Browse Topic: Lightning
This paper experimentally investigates direct effects of lightning strikes on flax fiber-reinforced polymers. Highcurrent artificial lightning strikes are conducted on coupon level to evaluate thermo-mechanical damage and to quantify the sufficiency of copper wire mesh as lightning strike protection (LSP). The dataset shall also serve for verification of prospected numerical simulation. The natural fiber flax, as a sustainable source of composite reinforcement, has been demonstrated to be suitable for semi-structural parts of rotorcraft. However, its low electrical and thermal conductivity requires a functional LSP layer for aviation applications. The test panels are investigated regarding their material combination, stacking sequence and level of LSP. Results show that two as well as three layers of 72 g/m2 copper mesh are not sufficient to withstand the standardized lightning current component A waveform of 200 kA. The high induced currents and low capability of energy dissipation leads to electro-explosion of metal and transient mechanical forces from shock waves causing mechanical damage on the test panels. Back surface-velocities increase with higher peak currents and higher level of protection results in lower damage. It is shown that a stacking of copper wire mesh results in less arc root dispersion.
Northrop Grumman Corporation is developing AN/APG-85, an advanced Active Electronically Scanned Array (AESA) radar for the F-35 Lightning II. Northrop Grumman currently manufactures the AN/APG-81 active electronically scanned array (AESA) fire control radar, the cornerstone to the F-35 Lightning II’s sensor suite.
The Current Icing Product (CIP; Bernstein et al. 2005) and Forecast Icing Product (FIP; Wolff et al. 2009) were originally developed by the United States’ National Center for Atmospheric Research (NCAR) under sponsorship of the Federal Aviation Administration (FAA) in the mid 2000’s and provide operational icing guidance to users through the NOAA Aviation Weather Center (AWC). The current operational version of FIP uses the Rapid Refresh (RAP; Benjamin et al. 2016) numerical weather prediction (NWP) model to provide hourly forecasts of Icing Probability, Icing Severity, and Supercooled Large Drop (SLD) Potential. Forecasts are provided out to 18 hours over the Contiguous United States (CONUS) at 15 flight levels between 1,000 ft and FL290, inclusive, and at a 13-km horizontal resolution. CIP provides similar hourly output on the same grid, but utilizes geostationary satellite data, ground-based radar data, Meteorological Terminal Air Reports (METARS), lightning data, and voice pilot reports (PIREPs) in addition to the RAP model output to provide near-realtime icing guidance. This paper presents recent enhancements to the prototype versions of CIP and FIP (CIP v2.0 and FIP v2.0, respectively). The enhancements described are intended to take better advantage of enhanced model resolution and microphysics parameterization as well as state-of-the-art observations for icing diagnosis and forecasting.
This SAE Aerospace Standard (AS) provides general design and test requirements for a flat cut-off pressure compensated, variable delivery hydraulic pump for use in a civil aircraft hydraulic system with a rated system pressure up to 5000 psi (34500 kPa). NOTE: Hydraulic pumps may incorporate features such as a clutch in the input drive, which will not be covered by this standard.
This SAE Aerospace Information Report (AIR) is limited to the subject of aircraft fuel systems and the questions concerning the requirements for electrical bonding of the various components of the system as related to Static Electric Charges, Fault Current, Electromagnetic Interference (EMI) and Lightning Strikes (Direct and Indirect Effects). This AIR contains engineering guidelines for the design, installation, testing (measurement) and inspection of electrical bonds.
Fireflies have sparked the inspiration of MIT researchers. Taking a cue from nature, they built electroluminescent soft artificial muscles for flying, insect-scale robots. The tiny artificial muscles that control the robots’ wings emit colored light during flight.
Titan, Saturn’s largest moon and the only celestial body which is found to have a landmass composed of liquid hydrocarbons. Nitrogen - The building block of all life that exists on earth is found to be abundant in Titan’s atmosphere of up to 97%. Aerobots provide a great platform for exploring a celestial body with an atmosphere such as Titan. They have modest power requirements, longer mission duration, and can cover a longer distance in a shorter time. They are powered by a Radioisotope Thermoelectric Generator for optimal mission life. Aerobot’s altitude can be altered by varying the temperature of the air inside the balloon and yaw can be controlled using a Reaction Wheel and a motor-driven propeller for forwarding thrust. The proposed Aerobot will be equipped with four miniature deployable fixed weather stations that can be dropped from the aerobot to Titan's surface. They can be deployed at diverse locations such as the equator and Polar Regions to deeply explore the Titan’s climate and atmosphere. These weather stations contain payloads such as nitrogen, methane, oxygen sensor, and a spectrometer to analyze the composition of the atmosphere. Temperature sensors and wind speed sensors can be equipped. Also, a lightning detector can be used to trace lightning and thunderstorm, an essential element for organisms’ inhabitable environments. Radiation sensors both in weather stations and Aerobots can help us to understand the risks in its atmosphere. These weather stations are mounted on a floatable structure to float on rivers on Titan. They have an on-board memory storage facility to store data from sensors and transmit the saved data once the aerobot comes across them in the sky. Also, the aerobot will be inflated before landing on Titan to safeguard the aerobot without falling on to rivers of Titan. This work focused to design and computationally investigates the fluid dynamic behaviour and its structural impacts on the proposed Unmanned Aerobot under the environmental conditions of Titan.
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.
This paper provides an overview of the state of art on the lightning regulation and the means of compliance for lightning certification, based on both the simulation technics and the testing methods. Usual lightning protection solutions at helicopter level to fulfill lightning requirements are discussed, as well as advanced approaches used by Airbus Helicopters to minimize the weight penalty of the lightning protection, especially by a large use of the simulation for the optimization of both the indirect effects (LIE) and the lightning direct effects (LDE). Some perspectives are highlighted concerning the development of new lightning protection devices to withstand the higher induced currents coupled on equipment items installed in full composite airframe helicopters (H/C), and how the lightning may be avoided on future platforms like the emergent flying urban taxis.
Inspecting an aircraft after a known or suspected lightning strike can be a tedious and subjective task. While aircraft technical manuals do provide conditional inspections following a lightning strike, these inspections tend to be broad in their approach and based solely on the presence of visual damage. This paper discusses the simple technique of tracing the lightning path through the aircraft by the use of an analog magnetometer to identify ferromagnetic parts that have been magnetized by the substantial electrical current of a lightning strike. While this technique is not novel, it is not often published as an inspection technique. Knowing the approximate path of the lightning can assist aircrews and maintainers in the identification of suspect parts that may require further inspection, repair and/or replacement thereby increasing safety and ensuring continued airworthiness of the aircraft.
In this paper we investigate the importance of electrical contact efficiency between fasteners and skin-level expanded metal mesh and how it influences lightning current energy transport. Since carbon fiber reinforced polymer composites (CFRPs) are electrically anisotropic and typically exhibit relatively low conductivities which are directionally distinct, aerospace manufacturers frequently use metallic foil layers or an expanded metal mesh on outer surfaces of composite structures for lightning strike protection. Due to irregular topology and associated micro-texture of machined holes in composites it is shown non-uniform interface surfaces between the fastener and composite layers reduces electrical continuity, thereby impeding current flow as a result of increased contact resistance levels. Furthermore, lightning strike experiments have indicated that metal mesh intimacy around the perimeter of the fastener head directly affects overall electromagnetic response of the rotorcrafts outer surface when subjected to lightning currents due to impedance modification of the electrical network. The effect of electrical continuity between the fastener head and mesh strand contact points is calculated using a Multiphysics model to demonstrate the effects on current load distribution and fusing lifetime of the individual strands. Additionally, total number of fastener-mesh strand contact points and cross sectional area of each strand are shown as being important parameters which ultimately determine the amount of lightning current efficiently transferred across the rotorcraft skin surface.
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