Aircraft Landing Research Articles

Refined air-cooled battery sizing process for conceptual design of eVTOL aircraft

Recently, electric vertical takeoff and landing (eVTOL) aircraft have garnered significant interest as a primary mode of transportation in advanced air mobility (AAM). For the conceptual design of eVTOL aircraft, where a broad design space must be explored rapidly, a practical and reliable battery sizing process is essential. This process needs to employ models with low computational cost while comprehensively considering two key factors: voltage drop characteristics and thermal effects. However, existing research on battery sizing mainly relies on constant specific energy or power, neglecting these factors. This oversight can lead to significant discrepancies in battery sizing between the conceptual and detailed design phases. To address these limitations, this paper introduces a refined battery sizing process. Our approach incorporates models for battery voltage drop, heat generation, and a cooling system. A Thevenin equivalent circuit is used to model voltage drop and heat generation, with a novel calibration method developed for accurate predictions of voltage and temperature profiles. An air cooling system is adopted for its simplicity and lightweight design, and a corresponding model is constructed. Applying our process to eVTOL aircraft sizing revealed that incorporating temperature, along with the depth of discharge (DoD) and C-rate, as constraints in battery sizing led to a 4.6 % decrease in specific energy and a 4.2 % decrease in specific power. These findings underscore the importance of considering temperature in battery sizing. Additionally, sensitivity analyses provided insights into which thermal management system, air-cooled or liquid-cooled, is more appropriate for the battery under various operating conditions.

Short Takeoff and Vertical Landing Aircraft Deceleration Transition Control Based on L1 Adaptive Control

Short Takeoff and Vertical Landing Aircraft Deceleration Transition Control Based on L1 Adaptive Control

Control allocation optimization for an over-actuated tandem tiltwing eVTOL aircraft considering aerodynamic interactions

This paper describes control allocation strategies for a tandem tiltwing electric vertical take-off and landing (eVTOL) aircraft with distributed propulsion. The control mappings are constructed as local surrogate models that relate the control effectors to the aircraft's aeropropulsive forces and moments across the full flight envelope, including interactional aerodynamics effects. Control allocation optimization problems are formulated based on force and moment commands for specific flight conditions. Specifically, a nonlinear programming formulation based on nonlinear control mapping is proposed for control allocation optimization, and the problem is solved using a sparse nonlinear optimizer. The solutions obtained from different formulations such as the minimization of force and moment residuals and the minimization of control effort are investigated. Furthermore, these solutions are compared with the solutions obtained using linear control mapping-based formulations. Results presented for the cases of forward flight, low speed flight & hover, and flight in the transition corridor suggest that considering aerodynamic interactions while formulating and solving the control allocation problem is necessary for higher levels of accuracy compared to linear approaches. One-propeller-out scenarios and moment and force generation cases are also investigated. Finally, control allocation for steady and accelerated operation in the transition corridor is discussed. The contribution of the methods and results in the paper is a nonlinear control allocation methodology for the entire flight envelope of an over-actuated tandem tiltwing eVTOL aircraft.

Analysis of Noise Level in Soekarno Hatta International Airport Area

One of the environmental impacts in the operation of an airport is noise, which originates from aircraft activities. Soekarno-Hatta International Airport is a public service airport located in Tangerang. This study aims to determine the noise levels around Soekarno-Hatta International Airport.The research results indicate that the noise levels of aircraft around Soekarno-Hatta International Airport in the northern part were collected using a sound level meter and then analyzed using the Weighted Equivalent Continuous Perceived Noise Level (WECPNL) method from aircraft landing activities. The results show that the noise intensity is categorized within the Weighted Equivalent Continuous Noise Level (WECPNL) range from ≥ 75 to ≥ 80 dBA.The researchers suggest that the airport authorities conduct regular noise measurements to monitor and control noise levels following the established noise standards and regulations to prevent direct impacts on the surrounding communities of Soekarno-Hatta International Airport

Dynamic characteristics of aircraft landing gear retraction mechanism under the coupling effects of extreme conditions

Dynamic characteristics of aircraft landing gear retraction mechanism under the coupling effects of extreme conditions

Tiltwing eVTOL Transition Trajectory Optimization

This paper studies transition trajectory optimization for a tiltwing electrical vertical takeoff and landing (eVTOL) aircraft configuration and evaluates the benefits of equipping it with fluid injection active flow control (AFC). Using a three-degree-of-freedom model of the aircraft’s longitudinal dynamics, both hover-to-cruise (forward) and cruise-to-hover (backward) transition are investigated for a range of center-of-gravity (CG) positions to determine minimum-energy trajectories that achieve zero altitude variation while avoiding wing aerodynamic stall. It is demonstrated that constant-altitude transition can be achieved in the forward direction (with or without AFC), whereas the use of AFC in backward transition reduces the total altitude change by 24%. A comparative constant-altitude backward transition solution using a different airfoil with a higher stall limit suggests that a redesign of the tail wing of this unique tiltwing aircraft could better leverage the benefits of using AFC in this application. Additionally, it is also shown that, in the case of forward transition, AFC can be used to decrease the total transition time and increase the range of CG positions where constant-altitude transition can occur.

Simultaneous optimization of design and takeoff trajectory for an eVTOL aircraft

When designing a vertical takeoff and landing (VTOL) aircraft, it is crucial to consider various operating conditions, including hover, wing-borne cruise, and transition. Takeoff transition and climb phases are critical for vehicle conceptual design because they drive the motor and battery sizing. However, these flight phases are often ignored or simplified in the conceptual design literature due to the complexity of transition dynamics. To address this limitation, we propose simultaneous optimization of VTOL aircraft conceptual design and takeoff trajectory. Simultaneous optimization incorporates the takeoff transition and climb flight dynamics into VTOL design optimization in a fully coupled manner. This paper presents the design-trajectory optimization of lift-plus-cruise and tailsitter UAVs for delivery missions. As a result, simultaneous optimization reduces total energy consumption by 7.4% compared to uncoupled optimization and by 4.8% from iterative sequential optimization in the lift-plus-cruise configuration. It also achieves a 29% energy reduction from uncoupled optimization in the tailsitter configuration. Incorporating takeoff trajectory optimization in UAV sizing enables accurate estimation of takeoff and climb energy, which avoids undersizing or oversizing the battery. Furthermore, simultaneous optimization trades the vehicle weight penalty for a more energy-efficient climb with early transition. These system-level trade-offs can only be captured by simultaneous optimization; they cannot be captured by uncoupled or iterative sequential optimization.

Study on the evaluation method of pilot workload in eVTOL aircraft operation

This paper investigates the pilot control strategy and workload associated with the manned electric Vertical Take-Off and Landing (eVTOL) aircraft. This research aims to identify control strategies that are both rational and effective in reducing the pilot's workload. Although the Cooper-Harper rating (HQR, Handling Quality Rating) remains the prevalent benchmark for assessing pilot workload, its subjective nature often complicates the precise quantitative identification of the key factors influencing workload. This study introduces an assessment method for pilot control workload using wavelet transform to evaluate pilot workload, focusing on the correlation between pilot control magnitude, frequency components, and complexity. We begin with a review of control action analysis methods in both time and frequency domains. Subsequently, by selecting an appropriate wavelet function and a sampling frequency, we develop the assessment method for pilot control strategy and workload based on wavelet analysis. Finally, we assess pilot workload using real pilot inputs with HQRs obtained from helicopter flight tests and tilt-rotor aircraft conversion simulations. The results indicate that this approach is capable of precisely pinpointing the frequency components and energy levels within pilot control actions throughout different time periods. Furthermore, a significant correlation is observed between pilot control characteristics, frequency components, and HQRs. Consequently, the developed approach provides a rational framework for quantifying and analyzing pilot workload in a range of eVTOL aircraft scenarios.

Automatic Aircraft Landing System: A Review

The aircraft landing phase, marking the finishing of a flight plane, is a critical yet dangerous aerial maneuver. Even though it might seem simple, predicting the complexities of performance during landing presents a big challenge due to the dynamic characteristics of the phase, interaction with piloting methods, as well as inherent uncertainties in aerodynamics. Landing is executed in close proximity to the ground at reduced airspeed, the landing phase entails an escalated safety risk. Notably, incidents and accidents, particularly overruns where aircraft fail to slow sufficiently on the runway before landing, underscore the imperative for advanced landing technologies. This paper presents a comprehensive review of research spanning from 2000 to the present exploring smart techniques like fuzzy logic and machine learning, an array of control strategies ranging from classic PID control to sophisticated hybrid control approaches, and optimization procedures utilizing diverse optimization algorithms. The primary objective is to provide a comprehensive evaluation of the existing research landscape, offering insights that can propel the evolution of strategies for safer and more efficient landings and making sure the plane touches down safely.

Magnetic Hysteresis Analysis for Non-Destructive Evaluation of Aircraft Structural Steels

ABSTRACT This paper introduces non-destructive testing (NDT) techniques centered on measuring magnetic properties, offering insight into evaluating structural steels throughout aircraft production and service life. It highlights the method’s utility in quality control of steel components, particularly in detecting variations in microstructure affecting mechanical properties. The NDT method correlates material structural state with magnetic properties, utilizing parameters such as coercive force, remanence, and hysteresis loop area. Developed instruments, like the MA-05 Magnetic Analyzer and KRM-Ts coercive force meter, enable precise measurements in both closed and open magnetic circuits. Applications range from assessing heat treatment quality to monitoring materials degradation in challenging conditions. A set of 12 gas containers that have been in service in aircraft for more than 40 years are tested as a case study, demonstrating the method's efficacy in evaluating damage accumulation. Future prospects include other potential applications in testing aircraft landing gear components.

Integration of the Functional Hazard Assessment Within a Model-Based Systems Engineering Framework

A major challenge in developing novel aircraft concepts is demonstrating the safety of increasingly complex and multifunctional aircraft systems. Aircraft manufacturers are adopting model-based systems engineering approaches to develop these new aircraft. The safety assessment process follows suit with model-based safety assessment. However, system and safety engineers still transfer information that is mainly document-based during the system architecting process. This paper aims to improve this process. First, a framework for developing system architecture specification models is introduced using the Architecture Analysis and Design Integrated Approach (ARCADIA)/Capella methodology and tool, illustrated with an aircraft landing gear braking system. Secondly, the paper proposes enhancements to the system specification model to enable functional hazard assessment and to capture the results within the system architecture specification model, i.e., using color-coding of system functions according to the severity of their associated failures as a visual aid to the system architect. In addition, the proposed features in the system specification model can help the safety engineer analyze failure relationships better. In summary, the proposed method improves consistency between the system architect and the safety expert in making safety-informed architecting decisions early in the development process, improving its effectiveness.

Surrogate-Based Multidisciplinary Optimization for the Takeoff Trajectory Design of Electric Drones

Electric vertical takeoff and landing (eVTOL) aircraft attract attention due to their unique characteristics of reduced noise, moderate pollutant emission, and lowered operating cost. However, the benefits of electric vehicles, including eVTOL aircraft, are critically challenged by the energy density of batteries, which prohibit long-distance tasks and broader applications. Since the takeoff process of eVTOL aircraft demands excessive energy and couples multiple subsystems (such as aerodynamics and propulsion), multidisciplinary analysis and optimization (MDAO) become essential. Conventional MDAO, however, iteratively evaluates high-fidelity simulation models, making the whole process computationally intensive. Surrogates, in lieu of simulation models, empower efficient MDAO with the premise of sufficient accuracy, but naive surrogate modeling could result in an enormous training cost. Thus, this work develops a twin-generator generative adversarial network (twinGAN) model to intelligently parameterize takeoff power and wing angle profiles of an eVTOL aircraft. The twinGAN-enabled surrogate-based takeoff trajectory design framework was demonstrated on the Airbus A3 Vahana aircraft. The twinGAN provisioned two-fold dimensionality reductions. First, twinGAN generated only realistic trajectory profiles of power and wing angle, which implicitly reduced the design space. Second, twinGAN with three variables represented the takeoff trajectory profiles originally parameterized using 40 B-spline control points, which explicitly reduced the design space while maintaining sufficient variability, as verified by fitting optimization. Moreover, surrogate modeling with respect to the three twinGAN variables, total takeoff time, mass, and power efficiency, reached around 99% accuracy for all the quantities of interest (such as vertical displacement). Surrogate-based, derivative-free optimizations obtained over 95% accuracy and reduced the required computational time by around 26 times compared with simulation-based, gradient-based optimization. Thus, the novelty of this work lies in the fact that the twinGAN model intelligently parameterized trajectory designs, which achieved implicit and explicit dimensionality reductions. Additionally, twinGAN-enabled surrogate modeling enabled the efficient takeoff trajectory design with high accuracy and computational cost reduction.

An investigation of superstructure length on bi-stable ship wake flow

The variation in the geometry of a ship model has the potential to eliminate the flow asymmetry in ship wake and improve its aerodynamic performance. This study investigates the impact of the length of superstructure on the wake flow bi-stability of the ship model using IDDES at Re = 8 × 104. Also, this article studied the effect of ship's funnel structure using two models, with and without funnel, on the wake flow asymmetry, providing smooth transition into the study of the length of superstructure. The result indicates that when the funnel is removed, the length of flow reattachment after separation at the hanger increases for the top step and decreases for the second step for the case with no funnel. The asymmetric flow at wake persists, however, the configuration is different, showing difference in flow state. When the length of the superstructure is reduced, the turbulence at the wake increases, the size of recirculation bubble at the flight deck and behind the stern reduces and the overall pressure area decreases significantly. Behind the stern, all three cases indicate an asymmetrical flow, however, compared to Case 1, the asymmetry at the flight deck in Case 2 is weak, while a symmetrical flow is achieved with Case 3. Consequently, this research proposes a novel approach to improving wake flow and ensure safe aircraft take-off and landing operations on the ship deck.

Model test on dynamic response of coral sand in island dredging airport under wave, tidal and aircraft landing load

The construction of an island airport on a coral reef will inevitably encounter wave, tidal and aircraft takeoff and landing loads. To study the dynamic response of the coral sand island airport under these loads, a 1:50 laboratory model test was conducted with Meiji Reef Airport as the engineering background. The model test studied the pore water pressure characteristics of the coral sand strata beneath the airport runway under wave loads with different wave heights, tidal loads with different tidal heights, and aircraft impact loads with different cyclic loading times. Additionally, the displacement characteristics of the coral sand strata beneath the airport runway under the aircraft impact loads with different cyclic loading times were also studied. The results show that the pore water pressure of coral sand strata under the airport runway decreases with the increasing offshore distance under the wave and tidal loads. The change of wave height has little influence on the pore water pressure of coral sand strata, while the change of tidal water level has a significant effect on it. As the number of aircraft impact load cycles increases, the cumulative excess pore pressure in the coral sand strata under the airport runway no longer increases and plastic deformation occurs. The research can provide a reference for the runway foundation treatment of the island airport under construction and planning.

Real-time vision-inertial landing navigation for fixed-wing aircraft with CFC-CKF

Vision-inertial navigation offers a promising solution for aircraft to estimate ego-motion accurately in environments devoid of Global Navigation Satellite System (GNSS). However, existing approaches have limited adaptability for fixed-wing aircraft with high maneuverability and insufficient visual features, problems of low accuracy and subpar real-time arise. This paper introduces a novel vision-inertial heterogeneous data fusion methodology, aiming to enhance the navigation accuracy and computational efficiency of fixed-wing aircraft landing navigation. The visual front-end of the system extracts multi-scale infrared runway features and computes geo-reference runway image as observation. The infrared runway features are recognized efficiently and robustly by a lightweight end-to-end neural network from blurry infrared images, and the geo-reference runway is generated through projection of the runway’s prior geographical information and prior pose. The fusion back-end of the navigation system is the Covariance Feedback Control based Cubature Kalman Filter (CFC-CKF) framework, which tightly integrates visual observations and inertial measurements for zero-drift pose estimation and curbs the effect of inaccurate kinematic noise statistics. Finally, real flight experiments demonstrate that the algorithm can estimate the pose at a frequency of 100 Hz and fulfill the navigation accuracy requirements for high-speed landing of fixed-wing aircraft.

Research on battery heat generation characteristics and thermal management system applied to a typical eVTOL

Electric Vertical Takeoff and Landing (eVTOL) aircraft, as a highly promising future transportation mode, offers new possibilities for solving traffic congestion. Its unique flight mode and high power requirements present significant challenges for battery thermal management system design. Compared to electric vehicles, eVTOLs have totally different usage scenarios and operating conditions, leading to the fact that the thermal management system of conventional electric vehicles does not apply to eVTOLs. This paper proposes a battery thermal management design method for eVTOLs. The energy and power requirements for a short-distance eVTOL flight are determined through theoretical calculations. Additionally, experimental studies explore the thermal characteristics of a 61.5Ah lithium-ion battery under flight discharge conditions. Moreover, a battery thermal management system, which combines flat heat pipes and ram air, is analyzed through numerical simulations. Furthermore, this study investigates the effects of various air temperatures, air inlet mass flow rates, and fin spacing on the performance of the thermal management system. Finally, under the flight discharge cycle of a 61.5 Ah lithium-ion battery, with the environment temperature of 20 °C, the temperature can be controlled within 38.46 °C. The temperature difference can be cooled within 3.85 °C by the passive cooling system. Even at an extreme environment temperature of 40 °C, the battery temperature can still meet the standard. Meanwhile, comparing from multiple dimensions, this solution has a better overall performance than the traditional liquid cooling solution, which provides a foundation for designing a battery thermal management system for eVTOLs.

Rigid–flexible coupling design and reusable impact mitigation of the hierarchical-bistable hybrid metamaterials

Mechanical metamaterials with multistable unit cells featured by negative stiffness or quasi-zero stiffness is attracting increasing attention owing to their unique mechanical properties and reusable potential. In this paper, a hierarchical-bistable hybrid metamaterial with rigid–flexible coupling design is proposed, demonstrating excellent mitigation performance and protection against multiple impacts. The metamaterial consists of a multi-layer bistable beams with a central honeycomb and is manufactured by 3D printing. Firstly, the negative stiffness characteristics of the curved beams in the metamaterial are theoretically determined, and the convergence of the finite element model under different mesh sizes is analyzed. And the quasi-zero stiffness characteristics of the metamaterial have been confirmed, along with its more stable and uniform deformation pattern, through the quasi-static compression experiment. Then the buffering performance of the metamaterial is studied in ball impact tests, showing an average improvement of about 65% compared to the rigid control group, while verifying the accuracy of the finite element model. With the analysis of the deformation modes and strain energy, the mitigation mechanism of metamaterials is demonstrated to extend the contact time and disperse the impact load through the layered deformation to reduce the peak response, instead of relying on plastic strain. Finally, the reusability of the metamaterial is explored by the ten-times plate impacts simulation. The results demonstrate that the metamaterial decreases the plastic strain of its structure by 60% while reducing impact response, thereby preventing the premature failure of core components. These results demonstrate the great potential of the proposed metamaterials for various engineering applications, including aircraft or spacecraft landing protection, vehicle pedestrian protection, and the transportation protection of fragile objects or precision instruments.

Electric Taxiing System. Kinetic Energy Recovery System as an Electric Taxiing Solution: Economic and environmental analysis: Phenom 300 case study

The aviation industry has thrived in recent years, with a significant increase in passenger numbers, leading to the development of larger aircraft fleets and the expansion of airport infrastructure. In 2019, more than 4.5 billion passengers traveled by airplane, which represents an 80% increase compared to 2009. As a consequence, this growth has also resulted in longer taxiing times for aircraft, increasing fuel consumption and operational costs. The industry's CO2 emissions have quadrupled since the 1960s, with over 1 billion tons released in 2019, contributing to global warming. Given that the improvements being made to current propulsion systems and the production of over 600 million liters of SAF (Sustainable Aviation Fuel) in 2023 do not seem sufficient to meet the ambitious goals set by regulators and operators, the logical solution would be to develop a system capable of moving the aircraft on the ground using alternative, cleaner, and cheaper energies, such as electric power. This paper explores the latest advancements in electric propulsion systems, specifically focusing on external and onboard systems. After the state of the art is established, this paper will cover a case study and propose a new alternative for an onboard system called ETS – Electric Taxiing System. The ETS is a 100% electric system for ground handling operations designed to use only the kinetic energy stored in a battery pack, which is recovered during aircraft landing and braking events. Although there are some studies on this topic, the author considers this paper to be more comprehensive as the results computed here take into account 96 variables, 60 simulations, several flight plans, and real-world data. The case study focuses on the implementation and dimensioning of the ETS, considering electric motor power and torque, and battery capacity for the Embraer Phenom 300. A brief economic and environmental analysis was also conducted, considering the operation of NetJets Europe, the world's leading and largest private jet company.

Urban Air Mobility for Last-Mile Transportation: A Review

Urban air mobility (UAM) is a revolutionary approach to transportation in densely populated cities. UAM involves using small, highly automated aircraft to transport passengers and goods at lower altitudes within urban and suburban areas, aiming to transform how people and parcels move within these environments. On average, UAM can reduce travel times by 30% to 40% for point-to-point journeys, with even greater reductions of 40% to 50% in major cities in the United States and China, compared to land transport. UAM includes advanced airborne transportation options like electric vertical takeoff and landing (eVTOL) aircraft and unmanned aerial vehicles (UAVs or drones). These technologies offer the potential to ease traffic congestion, decrease greenhouse gas emissions, and substantially cut travel times in urban areas. Studying the applications of eVTOLs and UAVs in parcel delivery and passenger transportation poses intricate challenges when examined through the lens of operations research (OR). By OR approaches, we mean mathematical programming, models, and solution methods addressing eVTOL- and UAV-aided parcel/people transportation problems. Despite the academic and practical importance, there is no review paper on eVTOL- and UAV-based optimization problems in the UAM sector. The present paper, applying a systematic literature review, develops a classification scheme for these problems, dividing them into routing and scheduling of eVTOLs and UAVs, infrastructure planning, safety and security, and the trade-off between efficiency and sustainability. The OR methodologies and the characteristics of the solution methods proposed for each problem are discussed. Finally, the study gaps and future research directions are presented alongside the concluding remarks.

Conceptual design and analysis of a box fan-in-split-wing tiltrotor eVTOL aircraft

PurposeWith the advancements in electric vertical take-off and landing (eVTOL) aircraft technology such as batteries, mechanisms, motors, configurations and so on, designers and engineers are encouraged to create unique and unconventional configurations of eVTOL aircraft to provide better capabilities and higher efficiencies to compete in the market. The box fan-in-split-wing tiltrotor eVTOL aircraft is an innovative design that aims to address the aerodynamic inefficiencies such as propeller effects in cruise and engine mounts drag that existed in traditional eVTOL aircraft designs such as vectored thrust, rotorcraft, lift + cruise and multi-copter configurations. This paper aims to propose a multi-disciplinary design process to conceptually design the box fan-in-split-wing Tiltrotor eVTOL aircraft.Design/methodology/approachAn unconventional methodology was used to design the UAM aircraft, and the following parameters are considered: capable of vertical take-off and landing, highly aerodynamic with a high lift-to-drag ratio, low Cd0 modern and appealing, rechargeable or battery swappable and feature to minimise or negate propeller drag. A heavy emphasis on improving performance and weight based on aerodynamics was enforced during the conceptual design phase. MAPLA and XFOIL were used to identify the aerodynamic properties of the aircraft.FindingsUpon determining the key parameters and the mission requirements and objectives, a list of possible VTOL configurations was derived from theoretical and existing designs. The fan in the wing/split wing was selected, as it could stow the propellers. A tiltrotor configuration was selected because of its ability to reduce the total number of lift props/motors, reducing powerplant weight and improving aerodynamic efficiency. For the propulsion configuration, a battery–motor configuration with a hexa-rotor layout was chosen because of its ability to complement the planform of the aircraft, providing redundant motors in case of failure and because of its reliability, efficiency and lack of emissions. Coupled with the fan-in-wing / split wing concept, the box wing seamlessly combines all chosen configurations.Originality/valueThe box fan-in-split-wing Tiltrotor eVTOL aircraft aims to address the aerodynamic inefficiencies of earlier designs such as propeller effects in cruise and engine mounts drag. The potential benefits of this aircraft, such as increased range, endurance and payload capacity, make it an exciting prospect in the field of Urban Air Mobility.