Vertical Tail Plane Research Articles

Automated sizing chain of aircraft structures: A Vertical Tail Plane use case

Current developments in preliminary design emphasise the potential benefit of addressing detailed sizing cases in the early design stages. This implies a sound understanding of the loads that the structure must withstand and for which it must demonstrate compliance. In aircraft structural practices, stringent safety requirements demand robust designs. It is understood that the foremost limitation and very challenging aspect, in the aviation sector, consists in complying with those requirements while targeting a contained mass. In this respect, the presented work aims to propose an automated implementation of the dimensioning chain by foregrounding a specific subsystem application, id est the Vertical Tail Plane. The conditions corresponding to a set of critical flight loads are identified and used for the sizing process. The use case intends to standardise the process, narrowing down the large number of unknowns on the overall loosely defined design method.

Influence of Electric Wing Tip Propulsion on the Sizing of the Vertical Stabilizer and Rudder in Preliminary Aircraft Design

During preliminary aircraft design, the vertical tail sizing is conventionally conducted by the use of volume coefficients. These represent a statistical approach using existing configurations’ correlating parameters, such as wing span and lever arm, to size the empennage. For a more detailed analysis with regard to control performance, the vertical tail size strongly depends on the critical loss of thrust assessment. This consideration increases in complexity for the design of the aircraft using wing tip propulsion systems. Within this study, a volume coefficient-based vertical tail plane sizing is compared to handbook methods and the possibility to reduce the necessary vertical stabilizer size is assessed with regard to the position of the engine integration and their interconnection. Two configurations, with different engine positions, of a hybrid-electric 19-seater aircraft, derived from the specifications of a Beechcraft 1900D, are compared. For both configurations two wiring options are assessed with regard to their impact on aircraft level for a partial loss of thrust. The preliminary aircraft design tool MICADO is used to size the four aircraft and propulsion system configurations using fin volume coefficients. These results are subsequently amended by handbook methods to resize the vertical stabilizer and update the configurations. The results in terms of, e.g., operating empty mass and mission fuel consumption, are compared to the original configurations without the optimized vertical stabilizer. The findings support the initial idea that the connection of the electric engines on the wing tips to their respective power source has a significant effect on the resulting torque around the yaw axis and the behaviour of the aircraft in case of a power train failure, as well as on the empty mass and trip fuel. For only one out of the four different aircraft designs and wiring configurations investigated it was possible to decrease the fin size, resulting in a 53.7% smaller vertical tail and a reduction in trip fuel of 4.9%, compared to the MICADO design results for the original fin volume coefficient.

Modular lightweight robot system for aircraft production using a generic OPC UA skill concept

There is a continuing trend in the aircraft industry to automate production. In order to be able to react to shortages of skilled workers, high order fluctuations and machine breakdowns, cost-effective, mobile and flexible systems are required to support the workers. This paper focuses on the integration of existing skill-based engineering concepts into production using standard OPC Unified Architecture interface, where production systems can be built quickly by simply interconnecting modules. The interconnected modules together form higher level subsystems enabling reusability of the individual modules as well as the assembled subsystems across several use cases. The approach is evaluated on a production related mobile robot system, whose task is to drive to the workstation, reference the component and drill holes in a vertical tail plane section of an aircraft. All devices from different suppliers contain skill-based modules based on standards defined by OPC Foundation and communicate via OPC UA-based Client/Server communication.

Fluidic-Oscillator-Based Pulsed Jet Actuation on a Vertical Tail

An industry-relevant vertical tail plane (VTP) model equipped with fluidic-oscillator-based pulsed jet actuators was tested with different active flow control (AFC) settings, rudder deflection, and sideslip angles at a chord Reynolds number of 1.3 million. In addition to pressure and force measurements, tuft visualizations and stereoscopic particle image velocimetry measurements were used to investigate AFC effects. With a total momentum coefficient of 1.5%, the control authority (lateral force) of the VTP was increased by a maximum of 34% when actuators were distributed along the rudder span. Additionally, flow control at dedicated positions on the rudder was investigated by using individual actuator segments. It was found that AFC is particularly effective at the position of the maximum load in the spanwise direction. The measurements also confirmed that local application of AFC actuators may simulate the effect of a boundary-layer fence. Finally, a comparison with existing results obtained with sweeping jet actuators shows that these two specific AFC implementations are most effective in different ranges of the momentum and the power coefficients.

Numerical Design Studies on the Roll Stability of a Multi-Delta-Wing Configuration

The current investigations look at the vortical flow physics and aerodynamic performance of a generic sharp leading-edge multi-delta-wing configuration. This work is part of the DLR project Diabolo looking at technologies and design requirements for next-generation fighter aircraft. The core of the investigation is a common planform geometry to demonstrate the design capability needed. Based on the initial planform, several design tasks in different domains have to be conducted. The present paper is dealing with the aerodynamic task to evaluate the effect of vortex interaction over the configuration progressing from the forebody, strakes, and main wing at asymmetric on flow conditions. The focus is on the roll stability at medium to high angle of attack. The aim is to find a planform and control surface setup which effects the vortex interaction on the main wing in a way to provide a stable aerodynamic roll without taking vertical and horizontal tail planes into consideration at this stage.

Aspects of yaw control design of an aircraft with distributed electric propulsion

Distributed electric propulsion (DEP) offers new options in aircraft design. Besides the optimization of the wing, another area of optimization is the vertical tail plane (VTP) and yaw control. The large number of engines significantly relaxes the one-engine-inoperative (OEI) case during take-off, which is mostly the sizing case for the VTP. This offers the possibility to reduce the VTP and rudder size to a certain amount. Also, the dynamics of electric motors offer the possibility to use differential thrust for yaw control. This can compensate at least some of the reduced rudder effectiveness coming from the smaller VTP size. In the framework of the German nationally funded project SynergIE, different aircraft designs of a hybrid-electric regional aircraft were investigated. Three aircraft concepts with 2, 6 and 12 propellers were designed in the project, for which reasonable minimum VTP sizes were investigated. For the 12-propeller aircraft, the investigations showed that the VTP could be reduced by 50%, still allowing the compensation of OEI during take-off and the generation of sideslip angle during crosswind operations. This reduction in VTP size results in a reduction of the block fuel by about 4%. For the 12-engine aircraft, a 6-degrees-of-freedom simulation model was developed including flight control laws for yaw control using the rudder and differential thrust. Virtual flight tests were performed in a full-flight simulator. The tests generally showed a good agreement with the theoretical results from the handling quality analysis but also outlined deficiencies in aircraft handling at low speed with full flaps. The use of a flight simulator at this early stage of aircraft design has proven to be a useful tool to investigate such unconventional designs.

Design of hybrid-electric aircraft with fault-tolerance considerations

The potential benefits of hybrid-electric or all-electric propulsion have led to a growing interest in this topic over the past decade. Preliminary design of propulsion systems and innovative configurations has been extensively discussed in literature, but steps towards higher levels of technological readiness, optimisation algorithms based on reliable weight estimation and simulation-based mission analysis are required. This paper focuses on the integration of a method for evaluating the lateral-directional controllability of an aircraft within a design chain that integrates aero-propulsive interactions, accurate modelling of the fuel system, and mid-fidelity estimation of the structural weight. Furthermore, the present work proposes a strategy for powerplant management in scenarios with an inoperative chain element. Benefits of hybrid-electric propulsion on the design of the vertical tail plane are evaluated involving the analysis of multiple failure scenarios and certification requirements. The proposed application concerns a commuter aircraft.

Influence of Fluid Viscosity and Compressibility on Nonlinearities in Generalized Aerodynamic Forces for T-Tail Flutter

The numerical assessment of T-tail flutter requires a nonlinear description of the structural deformations when the unsteady aerodynamic forces comprise terms from lifting surface roll motion. For linear flutter, a linear deformation description of the vertical tail plane (VTP) out-of-plane bending results in a spurious stiffening proportional to the steady lift forces, which is corrected by incorporating second-order deformation terms in the equations of motion. While the effect of these nonlinear deformation components on the stiffness of the VTP out-of-plane bending mode shape is known from the literature, their impact on the aerodynamic coupling terms involved in T-tail flutter has not been studied so far, especially regarding amplitude-dependent characteristics. This term affects numerical results targeting common flutter analysis, as well as the study of amplitude-dependent dynamic aeroelastic stability phenomena, e.g., Limit Cycle Oscillations (LCOs). As LCOs might occur below the linear flutter boundary, fundamental knowledge about the structural and aerodynamic nonlinearities occurring in the dynamical system is essential. This paper gives an insight into the aerodynamic nonlinearities for representative structural deformations usually encountered in T-tail flutter mechanisms using a CFD approach in the time domain. It further outlines the impact of geometrically nonlinear deformations on the aerodynamic nonlinearities. For this, the horizontal tail plane (HTP) is considered in isolated form to exclude aerodynamic interference effects from the studies and subjected to rigid body roll and yaw motion as an approximation to the structural mode shapes. The complexity of the aerodynamics is increased successively from subsonic inviscid flow to transonic viscous flow. At a subsonic Mach number, a distinct aerodynamic nonlinearity in stiffness and damping in the aerodynamic coupling term HTP roll on yaw is shown. Geometric nonlinearities result in an almost entire cancellation of the stiffness nonlinearity and an increase in damping nonlinearity. The viscous forces result in a stiffness offset with respect to the inviscid results, but do not alter the observed nonlinearities, as well as the impact of geometric nonlinearities. At a transonic Mach number, the aerodynamic stiffness nonlinearity is amplified further and the damping nonlinearity is reduced considerably. Here, the geometrically nonlinear motion description reduces the aerodynamic stiffness nonlinearity as well, but does not cancel it.

Accuracy Analysis for a Flow Line Process using a Mobile Holding Fixture for Machining CFRP Components

<div class="section abstract"><div class="htmlview paragraph">The aerospace sector is challenged to produce airplanes more efficiently and resiliently in the future. This leads to an increasing demand for improving productivity and flexibility as well as providing solutions for sustainable developments. A bottleneck in production is the machining of large-scale components. Apart from the machining tasks, non-productive operations like fixture adjustment, component handling, referencing and localization are performed within the machining station and can constitute up to 50% of the overall workload. In the UniFix project, Fraunhofer IFAM is participating in the development of a mobile fixture system for large-scale aircraft components, like vertical tail plane and landing flap components of the single aisle aircrafts. By installing components into a mobile holding fixture with an according referencing scheme, a flow line can be established that is composed of specialized workstations discharging the machining station from non-productive processes, leading to higher productivity.</div><div class="htmlview paragraph">This paper focusses on the component localization and referencing strategies for this mobile holding fixture. Here, specific challenges are caused by the transport in between the referencing and the machining process. Therefore, influences that contribute to the overall geometric uncertainty of the referencing process for machining are evaluated in detail. In this work, an automated laser scanner based localization of the components will be presented. Furthermore, estimations on the uncertainty in the involved systems will be conducted and propagated through the localization process.</div></div>

Investigation of propeller slipstream effects on lateral and directional static stability of transport aircraft

ABSTRACT The aerodynamic characteristics of turboprop aircraft are greatly affected by the running propellers. In this paper, propeller slipstream effects on the static lateral-directional stability characteristics of a typical twin-engine turboprop aircraft with clockwise rotating propellers were investigated through unsteady computational fluid dynamics (CFD) simulations and wind tunnel experiments. The propeller slipstream led to a significant decrease in the lateral static stability contribution of the wing-body-nacelle (WBN), and the most affected wing sections were located near the left boundary of the port propeller slipstream region. Moreover, the influence of the propeller slipstream on the lateral static stability contribution of the vertical tail plane (VTP) significantly altered the rolling moment curve slope of the entire airframe. Due to the effects of the propeller slipstream on the local dynamic pressure and therefore the effectiveness of the VTP, the aircraft showed significantly different directional static stability behaviors between the positive and negative sideslip conditions. Furthermore, it was found that the configurations with clockwise rotating propellers readily experience dramatic losses in directional static stability at large negative sideslip angles.

Dry carbon fiber applications in aerospace sector and automation options

Considering the latest introduction of the dry multiaxial fabrics into Aeronautical applications/programs (wing skins, Vertical Tail Plane [VTP] skins, winglets, bulkheads, cargo doors, etc.), together with the lack of automation for the preform creation and its deposition onto the corresponding molds, this paper will cover different potential solutions for the manufacturing of skins and stiffeners. In all cases, looking to the automated dry multiaxial fabric preform creation, lay-up and forming.

Verification of a chamberless HLFC design with an outer skin of variable porosity

A chamberless HLFC leading edge segment featuring an outer skin with variable porosity has been designed, manufactured and wind tunnel tested under flight Reynolds-number conditions. The aerodynamic design involved the extention of current HLFC design routines to variable pressure loss characteristics of the outer skin. Advanced options for structural design and manufacturing solutions with focus on industrialization, arising from the avoidance of aerodynamically driven chambering, are explored. The leading edge segment has been installed on an existing vertical tail-plane model and tested at the large low-speed wind-tunnel facility DNW-LLF. The design process and some results of the successful verification of the chamberless design are presented herein.

T-tail flutter simulations with regard to quadratic mode shape components

It is known that the dynamic aeroelastic stability of T-tails is dependent on the steady aerodynamic forces at aircraft trim condition. Accounting for this dependency in the flutter solution process involves correction methods for doublet lattice method (DLM) unsteady aerodynamics, enhanced DLM algorithms, unsteady vortex lattice methods (UVLM), or the use of CFD. However, the aerodynamic improvements along with a commonly applied modal approach with linear displacements results in spurious stiffness terms, which distort the flutter velocity prediction. Hence, a higher order structural approach with quadratic mode shape components is required for accurate flutter velocity prediction of T-tails. For the study of the effects of quadratic mode shape components on T-tail flutter, a generic tail configuration without sweep and taper is used. Euler based CFD simulations are applied involving a linearized frequency domain (LFD) approach to determine the generalized aerodynamic forces. These forces are obtained based on steady CFD computations at varying horizontal tail plane (HTP) incidence angles. The quadratic mode shape components of the fundamental structural modes for the vertical tail plane (VTP), i.e., out-of-plane bending and torsion, are received from nonlinear as well as linear finite element analyses. Modal coupling resulting solely from the extended modal representation of the structure and its influence on T-tail flutter is studied. The g-method is applied to solve for the flutter velocities and corresponding flutter mode shapes. The impact of the quadratic mode shape components is visualized in terms of flutter velocities in dependency of the HTP incidence angle and the static aerodynamic HTP loading.

Hybrid Laminar Flow Control on A320 Fin: Retrofit Design and Sample Results

A flight test with a simplified hybrid laminar flow control (HLFC) system on the vertical tail plane (VTP) of an A320 aircraft was performed in April/May 2018. This HLFC system was a prototype for a simplified system that might be attractive for drag reduction of commercial long-range aircraft. The paper presents the design principles of a simplified HLFC system, including passive suction, and shows their application to aerodynamic and suction system design for the retrofit of an A320 VTP. Furthermore, sample flight test results will be presented and discussed.

Performance Enhancement of a Vertical Tail Model with Sweeping Jets

Active flow control to delay the flow separation on the rudder of two different models has been investigated in the ONERA L1 wind tunnel. The first model was used as a simplified test case to investigate different types of actuations and consisted of a flat plate with a rudder. The different types of actuation investigated were continuous/pulsed blowing through slots, continuous blowing through segmented slots, and sweeping jets. The lift increments of these different types of actuation were compared in terms of not only mass flow rate but also momentum coefficient and power coefficient. Then, active flow control by sweeping jets was selected to be tested on the second model, which is a scale vertical tail model of a generic business jet. Side force increments up to 80% were achieved with a 2% value of . Side force increments of 50% were also reached with a lower value of 0.5%. These side force increments could lead to a reduction of vertical tail plane wetted area and weight and consequently to a reduction of cruise drag and fuel consumption.

Numerical investigation of tangential blowing over the rudder of a vertical tailplane

Tangential blowing over the shoulder of a deflected rudder is applied on a vertical tailplane. For a large rudder deflection angle and without blowing the flow is mostly separated on the rudder. Three configurations are investigated in a numerical study with the aim to increase the side force coefficient. The first one is the baseline without blowing, the second one has a continuous full span slot and for the third one discrete slots are used. With sufficient blowing through the continuous slot the separation on the rudder can be removed completely while the separation extent is greatly reduced when using discrete slots. This is investigated for different sideslip angles. An approximately linear increase in the side force coefficient can be found until a sudden side force breakdown occurs. In a further study, the jet blowing velocity is varied. A smaller jet velocity leads to a smaller increase in the side force coefficient. Comparing the continuous and discrete slot configurations shows that for a similar increase in the side force coefficient a much smaller mass flow rate is needed for the discrete slots. However, for jet velocities below the sonic speed the increase in the side force coefficient is limited. It can only be increased by a larger slot extent in spanwise direction but this comes at the expense of an increase in the required mass flow rate.

Control device effectiveness studies of a 53∘ swept flying wing configuration. Experimental, computational, and modeling considerations

The present investigation covers studies of different control devices on several 53∘ swept flying wing configurations without a vertical tail plane. The wings considered share the same planform but differ in their spanwise profile shapes. The planform, developed under the NATO AVT-251 Task Group, is referred to as the MULDICON (or MULti-DIsciplinary CONfiguration). The objectives of this article are twofold: (1) to design yaw control surfaces for the MULDICON wing using an experimental/computational approach and (2) to develop aerodynamic models that rapidly and accurately predict the effectiveness of control surfaces over a wide range of flight conditions. The yaw control surface design (position and size) should provide sufficient yaw moment with almost no contribution in roll and pitch moment. To identify such concepts, a number of preliminary experiments on a generic flying wing configuration have been conducted. Two promising concepts from wind tunnel tests were then numerically examined for being implemented in the MULDICON baseline wing. Concepts with spoilers and a split flap were specifically considered. For medium to high angles of attack, the flow topology of the baseline wing is dominated by a vortical flow field on the upper outer wing. This leads to interactions between vortex and the control device which influences the flow and the attitude of the control device on the upper wing side. Furthermore, this work considers developing aerodynamic models for predicting stability derivatives of several MULDICON designs over a wide range of flight conditions. Aerodynamic loads models are only developed for normal force and pitch moment coefficients, however, the developed approach can easily being extended to include lateral aerodynamic coefficients as well. Quasi-steady models of this work are power series expansions of traditional linear aerodynamic models to capture nonlinear effects. Additionally, the models can estimate static and dynamic stability derivatives and the control surface powers.

Numerical investigation of slot variations on the efficiency of tangential blowing at a vertical tailplane with infinite span

On a swept vertical tailplane with infinite span tangential blowing over the shoulder of a deflected rudder is applied. For large rudder deflection angles the flow on the rudder is separated without blowing. A numerical study is conducted with the aim to increase the side force coefficient. This could, for example, be required during take-off if the engine on one side fails, necessitating the compensation of a large yawing moment. If this criterion is critical for the sizing of the vertical tailplane, active flow control like tangential blowing could help to reduce the size of the vertical tailplane and thus save weight and fuel. With a continuous slot it is demonstrated that the separation on the rudder can be reduced or avoided. It is shown that using discrete slots this can be achieved with a smaller momentum coefficient. To analyze the effects of the discrete slots and their jets on each other and their effectivity with regard to the gain in side force coefficient a parameter study is conducted. The number of slots as well as the size of the slots in spanwise direction is varied and the impact of jet velocity changes is also studied. In comparing the results for a constant increase in side force and constant slot size in spanwise direction the configuration with the smaller number of slots but a higher jet velocity proved to be the most effective one.

Morphed Vertical Tailplane Assessment for Certification Requirements

Morphed Vertical Tailplane Assessment for Certification Requirements

Modal parameter identification of a compression-loaded CFRP stiffened plate and correlation with its buckling behaviour

In order to study the dynamic response and the buckling behaviour of several load-carrying structural components of civil aircraft when subjected to transient load scenarios such as gusts or a landing impact, a generic mid-size aircraft is defined within the European research project DAEDALOS. From this aircraft, several sections or panels in different regions such as wing, vertical tailplane and fuselage are defined. The stiffened carbon-fibre-reinforced plastic (CFRP) plate investigated within the present work represents a simplified version of the wing panel selected from the generic aircraft. As part of the current work, the buckling behaviour and the modal properties of the stiffened plate under the effect of a static in-plane compression load are studied. This is accomplished by means of a test series including quasi-static buckling tests and an experimental modal analysis (EMA). One of the key objectives pursued is the correlation of the modal properties to the buckling behaviour by studying the relationship between the natural frequencies of the stiffened plate and its corresponding buckling load. The experimental work is verified by a finite element analysis.