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In response to the ice crystal icing hazard identified twenty years ago, aviation industry, regulation authorities, and research centers joined forces into the HAIC-HIWC international collaboration launched in 2012. Two flight campaigns were conducted in the high ice water content areas of tropical mesoscale convective systems in order to characterize this environment conducive to ice crystal icing. Statistics on cloud microphysical properties, such as Ice Water Content (IWC) or Mass Median Diameter (MMD), derived from the dataset of in situ measurements are now being used to support icing certification rulemaking and anti-icing systems design (engine and air data probe) activities. This technical paper focuses on methodological aspects of the derivation of MMD. MMD are estimated from PSD and IWC using a multistep process in which the mass retrieval method is a critical step.

Glaciated icing conditions potentially leading to in-service event are often encountered in the vicinity of deep convective clouds. Nowcasting of these conditions with space-borne observations would be of a great help for improving flight safety and air-traffic management but still remains challenging. In the framework of the HAIC (High Altitude Ice Crystals) project, methods to detect and track regions of high ice water content from space-based geostationary and low orbit mission are investigated. A first HAIC/HIWC field campaign has been carried out in Australia in January-March 2014 to sample meteorological conditions potentially leading to glaciated icing conditions. During the campaign, several nowcasting tools were successfully operated such as the Rapid Development Thunderstorm (RDT) product that detects the convective areas from infrared geostationary imagery.

This study presents the results of the ICE GENESIS 2021 Swiss Jura Flight Campaign in a way that is readily usable for ice accretion modelling and aims at improving the description of snow particles for model inputs. 2D images from two OAP probes, namely 2D-S and PIP, have been used to extract 3D shape parameters in the oblate spheroid assumption, as there are the diameter of the sphere of equivalent volume as ellipsoid, sphericity, orthogonal sphericity, and an estimation of bulk density of individual ice crystals through a mass-geometry parametrization. Innovative shape recognition algorithm, based on Convolutional Neural Network, has been used to identify ice crystal shapes based on these images and produce shape-specific mass particle size distributions to describe cloud ice content quantitatively in details. 3D shape descriptors and bulk density have been extracted for all the data collected in cloud environments described in the regulation as icing conditions.

Measurements in snow conditions performed in the past were rarely initiated and best suited for pure and extremely detailed quantification of microphysical properties of a series of microphysical parameters, needed for accretion modelling. Within the European ICE GENESIS project, a considerable effort of natural snow measurements has been made during winter 2020/21. Instrumental means, both in-situ and remote sensing were deployed on the ATR-42 aircraft, as well as on the ground (ground station at ‘Les Eplatures’ airport in the Swiss Jura Mountains with ATR-42 overflights). Snow clouds and precipitation in the atmospheric column were sampled with the aircraft, whereas ground based and airborne radar systems allowed extending the observations of snow properties beyond the flight level chosen for the in situ measurements.

The work describes a concept application that aids a safety engineer to create a layup of equipment models by using an image scan of a schematic and a library of predefined standard component and their symbols. The approach uses image recognition techniques to identify the symbols within the scanned image of the schematic from a given library of symbols. Two recognition approaches are studied, one uses General Hough Transform; the other is based on pixel-level feature computation combining both structure and statistical features. The application allows the user to accept or edit the results of the recognition step and allows the user to define new components during the layup step. The tool then generates an output file that is compatible with a formal safety modeling tool. The identified symbols are associated to behavioral nodes from a model based safety tool.

The objective of this paper is to present a numerical method to rank thick ice shapes for aircraft by comparing the ice accretion effects for different icing scenarios in order to determine the more critical ice shape. This ranking allows limiting the demonstration of the aerodynamic characteristics of the aircraft in iced condition during certification to a reduced number of ice shapes. The usage of this numerical method gives more flexibility to the determination of the critical ice shapes, as it is not dependent of the availability of physical test vehicles and/or facilities. The simulation strategy is built on the Lattice Boltzmann Method (LBM) and is validated based on a representative test case, both in terms of aircraft geometry and ice shapes. Validation against existing experimental results shows the method exhibits an adequate level of reliability for the ranking of thick ice shapes.

The High Altitude Ice Crystals (HAIC) Sub-Project 3 (SP3) focuses on the detection of cloud regions with high ice water content (IWC) from current available remote sensing observations of space-based geostationary and low-orbit missions. The SP3 activities are aimed at supporting operationally the two up-coming HAIC flight campaigns (the first one in May 2015 in Cayenne, French Guyana; the second one in January 2016 in Darwin, Australia) and ultimately provide near real-time cloud monitoring to Air Traffic Management. More in detail the SP3 activities focus on the detection of high IWC from space-borne geostationary Meteosat daytime imagery, explore the synergy of concurrent multi-spectral multiple-technique observations from the low-orbit A-Train mission to identify specific signatures in high IWC cloud regions, and finally develop a satellite-based nowcasting tool to track and monitor convective systems over the Tropical Atlantic.

The Environmental Control System is a relevant element of any conventional or More Electric Aircraft (MEA). It is either the key consumer of pneumatic power or draws a substantial load from the electric power system. The objective of this paper is to present a tool for the design of Environmental Control Systems and to apply it to an unconventional system. The approach is based on a recently proposed methodology, which is improved with respect to flexibility and ease-of-use. Furthermore, modeling and simulation of vapor compression cycles is discussed, which are candidate technological solutions for More Electric Aircraft concepts. A steady-state moving boundary method is presented to model heat exchangers for such applications. Finally, the resulting design environment is applied to optimization of an unconventional ECS architecture and exemplary results are presented.

In 1994, an ATR-72 crashed at Roselawn, Indiana, USA. It has been speculated that accident was due to Supercooled Large Droplet (SLD) icing. This accident led to a modification of the regulation rules with the definition of the Appendix O which includes freezing drizzle and freezing rain icing conditions. The associated NPRM (Notice of Proposed Rule Making) has been distributed to industry for comments on 29th June 2010 and could be applicable by beginning 2012. In order to comply with this new rule, the simulation tools, as Acceptable Means of Compliance, have to be improved and validated for these conditions. The paper presents the work performed within Airbus to review, improve and assess simulation tools capability to accurately predict physical phenomena related to SLD. It focuses in particular on splashing and bouncing phenomena which have been highlighted as the first order effects.

Model Based Safety techniques have been developed for a number of years, though the models have not been customised to help address the safety considerations/ actions at each refinement level. The work performed in the MISSA Project looked at defining the content of “safety models” for each of the refinement levels. A modelling approach has been defined that provides support for the initial functional hazard analysis, then for the systems architectural definition level and finally for the systems implementation level. The Aircraft functional model is used to apportion qualitative and quantitative requirements, the systems architectural level is used to perform a preliminary systems safety analysis to demonstrate that a system architecture can satisfy qualitative and quantitative requirements.

Water is a contaminant that can lead to fuel system icing, microbial contamination, corrosion and fuel quantity gauging problems and therefore an efficient water management system is required in order to maximise the performance of an aircraft's fuel system. This paper describes a time-transient aircraft fuel tank model with water contamination, due to the principal mechanisms of dissolution, suspension, condensation and transportation. The tank model presented is a component of the NEPTUNE fuel system model which was developed for Airbus using the A380 as an example aircraft. A description of the physics of water contaminated fuel is given and of how this has been incorporated into a mathematical model of an aircraft fuel tank. A modular approach is demonstrated which enables interconnecting fuel tanks to be configured in larger systems in a flexible and easily understood manner.

A system has been designed for the A400M wherein engine air intake ice protection is provided by hot air bled from the engine cooled by air from inside the nacelle with a jet pump. Two variants of the system were developed. The first had an active temperature and pressure control downstream of the jet pump, and the second was without temperature control. Maximum temperature was a constraint for the design of the system since the engine air intake is manufactured in aluminum. In addition, several other constraints appeared during the detailed design of the system; the tight space allocation inside the nacelle limited the length of the jet pump, the low temperature provided by the engine bleed in flight idle limited the secondary flow used to cool the engine bleed, and the complex air distribution needed to supply air to the intake areas.

The PLANET System was used for real-time satellite data transmission during the HAIC-HIWC Darwin field campaign (January to March 2014). The basic system was initially providing aircraft tracking, chat, weather text messages (METAR, TAF, etc.), and aeronautical information (NOTAMs) in a standalone application. In the framework of the HAIC project, many improvements were made in order to fulfill requirements of the onboard and ground science teams for the field campaign. The aim of this paper is to present the main improvements of the system that were implemented for the Darwin field campaign. New features of the system are related to the hardware component, the communication protocol, weather and tracking display, geomarkers on the map, and image processing and compression before onboard transfer.

In order to comply with applicable certification regulations, airframers have to demonstrate safe operation of their aircraft in icing conditions. Part of this demonstration is often a numerical prediction of the potential ice accretion on unprotected surfaces. The software ONICE2D, originally developed at the Office National d'Études et de Recherche Aérospatial (ONERA), is used at Airbus for predicting ice accretions on wing-like geometries. The original version of the software uses a flow solution of the 2D full-potential equation on a structured C-grid as basis for an ice accretion prediction. Because of known limitations of this approach, an interface was added between ONICE2D and TAU [6], a hybrid flow solver for the Navier-Stokes equations. The paper first details the approach selected to implement the interface to the hybrid flow solver TAU. It continues to explain how an automatic impingement and ice accretion calculation on multi-element configurations has been achieved.

Accurate calculation of the catch efficiency β is of paramount importance for any ice accretion calculation since β is the most important factor in determining the mass of ice accretion. A new scheme has been proposed recently in [1] for accurately calculating β on a discretized two-dimensional geometry based on the results of a Lagrangian droplet trajectory integrator (start and impact conditions). This paper proposes an extension to the algorithm in Ref. [1], which is applicable to three-dimensional surfaces with arbitrary surface discretization. The 3D algorithm maintains the positive attributes of the original 2D algorithm, namely mass conservation of the impinging water, capability to deal with overlapping impingement regions and with crossing trajectories, computational efficiency of the algorithm, and low number of trajectories required to reach good accuracy in catch efficiency.

A test has been performed using a scaled aircraft wing section in an icing tunnel facility. The model had an electro-thermal ice protection system installed. The tests performed considered both anti-icing and de-icing modes of operation. The results have been assessed using numerical codes and the effect of model scaling has been considered. The non-scaled skin thickness of the model was found to modify the predicted behaviour of a full-scale installation, predominantly due to lateral conduction effects. The extent of this has been assessed and recommendations are made as to the performance that may be expected at full-scale.

Traditionally, software in avionics has been totally separated from open-world software, in order to avoid any interaction that could corrupt critical on-board systems. However, new aircraft generations need more interaction with off-board systems to offer extended services, which makes these information flows potentially dangerous. In a previous work, we have proposed the use of virtualization to ensure dependability of critical applications despite bidirectional communication between critical on-board systems and untrusted off-board systems. We have developed a test bed to assess the performance impact induced by the use of virtualization. In this work, various configurations have been experimented that range from a basic machine without an OS up to the complete architecture featuring a hypervisor and an OS running in a virtual machine. Several tests (computation, memory, network) are carried out, and timing measures are collected on different hypervisors.

The intent of this paper is to provide a general overview of the main engineering and test activities conducted in order to support A350XWB Ice and Rain Protection Systems certification. Several means of compliance have been used to demonstrate compliance with applicable Certification Basis (CS 25 at Amendment 8 + CS 25.795 at Amendment 9, FAR 25 up to Amendment 129) and Environmental protection requirements. The EASA Type Certificate for the A350XWB was received the 30th September 2014 after 7 years of development and verification that the design performs as required, with five A350XWB test aircraft accumulating more than 2600 flight test hours and over 600 flights. The flight tests were performed in dry air and measured natural icing conditions to demonstrate the performance of all ice and rain protection systems and to support the compliance demonstration with CS 25.1419 and CS25.21g.

The work describes a concept application to aid a safety engineer to perform an audit of a production aircraft against safety driven installation requirements. The capability is achieved using the following steps: A) Image capture of a product and measurement of distances between datum points within the product with/without references to a planar surface B) A digital reconstruction of the fabricated product by using multiple captured images to reposition parts according to the actual model. C) The projection onto the 3D digital reconstruction of the safety related installation constraints, respecting the original intent of the constraints that are defined in the digital mock-up.