Refine Your Search

Topic

Search Results

Viewing 1 to 15 of 15
Technical Paper

Prediction of Airfoil Performance with Leading Edge Roughness

1998-09-28
985544
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.
Technical Paper

Landing Gear Integration in an Industrial Multi-Disciplinary Optimization Environment

2013-09-17
2013-01-2319
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%).
Technical Paper

Flying Qualities Evaluation of a Commuter Aircraft with an Ice Contaminated Tailplane

2000-05-09
2000-01-1676
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.
Technical Paper

Drag Prediction Using the Euler/Navier-Stokes Code FANSC

2003-09-08
2003-01-3022
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.
Technical Paper

Contending with Airframe Icing

2002-04-16
2002-01-1518
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.
Technical Paper

More About Lightning Induced Effects on Systems in a Composite Aircraft

2013-09-17
2013-01-2156
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).
Technical Paper

Efficient 3D Artificial Ice Shapes Simulations with 2D Ice Accretion Codes using a 3-Level Correction

2013-09-17
2013-01-2136
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.
Technical Paper

An Anecdote - Order of Magnitude Cost and Time Reduction in Delivering an Aircraft Manufacturing Solution

2013-09-17
2013-01-2335
From purchase order to production womb-to-tomb in 5 months to the day, Bombardier's Fuselage Assembly line was upgraded and made into a fuselage automated assembly pulse line. This was accomplished with a factory move of the assembly line while maintaining production of this legacy line without missing one aircraft. Early in 2012, a bold decision was made to change the plan from a manual process to an automated process and implemented on schedule. This was applying automation to a legacy aircraft assembly line. It worked. Both technology and recurring cost savings will be addressed in this paper.
Technical Paper

Development of Low Cost Fuselage Frames by Resin Transfer Molding

2013-09-17
2013-01-2325
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.
Journal Article

Electromagnetic Protection Hazards on Composite versus Metallic Aircraft

2013-09-17
2013-01-2157
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).
Journal Article

Aircraft Structure Paint Thickness and Lightning Swept Stroke Damages

2013-09-17
2013-01-2135
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.
Journal Article

Monitor Points Method for Loads Recovery in Static/Dynamic Aeroelasticity Analysis with Hybrid Airframe Representation

2013-09-17
2013-01-2142
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.
Journal Article

Preforming of a Fuselage C-Shaped Frame Manufactured by Resin Transfer Molding

2013-09-17
2013-01-2214
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.
Journal Article

Challenges Associated with a Complex Compound Curvature Passenger Doors

2013-09-17
2013-01-2217
This study investigates challenges associated with integrating a passenger (PAX) door on complex compound curvature (CCC) fuselages. Aerospace companies are investigating concepts that no-longer have constant cross-section (CS) fuselages. The PAX door is based on a generic semi-plug door for a long range business jet (BJ). This study investigates limitations of locating the door by varying the transition zone angle. A parametric CATIA tool, coupled with the use of finite element model (FEM) results can highlight key drivers in the design and location of PAX doors, creating a first-draft structural layout. The associated impact on the design and structural architecture for a fold down PAX door with integrated stairs is discussed. The impact of CCCs on the PAX door design is investigated with consideration to location, kinematics and function of the door.
Technical Paper

The Effect of Wing Leading Edge Contamination on the Stall Characteristics of Aircraft

2007-09-24
2007-01-3286
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.
X