Flight Characteristics Research Articles

Prop-Plane — new convertible VTOL UAV as a combination of a longitudinal bicopter and a flying wing with a tilt-rotor powertrain

Vertical take-off and landing (VTOL) unmanned aircrafts are the newest and rapidly developing topic which is not only capable of improving Unmanned Aerial Vehicles (UAV) potential but also to create new use cases. This paper proposes a new convertible VTOL concept designed to obtain optimum flight characteristics for monitoring or flying over long objects. The distinctive feature of the proposed design is a combination of a flying wing with a longitudinal bicopter. The aircraft folds the wings down along the main axis of the aircraft during vertical take-offs and landings to descend the center of gravity and increase stability in bicopter mode. The convertible plane maximizes performance during horizontal flight while maintaining vertical take-off and landing capabilities.The design has been implemented in prototype, and the internal systems and the airframe have been designed and manufactured. As a result, the calculated technical characteristics of the UAV including wind resistance capability were described, the principal elements and components of the design were discussed, and the flight tests of the prototype created were conducted and results presented. Furthermore, the advantages and disadvantages of the concept are reviewed and further development of the project is discussed. The conducted work allows us to confirm the assumption that the developed concept can be used for real-world monitoring missions and to continue developing the concept for a full-scale UAV.

Testing of an indirect ice detection methodology in the Horizon 2020 project SENS4ICE

AbstractSupercooled large droplets (SLD) icing conditions have been the cause of severe aircraft accidents over the last decades. Existing countermeasures, even on modern airplanes, are not necessarily effective against the resulting ice formations, which raises a demand for reliable detection of SLD in all conditions for safe operations. The EU-funded Horizon 2020 project SENS4ICE focused on new ice detection approaches and innovative sensor hybridization to target a fast and reliable (SLD-)ice detection. The performance-based (indirect) ice detection methodology is key to this approach and based on the changes of airplane flight characteristics under icing influence. This paper provides a short overview of the development and implementation of the indirect ice detection (IID) algorithms in SENS4ICE. Moreover, it gives and discusses first exemplary results from the IID tests in classical icing conditions during the SENS4ICE North America flight test campaign conducted in February/March 2023 out of St. Louis Regional Airport in Alton (Illinois, USA).

Reproductive and Flight Characteristics of Lymantria xylina (Lepidoptera: Erebidae) in Fuzhou, China.

The biological characteristics of Lymantria xylina Swinhoe (Lepidoptera: Erebidae), a moth that threatens coastal forests in Fuzhou, China, are closely linked to its spread risk. To characterize these traits, we primarily investigated emergence, reproductive, and flight behaviors. Our findings show that females typically emerge, mate, and copulate during specific times of day. The peak hours of emergence, courtship, and copulation are 13:00-14:00, 19:00-21:00, and around 0:00, respectively. The starting time of oviposition was concentrated before dawn and during the daytime. They preferentially lay eggs on columnar objects, including artificial ones. On average, females laid 361 eggs, lived for 4.5 days, and weighed 0.74 g. Non-ovipositing females were observed to fly for short distances, especially during the evening. Field observations suggest that these females can potentially travel up to 184.5 m in total and 34.5 m continuously. While this indicates a theoretical risk of long-distance dispersal, our findings suggest that the overall risk is limited. These results contribute to our understanding of the biology and dispersal potential of L. xylina.

Helicopter emergency medical services in Iceland between 2018 and 2022-A retrospective study.

Helicopter emergency services (HEMS) are widely used to bring medical assistance to individuals that cannot be reached by other means or individuals that have time-critical medical conditions, such as chest pain, stroke or severe trauma. It is a very expensive resource whose use and importance depends on local conditions. The aim of this study was to describe flight and patient characteristics in all HEMS flights done in Iceland, a geographically isolated, mountainous and sparsely populated country, over a 5-year course. This retrospective study included all individuals requiring HEMS transportation in Iceland during 2018-2022. The electronic database of the Icelandic Coast Guard was used to identify the individuals and register flight data. Electronic databases from Landspitali and Akureyri hospitals were used to collect clinical variables. Descriptive statistics was applied. The average number of HEMS transports was 3.5/10,000 inhabitants and the median [IQR] activation time and flight times were 30 min [20-42] and 40 min [26-62] respectively. The vast majority of patients were transported to Landspitali Hospital in Reykjavik. More than half of the transports were due to trauma, the most common medical transports were due to chest pain or cardiac arrests. Advanced medical therapy was provided for 66 (10%) of individuals during primary transports, 157 (24%) of individuals were admitted to intensive care, 188 (28%) needed surgery and 53 (7.9%) needed a coronary angiography. In Iceland, the number of transports is lower but activation and flight times for HEMS flights are considerably longer than in other Nordic countries, likely due to geographical features and the structure of the service including utilizing helicopters both for HEMS and search and rescue operations. The transport times for some time-sensitive conditions are not within standards set by international studies and guidelines.

Using three turbulence simulation methods for modeling the flying of high-speed railway tunnel lining blocks under piston airflow

The detached tunnel lining concrete blocks poses a serious threat to the safety of moving high-speed train. Understanding the flight characteristics of detached blocks from the tunnel soffit under train piston airflow is essential for devising appropriate measures to mitigate such risks during train operation. Computational Fluid Dynamics (CFD) simulation methods, known for their high efficiency and good repeatability, are effective approaches to study this subject. Large Eddy Simulation (LES), Improved Delayed Detached Eddy Simulation (IDDES), and Unsteady Reynolds-Averaged Navier-Stokes (URANS) are three commonly used turbulence simulation methods in the CFD simulation of train/tunnel aerodynamics. In this study, a three-dimensional CFD simulation model based on the three turbulence simulation methods is established for the airflow-tunnel-train-detached block system, and an experiment is conducted for validating the CFD model. Using the established models, the influence of different turbulence simulation methods on the flight trajectory and aerodynamic coefficients of detached lining blocks under train-induced airflows is compared. By visualizing the macroscopic flow field inside the tunnel and the local flow field near the detached block, the flow mechanisms of detached blocks under different turbulence simulation method conditions are revealed. The results showed that in the 1st stage (BTT stage), the flight of the detached block is influenced by the airflow near the train body, while in the 2nd stage (ATT stage), it is mainly affected by the train wake vortex. Compared with experimental results, the errors of LES and IDDES in simulating the longitudinal direction displacement of the block are only 2.3 % and 5.5 %, respectively, while the error of URANS is 10.6 %. The simulation error of URANS for the longitudinal direction flight speed reached 8.8 % in the ATT stage. In the BTT stage, LES and IDDES predicates more and larger leeward side vortex structures of the detached block, while URANS predicates fewer and smaller vortex structures. Compared with URANS method, the dissipation rate of the vortex structures simulated by LES and IDDES in the ATT stage is slower. These are the main reasons explaining why the flight characteristics of detached lining blocks obtained by URANS method are different from the LES and IDDES methods.

The superiority of feasible solutions-moth flame optimizer using valve point loading

The optimal power flow (OPF) problem deals with large-scale, nonlinear, and non-convex optimization challenges, often accompanied by stringent constraints. Apart from the primary operational objectives of an energy system, ensuring load bus voltages remain within acceptable ranges is essential for providing high-quality consumer services. The Moth-Flame Optimizer (MFO) method is inspired by the unique night flight characteristics of moths. Moths, much like butterflies, undergo two distinct life stages: larval and mature. They have evolved the ability to navigate at night using a technique called transverse orientation. This article presents a methodology for determining the optimal energy transmission system configuration by integrating power producers. The MFO, Grey Wolf Optimizer (GWO), Success-history-based Parameter Adaptation Technique of Differential Evolution - Superiority of Feasible Solutions (SHADE-SF), and Superiority of Feasible Solutions-Moth Flame Optimizer (SF-MFO) algorithms are applied to address the OPF problem with two objective functions: (1) reducing energy production costs and (2) minimizing power losses. The efficiency of MFO, SF-MFO, SHADE-SF, and GWO for the OPF challenge is evaluated using IEEE 30-feeder and IEEE 57-feeder systems. Based on the collected data, SF-MFO demonstrated the best performance across all simulated instances. For instance, the electricity production costs generated by SF-MFO are $845.521/hr and $25,908.325/hr for the IEEE 30-feeder and IEEE 57-feeder systems, respectively. This represents a cost savings of 0.37 % and 0.36 % per hour, respectively, compared to the lowest values obtained by other comparative methods.

CGull: A Non-Flapping Bioinspired Composite Morphing Drone.

Despite the tremendous advances in aircraft design that led to successful powered flights of aircraft as heavy as the Antonov An-225 Mriya, which weighs 640 tons, or as fast as the NASA-X-43A, which reached a record of Mach 9.6, many characteristics of bird flight have yet to be utilized in aircraft designs. These characteristics enable various species of birds to fly efficiently in gusty environments and rapidly change their momentum in flight without having modern thrust vector control (TVC) systems. Vultures and seagulls, as examples of expert gliding birds, can fly for hours, covering more than 100 miles, without a single flap of their wings. Inspired by the Great Black-Backed Gull (GBBG), this paper presents "CGull", a non-flapping unmanned aerial vehicle (UAV) with wing and tail morphing capabilities. A coupled two degree-of-freedom (DOF) morphing mechanism is used in CGull's wings to sweep the middle wing forward and the outer feathered wing backward, replicating the GBBG's wing deformation. A modular two DOF mechanism enables CGull to pitch and tilt its tail. A computational model was first developed in MachUpX to study the effects of wing and tail morphing on the generated forces and moments. Following the biological construction of birds' feathers and bones, CGull's structure is mainly constructed from carbon-fiber composite shells. The successful flight test of the proof-of-concept physical model proved the effectiveness of the proposed morphing mechanisms in controlling the UAV's path.

Risk Assessment of Bird Collisions with a Wind Turbine Based on Flight Parameters

The study addresses the challenge of bird collisions with wind turbines by developing an autonomous risk assessment method. The research uses data from the stereoscopic Bird Protection System (BPS) to anticipate potential collision threats by analysing flight parameters and distance from turbines. The danger factor depends on the flight characteristics of the identified bird species and the parameters of the wind turbine control system. The paper proposes an online quantitative risk assessment model that operates in real time, with the aim of minimising unnecessary turbine shutdowns while improving bird conservation. The model is validated through field data from bird flights. The findings suggest that adaptive management of turbine operations based on real-time bird flight data can significantly reduce collision risks without compromising energy production efficiency. The research underscores the balance between ecological considerations and the economic viability of wind energy, proposing an adaptive strategy that reduces unnecessary turbine stoppages while ensuring the safety of avian species.

Evaluating high-resolution aviation emissions using real-time flight data

Amidst robust global economic growth and advancing globalization, the aviation market is poised for significant expansion. Consequently, the environmental impact of aviation emissions is growing in significance. However, due to limitations in real flight data and aviation emissions index models, further clarification of the emission characteristics throughout entire flights is necessary. To better assess the emission characteristics of entire flights, this study employs real Quick Access Recorder (QAR) data and a high-precision aviation emissions index model, yielding four-dimensional emission data (time, longitude, latitude, altitude) from flights. The analysis compares QAR data with emissions from scheduled flight data (SFD) and Broadcast Automatic Correlation Monitoring (ADS-B) projections, explores seasonal variations in aviation emissions, and assesses the impact of sustainable aviation fuels (SAFs) on emissions reductions. For both number and mass of nvPM emissions, as well as nitrogen oxide emissions, the rankings are: ADS-B-E > SFD-E > QAR-E; for CO, SFD-E > ADS-B-E > QAR-E, particularly during the climb-cruise-descent (CCD) cycle. There are significant differences in the emission of aviation pollutants in airport area and high-altitude area in different seasons. Employing four types of Sustainable Aviation Fuels (SAFs) significantly reduces both the mass and the number of nvPM emissions. Therefore, it is recommended to utilize more QAR data to refine the assessment of the environmental impact of aviation emissions.

Measuring prairie snow water equivalent with combined UAV-borne gamma spectrometry and lidar

Abstract. Despite decades of effort, there remains an inability to measure snow water equivalent (SWE) at high spatial resolutions using remote sensing. Passive gamma ray spectrometry is one of the only well-established methods to reliably remotely sense SWE, but airborne applications to date have been limited to observing kilometre-scale areal averages. Noting the increasing capabilities of unoccupied aerial vehicles (UAVs) and miniaturization of passive gamma ray spectrometers, this study tested the ability of a UAV-borne gamma spectrometer and concomitant UAV-borne lidar to quantify the spatial variability of SWE at high spatial resolutions. Gamma and lidar observations from a UAV (UAV-gamma and UAV-lidar) were collected over two seasons from shallow, wind-blown, prairie snowpacks in Saskatchewan, Canada, with validation data collected from manual snow depth and density observations. A fine-resolution (0.25 m) reference dataset of SWE, to test UAV-gamma methods, was developed from UAV-lidar snow depth and snow survey snow density observations. The ability of UAV-gamma to resolve the areal average and spatial variability of SWE was promising with appropriate flight characteristics. Survey flights flown at a velocity of 5 m s−1, altitude of 15 m, and line spacing of 15 m were unable to capture the average or spatial variability of SWE within the uncertainty of the reference dataset. Slower, lower, and denser flight lines at a velocity of 4 m s−1, altitude of 8 m, and line spacing of 8 m were able to successfully observe areal average SWE and its variability at spatial resolutions greater than 22.5 m. Using a combination of UAV-based gamma SWE and UAV-based lidar snow depth improved the spatial representation of SWE substantially and permitted estimation of SWE at a spatial resolution 0.25 m with a ± 14.3 mm error relative to the reference SWE dataset. UAV-borne gamma spectrometry to estimate SWE is a promising and novel technique that has the potential to improve the measurement of shallow prairie snowpacks, and when combined with UAV-borne lidar snow depths, can provide fine-resolution, high-accuracy estimates of prairie SWE. Research on optimal hardware, data processing, and interpolation techniques is called for to further improve this remote sensing product and explore its application in other environments.

Design and Implementation of a Land-Air Omnidirectional Mobile Robot

This paper proposes a new type of omnidirectional mobile robot for land and air, which has three motion modes, combines the motion characteristics of land motion and air flight, has the ability to climb walls, and can be actively deformed to adapt to the working conditions according to the current working environment. The robot incorporates an innovative “rotor blade–single row omnidirectional wheel” composite structure, which is mainly characterized by a single row of continuous switching wheels covering the outside of each rotor blade, and does not need to provide additional power when moving on the ground and walls, relying on the driving force generated by the rotor blades to drive the continuous switching wheels driven by the rotor blades. This structure can effectively combine the land movement mode, wall crawling mode, and air flight mode, which reduces the energy consumption of the robot without increasing the weight, and we design a deformation device that can realize the transformation of the three modes into each other. This paper mainly focuses on the design of the robot structure and the analysis of the movement method, and the land omnidirectional movement experiments, wall crawling experiments, and air flight experiments were, respectively, carried out, and the results show that the proposed land and air omnidirectional mobile robot has the ability to adapt to the movement of each scene, and improves the upper limit of the robot’s operation.

Predicted Trajectory Accuracy Requirements to Reduce Aviation Impact of Space Launch Operations

Thousands of aircraft flight plans are affected by space launch and reentry operations each year, increasing the distances flown, causing flight delays, and increasing air traffic controllers workload. Due to regulations and procedures, predefined Aircraft Hazard Areas (AHAs) are used to protect aircraft from the risks of space launch and reentry debris, thus constraining the available airspace for other airspace users. While disruptive, there is no less impactful approach at present that adequately protects the flying public. In this paper, we explore the application of trajectory-based operations to evaluate the impact of an AHA on commercial aircraft, with the aim of reducing the number of flights that must be rerouted or rescheduled. This approach relies on precise trajectory predictions to the AHA boundary to determine which flights are expected to clear the AHA before its activation or remain clear of the AHA until after its deactivation. This paper derives the required predicted trajectory accuracy for air traffic automation systems to effectively predict flights impacted by an AHA. The required accuracy is derived based on a model for managing flights relative to the AHA using speed changes alone (as opposed to reroutes or holding) in the context of operational uncertainties like departure time delays and flight characteristics. Additionally, we derived a model to relate scheduling buffers to the AHA activation time, delivery accuracy at the AHA boundary, and AHA violation probability.

The Impact of Surface Structure Changes on the Aerodynamic Characteristics of Modern Soccer Balls

PURPOSE This study comprehensively examined the aerodynamic and flight characteristics of modern soccer balls, focusing on their design evolution and performance attributes. METHODS The aerodynamic characteristics of five types of World Cup balls (2006 Germany World Cup, 2010 South Africa World Cup, 2014 Brazil World Cup, 2018 Russia World Cup, 2022 Qatar World Cup) and five types of Euro tournament balls (EURO2008, EURO2012, EURO2016, EURO2020, EURO2024) were examined, along with their respective design changes. RESULTS Through detailed analysis, significant variations in aerodynamic properties among soccer balls used in various tournaments were identified. Recent advancements have resulted in faster transitions towards critical Reynolds numbers, indicating improved stability in flight trajectories. This enhancement was attributed to the augmentation of surface roughness, which plays a crucial role in enhancing aerodynamic stability and overall performance. 2D simulations simulating powerful goalkeeper kicks revealed distinct differences in flight distances among different soccer balls; the Jabulani ball used in the 2010 World Cup exhibited the longest flight distance, while that of the 2024 Euro ball was the shortest. CONCLUSIONS Variations in surface texture significantly impact aerodynamic properties, affecting flight distance, arrival time, and height. This study underscores the significant design enhancements in modern soccer balls that optimize aerodynamic stability and performance, with modifications aimed at improving flight characteristics and enriching player experience.

Air Traffic Controllers' Perspectives on Unmanned Aerial Vehicles Integration into Non-Segregated Airspace

The integration of Unmanned Aerial Vehicles (UAVs) into non-segregated airspace presents both opportunities and challenges for air traffic control (ATC). The aim of the study is to explore the perspectives of air traffic controllers on the current and anticipated challenges, workload, stress factors, performance errors, and mitigation strategies related to UAV integration. The sample consisted of 213 air traffic controllers in Türkiye. UAV operations have been available in Türkiye not only for military purposes but also for purposes such as forest fires, earthquakes, security, and others for a long time, and these UAV operations are provided with air traffic services (ATS) by air traffic controllers. The results show that air traffic controllers are concerned about mid-air collisions due to UAV technology limits and regulatory gaps, along with managing risks and unique flight characteristics. Addressing technology limitations, regulatory ambiguity, and other factors necessitates a comprehensive strategy. Solutions must prioritize collision avoidance systems, clear communication guidelines, and defined no-fly zones. It is recommended that future studies focus on the comprehensive impact of UAVs on air traffic operations and the development of regulations.

Morphometric identification of Bursa Oynarı pigeon varieties

Aim: This study was carried out to make morphometric identification of male and female individuals of Karabaş, Yaşmaklı, Muskalı, Kalaça and Beyaz genotypes in Bursa Oynarı pigeons. Materials and Methods: For this purpose, a total of 100 pigeons, 10 females and 10 males, 12-14 months from each genotype, were examined. Results: : The Oynar breed's average live weight was determined to be 306.27±1.32 g. Average body weights for males and females, genotypes, and gender x genotypes were discovered to be similar (p>0.05). Males were found to have longer heads (p<0.05), but there was no statistically significant difference between males and females in terms of other body traits (p>0.05). Different averages were determined in the genotypes in terms of beak length, beak depth, trunk length, body length, wing length, chest circumference, chest depth, and tail length (p<0.05). In general, the averages were lower in the Yaşmaklı genotype than in other genotypes, and higher in the Beyaz and Muskalı genotypes (p<0.05). The interaction between gender and genotypes was significant in beak depth (p<0.001). Conclusion: As a result, it was anticipated that the characteristics detected for the first time in the Oynar breed varieties would contribute to the definition of this breed. It was also estimated that differences in the body structures of the varieties may impact their flight characteristics, and the findings on this subject will attract the attention of pigeon breeders. Considering their body structures, it was determined that the Kalaça, Muskalı, and Beyaz genotypes may have superior characteristics in terms of flight time, and the Yaşmaklı genotype may have superior characteristics in terms of flight speed.

Investigating the Mechanical Performance of Bionic Wings Based on the Flapping Kinematics of Beetle Hindwings.

The beetle, of the order Coleoptera, possesses outstanding flight capabilities. After completing flight, they can fold their hindwings under the elytra and swiftly unfold them again when they take off. This sophisticated hindwing structure is a result of biological evolution, showcasing the strong environmental adaptability of this species. The beetle's hindwings can provide biomimetic inspiration for the design of flapping-wing micro air vehicles (FWMAVs). In this study, the Asian ladybird (Harmonia axyridis Pallas) was chosen as the bionic research object. Various kinematic parameters of its flapping flight were analyzed, including the flight characteristics of the hindwings, wing tip motion trajectories, and aerodynamic characteristics. Based on these results, a flapping kinematic model of the Asian ladybird was established. Then, three bionic deployable wing models were designed and their structural mechanical properties were analyzed. The results show that the structure of wing vein bars determined the mechanical properties of the bionic wing. This study can provide a theoretical basis and technical reference for further bionic wing design.

The Effects of a Seagull Airfoil on the Aerodynamic Performance of a Small Wind Turbine

Birds’ flight characteristics such as gliding and dynamic soaring have inspired various optimizations and designs of wind turbines. The implementation of biological wing geometries such as the airfoil profile of seabirds has improved wind turbine performance. However, the field can still benefit from further investigation into the aerodynamic characteristics of an inspired design. Therefore, this study evaluated the effect of a seagull airfoil design on the aerodynamic performance of the National Renewable Energy Laboratory (NREL) Phase VI wind turbine. By replacing its S809 airfoil with the laser-scanned profile of the seagull airfoil, the aerodynamic behavior at key locations of the NREL Phase VI wind turbine blade was numerically simulated in a three-dimensional environment using the Ansys Fluent 2022 R1 computational fluid dynamics (CFD) code. The results were validated against the experimental data, and analysis of the torque outputs, pressure distributions, and velocity profiles that were generated by both the baseline and modified models demonstrated the ability of the seagull airfoil profile to modify regions of minimum and maximum local velocities to achieve highly favorable pressure differentials, significantly increasing the torque output of the NREL Phase VI wind turbine by 350, 539, 823, and 577 Nm at 10, 15, 20, and 25 m/s inlet velocities, respectively.

Study of Turbulent Behavior and Particle Flight Characteristics Based on Different Turbulence Models During HVOF Spraying

Study of Turbulent Behavior and Particle Flight Characteristics Based on Different Turbulence Models During HVOF Spraying

First transcriptomic insight into the working muscles of racing pigeons during a competition flight

BackgroundThe currently known homing pigeon is a result of a sharp one-sided selection for flight characteristics focused on speed, endurance, and spatial orientation. This has led to extremely well-adapted athletic phenotypes in racing birds.MethodsHere, we identify genes and pathways contributing to exercise adaptation in sport pigeons by applying next-generation transcriptome sequencing of m.pectoralis muscle samples, collected before and after a 300 km competition flight.ResultsThe analysis of differentially expressed genes pictured the central role of pathways involved in fuel selection and muscle maintenance during flight, with a set of genes, in which variations may therefore be exploited for genetic improvement of the racing pigeon population towards specific categories of competition flights.ConclusionsThe presented results are a background to understanding the genetic processes in the muscles of birds during flight and also are the starting point of further selection of genetic markers associated with racing performance in carrier pigeons.

Quasi-steady aerodynamic modeling and dynamic stability of mosquito-inspired flapping wing pico aerial vehicle.

Recent exploration in insect-inspired robotics has generated considerable interest. Among insects navigating at low Reynolds numbers, mosquitoes exhibit distinct flight characteristics, including higher wingbeat frequencies, reduced stroke amplitudes, and slender wings. This leads to unique aerodynamic traits such as trailing edge vortices via wake capture, diminished reliance on leading vortices, and rotational drag. This paper shows the energetic analysis of a mosquito-inspired flapping-wing Pico aerial vehicle during hovering, contributing insights to its future design and fabrication. The investigation relies on kinematic and quasi-steady aerodynamic modeling of a symmetric flapping-wing model with a wingspan of approximately 26 mm, considering translational, rotational, and wake capture force components. The control strategy adapts existing bird flapping wing approaches to accommodate insect wing kinematics and aerodynamic features. Flight controller design is grounded in understanding the impact of kinematics on wing forces. Additionally, a thorough analysis of the dynamic stability of the mosquito-inspired PAV model is conducted, revealing favorable controller response and maneuverability at a small scale. The modified model, incorporating rigid body dynamics and non-averaged aerodynamics, exhibits weak stability without a controller or sufficient power density. However, the controller effectively stabilizes the PAV model, addressing attitude and maneuverability. These preliminary findings offer valuable insights for the mechanical design, aerodynamics, and fabrication of RoboMos, an insect-inspired flapping wing pico aerial vehicle developed at UPM Malaysia.