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The History of the XV-15 Tilt Rotor Research Aircraft from Concept to Flight
Abstract and Figures
This monograph is a testament to the efforts of many people overcoming multiple technical challenges encountered while developing the XV-15 tilt rotor research aircraft. The Ames involvement with the tilt rotor aircraft began in 1957 with investigations of the performance and dynamic behavior of the Bell XV-3 tilt rotor aircraft. At that time, Ames Research Center was known as the Ames Aeronautical Laboratory of the National Advisory Committee for Aeronautics (NACA). As we approach the new millennium, and after more than 40 years of effort and the successful completion of our initial goals, it is appropriate to reflect on the technical accomplishments and consider the future applications of this unique aircraft class, the tilt rotor. The talented engineers, technicians, managers, and leaders at Ames have worked hard with their counterparts in the U.S. rotorcraft industry to overcome technology barriers and to make the military and civil tilt rotor aircraft safer, environmentally acceptable, and more efficient. The tilt rotor aircraft combines the advantages of vertical takeoff and landing capabilities, inherent to the helicopter, with the forward speed and range of a fixed wing turboprop airplane. Our studies have shown that this new vehicle type can provide the aviation transportation industry with the flexibility for highspeed, long-range flight, coupled with runway-independent operations, thus having a significant potential to relieve airport congestion. We see the tilt rotor aircraft as an element of the solution to this growing air transport problem.
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... There have been many previous whirl flutter analyses of gimballed proprotors, but few have focused on hingeless proprotors. In 1956, the whirl flutter of the tiltrotor first occurred during XV-3 flight tests using an articulated rotor [9]. Subsequently, the XV-3 rotor was replaced with a stiff in-plane teetering rotor and the mechanism of whirl flutter for tiltrotor aircraft was understood via wind tunnel and flight tests [10]. ...
This study investigates and compares the whirl flutter characteristics of two different hub models, gimballed and hingeless hubs, for the tiltrotor aircraft in cruise flight. This study uses the rotorcraft comprehensive analysis code, CAMRAD II, to model the proprotor, semi-span wing, and pylon, and to investigate the whirl flutter instability. The two analytical tiltrotor models are based on two proprotors developed by the U.S. Army/NASA, and KARI. The proprotor frequency characteristics depend on the hub type and have influence on the wing-rotor interaction to cause whirl flutter. In addition, it is shown that the rotor regressive lag mode frequency is an important system design parameter for a hingeless tiltrotor, whereas the rotor regressive gimbal mode is important for a gimballed tiltrotor.
... A detailed tiltrotor model, representative of the Bell XV-15 research aircraft with Advanced Technology Blades (ATBs) [42], has been built in DUST-MBDyn using data published by Acree in Ref. [28]. The general characteristics are summarized in Table 1. ...
This work presents a comprehensive numerical environment, obtained by the coupling of a mid-fidelity aerodynamic solver based on a vortex particle method with a multibody dynamics tool, for aeroelastic simulations suitable for the analysis and design of next-generation rotary-wing aircraft. Indeed, the presence of multiple propellers and rotors, together with interactional aerodynamics, have a strong impact on dynamic loads and performance indexes on rotorcraft. A mid-fidelity approach provides an ideal trade-off between the accuracy of the solution and the speed of execution required in the preliminary design phases of these vehicles. A tiltrotor model representative of the Bell XV-15 with different levels of complexity is proposed as a test benchmark , whose characteristics can be similar to an eVTOL. The coupled solver shows the capability to determine the trim conditions in airplane mode and predicts steady and periodic trim loads. Transient analyses are presented as well, considering a roll maneuver and highlighting the importance of the accurate representation of rotary wing aerodynamics provided by the vortex particle method for load evaluation and vibrational assessment.
... o r g / 1 0 . 2 5 1 4 / 1 . C 0 3 7 1 0 1 rotors has been reported in the development of an XV-15 tiltrotor [19]. Sanchez-Cuevas et al. experimentally ...
https://arc.aiaa.org/doi/10.2514/1.C037101 (Now online in advance) Wake visualizations and thrust measurements of a quadrotor model were conducted to clarify the relationship between thrust and wake flow structure in-ground effects. The adjacent rotor distance, rotor height above ground, and the presence of a plate representing a generic quadrotor centerbody were varied. Thrust decreased when lowering the quadrotor to the ground when the adjacent rotor distance was over 2.2 times the rotor radius. Laser light sheet flow visualization showed quadrotor wake flow structures. Furthermore, visualization using particle image velocimetry showed an averaged vector map of wakes and fountain flow at the center of the quadrotor wake, which caused circulation with rotor passing flow and decreased rotor thrust. The center plate increased the sum of the rotor thrust and plate lift; however, circulation flow formed under the plate and caused the rotor thrust to decrease the in-ground effect. The results clarified that fountain flow development decreased the quadrotor thrust in-ground effect. Reducing the adjacent rotor distance weakened the development of fountain flow in the quadrotor wake and eliminated the decrease in rotor thrust near the ground.
... These forces and moments are related to the collective pitch θ b , the longitudinal periodic pitch θ a , the elevator deflection δ e , and the mast angle β M . Maisel et al. (2000) presented the conversion corridor with respect to the mast angle β M and the air speed V , which can guarantee a safe tilting process. By selecting N operating points in the conversion corridor, trimming the nonlinear model of conversion mode (1), and taking the Jacobian linearization, a cluster of linear models are obtained. ...
This paper investigates the state-tracking control problem in conversion mode of a tilt-rotor aircraft with a switching modeling method and a smooth interpolation technique. Based on the nonlinear model of the conversion mode, a switched linear model is developed by using the Jacobian linearization method and designing the switching signal based on the mast angle. Furthermore, an ℋ∞ state-tracking control scheme is designed to deal with the conversion mode control issue. Moreover, instead of limiting the amplitude of control inputs, a smooth interpolation method is developed to create bumpless performance. Finally, the XV-15 tilt-rotor aircraft is chosen as a prototype to illustrate the effectiveness of this developed control method.
... A detailed tiltrotor model, representative of the Bell XV-15 research aircraft with advanced technology blades (ATBs) [21], has been built in CAMRAD/JA [22] using data published by Acree in Ref. [20]. The dynamic model setup includes 1) the airframe structural model, 2) the airframe stability and control derivatives, 3) aeroelastic rotors, and 4) a lumped parameter engine drive-train governor system. ...
This paper investigates the influence of tiltrotor blade twist on whirl-flutter stability boundaries. Preliminary evaluations indicate that the whirl-flutter speed can be increased if the blade twist slope is reduced. This positive effect results from the shift in the overall thrust toward the blade tip, increasing the flapwise bending moment at the blade root and the trim coning angle. This, in turn, generates a positive pitch-lag coupling, increasing the whirl-flutter speed. However, the shift of high sectional thrust forces toward the blade tip sections returns a higher induced drag, showing the tendency to increase the power required. The paper shows that, by using blade twist laws based on piecewise linear functions and adding the wing airfoil thickness as a second design parameter, it is possible to identify aircraft configurations that improve the whirl-flutter stability boundaries without penalizing the power required in airplane and helicopter mode flight. This is possible because the blade twist and the wing airfoil thickness have an impact on both power required and whirl-flutter speed, so a simple optimization algorithm can identify good tradeoffs. A detailed tiltrotor model representative of the Bell XV-15 is used to display the effectiveness of the proposed approach. The examples show that increases up to 21% on the whirl-flutter speed are achievable without penalties in the aircraft power required and with the additional benefit of a benign impact on rotor pitch link loads.
... In turn, the cause of this can be derived from the relatively low efficiency of the EDFs. Ducted rotors are inherently more efficient as compared to non-ducted rotors of equal diameter, but even so all propellers are inherently more efficient the larger they are [5]. However, due to the packaging/layout of the first stage the EDF diameter, which in the final iteration of design loop 1 was set to 320 mm, could not be increased any further without making the first stage too wide, as can be seen in Figure 4. ...
The Recovery and Return-To-Base European Reusable Micro-Launcher project, part of the European Commission’s H2020 programme, intends to develop a novel reusable micro launcher system to bring independent and cost-effective access-to-space for the European small satellite market. The multi-disciplinary project focuses on the optimization of aerospike tail-first atmospheric re-entry of the MESO vehicle, together with the design and manufacturing of reusable cryogenic tanks, and the effort is divided into two design loops, where each design loop starts from establishing early design decisions and assumptions so that dedicated subsystem work may progress immediately. The multiple design loop approach allows for unsuitable design decisions, or risky and speculative assumptions to be revised or excluded at the project half-way point, thereby acting as a form of risk management. Throughout the work performed in the first design loop several conclusions were reached. The design presented both novel design features, but also critical issues which became better understood as the fidelity of the subsystem designs and mission analysis increased. These issues ultimately lead to the overall system design and CONOPS to be updated for the second loop, with several of the early design choices being modified, especially through the removal of the EDF landing system, based on the results of the first loop. For the second design loop, the design is updated to alleviate the most critical problem drivers, and to improve the system’s ability to fulfil the top-level requirements and objectives. The updated design uses a Mid-Air Catch approach, and leverages on the heritage of the previous design loop, implementing tailored changes based on the outcome of the trade-offs performed at mission and system levels.
... In the early 1920s, Berliner proposed a fixed-wing biplane with propellers placed on the tips of each wing and angled for forward flight. At the same time, Lehberger received a patent in 1930 for a model that achieved vertical lift through the principle of a tilt-rotor aircraft [15]. In 1953, the XV-3 was developed as a test aircraft to evaluate the stability of tilt-rotor planes and collect data for future tilt-rotor VTOL models. ...
Vertical Take Off and Landing Vehicles (VTOLs) could land and take off from the same location, eliminating the need for a prolonged runway. There has been a plethora of research work on VTOL and its applications. However, most of the available literature is based on the military benefits of VTOL. This paper presents a pilot study that combines all the available literature on Non-military/civilian applications of VTOL. Initially, we provided an overview of several kinds of VTOLs, including their benefits over typical aircraft. Afterward, a comprehensive literature review of the available work is delivered. Moreover, a detailed analysis of commercial applications of VTOL is described and analyzed. According to the study’s findings, a standard VTOL has enormous non-military potential and can be used for a wide range of practical tasks that would be challenging or impossible with the infrastructure that is now in place. The consequences of VTOL in civil and the future gap served as our conclusion.
... Magnetization as a function of applied fields[25] ...
This study introduces the simulation of a tri-rotor contra-rotating propeller for thrust force and hover lift efficiency during vertical take-off. Vertical take-off or landing is a method used by many aircraft and makes the vehicle more convenient and easier to use. The second rotor revolved in the opposite direction of the first and third rotors. The proposed multi-rotor system has NACA 0012 untwisted and symmetric airfoil and includes three rotors with two blades for each. The airflow analysis was optimized with computational fluid dynamics simulation by using different pitch combinations to achieve the highest hover lift efficiency with sufficient overall thrust value. The critical angle of attack for the chosen airfoil gave the boundary conditions for the pitch of rotors. The results showed us that the most efficient combinations for three rotors work better with an increase of pitch angle from top to bottom so that there is a difference of at least two degrees between propellers. Experiments with angles of attack within the boundary conditions showed that the blade combinations starting from three degrees and increasing values gave positive and adequate results in many cases. In addition, the results showed that a regular increase in the angle of attack does not relate to a regular increment in thrust force.
In view of the increasing awareness of the population to noise pollution, reduction of aircraft noise annoyance to an acceptable level becomes one of the necessary conditions for the acceptability of aircraft operations close to populated areas. In particular, reducing the subjective acoustical annoyance of VTOL aircraft to the surrounding community should become the common objective of aircraft manufacturers, airport planners, potential aircraft operators and the community itself if the latter is to benefit from all the possible advantages of VTOL service.
This paper presents the maneuver performance, rotor and airframe aerodynamic capabilities, and rotor maneuvering loads as measured during the XV‐15 flight test program. Correlation is shown with analysis to establish the basis for maneuver capability predictions of tiltrotor variants. An advanced tiltrotor design is presented which demonstrates agility and maneuverability for air‐to‐air combat and gunship‐type missions. The new design, which is called the Super XV‐15, applies advanced aerodynamic and structural technology which is being used on the V‐22 Osprey. The XV‐15 and Super XV‐15 are compared an the basis of aerodynamic capability, control response, rotor loads, acceleration and deceleration capability, and maximum rate of climb.
This article is about the tilt rotor - that remarkable aircraft that combines the vertical take-off advantages of the helicopter with the efficient cruise speed of the turboprop airplane. This type of aircraft is just now coming to fruition, even though it has been studied and subject to experimentation for over 50 years. The tilt rotor will change the way men fly. It will: put a new cutting edge in our arsenal of both offensive and defensive conventional weapons; alleviate air and airport congestion; hasten the development of the underdeveloped nations without the cost burden of rail, seaport, and even airport infrastructures, and will someday provide true intercity mass air transportation.
Rotor performance and wing download data acquired by testing a large-scale model of the rotor and wing for the V-22 multi-mission tilt rotor aircraft is presented. Performance of the rotor was measured in isolation and with a scale model of the V-22 wing in place. The effect of the opposite rotor was simulated by using a large image plane. It was determined that the isolated rotor maximum figure of merit was 0. 808. With the image plane in place, rotor thrust was slightly reduced compared to the isolated rotor value and was caused by the development of a region of recirculating flow near the image plane/wing junction. The wing download and the distribution of the load was determined. With flaps deflected the ratio of download to thrust was 0. 093. Comparisons with theory are presented.
