Search Results

This paper presents CHT2D, a 2D hot air anti-icing simulation tool developed by the Advanced Aerodynamics group of Bombardier Aerospace. The tool has been developed from two main modules: the ice prediction code CANICE and the Navier-Stokes solver NSU2D, which is used to solve the hot air internal flow. A “weak” coupling beween the two modules based on function calls and information exchange has been priviledged. Three validation test cases are presented: for dry air conditions. Predictions from CHT2D agree quite well with the experiments. Preliminary results are also presented for a test case in icing conditions for different heat loads from the anti-icing system, to study the effect on the accumulated ice.

Lessons learned from analysis of in-service icing incidents are described. The airfoil and wing design factors that define an aircraft's natural stall characteristics are explored, including the aerodynamic effects of contamination. Special attention is given to contamination in the form of “roughness” along wing leading edges typical of frost. In addition, the key aerodynamic effects of ground proximity and sideslip/crosswind during the take-off rotation are described. An empirical method, that can be used to predict a wing's sensitivity to wing leading edge roughness, is demonstrated. The paper explores the in-service differences of aircraft that incorporate “hard”, “supercritical” and “slatted” wings. The paper attempts to explain why the statistical evidence appears to favor the slatted wing for winter operations.

The Learjet 85 is a business jet with an unpowered manual elevator control and is designed for a maximum dive Mach number of 0.89. During the early design, it was found that the stick force required for a 1.5g pull-up from a dive would exceed the limit set by FAA regulations. A design improvement of the tailplane was initiated, using 2D and 3D Navier-Stokes CFD codes. It was discovered that a small amount of positive camber could reduce the elevator hinge moment for the same tail download at high Mach numbers. This was the result of the stabilizer forebody carrying more of the tail download and the elevator carrying less. Consequently, the elevator hinge-moment during recovery from a high-speed dive was lower than for the original tail. Horizontal tails are conventionally designed with zero or negative camber since a positive camber can have adverse effects on tail stall and drag.

Bombardier faced new manufacturing process challenges drilling and fastening CSeries* aircraft panels with multi-material stacks of composite (CFRP), titanium and aluminum in which Gemcor responded with a unique, flexible CNC Drivmatic® automatic fastening system, now in production at Bombardier. This joint technical paper is presented by Bombardier, expounding on manufacturing process challenges with the C Series aircraft design requirements and Gemcor presenting a unique solution to automatically fasten CFRP aft fuselage panels and aluminum lithium (Al Li) cockpit panels with the same CNC Drivmatic® system. After installation and preliminary acceptance at Bombardier, the CNC system was further enhanced to automatically fasten the carbon fiber pressure bulkhead dome assembly.

The need for efficient manufacturing approaches has emerged with the increasing usage of composites for structural components in commercial aviation. Resin Transfer Molding (RTM), a process where a fiber preform is injected with resin into a closed tool, can achieve high fiber content required for structural components as well as improved dimensional accuracy since all surfaces are controlled by a tool surface. Moreover, RTM is well suited for parts that can be standardized throughout the aircraft, such as a fuselage frames and stringers. The objective of this investigation is to develop a preforming approach for a C-Shaped Fuselage frame. Two approaches are proposed: tri-axial braiding and hand lay-up of Non-Crimp Fabrics. The fiber architecture of the basic materials as well as the complete preforms is explained. The necessary preforming operations are detailed. The quality control measurement of fiber orientation and thickness are presented.

Leading edge roughness is known to influence the aerodynamic performance of wings and airfoil sections. Aerodynamic tests show that these effects vary with the type and texture of the applied roughness. The quantification of the relationship between different types of roughness is not very clear. This makes the comparison of results from different tests difficult. An attempt has been made to find a relationship between randomly distributed roughness using cylinders of different heights and densities, roughness using ballotini, and equivalent sand grain roughness. A CFD method based on the Cebeci-Chang roughness model was used to generate correlations with experimental data. It is found that the variation of the size and density of individual roughness elements can be represented using one roughness parameter, Rp, which is equivalent to the sand grain roughness parameter used in the Cebeci-Chang model.

In order to guarantee systems immunity, lightning induced electromagnetic energy has to be lower than the system's susceptibility threshold. This can be achieved, if the aircraft structure provides a good protection against lightning current as well as against its electromagnetic induced field. Moreover such a structure is also required to constitute a ground plane that guarantees very low common mode impedance between all grounded systems in order to keep them at the same electrical potential. The interaction of lightning with aircraft structure, and the coupling of induced energy with harnesses and systems inside the airframe, is a complex phenomenon, mainly for composite aircraft. Composite structures are either not conductive at all (e.g., fiberglass) or are significantly less conductive than metals (e.g., carbon fiber).

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.

A landing gear design automation tool has been developed and integrated in the conceptual multi-disciplinary optimization (MDO) environment at Bombardier Aerospace (BA). The tool allows an optimization to consider the landing gear integration at each design iteration. It uses design rules followed at BA to determine positions and ground contact points for the nose and main landing gears, while performing all necessary checks such as tip over, tail strike, and wing-tip strike angles. Subject to maximum loads from a set of predefined cases, the landing gear structure is sized and the tires and rims are selected from an embedded database. Once the landing gear is defined, a full kinematic analysis is performed to optimize the pivot axis and stowage of the gear in the fuselage. The tool was validated with actual data from several aircraft showing minimal errors in landing gear positioning and sizing (± 3%).

During the NASA/FAA Tailplane Icing Program, pilot evaluations of aircraft flying qualities were conducted with various ice shapes attached to the horizontal tailplane of the NASA Twin Otter Icing Research Aircraft. Initially, only NASA pilots conducted these evaluations, assessing the differences in longitudinal flight characteristics between the baseline or clean aircraft, and the aircraft configured with an Ice Contaminated Tailplane (ICT). Longitudinal tests included Constant Airspeed Flap Transitions, Constant Airspeed Thrust Transitions, zero-G Pushovers, Repeat Elevator Doublets, and, Simulated Approach and Go-Around tasks. Later in the program, guest pilots from government and industry were invited to fly the NASAT win Otter configured with a single full-span artificial ice shape attached to the leading edge of the horizontal tailplane.

Many uncertainties in an in-flight ice shape prediction are related to convection heat transfer coefficient, which in turn depends on the flow, turbulence and laminar/turbulent transition models. The height of ice roughness element used to calculate the Equivalent Sand Grain Roughness height (ESGR) is a very important input of the turbulence model as it strongly influences the shape of the accreted ice. Unfortunately, for in-flight icing, the ESGR is unknown and generally calculated using semi-empirical models or empirical correlations based on a particular ice shape prediction code. Each ice shape prediction code is unique due to the models and correlations used and the numerical implementation. Ice roughness correlations do not have the same effect in each ice shape prediction code. A new approach to calculate the ESGR correlation taking into consideration the particularities of the ice shape prediction code is developed, calibrated and validated.

The lightning represents a fundamental threat to the proper operation of aircraft systems. For aircraft protection, Electromagnetic Compatibility requires conductive structure that will provide among all, electromagnetic shielding and protection from HIRF and atmospheric electricity threat. The interaction of lightning with aircraft structure, and the coupling of induced energy with harnesses and systems inside the airframe, is a complex subject mainly for composite aircraft. The immunity of systems is governed by their susceptibility to radiated or conducted electromagnetic energy. The driving mechanism of such susceptibility to lightning energy is the exposure to the changing magnetic field inside the aircraft and IR voltage produced by the flow of current through the structural resistance of the aircraft. The amplitude of such magnetic field and IR voltage is related to the shielding effectiveness of the aircraft skin (wiremesh, composite conductivity).

3D ice accretion codes have been available for a few decades but, depending on the specific application, their use may be cumbersome, time consuming and requiring a great deal of expertise in using the code. In particular, simulations of large 3D glaze ice accretions using multiple layers of ice is a very challenging and time consuming task. There are several reasons why 2D icing simulations tools are still widely used in the aircraft industry to produce realistic glaze ice shapes. 2D codes are very fast and robust, with a very short turn-around time. They produce adequate results in areas of the aircraft where 3D effects on airflow or droplets concentration can be neglected. Their use can be extended to other areas of the aircraft if relevant 3D effects can be taken into account. This paper proposes a simulation methodology that includes three levels of corrections to extend the use of 2D icing codes to most of the aircraft surfaces.

Aerodynamic drag predictions using the block-structured Euler/Navier-Stokes flow solver FANSC, developed at Bombardier Aerospace for the analysis of the flow around complete aircraft configurations, are presented in this paper. To this end, the traditional far-field method, complemented with semi-empirical relations, is used for evaluating induced, form and viscous drag on a complete aircraft configuration from Euler/boundary-layer flow solutions. Recent advances in Navier-Stokes CFD methods technology are also used to yield near-field integration of the aerodynamic forces. Theoretical developments are briefly discussed on the numerical methods: the basic flow solver (discretization, time-integration, etc…), Euler/boundary-layer coupling methods (direct, semi-inverse and quasi-simultaneous) and Navier-Stokes method. The far-field and near-field drag prediction methods are discussed with emphasis on the relationship they carry with the CFD flow solution.

This paper presents work on the development of a low cost fuselage C-frame for aircraft primary structure using a Light Resin Transfer Molding (RTM) process. Compared to labor intensive hand layup prepreg technologies, Light RTM offers some substantial advantages by reducing infrastructure requirements such as hydraulic presses or autoclaves. Compared to Prepreg, Light RTM tooling creates two finished surfaces, which is an advantage during installation due to improved dimensional accuracy. The focus of this work was to develop means of achieving high fiber volume fraction structural frames using low cost tooling and a low volume manufacturing strategy. In this case a three piece Light RTM mold was developed using an internal mandrel. To achieve the strength requirements, a combination of crimped and non-crimped fabrics were selected for the reinforcing preform.

A particular field of aerospace engineering is dedicated to the study of aircraft that are so energetically efficient, that the power produced by a human being enables it to takeoff and maintain sustained flight without any external or stored energy. These aircraft are known as Human-Powered Aircraft (HPA). The objective of the present work is to design a single-seat HPA applying multidisciplinary optimization techniques with an objective function that minimizes both the power required and the stall speed, representing respectively, an easier and safer aircraft to fly. In the first stage, a parametric synthesis model is created to generate random aircraft and assess their aerodynamic(utilizing a 3D vortex lattice method code and a component drag buildup method for the drag polar), stability and control(utilizing static stability criteria), weight (estimated using historical data) and performance (using the thus calculated data) characteristics.

Implementing Design for Environment (DfE) into the design process requires a strategic integration. Furthermore, as DfE is continuously evolving, flexible processes need to be implemented. This article focuses on the integration of DfE into an optimization framework with the objective of influencing next-generation aircraft. For this purpose, DfE and Structures groups are developing together a set of new environmental indicators covering all life cycle stages of the product by coupling a list of yes/no questions with an environmental matrix. The following indicators are calculated: Regulation risk, Impact of manufacturing the part, CO2 emissions and Recyclability potential. These indicators will be used as constraints in the multi-disciplinary design optimization (MDO) framework, meaning that the structure will be designed while complying with environmental targets and anticipating future regulation changes.

Statistical process control (SPC) has been extensively used in many different industries including automotive, electronics, and aerospace, among others. SPC tools such as control charts, process capability analysis, sampling inspection, etc., have definitive and powerful impact on quality control and improvement for mass production and similar production systems. In aerospace manufacturing, however, applications of SPC tools are more challenging, especially when these tools are implemented in processes producing products of large sizes with slower production rates. For instance, following a widely accepted rule-of-thumb, about 100 units of products are required in the first phase of implementing a Shewhart type control chart. Once established, it then can be used for process control in the second phase for actual production process monitoring and control.

Pilots need to be aware, under certain icing conditions, of the limitations of ice protection on their particular aircraft. FAA certification for flight into known icing does not ensure complete safety of flight in all icing encounters regardless of skills or aircraft capability. Too many accidents where icing was a contributing factor attest to these facts. Most of the time flight crews will not encounter an extremely severe condition. However, icing conditions are so widely variable that by chance they will encounter a condition in which they are unprepared. Many years of flight research in icing by the authors have provided the opportunity to experience and measure a wide range of icing conditions in which the performance losses and flying qualities of the aircraft were determined. These results are described in this paper.

Ice adhesion on critical aircraft surfaces is a serious potential hazard that runs the risk of causing accidents. For this reason aircraft are equipped with active ice protection systems (AIPS). AIPS increase fuel consumption and add complexity to the aircraft systems. Reducing energy consumption of the AIPS or replacing the AIPS by a Passive Ice Protection System (PIPS), could significantly reduce aircraft fuel consumption. New coatings with superhydrophobic properties have been developed to reduce water adherence to surfaces. Superhydrophobic coatings can also reduce ice adhesion on surfaces and are used as icephobic coatings. The question is whether superhydrophobic or icephobic coatings would be able to reduce the cost associated with AIPS.