Browse Topic: Airframes
The mystery of how futuristic aircraft embedded engines, featuring an energy-conserving arrangement, make noise has been solved by researchers at the University of Bristol. University of Bristol, Bristol, UK A study published in Journal of Fluid Mechanics, reveals for the first time how noise is generated and propagated from these engines, technically known as boundary layer ingesting (BLI) ducted fans. BLI ducted fans are similar to the large engines found in modern airplanes but are partially embedded into the plane's main body instead of under the wings. As they ingest air from both the front and from the surface of the airframe, they don't have to work as hard to move the plane, so it burns less fuel. The research, led by Dr. Feroz Ahmed from Bristol's School of Civil, Aerospace and Design Engineering under the supervision of Professor Mahdi Azarpeyvand, utilized the University National Aeroacoustic Wind Tunnel Facility. They were able to identify distinct noise sources originating
A study published in Journal of Fluid Mechanics, reveals for the first time how noise is generated and propagated from these engines, technically known as boundary layer ingesting (BLI) ducted fans. BLI ducted fans are similar to the large engines found in modern airplanes but are partially embedded into the plane’s main body instead of under the wings. As they ingest air from both the front and from the surface of the airframe, they don’t have to work as hard to move the plane, so it burns less fuel.
Equipment used in aerospace non-destructive inspection presents opportunity for modernization. Many inspection cells in production operate using a widely available control system software that is suitable for most inspection applications with minimal customization. The size and complex geometry of airframe components demand more application-specific system design to ensure the reliability and cycle time required for an aerospace production schedule. Ordinary inspection systems require manual teaching for program generation and lack datum-finding systems required to rerun programs without modification. Integration of offline programming software and machine vision instruments can save inspection technicians hours or shifts per part by eliminating the need for program retraining due to variation in part delivery position. Modernized inspection cells will reduce labor burden on technicians and provide reliable cycle time information to production planners.
Most of current jet aircraft circulate fuel on the airframe to match heat loads with available heat sink. The demands for thermal management in wide range of air vehicle systems are growing rapidly along with the increased mission power, vehicle survivability, flight speeds, and so on. With improved aircraft performance and growth of heat load created by Aircraft Mounted Accessory Drive (AMAD) system and hydraulic system, effectively removing the large amount of heat load on the aircraft is gaining crucial importance. Fuel is becoming heat transfer fluid of choice for aircraft thermal management since it offers improved heat transfer characteristics and offers fewer system penalties than air. In the scope of this paper, an AMESim model is built which includes airframe fuel and hydraulic systems with AMAD gearbox of a jet trainer aircraft. The integrated model will be evaluated for thermal performance. JP-8 fuel is recirculated on the airframe to maintain cooling the oil for AMAD
The F-35 Lightning II is an all-weather stealth combat aircraft that is intended to perform warfare strike missions and electronic surveillance capabilities at speeds up to 1.6 Mach. Composites comprise 35% of the airframe weight, with the majority being bismaleimide, as well as some carbon nanotube-re-enforced epoxy, which has a tensile strength approximately 100-times greater than steel. Any deviations in external dimensions can interfere with stealth capabilities, and at supersonic speeds, prove catastrophic to both plane and pilot.
Avionics systems provide electronic guidance, navigation, and communications through harsh and hostile environments for a wide range of airframes. Operating environments present elevated levels of shock and vibration; vacuum-like conditions of high altitudes; corrosive effects of hydraulic fluids, fuels, and other chemicals; and the effects of wide temperature ranges. Avionics systems must handle such challenging environments even as they are being designed with greater functionality into smaller payload spaces.
The conventional approach in aircraft landing loads analysis, such as for shock absorber development, is using a nonlinear set of equations and a modal representation of the airframe. For preliminary shock absorber design studies, a linearized set of equations may provide a highly efficient simulation method to limit the parameter space of linear shock absorber models. This article develops a set of linearized equations of motion to simulate the landing touchdown event while capturing airframe flexibility effects using a transfer function. The linearized flexible model demonstrates the ability to generally capture flexibility effects and output responses of interest with a significantly reduced simulation time compared to both fully flexible and nonlinear reduced-order models. The linearization of a Fiala tire model is accomplished by scaling the longitudinal tire stiffness such that the peak tire drag force matches that of the nonlinear model, and the vertical tire stiffness is
With air traffic demand constantly increasing and several years of aircraft production in their backlog, major aircraft manufacturers are now shifting their focus toward improving assembly process efficiency. One of the most promising solutions, known as “One Side Assembly”, aims to perform the whole assembly sequence from one side of the structure (drilling, temporary fastener installation and removal, blind fastener installation, assembly control) and with a high level of integrated automation. Investments in robotic equipment, automation engineering and innovation are very active and automation capabilities have already increased a lot in the aerospace industry. As an example, drilling operations for large dimensions airframe are clearly moving from manual to automated. However, despite more and more clever and sophisticated robotics, the use of historical fasteners with two side installation method remains a strong limitation to innovative automated assembly sequences. A blind
The demanded development towards various emission reduction goals set up by several institutions forces the aerospace industry to think about new technologies and alternative aircraft configurations. With these alternative aircraft concepts, the landing gear layout is also affected. Turbofan engines with very high bypass ratios could increase the diameter of the nacelles extensively. In this case, mounting the engines above the wing could be a possible arrangement to avoid an exceedingly long landing gear. Thus, the landing gear could be shortened and eventually mounted at the fuselage instead of the wings. Other technologies such as high aspect ratio wings have an influence on the landing gear integration as well. To assess the difference, especially in weight, between the conventional landing gear configuration and alternative layouts a method is developed based on preliminary structural designs of the different aircraft components, namely landing gear, wing and fuselage. Simplified
Over the last decades, a new class of reusable temporary fasteners having expanding mandrels have come to market. Their large-scale implementation has resulted in these fasteners being utilized in high shear stress environments resulting in the identification of several limitations. Parts shifting as a result of shear forces in the airframe assembly during temporary fastener installation or removal can cause current mandrel-based fasteners to become damaged and difficult to remove from the hole. Additionally, enhanced fastener shear resistance is desirable in very high shear forces environments. This paper examines current mandrel based temporary fasteners while also examining two new concepts in reusable temporary fasteners that are specifically designed to offer mitigations to the aforementioned limitations.
This SAE Aerospace Recommended Practice (ARP) establishes methods for testing airframe plain bearings. The purpose of ARP5448 and its associated slash sheets is to document test methods commonly used to evaluate airframe bearings. These test methods may be referenced in specifications, part standards, purchase orders, etc., when the test is deemed appropriate to the intended use of the bearing by the end user of the bearing. These test methods are not intended to encompass every conceivable requirement for an airframe bearing. The end user of the bearing must exercise engineering judgment to determine the most appropriate standard and/or nonstandard tests for the application.
NASA’s Langley Research Center has developed a deployable and stowable mechanical design for filling the cavity behind the leading-edge slat (i.e., slat cove) when it is extended upon landing an aircraft. Aerodynamic flow over an unfilled cavity typically exhibits strongly unsteady behavior that is a source of aeroacoustic noise. Conventional leading-edge slat devices for high lift are a good example of such geometric and flow conditions, and are a prominent source of airframe noise. Experimental and computational results have shown that a slat-cove filler device could significantly reduce the noise produced by slat structures. The proposed structural concept will enable autonomous achievement of the desired deployed shape. The design will facilitate a clean cruise configuration with minimal weight addition to the aircraft. NASA is seeking development partners and potential licensees.
Combat aircraft maneuvering at high angles of attack or in landing approach are likely to encounter conditions where the flow over the swept wings is yawed. This paper examines the effect of yaw on the spectra of turbulence above and aft of the wing, in the region where fins and control surfaces are located. Prior work has shown the occurrence of narrowband velocity fluctuations in this region for most combat aircraft models, including those with twin fins. Fin vibration and damage has been traced to excitation by such narrowband fluctuations. The narrowband fluctuations themselves have been traced to the wing surface. The issue in this paper is the effect of yaw on these fluctuations, as well as on the aerodynamic loads on a wing, without including the perturbations due to the airframe. A 42 degree delta wing with rounded leading edges, roughly equivalent to a 1/20 scale of existing combat aircraft, is used in a 2.74 m low speed wind tunnel in the angle of attack range 18 to 35
The present work focuses on developing an integrated airframe, distributed propulsion, and power management methodology for liquid-hydrogen-fuelled HALE UAVs. Differently from previous studies, the aim is to assess how the synergies between the aforementioned sub-systems affect the integrated system power requirement, production, and distribution. A design space exploration study was carried out to assess the influence of distributing motor-driven fans on three different airframes, namely a tube-and-wing, a triple-fuselage, and a blended-wing-body. For the considered range of take-off masses from 5,000 to 15,000 kg, the 200 kW payload power requirement under examination was found to re-shape the endurance trends. In fact, the drop in specific fuel consumption due to the engine design point change alters the trends from nearly flat to a 25% maximum endurance increase when moving towards heavier take-off masses. For the selected distributed propulsion system, the BWB airframe was found
In-service data from two Bombardier business jets, a Global 5000 and a Global Express XRS, have been compared. Flight data has been analyzed from both airframes with comparable number of ground-air-ground cycles. Individual flight phase have been examined and compared between the two airframes. Primary emphasis has been placed on airframe usage. The influence of primary mission on ground-air-ground cycles has been highlighted in the form of ground and flight loads, as well as dynamics of the flights. It is demonstrated that safe-life maintenance approach may have to be adjusted to account for the airframe usage.
Airframe icing caused by supercooled large droplets (SLD) has been identified as a severe hazard in aviation. This study presents an investigation of impact of a supercooled drop onto superhydrophobic and partially wettable substrates. Drop impact, spreading and rebound were observed using a high-speed video system. The maximum spreading diameter of an impacting drop on partially wettable surfaces was measured. The temperature effect on this parameter was only minor for a wide range of the drop and substrate temperatures. However solidification hindered receding when both the drop and substrate temperatures were below 0°C. The minimum receding diameter and the speed of ice accretion on the substrate were measured for various wall and drop temperatures. The two parameters increased almost linearly with the decrease of the wall temperature, but eventually leveled off beyond a certain substrate temperature. The speed of ice accretion on the substrate was significantly higher than the
There is definitely a degree of overlap in the regional and business jet sectors, both in terms of airframes and the engines that power them. At the high end of the market are aircraft such as the Boeing 737 BBJ and Airbus A319 Corporate Jet, which typically carry up to a dozen VIP passengers in spacious luxury, but which in airline service carry around 130 passengers.
The maturity of RF photonic components has reached the point where fiber optic links are being system-tested to replace traditional copper coax links on avionic platforms. Many demonstrations of RF photonic links have been made with traditional and non-traditional modulation formats to improve the RF performance of the link. While the advantages of RF photonic links in regard to size and weight are important, the large instantaneous bandwidth of the fiber optic links is a key driver for the use of this technology in the airframe.
One of the more critical constraints to the continued growth of air traffic is the related concern regarding aircraft noise. This concern has resulted in increasingly stringent noise restrictions for airports, both nationally and internationally. One of the major stretch goals for NASA is to develop noise reduction concepts that will allow the objectionable noise to be contained within the boundaries of a normal airport.
An Airbus methodology for the assessment of accurate fuel pressure surge at early program stages in the complete aircraft and engine environment based on joint collaboration with LMS Engineering is presented. The aim is to comfort the prediction of the fuel pressure spike generated by an engine shutdown in order to avoid late airframe fuel system redesign and secure the aircraft entry-into-service.
The demand of fulfilling increasing Prime Customer requirements forces Tier 1 suppliers to continually improve their system solutions. Typically, this will involve integration of “state of the art” tools to afford the Tier 1 supplier a throughput and cost advantage. The subject “Production Optimization Approach” addresses the machine and process optimization of automated fastening machines in operation at customer factories. The paper will describe and focus on the main aspects of production optimization of existing machines to meet and exceed the required customer production and reporting criteria. Furthermore, the paper will present existing examples based on use of the established diagnostic tools
Aircraft noise is a significant problem with both economic and public health implications, especially for communities near airports. As a result, increasingly stringent constraints are being placed on aircraft carriers worldwide to reduce this noise. The current disclosure focuses on airframe noise generated at or near the surface of the flap-side edge.
Titanium alloys parts are ideally suited for advanced aerospace systems because of their unique combination of high specific strength and superior resistance to many corrosive environments, in addition to excellent composite compatibility. Despite these features, use of titanium alloys in engines and airframes is limited by cost. Therefore, the improvement of processing techniques for titanium alloys production became a trend of the modern metallurgic technology. This work presents results of the microstructural development of Ti-6Al-2Sn-4Zr-2Mo alloy produced by arc melting and powder metallurgy processes. This alloy has important applications in aerospace area, in sections exposed to high temperatures. Samples of this alloy were characterized by SEM (scanning electron microscopy), XRD (X-ray diffraction), Vickers microhardness measurements and density. The results indicate that it is necessary the complete dissolution of beta-stabilizer element (Mo) for total homogenization of the
The paper is devoted to further development of numerical methods for simulation of riveting process during aircraft assembly (see [3, 4]). Algorithm modifications that increase computation accuracy, speed and complexity are given. These modifications involve the dual problem solving, incorporation of multiple calculation nets and special two stage procedure for calculation of deformations and stresses arising during assembly.
During its flight an aircraft can be struck by lightning and the induced high current will require a highly conductive airframe skin structure in order for it to propagate through with minimum damage. However an aircraft skin is generally coated with paint and the airframer does not always have control on the paint thickness. Paint thickness generates heightened concerns for lightning strike on aircraft, mainly because most of coatings dedicated to that purpose are non-conductive. Using insulating material or non-conductive coating with certain thickness may contribute to or increase damage inflicted by the swept stroke lightning energy, even on metallic structures Due to its high relative permittivity, a non-conductive paint or coating on a fuselage skin surface will contribute to slow down the lightning current propagation through structure. With this comes the risk of increasing heat that will favor structural damage and possible melt through. The correlation between paint thickness
With the high design/performance requirements in modern aircrafts, the need for a flexible airframe structural modeling strategy during the different phases of the airframe development process becomes a paramount. Hybrid structural modeling is a technique that is used for aircraft structural representation in which several Finite Element Modeling concepts are employed to model different parts of the airframe. Among others, the Direct Matrix Input at a Grid-Point (DMIG) approach has shown superiority in developing high fidelity, yet, simplified Finite Element Models (FEM's). While the deformation approach is a common choice for loads recovery in structures represented by stick models, using structural models simulated by the DMIG representation requires the adoption of a different approach for loads recovery applications, namely, the momentum approach. In this paper, the Monitor Points (MP) Method is introduced as an efficient methodology for loads recovery in static and dynamic
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