Browse Topic: Entry, descent, and landing
Electric Vertical Takeoff and Landing (eVTOL) aircraft present a series of challenges to traditional aviation infrastructure that was designed for conventional rotorcraft. Questions have arisen within the vertical flight community as to the validity and applicability of applying current heliport markings and symbology to vertiports. Several of these questions were addressed in a previous paper from VFS Forum 80: "A Comparison of Proposed Concepts for Vertiport Markings and Symbology" (Ref. 6). In contrast, this paper extends that work and presents the results of additional research to enhance the visibility of the Federal Aviation Administration’s (FAA) “Broken Wheel” symbology. These notional enhancements to the "Broken Wheel" symbology were evaluated over the course of an experimental study using helicopter-rated pilots in the FAA William J. Hughes Technical Center’s S76-D and Loft Dynamics H125 and R22 rotorcraft flight simulators.
The Rotor Blown Wing (RBW) is a tailsitter Vertical Takeoff and Landing (VTOL) Unmanned Aerial System (UAS) configuration that leverages cutting-edge autonomous flight controls through Sikorsky's MATRIX™ technology to create a highly capable, efficient, and scalable technology platform. By combining the benefits of fixed- and rotary-wing aircraft, the RBW configuration eliminates the need for traditional UAS launch and recovery infrastructure. This paper describes the RBW-5 prototype, a 100-pound, dual 5-foot diameter proprotor demonstrator, and discusses the comprehensive evaluation of its design and operability through a combination of flight tests, wind tunnel experiments, and computational fluid dynamics (CFD) simulations. The results demonstrate the maturity of the UAS and highlights key accomplishments of the RBW-5 program, including successful autonomous takeoff and landing and transitions between hover and forward flight, the extraction of critical "blown-physics" underlying
Helicopters' Vertical Take-Off and Landing (VTOL) capabilities are essential for maritime operations, especially for small-deck naval vessels. Unmanned Aerial Vehicles (UAVs) offer a cheaper, expendable, and efficient alternative for certain tasks, such as reducing pilot risk and lowering fuel consumption. While the procedures to approach and land on (moving) ships are standardized and bound to established operational limits in the case of crewed helicopters, UAVs lack such guidelines. This study investigates optimal rotary-wing UAV approach trajectories to a moving ship, for varying wind conditions and relative initial positions, and for different objectives. The goal is to provide preliminary guidelines for maritime UAV recovery operations, and a preliminary estimation of performance-based operational limits. The optimal trajectories are obtained using a global path-performance optimization framework based on Optimal Control Theory. The trajectories are compared to each other and to
By its seventh flight after the first take-off, the RACER (Rapid And Cost-Effective Rotorcraft) demonstrator smoothly reached the targeted 220kts speed in stabilized forward flight, validating the high-speed compound architecture developed by Airbus Helicopters in the frame of Clean Sky 2 programme. During the flight envelope exploration, the dynamic behavior of the main rotor was carefully assessed, by monitoring the vibratory loads and validating its aeroelastic stability. Particular care was taken to validate the predicted stability domain of the Dual Rotor phenomenon, a particular case of flap-lag coupling associated with high-speed flight conditions. This paper presents the most significant results shaping the success of RACER flight test campaign. After having introduced the theoretical background and the associated analytical equations, the simulation framework based on the comprehensive analysis tool STORM is presented to discuss the numerical resolution of the stability
This paper investigates optimal wing arrangements for electric Vertical Take-Off and Landing (eVTOL) aircraft, leveraging on their design flexibility with electric propulsion system. The study employs a multidisciplinary approach with the objective of integrating aerodynamic analysis, static and dynamic stability assessments, and pilot feedback to evaluate various wing configurations. Analytical techniques were adopted to evaluate aerodynamic performance and static stability, while experimental flight testing on scale models was conducted to validate these findings. Additionally, the Cooper-Harper rating system was introduced to capture pilot perceptions of aircraft handling qualities. Results inform eVTOL designers on wing arrangements that offer enhanced aerodynamic efficiency, stability, and handling qualities, ultimately expanding the operational scope and applications of eVTOL aircraft. The study concludes the versatility of the high aspect ratio conventional wing on eVTOL
No Abstract - 40th Annual VFS Student Design Competition, Undergraduate Category
This paper deals with the influence of engine failure during hover on the wiring harness mass of electrical Vertical Take-Off and Landing (eVTOL) aircraft. It starts by presenting possible strategies which can be used to distribute the additional thrust needed during an engine failure among the remaining engines. The most efficient strategy is selected and the impact of different single engine failures on the overall thrust share, while using this strategy, is discussed. The paper proceeds by applying the selected thrust compensation strategy to the mission simulation of three common reference models, which are representative of current eVTOL aircraft configurations. This simulation is used to determine the worst flight phase for the One Engine Inoperative (OEI) condition to occur. The main purpose of the simulation is to optimize the wire sizes of the wiring harness of each configuration while satisfying different design objectives. The results of these optimizations are used to
The paper presents a novel strategy for minimum energy consumption in automatic conversion control of tiltrotor eVTOL aircraft, exemplified by the Aston Martin Volante Vision model. We introduce a tilt schedule methodology that strategically balances conversion and reconversion performance with climb, descent, and cruise phases to minimize overall energy expenditure. Our approach accounts for critical factors such as blade loading, operation handling qualities, and passenger ride comfort within a predefined conversion corridor. The optimized trajectories approximate the minimum energy pathway, essential for operational efficiency in urban air mobility. Analytical results demonstrate that our proposed conversion and reconversion phase profiles significantly reduce energy consumption, contributing to the sustainability of tiltrotor flight operations. This research not only enhances understanding of tiltrotor dynamics but also serves as a pivotal step toward achieving globally optimized
The development of turbulence criteria to provide early guidance for the design of vertiports is presented in this paper. For any aircraft, winds, in particular crosswinds and gusty winds, are top of mind for all pilots engaging in take-off and landing maneuvers. It is anticipated that the same will be true for VTOL and eVTOLs landing on vertiports, in particular as new vertiports are built closer and closer to urban centres. First, a review of the current design criteria for vertiports around the world related to wind is presented, highlighting the commonality between the guidance and the gaps in their content. Second, the controllability criteria that VTOL and eVTOLs will likely need to meet in the pursuit of an airworthiness certification are reviewed and their pertinence with regards to vertiport design are discussed. Third, the characters of the wind and their impact on eVTOL flights at or near take-off and landing infrastructure is explored. Finally, a set of turbulence criteria
This paper addresses the urgent need to enhance rotorcraft safety and performance by developing a prediction methodology for the onset of the Vortex Ring State (VRS), and therefore verifying the VRS avoidance diagram. The objectives of this research are to assess the correlation between predictions generated by a comprehensive flight dynamics code and the latest and most accurate VRS boundary models, validate the VRS avoidance diagram across diverse descending flight conditions, and identify specific parameters indicating the rotor's entry into the VRS. The methodology involves a detailed investigation of 8 descent manoeuvres using a comprehensive flight dynamics code coupled with an advanced free vortex wake model. Results show that the pitch and roll oscillations and thrust fluctuations experienced by helicopters during the VRS are also observed in the model response to steep descent maneuvers. The findings confirm the reliability and applicability of the VRS avoidance diagram
This study addresses safety concerns within the rapidly evolving Electric Vertical Takeoff and Landing (eVTOL) aircraft domain, focusing on efficient tools to quantify uncertainties in lithium-ion battery behavior - a critical aspect of eVTOL. One major issue with quantifying uncertainty is the prohibitive computational cost associated with many queries of an expensive-to-evaluate computational model. This work employs three physics-based battery models models of varying fidelity and cost to estimate the mean and the variance of the selected quantities of interest through a multifidelity method to reduce the computation cost. By combining information from multiple cheaper, lower-fidelity models through the Multifidelity Monte Carlo method, we significantly reduce the number of high-fidelity samples required for a prescribed mean-squared error, consequently reducing computational costs down to a tractable level. The proposed methodology is applied to estimate the mean and the variance
No Abstract - 40th Annual VFS Student Design Competition, Graduate Category
Revealed in 1941, the Dirigible Helicopter or 'Koun's Craft,' was an ambitious but ill-fated fusion of convertiplane and lighter-than-air technology. This S/VTOL (Short/Vertical Take Off and Landing) concept (a veritable puzzle of diverse airplane parts) was powered by a single, tilting propeller engine and was affixed with wing mounted, helium filled enclosures for additional buoyancy. Dismissed historically as being an eccentric folly of its layman inventor, Korean-American Young Ha Koun, the development of the Dirigible Helicopter has never been thoroughly studied. This paper will examine the origins of this unique design, its creator's possible motivations for building such an aircraft, and successor convertiplane concepts that attempt to achieve the same purpose to this day.
Joby Aviation is developing an all-electric air taxi for commercial passenger service. The aircraft takes off and lands vertically using six tilting propellers. Classified as powered lift aircraft by the Federal Aviation Administration, it has many similarities with, and important differences from, traditional helicopters. Joby Aviation partnered with the Federal Aviation Administration to measure the outwash of the Joby Aviation S4 pre-production prototype aircraft and a Robinson R44 light helicopter. The measured data shows that the Joby S4 has similar outwash magnitudes to the R44 despite being flown at approximately twice the weight. It also shows that the caution and hazard zones for outwash based on the 95% maximum velocity and PAXman analysis are very close to the aircraft and well within the established safety areas. The data shows that the outwash of the Joby S4 aircraft does not present an increased risk over traditional light helicopters.
The unique designs and capabilities of electric Vertical Takeoff and Landing (eVTOL) aircraft present a series of challenges to traditional infrastructure that was designed for conventional rotorcraft. Currently, several civil aviation authorities have released interim, preliminary guidance on aspects of vertical flight infrastructure. This paper presents a comparison of two of the proposed concepts for vertiport markings and symbology, the Federal Aviation Administration (FAA) "Broken Wheel" and the European Union Aviation Safety Association (EASA) "V". These concepts were evaluated over the course of two experimental studies using helicopter-rated pilots in the FAA William J. Hughes Technical Center's S76-D and Loft Dynamics H125 & R22 rotorcraft flight simulators.
ABSTRACT For many rotorcraft platforms, incorrect timing of the autorotation flare and deceleration maneuvers may result in significant aircraft damage and injury to the crew, or worse. There is a clear need for new pilot cueing and control augmentation technologies that lead to a higher probability of a successful autorotation landing. This paper describes a recent effort to develop two different Tau (time-to-contact)-based autorotation controllers that can be used to drive visual aids to help guide a pilot to apply the required control inputs to complete a safe autorotative landing. Such controllers may also be useful for fully autonomous autorotation landing for unmanned vehicles.
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The objective of this investigation is three-fold. First, to assess the flight dynamics of an electric Vertical Take-Off and Landing (eVTOL) concept aircraft with a propeller-driven rotor. Second, to develop a Stability and Control Augmentation System (SCAS) for this concept aircraft. Third, to verify the potential safety benefits of the concept aircraft by analyzing the autorotation performance following a total loss of power. The paper begins with a description of the simulation model, including a detailed discussion on the inflow model of the propellers that drive the main rotor. Next, the flight dynamics are assessed at hover and in forward flight. A SCAS based on Dynamic Inversion (DI) is developed to provide stability and desired response characteristics about the roll, pitch, yaw, and heave axes for speeds ranging from hover to 80 kts. Additionally, an RPM governor is implemented to hold the main rotor angular speed constant at its nominal value. Finally, simulations that make
The paper discusses the application of the Array Controlled Turn-less Structures (ACTS) motor for VTOL application. The motor enhances the three main competing characteristics of electric motors; namely specific power, efficiency and reliability. The motor arrays an ensemble of elemental turn-less motors which include turn-less elements each with their dedicated inverters which are operated in synchronism. The resulting small pole size enhances the power density, the enhanced conductor packing enhances the efficiency, and the massive parallelism enhance the reliability. Vertical takeoff requires much higher thrust compared to wing assisted takeoff. With limited on-board power, this higher thrust is presently provided by in ordinary larger propulsion disk area which reduces the craft aerodynamics, and the cruising Lift-to-Drag (L/D) ratio and accordingly the flight efficiency and range. The high specific power of the ACTS motor allows for a different scenario and thus craft architecture
Recently, studies on the flight dynamics of unmanned aerial vehicle (UAV) affected by gust have been performed. However, only few studies focused on the aspect of the robust controller design and those did not consider aerodynamic effect by gust. Therefore, the goal of this paper is establishing a non-linear flight dynamics simulation which is intended to analyze gust. First, the aerodynamic analysis is composed with dynamic inflow, blade element theory (BET), and ring vortex method for descent. A nonlinear flight simulation is constructed based on aerodynamic analysis and a procedure is established to verify it. To estimate the controller gain, system identification and parametric estimation are performed. Based on such estimation, a position controller is designed and reliability of the controller is validated by the two-point flight test. Additionally, wind tunnel test is performed and the trajectory of UAV shows a good tendency when compared with experiment. As a result, the
The Urban/Advanced Air Mobility (UAM/AAM) transportation concept has been studied and shown to offer advantages in travel time-savings to individuals over the automobile, mass transit, and in many cases, commercial air transport alternatives. This paper presents a study of this new market using a parametric approach that accounts for the performance of Electric Vertical Takeoff and Landing (eVTOL) aircraft, takeoff and landing infrastructure (vertiports), and the demand for ridership given a ticket price and time saved. One of the key mode choice drivers in switching from existing transportation options to an AAM service is the value gained in saving time, which is also tightly correlated with people's income level. The analysis framework can facilitate market feasibility analysis by considering various scenarios and constraints. The results suggest that near-term profitability is possible even though vertiport throughput capacities are limited by existing footprint and operational
To aid in the development of electric Vertical Take-off and Landing (eVTOL) technology, the National Aeronautics and Space Administration has undertaken research initiatives to evaluate and optimize design features of eVTOL aircraft. One such initiative has been to develop energy attenuating design mechanisms to improve eVTOL vehicle crashworthiness. In this study, crashworthiness design mechanisms, implemented within a six-passenger lift plus cruise (LPC) eVTOL concept vehicle, were evaluated under multi-axis dynamic loading conditions. This work builds upon crashworthiness design concepts previously optimized within a simplified vehicle-loading environment. The results of this study found the effectiveness of energy attenuating design mechanisms to be dependent on the complexity of load environment in which they were employed. An increase in off-axis loading resulted in a decrease in occupant protective capability. These results indicate the necessity for evaluating vehicle design
In application, the Aeronautical Design Standard for the handling qualities of military rotorcraft, ADS-33E-PRF, provides the means to effectively predict rotorcraft handling qualities via validated criteria and demonstrate actual handling qualities in flight test using mission task elements. Besides a definition, a note that rotorcraft shall have no tendencies, and a note regarding Attitude Command Response-Types and gain bandwidth frequency, the topic of pilotinduced oscillations (PIO) is not addressed via specific criteria or flight test techniques. As the use of full authority fly-by-wire flight control continues to expand in Vertical Takeoff and Landing (VTOL) aircraft, the likelihood of encountering PIO will also expand. In the fixed wing world where PIO has been commonplace, at least in developmental test if not operations, predictive analytical methods that can also be used for detection of PIO in realtime have been developed, which can also be applied to rotorcraft
Helicopter is a complex system regarding integration of systems. During development phase of a new H/C, design office deal with MMEL (Master Minimum List Equipment), Optional equipment package for specific missions (i.e. Oil & Gas, SAR...) and Manufacturing constraints for lead-time and cost optimization. The Geometrical Management presented today is derived from ARP4754A standard in Aeronautics. The Aerospace Recommended Practice (ARP) is a guideline for development of civil aircraft and systems. This process, based on end to end philosophy defines the way of managing geometrical specifications concerning the aircraft during its complete lifecycle. System geometrical Management starts with System Engineering by functional analysis of the Helicopter vehicle during Design development phase, then APQP focus on industrial maturity and repeatability during industrialization phase and finally control plan is deployed after Entry into service for serial life This is a top-down approach
A real-time path planning algorithm is developed to generate time-optimal trajectory for helicopter shipboard landing. The trajectory optimization problem is translated to the lower dimensional flat output space by exploiting the differential flatness property of the simplified helicopter model. Then, the flat outputs are parameterized using piecewise spline functions with adjustable coefficients, which are used to shape the trajectory and approximate the optimal solution. Further, by allowing the flexible selection of each spline segment's time-duration and enforcing additional path constraints, the time-optimality of the planned trajectory is largely preserved without violation of state and input bounds. Compared to pure temporal discretization methods, the proposed algorithm employs considerably less decision variables and significantly reduces the computational time by 75%, which only leads to a 0.5% growth in the optimal flight time as the trade-off. The improvement in
Jaunt Air Mobility LLC is developing an all-electric Vertical Take-off and Landing (VTOL) aircraft suitable for Urban Air Mobility (UAM) and On-Demand Mobility (ODM) markets. Salient features of Jaunt include the quietest, safest, and most efficient hovering and cruise flight air vehicle than any other configuration suitable for UAM missions. Jaunt represents a Reduced Rotor Operating Speed Aircraft (ROSA™) with core technologies proven in over 250 hours of successful demonstration flights. Jaunt represents the metamorphosis of the best features available from helicopters and fixed-wing airplanes. ROSA™ technologies offers several innovative features that significantly reduce total noise. These include all-electric powertrain, 75 percent reduction in main rotor tip speed from hover to cruise flight, scimitar design propellers offering a 60% speed reduction from hover to cruise flight, and a tilting mast which provides efficient management of the resulting thrust vector. Jaunt
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