Browse Topic: Entry, descent, and landing
Air Traffic Management (ATM) must be familiar with the exact Aircraft Take-off Weights (ATOWs) of airplanes to make the most use of runways, maintain safety margins high, and keep utilization and resources in balance. This paper aims to present a dependable ATOW forecasting methodology that can assist the air transport industry in enhancing operational decision-making. This research used datasets acquired from the EUROCONTROL Performance Review Commission (PRC) 2024 Aircraft Take-Off Weight Estimation dataset featuring 527,000 flights over Europe containing aircraft details, air trips and flight conditions. Technique comprises structured data input, inspection of missing data, timestamp aggregation to identify demand cycles over time, and domain-specific feature engineering using distance_per_minute, block_minutes, taxiout_ratio, and a strong wake turbulence metric The two supervised learning models used were Linear Regression (LR) for understanding and XGBoost for performance
Tire is the only part of the aircraft that contacts the ground, which not only bears the vertical load and lateral load of the whole aircraft, but also provides adequate ground friction to decelerate the aircraft when braking, so the tires are important parts for aircraft take-off and landing. Besides safety concerns, tire physical properties such as vertical, lateral stiffness as static performance and rolling relaxation length, yawed rolling cornering force as dynamic performance are often required by aircraft manufacturers for analyzing aircraft maneuverability. Besides analysis or similarity by experience from other aircraft projects, tires are often qualified by a number of tests, both static and dynamic, to ensure the safety of tires and acquire tire physical performance data.
Researchers from Brazil are collaborating with a team at Embry-Riddle Aeronautical University to develop new methods for controlling heat spikes generated by electric aircraft during the takeoff phase of flight. Embry-Riddle Aeronautical University, Daytona Beach, FL Researchers at Embry Riddle Aeronautical University and Brazil's Instituto Tecnológico de Aeronáutica (ITA) will combine forces on one of the main challenges of electric aircraft - controlling the heat spikes they generate at takeoff. The collaboration is supported by a $450,000 National Science Foundation International Research Experiences for Students (NSF IRES) grant.
Researchers at Embry Riddle Aeronautical University and Brazil’s Instituto Tecnológico de Aeronáutica (ITA) will combine forces on one of the main challenges of electric aircraft — controlling the heat spikes they generate at takeoff.
Innovators at NASA Johnson Space Center have developed additively manufactured thermal protection system (AMTPS) comprised of two printable heat shield material formulations. These formulations are directly applied by 3D printer or other robotic extrusion system and bonded to a spacecraft to devise a heat shield suitable for atmospheric entry. This technology could significantly decrease heat shield or thermal protection system (TPS) fabrication cost and time.
The return to Earth is a rough ride for astronauts, from the violent turbulence of atmospheric entry to a jarring landing. Hitting the ground in a Soyuz capsule is the equivalent of driving a car backward into a brick wall at 20 mph, and it’s resulting in more head and neck injuries than NASA computer models predicted. To collect more data, NASA’s Johnson Space Center in Houston commissioned a Small Business Innovation Research (SBIR) project to develop a wearable data recorder for astronaut spacesuits. One result, created by Diversified Technical Systems Inc. (DTS), is a miniature commercial device that now collects and transmits data for any application from airplane test flights to tracking high-value shipments.
Electric Vertical Take-Off and Landing (eVTOL) aircraft, conceptualized to be used as air taxis for transporting cargo or passengers, are generally lighter in weight than jet-fueled aircraft, and fly at lower altitudes than commercial aircraft. These differences render them more susceptible to turbulence, leading to the possibility of instabilities such as Dutch-roll oscillations. In traditional fixed-wing aircraft, active mechanisms used to suppress oscillations include control surfaces such as flaps, ailerons, tabs, and rudders, but eVTOL aircraft do not have the control surfaces necessary for suppressing Dutch-roll oscillations.
In this paper, we develop a new feature-based algorithm using stereo cameras to estimate stochastic ship-deck motion at high sea states. Unlike our previous algorithms, this algorithm is able to estimate the motion of arbitrary ship structures without prior information on the ship's visual appearance or geometry. The algorithm requires an initial pose and suffers from drift over time, which was resolved by fusing it with our previous 2D feature-based vision algorithm. The combined vision algorithm is validated using a simulated ship featuring 3D ship structures and 2D flight deck markings representative of a DDG-51 ship. The results indicate that the algorithm can accurately estimate the pose of a simulated ship undergoing Sea-State 6 motion. The vision algorithm was further validated in a simple free-flight test.
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
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.
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 presents a robust and adaptable control system for tilt-wing aircraft, developed by Dufour Aerospace. The transitional tilt-wing aircraft, Aero2, combines the vertical takeoff/landing capabilities of helicopters with the high-speed range of fixed-wing aircraft. Addressing the inherent control complexities required to maintain control and stability, the developed system employs established control techniques, utilizing linearization at trim points and gain scheduling based on wing tilt. The architecture comprises a Control Allocation module for optimal actuator management, a Control Augmentation System utilizing an LQRI controller enhanced with a feedforward component for precise attitude tracking, and a Unified Velocity Controller for seamless transitions between ground speed tracking in hover and airspeed tracking in cruise. Special challenges unique to transitioning aircraft to ensure control in all axes, including in windy conditions are addressed with operational
This paper outlines observations from an FAA-sponsored research project that examined aviation Fly-By-Wire (FBW) accidents. The goal was to identify risk areas that will help guide a focus for FAA certification testing. Part of this study specifically focused on current powered-lift tiltrotors, identifying six general categories of causal factors for accidents, which will be discussed in detail regarding how they influenced flight control designs. The results of this survey, along with extrapolation to current designs, will be discussed and will illustrate why manufacturers are moving toward state-based flight control designs. In a state-based flight control scheme, the pilot does not have direct control over aircraft attitudes and motor tilt angles. Instead, the pilot requests a speed and or flight path with inceptor input, and the commanded attitudes and motor tilts are scheduled by the flight control computer. Additionally, recent lessons learned from electric Vertical Takeoff and
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
There are certain situations when landing an Advanced Air Mobility (AAM) aircraft is required to be performed without assistance from GPS data. For example, AAM aircraft flying in an urban environment with tall buildings and narrow canyons may affect the ability of the AAM aircraft to effectively use GPS to access a landing area. Incorporating a vision-based navigation method, NASA Ames has developed a novel Alternative Position, Navigation, and Timing (APNT) solution for AAM aircraft in environments where GPS is not available.
Over the past decade, NASA’s Space Technology Mission Directorate and its team of development partners have developed several unique thermal protection system (TPS) technologies designed to protect spacecraft from the extreme heat conditions and entry environments that space missions face. Working closely with the NASA Ames Research Center, Bally Ribbon Mills (BRM), along with several other partners, have developed a new generation of unique strong and robust materials produced using three-dimensional (3D) weaving.
Innovators at NASA Johnson Space Center have developed and successfully flight tested a high-performance computing platform, known as the Descent and Landing Computer (DLC), to suit the demands of safe, autonomous, extraterrestrial spacecraft landings for robotic and human exploration missions.
Batteries for eVTOL aircraft need to deliver high power for efficient takeoff and landing, as well as high energy for the cruise period. To meet these demands, designers must consider the power-energy tradeoff of batteries and integrate a reliable battery management system into the overall design. Multiphysics simulation can be used to evaluate this tradeoff and consider all design requirements in a way that is comprehensive and saves time. In recent years, more and more organizations have announced their development of electric vertical take-off and landing (eVTOL) systems and, in some cases, are even showing previews of systems that are intended to hit the market in just a few years. As new design ideas emerge, there is one important question that needs to be asked: To keep up with the developments in eVTOL aircraft, what design requirements need to be considered for the batteries that power them?
A structural load estimation methodology was developed for RLV-TD HEX-01 hypersonic experimental mission, the maiden winged body technology demonstrator vehicle of ISRO. Primarily the method evaluates time history of station loads considering effects of vehicle dynamics and structural flexibility. Station loads of critical structures are determined by superposition of quasi-static aerodynamic loads, dynamic inertia loads, control surface loads and propulsion loads based on actual physics of the system, improving upon statistical load combination approaches. The technique characterizes atmospheric regime of flight from vehicle loads perspective and ensures adequate structural margin considering atmospheric variations and system level perturbations. Features to estimate change in loads due to wind variability and atmospheric turbulence are incorporated into the load estimation methodology. Augmentation in loads due to structural flexibility is assessed along the trajectory using vehicle
With regards to any aerospace mission, it is very useful to have awareness about the state of vehicle, i.e., the information about its position, velocity, attitude, rotational rates and other concerned data such as control surface deflections, landing gear touchdown, working of mechanisms and so on. The sensor data from the vehicle that is communicated to the ground can be difficult to perceive and analyze. A frame work for real-time motion simulation of an aerospace vehicle from onboard telemetry data is henceforth developed in order to improve the understanding about the current state of the mission and aid in real-time decision making if required. The telemetry data, that is transmitted through User Datagram Protocol (UDP), is received and decoded to usable format. The visualization software accepts the data in a fixed time interval and applies the required transformations in order to ensure one-to-one correspondence between actual vehicle and simulation. The transformations
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.
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
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
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
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
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.
No Abstract - 40th Annual VFS Student Design Competition, Graduate Category
Many traditional ship-rotorcraft interactional simulation approaches, including those used for pilot training, use a one-way coupling between aerodynamics and flight dynamics. In a one-way coupled method, the standalone ship airwake is superimposed on the rotor, modifying its inflow. However, because the rotor wake does not alter the ship airwake in such a simulation, one-way coupling may not capture all relevant phenomena, such as dynamic ground and wall effects; two-way fully-coupled simulations may be needed. In this study, one- and two-way coupled realtime and near-real-time simulation models of the ship-rotorcraft problem were developed using a GPU-accelerated Lattice-Boltzmann Method (LBM) flow field solver. Comparing flow fields and rotor hub loads, the two-way coupled simulations showed good agreement with new ship-rotor experimental data from Georgia Tech. Real-time full-scale rotorcraft ship approach maneuvers of a notional UH-60A landing on the NATO Generic Destroyer were
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
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.
In commercial aerospace, the application areas for motors are wide and varied, each with their own unique requirements. From electric vehicle take-off and landing (eVTOL) air taxis to business jets to long-haul commercial transport aircraft, DC motors must endure various environmental conditions like extreme temperatures, shock and vibration, atmospheric pressures and signal interference, to name just a few. These applications may also demand motors that provide a fast response, high power or torque density. In addition to these requirements, the aerospace industry perpetually calls for lightweight materials and smaller installation spaces. Taken together, it can be very difficult to specify and buy a reliable motor for mission-critical equipment. This article will present common commercial aerospace applications that pose performance and environmental challenges for DC motors along with a summary of the stringent aerospace industry standards that the motors must satisfy. It will also
Lunar landing and launch pads represent critical infrastructure for enabling a sustained presence on the Moon or other planetary bodies. Such a Moon presence would require repeated lunar landings and takeoffs, preferably near an outpost or habitat. In the absence of takeoff and landing pads, such vehicles could project lunar regolith at high velocities, sandblasting the surrounding infrastructure and causing damage.
Direct debugging of a vertical takeoff and landing (VTOL) fixed-wing aircraft’s control system can easily result in risk and personnel damage. It is effectively to employ simulation and numerical methods to validate control performance. In this paper, the attitude stabilization controller for VTOL fixed-wing aircraft is designed, and the controller performance is verified by MATLAB and visual simulation software, which significantly increases designed efficiency and safety of the controller. In detail, we first develop the VTOL fixed-wing aircraft’s six degrees of freedom kinematics and dynamics models using Simulink module, and the cascade PID control technique is applied to the VTOL aircraft’s attitude stabilization control. Then the visual simulation program records the flight data and displays the flight course and condition, which can validate the designed controller performance effectively. It can be concluded that the designed VTOL fixed-wing aircraft control visual simulation
NASA’s Langley Research Center Hampton, VA
In-flight icing significantly influences the design of large passenger aircraft. Relevant aspects include sizing of the main aerodynamic surfaces, provision of anti-icing systems, and setting of operational restrictions. Empennages of large passenger aircraft are particularly affected due to the small leading edge radius, and the requirement to generate considerable lift for round out and flare, following an extended period of descent often in icing conditions. This paper describes a CFD-based investigation of the effects of sweep on the aerodynamic performance of a novel forward-swept horizontal stabilizer concept in icing conditions. The concept features an unconventional forward sweep, combined with a high lift leading edge extension (LEX) located within a fuselage induced droplet shadow zone, providing passive protection from icing. In-flight ice accretion was calculated, using Ansys FENSAP-ICE, on 10°, 15° and 20° (low, intermediate, and high) sweep horizontal stabilizers, with
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