result shows: good consistency of valve operation is obtained by using pure mechanical transmission. During the braking process, the in-cylinder pressure acts directly on the valves and significantly affects the maximum valve lift of the CR phase, therefore excessive in-cylinder pressure will reduce the reliability of the braking device. When the CR lift increases from 1.9 to 2.8 mm, the braking power per liter increases at low altitude, but first increases and then decreases at high altitude. The decrease in engine speed and compression ratio as well as the increase in altitude lead to the decrease in braking power per liter. A benchmark of braking performance was taken from a high-compression-ratio (17) engine with a four-stroke decompression brake. For the high-compression-ratio (17) engine with two-stroke brake, the maximum in-cylinder pressure was reduced from 6.30 to 3.84 MPa, and the braking power per liter was increased by 24.5%–32.3% at low altitude and 93.2%–110.2% at high altitude. For the low-compression-ratio (11.6) engine with two-stroke brake, the maximum in-cylinder pressure is reduced to 2.83 MPa, and the braking power per liter changes less at low-altitude conditions and increases by 54.8%–67.1% at high-altitude conditions. The two-stroke braking device will greatly improve the braking safety and device components’ reliability on heavy-duty trucks, broaden the operating speed range, and promote the popularization and application of low-compression-ratio engines such as natural gas engines and methanol engines.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Exhaust sound quality is one of the most important factors for attractive motorcycles. It is desirable to quantitatively and objectively examine the exhaust sound quality during the development process.</div><div class="htmlview paragraph">In our previous study, we developed evaluation models that could be applied to various exhaust sounds. However, due to the limitation of the model, it could not be applied to varying conditions, such as from acceleration to steady driving and then to deceleration. In this study, we developed more practical evaluation models that can be applied to various driving conditions.</div><div class="htmlview paragraph">To cover a wide variety of sounds under different driving conditions, we prepared more than 300 sound stimuli and collected subjective evaluation data on those sounds. As the evaluation method, we used a pairwise comparison method to make decision making easy for the participants. However, if the pairwise comparison was simply performed for such sample size, the experiment cannot be done in a realistic experimental scale because the number of evaluation pairs gets very large. To solve this issue, we allocated evaluating pairs among multiple participants and used the Bradley-Terry model for estimation of the subjective quality rate. With these methods, the number of evaluations per participant was reduced to 1/300 of that required with the naive method.</div><div class="htmlview paragraph">We constructed the models based on a multiple regression analysis on the subjective evaluation data with waveform feature values as independent variables. We confirmed that these models accurately predicted the motorcycle developers' subjective impression of the exhaust sound of actual vehicles under a wide range of driving conditions.</div></div>