Download or read book A Study in Drag Reduction of Close Formation Flight Accounting for Flight Control Trim Positions and Dissimilar Formations written by Michael T. Morgan and published by . This book was released on 2005 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aircraft Drag Reduction Through Extended Formation Flight written by Simeon Andrew Ning and published by Stanford University. This book was released on 2011 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: Formation flight has the potential to significantly reduce the fuel consumption of long range flights, even with existing aircraft. This research explores a safer approach to formation flying of transport aircraft, which we term extended formation flight. Extended formations take advantage of the persistence of cruise wakes and extend the streamwise separation between the aircraft by at least five wingspans. Classical aerodynamic theory suggests that the total induced drag of the formation should not change as the streamwise separation is increased, but the large separation distances of extended formation flight violate the simple assumptions of these theorems. At large distances, considerations such as wake rollup, atmospheric effects on circulation decay, and vortex motion become important to consider. We first examine the wake rollup process in the context of extended formations and develop an appropriate physics-based model. Using this model, this dissertation addresses three aspects of formation flight: longitudinally extended formations, compressibility effects, and formations of heterogeneous aircraft. Uncertainty analysis is used to investigate the induced drag savings of extended formations in the presence of variation in atmospheric properties, limitations of positioning accuracy, and uncertainty in model parameters. Next, the methodology is integrated with an Euler solver to assess the impact of compressibility while flying in formation. Finally, we examine the important considerations for optimally arranging formations of non-identical aircraft.
Download or read book Modeling Analysis and Control of Close Formation Flight written by Qingrui Zhang and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Close formation flight is extensively investigated from the perspectives of dynamic modeling, aerodynamic analysis, and control design. A lifting-line based aerodynamic model is presented to describe the aerodynamic coupling between two aircraft in close formation. The introduced aerodynamic model is validated via the comparison with a single horseshoe vortex-based model, a vortex lattice method-based model, and experimental results. Comprehensive analysis is thereafter conducted to investigate the drag reduction variations with respect to different relative positions, angles of attack, sideslip angles, and leader-to-follower wing span ratios. The analysis indicates that the drag reduction performance of close formation flight is sensitive to the formation position accuracy. Additionally, basic requirements are formulated for close formation flight control. In terms of the proposed aerodynamic model, a linear robust adaptive formation controller is developed specifically for close formation at level and straight flight. The proposed robust adaptive controller shows dramatic increase in both transient performance and robustness against model uncertainties and disturbances. The nonlinear robust close formation control problem is thereafter studied under a leader-following architecture. Nonlinear robust close formation controllers with different considerations are proposed based on a command filtered backstepping method and an uncertainty and disturbance estimation technique. The proposed nonlinear robust formation controllers could accommodate more complex flight scenarios, for instance, different flight maneuvers and close formation of more than three aircraft. With the increase of the number of aircraft in close formation, a leader-following formation controller might become less and less efficient. Regarding the efficiency degradation issue of leader-following formation controllers, two cooperative control algorithms are introduced, which exhibit better tracking performance for close formation of a large number of aircraft. Extensive simulations are carried out to validate the effectiveness of all proposed close formation control algorithms.
Download or read book Close Formation Flight Control written by Andrew Proud and published by . This book was released on 1999-05-01 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this research the close formation flight control problem is addressed. The formation consists of a lead and wing aircraft, where the wing flies in close formation with the lead, such that the lead's vortices produce aerodynamic coupling effects, and a reduction in the formation's drag is achieved. A controller, i.e., a formation-hold autopilot for the wing aircraft, is designed such that the formation's geometry is maintained in the face of lead aircraft maneuvers. In the formation flight control system, the wing and lead aircraft dynamics are coupled due to kinematic effects, and, in the case of close formations, additional aerodynamic coupling effects are introduced. In the research these additional aerodynamic coupling effects are properly modeled. The most significant aerodynamic coupling effect introduced by close formation flight entails the coupling of the lateral/directional channel into the altitude-hold autopilot channel. It is shown that formation hold autopilots designed ignoring the aerodynamic coupling effects, yield satisfactory performance in close formation flight.
Download or read book Cathrine Zernichow written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Analytical Study of T 38 Drag Reduction in Tight Formation Flight written by and published by . This book was released on 2002 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis explores the benefits of flying in a tight formation, mimicking the natural behavior of migratory birds such as geese. The first phase of the research was to determine an optimal position for the wingman of a tight formation flight of T-38 Talon aircraft using the HASC95 vortex lattice code. A second wingman was then added to determine the benefit derived by increasing formation size. The second wingman was predicted to derive an even greater induced drag benefit than the first wingman for T-38s operating at Mach 0.54 at a 10,000-foot altitude. The predicted values were 17.5% savings for the second wingman versus 15% for the first wingman. The flight test phase flew two and three-ship formations to validate the computational work. The results of the two-ship flight tests showed with 80% confidence that the wingman saved fuel in the predicted optimal position (86% wingspan lateral spacing). This position yielded actual fuel savings of 8.8% 5.0% versus the predicted 15%. The other lateral positions did not show a statistically significant fuel savings. The flight test team felt that the three-ship formation data was inconclusive due to the difficulty of trying to fly a stable position as the third aircraft in the formation without station-keeping ability.
Download or read book An Analytical Study of T 38 Drag Reduction in Tight Formation Flight written by Eugene H. Wagner and published by . This book was released on 2002-03-01 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis explores the benefits of flying in a tight formation, mimicking the natural behavior of migratory birds such as geese. The first phase of the research was to determine an optimal position for the wingman of a tight formation flight of T-38 Talon aircraft using the HASC95 vortex lattice code. A second wingman was then added to determine the benefit derived by increasing formation size. The second wingman was predicted to derive an even greater induced drag benefit than the first wingman for T-38s operating at Mach 0.54 at a 10,000-foot altitude. The predicted values were 17.5% savings for the second wingman versus 15% for the first wingman. The flight test phase flew two and three-ship formations to validate the computational work. The results of the two-ship flight tests showed with 80% confidence that the wingman saved fuel in the predicted optimal position (86% wingspan lateral spacing). This position yielded actual fuel savings of 8.8% 5.0% versus the predicted 15%. The other lateral positions did not show a statistically significant fuel savings. The flight test team felt that the three-ship formation data was inconclusive due to the difficulty of trying to fly a stable position as the third aircraft in the formation without station-keeping ability.
Download or read book Evaluating and Augmenting Fuel saving Benefits Obtained in Aircraft Formation Flight written by Wendy Awele Okolo and published by . This book was released on 2015 with total page 235 pages. Available in PDF, EPUB and Kindle. Book excerpt: When an aircraft flies, it generates wake vortices, which induce a non-uniform wind distribution in its wake. A trail aircraft, placed in the wake of a lead's aircraft vortices experiences this non-uniform wind distribution with varying directions and magnitudes, depending on the location within the wake. It has been demonstrated that there is a "sweet spot" within the wake of a leader in which a trail can experience upwash which leads to reduced drag. Through this mechanism, aircraft can save significant amounts of fuel by flying at the sweet spot of the lead aircraft's wake. This dissertation provides two metrics of obtaining the sweet spot and evaluating the benefits to the trail aircraft at the sweet spot: a static and a dynamic study. The static study, similar to wind tunnel tests in which aircraft are statically placed in formation without trimming, investigates the induced aerodynamic forces and moments on the trail aircraft as it varies its position within the wake of the lead aircraft, and assigns the relative location of maximum lift-to-drag ratio as the static sweet spot. The dynamic study, similar to flight tests which account for trim, analyzes the control surface deflection and thrusts for the trail aircraft as it varies its position within the lead's wake and assigns the location of minimum thrust as the dynamic sweet spot. The static and dynamic analyses are applied to aircraft formations with different relative sizes and varying configurations of trail aircraft such as a flying-wing and a conventional aircraft. Results indicate that sweet spot locations and associated bene ts are dependent on the weight of the leader and the relative sizes of the aircraft pair in the formation. This dissertation then augments the fuel-savings by investigating alternate lateral trimming methods to reduce the need for drag-inducing control effector deflections required at the static sweet spot. Internal fuel transfer and differential thrusting are employed to increase the thrust saved at the static sweet spot, making it comparable to the dynamic sweet spot. Formation simulations of extended durations are also studied to understand the impact of significant weight variations in the leader on the formation benefits. In longduration flights, the lead and trail aircraft weights decrease due to fuel burn. Since the upwash generated by the leader decreases with lift and weight as fuel is burned, the magnitudes of the non-uniform wind induced and thus bene ts for the trail decrease. This decrease is investigated for a 6.5-hour formation simulation. Although there is a reduction in the benefits with time, the overall benefits of flying in formation is significant enough to motivate formations of such long durations. Finally, the feasibility of formation flying is also considered from a perspective of comfort levels for passengers or aircrew in the trail aircraft. Using international standards for likely reactions of a person subjected to discomforts characterized by vibrations, it is shown that there is no additional detrimental degradation of comfort levels for a person onboard a trail aircraft in formation as compared to a solo flight.
Download or read book Aircraft Drag Reduction Through Extended Formation Flight written by Simeon Andrew Ning and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Formation flight has the potential to significantly reduce the fuel consumption of long range flights, even with existing aircraft. This research explores a safer approach to formation flying of transport aircraft, which we term extended formation flight. Extended formations take advantage of the persistence of cruise wakes and extend the streamwise separation between the aircraft by at least five wingspans. Classical aerodynamic theory suggests that the total induced drag of the formation should not change as the streamwise separation is increased, but the large separation distances of extended formation flight violate the simple assumptions of these theorems. At large distances, considerations such as wake rollup, atmospheric effects on circulation decay, and vortex motion become important to consider. We first examine the wake rollup process in the context of extended formations and develop an appropriate physics-based model. Using this model, this dissertation addresses three aspects of formation flight: longitudinally extended formations, compressibility effects, and formations of heterogeneous aircraft. Uncertainty analysis is used to investigate the induced drag savings of extended formations in the presence of variation in atmospheric properties, limitations of positioning accuracy, and uncertainty in model parameters. Next, the methodology is integrated with an Euler solver to assess the impact of compressibility while flying in formation. Finally, we examine the important considerations for optimally arranging formations of non-identical aircraft.
Download or read book Aerodynamic Drag Reduction Technologies written by Peter Thiede and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 382 pages. Available in PDF, EPUB and Kindle. Book excerpt: ------------------------------------------------------------ This volume contains the Proceedings of the CEAS/DragNet European Drag Reduction Conference held on 19-21 June 2000 in Potsdam, Germany. This conference, succeeding the European Fora on Laminar Flow Technology 1992 and 1996, was initiated by the European Drag Reduction Network (DragNet) and organised by DGLR under the auspice of CEAS. The conference addressed the recent advances in all areas of drag reduction research, development, validation and demonstration including laminar flow technology, adaptive wing concepts, turbulent and induced drag reduction, separation control and supersonic flow aspects. This volume which comprises more than 40 conference papers is of particular interest to engineers, scientists and students working in the aeronautics industry, research establishments or academia.
Download or read book A Closed Form Trim Solution Yielding Minimum Trim Drag for Airplanes with Multiple Longitudinal Control Effectors written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-27 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: Airplane designs are currently being proposed with a multitude of lifting and control devices. Because of the redundancy in ways to generate moments and forces, there are a variety of strategies for trimming each airplane. A linear optimum trim solution (LOTS) is derived using a Lagrange formulation. LOTS enables the rapid calculation of the longitudinal load distribution resulting in the minimum trim drag in level, steady-state flight for airplanes with a mixture of three or more aerodynamic surfaces and propulsive control effectors. Comparisons of the trim drags obtained using LOTS, a direct constrained optimization method, and several ad hoc methods are presented for vortex-lattice representations of a three-surface airplane and two-surface airplane with thrust vectoring. These comparisons show that LOTS accurately predicts the results obtained from the nonlinear optimization and that the optimum methods result in trim drag reductions of up to 80 percent compared to the ad hoc methods. Goodrich, Kenneth H. and Sliwa, Steven M. and Lallman, Frederick J. Langley Research Center RTOP 505-66-01-02...
Download or read book Trim Drag Reduction Concepts for Horizontal Takeoff Single Stage To Orbit Vehicles written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-10-15 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results of a study to investigate concepts for minimizing trim drag of horizontal takeoff single-stage-to-orbit (SSTO) vehicles are presented. A generic hypersonic airbreathing conical configuration was used as the subject aircraft. The investigation indicates that extreme forward migration of the aerodynamic center as the vehicle accelerates to orbital velocities causes severe aerodynamic instability and trim moments that must be counteracted. Adequate stability can be provided by active control of elevons and rudder, but use of elevons to produce trim moments results in excessive trim drag and fuel consumption. To alleviate this problem, two solution concepts are examined. Active control of the center of gravity (COG) location to track the aerodynamic center decreases trim moment requirements, reduces elevon deflections, and leads to significant fuel savings. Active control of the direction of the thrust vector produces required trim moments, reduces elevon deflections, and also results in significant fuel savings. It is concluded that the combination of active flight control to provide stabilization, (COG) position control to minimize trim moment requirements, and thrust vectoring to generate required trim moments has the potential to significantly reduce fuel consumption during ascent to orbit of horizontal takeoff SSTO vehicles. Shaughnessy, John D. and Gregory, Irene M. Langley Research Center RTOP 505-64-40-01
Download or read book Bulletin of the Atomic Scientists written by and published by . This book was released on 1961-05 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Bulletin of the Atomic Scientists is the premier public resource on scientific and technological developments that impact global security. Founded by Manhattan Project Scientists, the Bulletin's iconic "Doomsday Clock" stimulates solutions for a safer world.
Download or read book Close Formation Flight Control written by Andrew W. Proud (CAPT, USAF.) and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Closed form Trim Solution Yielding Minimum Trim Drag for Airplanes with Multiple Longitudinal control Effectors written by Kenneth H. Goodrich and published by . This book was released on 1989 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings of the NASA Industry University General Aviation Drag Reduction Workshop written by Jan Roskam and published by . This book was released on 1984 with total page 468 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Design and Analysis Approach for Drag Reduction on Aircraft with Adaptive Lifting Surfaces written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Adaptive lifting surfaces, which can be tailored for different flight conditions, have been shown to be beneficial for drag reduction when compared with conventional non-adaptive surfaces. Applying multiple trailing-edge flaps along the wing span allows for the redistribution of lift to suit different flight conditions. The current approach uses the trailing-edge flap distribution to reduce both induced- and profile- components of drag with a trim constraint. Induced drag is reduced by optimally redistributing the lift between the lifting surfaces and along the span of each surface. Profile drag is reduced through the use of natural laminar flow airfoils, which maintain distinct low-drag-ranges (drag buckets) surrounding design lift values. The low-drag-ranges can be extended to include off-design values through small flap deflections, similar to cruise flaps. Trim is constrained for a given static margin by considering longitudinal pitching moment contributions from changes in airfoil section due to individual flap deflections, and from the redistribution of fore-and-aft lift due to combination of flap deflections. The approach uses the concept of basic and additional lift to linearlize the problem, which allows for standard constrained-minimization theory to be employed for determining optimal flap-angle solutions. The resulting expressions for optimal flap-angle solutions are presented as simple matrix equations. This work presents a design and analysis approach which is used to produce flap-angle solutions that independently reduce induced, profile, and total drag. Total drag is defined to be the sum of the induced- and profile-components of drag. The general drag reduction approach is adapted for each specific situation to develop specific drag reduction schemes that are applied to single- and multiple-surface configurations. Successful results show that, for the application of the induced drag reduction schemes on a tailless aircraft, near-elliptical lift dist.
