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This paper presents two new automatic landing systems (ALSs) for aircraft motion in longitudinal plane; the model of the landing geometry determines the flight trajectory and the aircraft calculated altitude; the flight trajectory during landing consists of two parts: the glide slope and the flare. Both designed ALSs have an adaptive system (ACS) for the aircraft output's control; for the first ALS, the output vector consists of the flying altitude and the longitudinal velocity, while, for the second ALS, the output variables are the pitch angle and the longitudinal velocity of aircraft. The second variant of ALS also contains an altitude controller providing the calculated pitch angle. The calculated altitude (for the first ALS), the calculated pitch angle (for the second ALS), and the desired flight velocity are provided to the ACS by means of a block consisting of two reference models. ACS is based on the dynamic inversion concept and contains an adaptive controller which includes a linear dynamic compensator, a state observer, a neural network, and a Pseudo Control Hedging block. The paper is focused both on the design of the two ALSs and on their complex software implementation and validation. [ABSTRACT FROM AUTHOR]

In the present paper, numerical investigations are carried out in a newly proposed propulsive system Aerial Coanda high-efficiency orienting jet nozzle (ACHEON), which supports thrust vectoring and its application to prototype unmanned aerial vehicles (UAVs). The ACHEON system is presently being proposed for propelling a new vertical and short takeoff (V/STOL) airplane in the European Union. This system is powered by two axial electric turbofans and uses the Coanda effect (attachment of the jet to a curved surface) to achieve precise control of the thrust angle. The present study investigates the thrust vectoring efficiency of this newly patented nozzle and its integration with UAVaircraft. This study numerically investigates the 3D effects on this new machine and proposes remedies to solve the associated problems. Further, swirling effects generated by electric turbofans were studied in great detail. The effect of uniform and nonuniform velocity profiles were investigated on thrust vectoring efficiency of the nozzle. Then, the aerodynamic features of prototype UAVs were determined under various flow conditions. The interaction of the exit nozzle flow with incoming airstream was studied. Computational fluid dynamics (CF) calculations were carried out using Reynolds averaged Navier-Stokes (RANS) equations. A numerical method based on finite volume formulation (FVM) was used. Turbulent flow is modeled by using the SST k-ω model. Numerical results show that the presence of swirling velocities in the flow field significantly affects the thrust vectoring efficiency of the nozzle. From numerical simulations of the aircraft, it was found that the aerodynamic characteristics are strongly affected by the exit air jet angle. [ABSTRACT FROM AUTHOR]

As part of the Collaborative Research Center 880, preliminary aircraft design activities are carried out for a new class of low-noise cruise-efficient short takeoff and landing (CESTOL) transport aircraft. A corresponding aircraft is quite different from a state-of-the-art commercial aircraft because of the use of a high-lift system with active flow control. The fact that new technologies are not sufficiently understood yet in combination with the assumption of common design data and the use of classical calculation methods expresses itself in uncertainties that are of epistemic character. The robustness of a deterministic CESTOL aircraft design toward parameters such as the necessary engine thrust, direct operating costs, and the maximum takeoff and landing distances is investigated here concerning the mentioned uncertainties. For this purpose, a stochastic description of parameter variations of the design is formulated. Stochastic quantities are computed by Monte Carlo sampling to rate the robustness. A distributed component-based software implementation is used to perform the Monte Carlo sampling. The software system is installed on a Linux cluster with several multi-CPU computers; a deterministic sample is simulated through the design program PrADO. [ABSTRACT FROM AUTHOR]

Preliminary design studies indicate that a cruise-efficient short takeoff and landing aircraft has enhanced takeoff performance at competitive direct operating costs when using high-speed propellers in combination with internally blown flaps. The original tractor configuration is compared to an over-the-wing propeller, which allows for noise shielding. An additional geometry with partially embedded rotor similar to a channel wing is considered to increase the beneficial interaction. This paper shows the aerodynamic integration effects with a focus on climb performance and provides an assessment of the three aforementioned configurations for a simplified wing segment at takeoff conditions. Steady Reynolds-averaged Navier-Stokes simulations have been conducted using an actuator disk model and were evaluated based on the overall design. Interacting with the blown flap, the conventional tractor propeller induces large lift and drag increments due to the vectored sliptream. Although this effect is much smaller for an over-the-wing configuration, by halving the lift augmentation, the lift-to-drag ratio and the propulsive efficiency are considerably improved. Besides a moderate lift gain, the main advantage of a channel wing design is the location of the thrust vector close to the center of gravity resulting in a smaller nosedown pitching moment due to thrust. A disadvantage of over-the-wing propellers is the inhomogeneons inflow at higher velocity, which leads to oscillating blade loads and reduced efficiency. [ABSTRACT FROM AUTHOR]

Abstract: The impingement of an underexpanded jet onto a solid object can be found in engineering applications. Takeoff and landing of V/STOL aircraft, and launching systems on a spaceship for solid rocket motors are some examples related to this complex phenomenon. Because most of the dynamic energy is converted to thermal energy when a high-speed flow is decelerated in front of a protruded solid body, impingement of the high-speed flow produces a severe thermal load to the body surface as well as aerodynamic loads on it. In this experimental study, the thermal characteristics on an inclined plate impinged by an underexpanded sonic jet were investigated. The recovery factor was retained by infrared thermography while the pressure distribution was measured using pressure transducers. Experiments were performed for four different inclinations of impinged plate, ranging from 0° to 30°. In addition, the effect of nozzle-to-plate distance was studied. From the results, the axi-symmetric pattern of recovery factor on an impinged surface is broken and the low recovery factor zone shifts to the downward region as the inclination angle increases. In addition, the cooling effect is weakened overall as the inclination angle increases. [Copyright &y& Elsevier]

Abstract: This work focuses on the control law design for a class of aerial systems able to perform transition maneuvers from hover to level flight configurations. An analysis of the aircraft dynamics and of the flight envelope of the vehicle, encompassing both the hover and the level flight conditions, is proposed in presence of wind disturbances. This analysis is used to derive a control strategy able to enforce the desired transition while maintaining the flight envelope within prescribed sets despite the influence of wind disturbances. To this end, a path following approach is adopted in which the time law is synthesized by a flight envelope protection controller. The paper complements our earlier work (Naldi & Marconi, 2011) in which optimal transition trajectories are computed. Simulation results, obtained with the parameters of a miniature tail-sitter prototype, show the effectiveness of the proposed approach. [Copyright &y& Elsevier]

This article explores, theoretically and experimentally, Coanda effect and upper surface blowing over an annular wing. Also, presented are a simple mathematical/empirical model and an experimental strategy to evaluate lift generated by a blown-annular wing. It has been shown that the wing is capable of deflecting the flow by ∼90° with an efficiency of ∼61 per cent with reference to the undeflected horizontal thrust from the source. The analytical review and experimental data presented will enable an aircraft designer to deduce this particular powered-lift system for V/STOL applications at the preliminary design stage. [ABSTRACT FROM AUTHOR]

The study of under-expanded supersonic impinging jet has been a popular subject not only because of its fundamental importance but also its practical importance in aerospace applications, such as Short Take-off and Vertical Landing(STOVL). In this paper, Large-Eddy Simulations (LES) of highly under-expanded supersonic jet impinging on large plate has been carried out. The numerical simulation successfully captures the shock wave structure in the jet plume and vortex structures with different scales in the internal and external shear layer and in the wall jet. The numerical results show the oscillation of the mach disk, and occurrence and disappearance of the annular shock in the peripheral supersonic flow during a period of oscillation. At the same time, through the numerical simulation, the evolution of the vortex in the internal shear layer has been observed. It can be seen that the formations of large-scale vortex structures associate with the oscillation of the Mach disk. Under the interaction of internal and external shear layer, the interlacing vortex structures in the wall jet are formed. [ABSTRACT FROM AUTHOR]

Abstract: This paper focuses on the problem of computing optimal transition maneuvers for a particular class of tail-sitter aircraft able to switch their flight configuration from hover to level flight and vice versa. Both minimum-time and minimum-energy optimal transition problems are formulated and solved numerically in order to compute reference maneuvers to be employed by the onboard flight control system to change the current flight condition. In order to guide the numerical computation and to validate its results, in a first stage approximated solutions are obtained as a combination of a finite number of motion primitives corresponding to analytical trajectories of approximated dynamic models. The approximated solution is then employed to generate an initial guess for the numerical computation applied to a more accurate dynamic model. Numerical trajectories computed for a small scale prototype of tail-sitter aircraft are finally presented, showing the effectiveness of the proposed methodology to deal with the complex dynamics governing this kind of systems. [Copyright &y& Elsevier]

Combined Vertical and short take-off and landing, or 'V/STOL' capability has been of great demand and interest in the field of aeronautics since the creation of the aircraft. V/STOL capability is a targeted capability for many projected or prototype future aircraft. Past V/STOL aircraft are reviewed and analysed with regard to their performance parameters. This research has found two embedded categories in this class of aircraft based on their propulsion systems, i.e. jet and non-jet propulsion, and highlights the significant performance differences between them. In light of historical experience the performance of a relatively new class of aircraft, the flying cars, has been evaluated. [ABSTRACT FROM AUTHOR]

The interaction of multiple jets with the ground is of great importance for the design and operation of short take-oft vertical landing aircraft. The fountain upwash flow, generated by the impingement of two axisymmetric, compressible, turbulent jets onto a ground plane was studied using laser-based particle image velocimetry and laser Doppler velocimetry. Measurements were made with nozzle pressure ratios of between 1.05 and 4, nozzle height-to-diameter ratios of between 24 and 84, nozzle splay angles of between ±15 degrees and a nozzle spacing-to-diameter ratio of seven. The effect of varying these parameters on the fountain velocity decay, spreading rate and momentum flux ratio are discussed. Mean fountain upwash velocity profiles were found to be self-similar for all test conditions. A distinct frequency of fountain oscillation was identified but only at a nozzle height of 44 diameters. [ABSTRACT FROM AUTHOR]

Short take-off and landing (STOL) systems can offer significant capabilities to warfighters and, for civil operators thriving on maximising efficiencies they can improve airspace use while containing noise within airport environments. In order to provide data for next generation systems, a wind tunnel test of an all-wing cruise efficient, short take-off and landing (CE STOL) configuration was conducted in the National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC) 14ft by 22ft Subsonic Wind Tunnel. The test's purpose was to mature the aerodynamic aspects of an integrated powered lift system within an advanced mobility configuration capable of CE STOL. The full-span model made use of steady flap blowing and a lifting centerbody to achieve high lift coefficients. The test occurred during April through June of 2007 and included objectives for advancing the state-of-the-art of powered lift testing through gathering force and moment data, on-body pressure data, and off-body flow field measurements during automatically controlled blowing conditions. Data were obtained for variations in model configuration, angles of attack and sideslip, blowing coefficient, and height above ground. The database produced by this effort is being used to advance design techniques and computational tools for developing systems with integrated powered lift technologies. [ABSTRACT FROM AUTHOR]

This paper presents a summary of the principles and processes used to design a ski-jump ramp profile for the UK's Future Aircraft Carrier (CVF) optimised for the Joint Strike Fighter (JSF). The paper includes an overview of the CVF and JSF programs, a history and summary of the ski-jump ramp and the principles of its use in the shipbome Short Take-Off (STO) manoeuvre. The paper discusses the importance of defining optimisation boundaries including specified objectives, aircraft configurations and environmental conditions. It then demonstrates the process of balancing the design drivers of air vehicle performance and landing gear loads to achieve an optimum profile. Comparisons are made between the proposed candidate CVF ramp profile and the current in service ski-jump design as designed for the Harier family of aircraft. The paper briefly covers some of the important issues and factors that have been experienced when a theoretical profile is translated into a physical ramp fitted to a ship, principally the effects on aircraft operations due to build and in-service variation from the nominal profile. [ABSTRACT FROM AUTHOR]

This paper presents the highlights of the F-35 STOVL Jet Effects (SJE) test effort during the complete four years of the System Development and Demonstration phase. A new 12%-scale F-35 SJE model was tested in the German-Dutch wind-tunnels Large Low Speed Facility in order to gather STOVL jet-induced Forces and Moments. Ten separate test entries were conducted, covering all STOVL flight regimes from pure hover in ground effect through transition to wing borne flight. This paper will present an overview of this programme, including a detailed description of the wind-tunnel model, testing techniques, test conditions, and accomplishments. [ABSTRACT FROM AUTHOR]

This paper describes the market for air vehicles that offer Very Short Take Off and Landing (VSTOL) capabilities, also known as VSTOL aircraft. A commercial VSTOL aircraft will only succeed if it provides profits to both manufacturers and airlines. Being able to operate out of shorter fields offers airlines greater flexibility and therefore provides a benefit to the airline. However, adding VSTOL performance also adds cost. Successful VSTOL aircraft designs must balance the added cost against the additional benefits VSTOL performance will provide. The first problem in any new VSTOL design is determining that field length provides the maximum benefit relative to cost. In order to be able to determine this one needs to know not only what it will cost to design and build the new aircraft, but its value to the airlines, as reflected by the demand for it and the price they are willing to pay. Only then is it possible to design the aeroplane the market wants at a sustainable price and in sufficient quantities to optimise the manufacturer's return on investment. This paper is a comprehensive parametric analysis of helicopters and aeroplanes that shows how much the market values short field performance by determining how much airline customers have been paying for it and how the market reacts to changes in its price. The analysis simultaneously considers over 230 currently produced models of fixed wing and rotary commercial aircraft, ranging in size from a Cessna 172 to an Airbus A380 and with balanced field lengths ranging from less than 150 to over 10,500ft. The data show that a single, statistically significant demand curve exists for all of these vehicles, with prices that range across several orders of magnitude. This curve consists of several segments or sub- markets including those for regional and rotary wing aircraft. Both of those markets offer vehicles over a wide range of prices. The analysis shows that VSTOL price is a function of the balanced field length provided by the vehicles within these market segments. Comparing demand and sustained price against cost reveals particular field lengths for which it will he possible to make a profit building VSTOL aircraft. Because the sustained price for a VSTOL aircraft is a function of its field length performance, and the quantity of a model sold is a function of its price, it follows that it is possible to predict the profit potential for a given VSTOL design in advance of its development. A thorough study of potential configurations therefore offers manufacturers the ability to design VSTOL aircraft that provide the maximum possible profit while fully satisfying the requirements of their airline customers. [ABSTRACT FROM AUTHOR]

This paper aims to demonstrate the viability of using the large eddy simulation (LES) CFD methodology to model a representative, complete STOVL aircraft geometry at touch down. The flowfleld beneath such a jet-borne vertical landing aircraft is inherently unsteady. Hence, it is argued in the present work that the LES technique is the most suitable tool to predict both the mean flow and unsteady fluctuations, and, with further development and validation testing, this approach could be a replacement, and certainly a complementary aid, to expensive rig programmes. The numerical method uses a compressible solver on a mixed element unstructured mesh. Examination of instantaneous flowfield predictions from these LES calculations indicate close similarity with many flow features identified from ground effect flow visualisations, which are well known to be difficult to model using RANS-based CFD. Whilst significant further work needs to be carried out, these calculations show that LES could be a practical tool to model , for example, Hot Gas Ingestion for the Joint Strike Fighter aircraft. [ABSTRACT FROM AUTHOR]

Focuses on the necessity of naval aircraft carriers for the security in Great Britain. Factors contributing to the downsizing of the military services; Problems encountered by the STOVL carrier; Recognition of the airplane as the key equipment in naval aviation.

A theory and technique is presented for estimating the business travel market shares of future V/STOL aircraft as functions of the nondemographic mode choice factors of time, cost, safety, comfort, convenience, and weather reliability. A linear mathematical model is described. Inputs to the model are derived directly from questionnaire surveys incorporating semantic differential and multiple choice questions. The technique is demonstrated on a city-pair 112 miles apart where business travel currently favors automobiles. Two V/STOL aircraft types competing with conventional modes in a hypothetical 1985 environment are predicted to attract 48 per cent of the business travel in this city-pair market. [ABSTRACT FROM AUTHOR]

This paper describes a cost-effectiveness study of the use of vertical or short takeoff and landing (VSTOL) aircraft for combat missions. A comparison is made with conventional (CTOL) aircraft as tactical fighters in a future NATO environment. The conditions under which VSTOL and CTOL aircraft can be considered to be competitive systems are carefully described. A model yielding the "probability of completing n successive missions" is used as a measure of combat effectiveness. A cost model was constructed to reflect the resource impact of the same variables or alternatives that affect the measure of effectiveness. This integrated format is a necessary condition for the selection of least-cost designs capable of providing a given level of mission performance. A graphical summary of such a format is provided. [ABSTRACT FROM AUTHOR]