Aircraft Velocity Research Articles

A Number of Conflicts at Route Intersections - Rectangular Model

A conflict is an infringement of minimum separation between at least two aircraft. Air traffic controllers build a protected area in front of an aircraft; its shapes and dimensions depend on the speed of an aircraft and on the minimum separation. The protected zone in this mathematical model is the horizontal rectangular zone. If an aircraft is inside this protected zone, a conflict occurs. The model is based on these assumptions: aircraft fly in level straight line routes; only an infringement of the lateral separation is considered; deviations are excluded; aircraft at the same flight level fly at the same average speed; aircraft fly towards an intersection and change direction after the intersection. Hence, conflicts mainly occur owing to the loss of minimum separation between aircraft flying at the same flight level. The calculation of average number of potential conflicts is designed for a long time interval; hence, aircraft velocity deviations are negligible. The mathematical model in this paper is intended to compare different alternative intersection configurations of air traffic service routes. The comparison is based on the following results: an average number of potential conflicts per hour at route intersections, index of conflict intensity, and intersection capacity.

Large scale image aided navigation

Currently, most airborne platforms use an Inertial Measurement Unit (IMU) to provide estimates of aircraft position, velocity, and attitude. Errors in the IMU result in a position solution that drifts over time. In order to counteract IMU drift, platforms typically integrate measurements from Global Navigation Satellite Systems (GNSS). However, many military and civilian scenarios encounter situations where GNSS may be unavailable due to intentional jamming, or when operating in challenging environments. Many solutions have been proposed that use images from an airborne camera to match features against a reference image to compute global position. These techniques require a relatively accurate prior estimate of position to converge. This leads to a situation where platforms being denied GNSS pass a threshold of position error due to IMU drift, from which current image-aided navigation system cannot recover. This paper presents a novel localization algorithm inspired by fusing state of the art Content Based Image Retrieval techniques with nonparametric Bayesian estimation strategies. We outline the framework for performing a search of a large-scale image database in order to provide a rough position estimate to an airborne platform. These techniques are analogous to solving the “kidnapped-robot” problem, applied to airborne platforms. This framework is evaluated using actual data collected from an airborne camera and navigation system.

Landing Auto‐Pilots for Aircraft Motion in Longitudinal Plane using Adaptive Control Laws Based on Neural Networks and Dynamic Inversion

AbstractThis paper presents two new automatic landing systems (ALSs) for aircraft motion in longitudinal plane; the model of the landing geometry determines the flight trajectory and the aircraft calculated altitude; the flight trajectory during landing consists of two parts: the glide slope and the flare. Both designed ALSs have an adaptive system (ACS) for the aircraft output's control; for the first ALS, the output vector consists of the flying altitude and the longitudinal velocity, while, for the second ALS, the output variables are the pitch angle and the longitudinal velocity of aircraft. The second variant of ALS also contains an altitude controller providing the calculated pitch angle. The calculated altitude (for the first ALS), the calculated pitch angle (for the second ALS), and the desired flight velocity are provided to the ACS by means of a block consisting of two reference models. ACS is based on the dynamic inversion concept and contains an adaptive controller which includes a linear dynamic compensator, a state observer, a neural network, and a Pseudo Control Hedging block. The paper is focused both on the design of the two ALSs and on their complex software implementation and validation.

The Geolocation Accuracy of LiDAR Footprint

This paper describes the geometric geolocation accuracy of LiDAR footprint, utilizing an aircraft configuration that supports a sensor designed to scan the surface of the Earth, a DGPS and INS/IMU system. It is presented a review of LiDAR's footprints accuracy as a relationship between the input parameters, which include errors of the orbital state, attitude information of the aircraft and the look vector errors of the active sensor (LiDAR scanner), that give us the coordinates of the point of intersection of the line of sight scanning system and the Earth's surface as a function of: terrestrial ellipsoid surface, aircraft position, aircraft velocity, aircraft attitude (spatial situation) and the orientation of the LiDAR scanner. Using the derived error formulas, based on the accuracy of the navigation solution, the boresight misalignment angles, the ranging and scan angle accuracy, and laser beam divergence, the achievable point positioning accuracy can be computed for any given LiDAR system which operates at different flying heights between 70 m - 6,000 m.

Development of Return to Base Flight Trajectory Generator Based on Dubins Path - Vector Field Method

In a Return to Base (RTB) situation, aircraft needs to immediately fly back to its origin airport. Since there is no published flight procedure for an RTB, an Air Traffic Controller (ATC) will assist the pilot for the flight procedure to fly. The objective of this work is to generate a flight trajectory in RTB situation based on the available airport flight procedures (departure and arrival) in Kertajati airport. The Dubins Path was used as a method to generate the flight trajectory and supported by the Vector-Field Methodology. The Python programming simulation was used to simulate the flight trajectory generation in the normal condition, second closest waypoint condition, and different parameters value condition. The trajectory was simulated based on flight characteristic of a single engine aircraft (Cesna 172) and multi-engine aircrafts (Boeing 737-800NG). The simulation results show that the Dubins Path and Vector-Field methodology success to generate the flight trajectory in different types of condition and parameters. The increase in aircraft velocity and the decrease in aircraft bank angle caused an increase in the aircraft turning radius. While, the decrease in aircraft flight path angle caused increase in the length of Dubins Path line.

Alternative Position and Navigation Based on DME Accumulated Delta Range

A method that estimates absolute aircraft position and velocity based on time-series of accumulated delta range measurements from distance measuring equipment (DME) ground transponders is analyzed. This method provides an Alternative Position and Navigation – but not quite Timing – system for use in airplanes as a back-up to a Global Navigation Satellite System such as GPS. The results show that a steady-state accuracy level better than 0.025 nm is achievable for the whole duration of a simulated flight trajectory with the tracking of four DME ground stations when aided by sporadic absolute range measurements. The system with only accumulated delta range measurements is challenged in low speed cases; however, this system exhibits convergence times of about 340 and 130 s, respectively, for an aircraft speed of 200 and 500 kn when tracking five DME ground stations.

Flight parameter estimation using instantaneous frequency and time delay measurements from a three-element planar acoustic array.

The acoustic signal emitted by a turbo-prop aircraft consists of a strong narrowband tone superimposed on a broadband random component. A ground-based three-element planar acoustic array can be used to estimate the full set of flight parameters of a turbo-prop aircraft in transit by measuring the time delay (TD) between the signal received at the reference sensor and the signal received at each of the other two sensors of the array over a sufficiently long period of time. This paper studies the possibility of using instantaneous frequency (IF) measurements from the reference sensor to improve the precision of the flight parameter estimates. A simplified Cramer-Rao lower bound analysis shows that the standard deviations in the estimates of the aircraft velocity and altitude can be greatly reduced when IF measurements are used together with TD measurements. Two flight parameter estimation algorithms that utilize both IF and TD measurements are formulated and their performances are evaluated using both simulated and real data.

Buoyancy Explains How Planes Fly

Buoyancy explains how planes fly. To fly a plane needs to displace a mass of air down equal to its own mass, each second. Planes are effectively floating on a cushion of air that the wings create by pushing air downwards. This is a similar explanation to how boats float according to Archimedes principle of buoyancy, and how birds fly by pushing air downwards. Correspondingly, this theory predicts that for all planes to fly, they must displace a mass of air down equal to its own mass each second. If the current equation for lift is adjusted to include “the distance down that air is displaced by the wing” Then a good estimate of the mass of air displaced by the wing (and thus buoyancy), is provided. Hence, the proposed new equation for lift is: Lift (Force) = Air Mass Displaced each second × Aircraft Velocity (i.e. F = mv) This theory is proposed as the current theories of flight have severe limitations and remain unproven. There is no scientific experiment on a real aircraft in realistic conditions that proves any theory to be correct. Pilots, aviation authorities, academics and engineers still debate the different theories of flight whereas; it is possible to prove buoyancy. Current theories of flight ignore buoyancy. This theory of flight has been presented to numerous pilots, engineers, and academics. No one has been able to provide a valid scientific argument or evidence to disprove it.

Aircraft localization using a passive acoustic method. Experimental test

A passive acoustic method for aircraft localization is experimentally tested in this paper. The method relies on the Doppler effect influencing the signals received by a mesh of microphones distributed over the acoustic area of interest. The relative Doppler stretch factors between the microphone signals are estimated using a one-dimensional version of the Ambiguity function. Then, a Genetic Algorithm is used to solve the non-linear system of equations that relates the aircraft's position and velocity to this relative stretch factors. This method is used in this study to locate a radio controlled airplane equipped with a Global Positioning System (GPS). Seven microphones are distributed in the airfield area. Although the localization errors are influenced by the uncertainty in the microphones position, the acoustic system succeeds at locating the airplane.

Choice of Measurement Scale for Evaluating Compliance of the Vertical Landing Velocity of Aircraft with Established Specifications

A scheme is proposed for correct analysis of the results of measurements in the concept of acceptable risk. The three basic methods for estimating the probability of finding a measured characteristic (nonparametric and parametric tolerance intervals and separate confirmation of specifications for the mathematical expectation and dispersion) within tolerance for different scales are compared for the example of measuring the accuracy characteristics of automatic aircraft landing systems. Recommendations are given for the use of the proposed methods and for the required number of measurements.

Dynamic modeling for a morphing aircraft and dynamic characteristics analysis

The physical model of a variable-span variable-sweep morphing aircraft was simplified. Based on Kane's method,the morphing movements were assumed to be controllable known input,and the wings' movements were expressed by constraint equations. The six components of the translational velocity and the angular velocity of the morphing aircraft's body in the body coordinate frame were selected as the generalized speeds. Six degree-of-freedom dynamic model was built. Additional forces and additional moments were defined to describe the dynamic influence imposed on the morphing aircraft by the morphing movement. The simulation results show that,in the condition of steady-state flight,the additional forces and moments cased by the wings' morphing are small compared to the variations of aerodynamic forces. The aircraft's longitudinal dynamic responses during the morphing process are simulated and analyzed at different morphing speeds. Results show that the aircraft 's height,velocity and pitch angle will change considerably during morphing process.

Airborne internet access through submarine optical fiber cables

Internet access for passengers travelling in aircrafts is thought to be one of the unresolved major challenges for ubiquitous Internet provision. Vast oceanic remote regions along the busy air routes of the world require low-cost, reliable, and high-speed Internet for the aircraft. Satellite links can provide Internet coverage in such remote areas; however, their services are still costly with low bandwidth and longer delays. Fortunately, the submarine optical cables deployed across the oceans pass along the same busy air routes. These cables can be utilized as high-speed Internet backbone for wireless Internet access to the aircraft. Dedicated ships stationed along these submarine optical fiber cables can be exploited to provide Internet, security, and navigation services to aircrafts and ships. A novel architecture for such a ground/sea-to-air access network is proposed. A complete solution, design, and analysis of the proposed technique are thoroughly discussed. In contrast to the traditional land mobile radio cellular systems, the high speed of the aircraft results in reduced available handover time margins. To address the challenges related to the high-speed mobility of aircraft, an analysis for the impact of various parameters on the performance of handovers is presented. Using the proposed analytical model, a mathematical relation for the handover margin with the velocity of aircraft, direction of the aircraft’s motion, and propagation environment is derived on the basis of path-loss propagation model.

A Simulation of Signal Collisions over the North Atlantic for a Spaceborne ADS-B Receiver Using Aloha Protocol

Automatic Dependent Surveillance-Broadcast (ADS-B) is an air traffic surveillance system in which aircraft broadcast GPS position, velocity and status on 1090 MHz at random intervals between 0.4 and 0.6 seconds. ADS-B networks for air traffic monitoring have been implemented worldwide, but ground stations cannot be installed in oceanic regions, leaving these areas uncovered. A solution for tracking aircraft over the ocean is through the monitoring of ADS-B signals by using spaceborne receivers. The Royal Military College of Canada has developed an ADS-B receiver that is scheduled to fly as a technology demonstrator on the Canadian Advanced Nanospace eXperiment-7 (CanX-7) nanosatellite. The payload will collect ADS-B data over the North Atlantic that will be compared to truth data provided by air traffic services. A potential issue for the CanX-7 payload is signal collisions. The extended footprint of the satellite coverage means that a large number of aircraft may be in view at any one time, leading to ADS-B messages that arrive simultaneously at the receiver not being decoded. A simulation of CanX-7 passage over the operations area was carried out to calculate the probability of signal collisions. Using the Aloha Protocol, it was determined that the loss of information as a result of signal collisions is well within the standards of ground based radars used by air traffic system agencies.

Comparison of Aircraft Tire Wear with Initial Wheel Rotational Speed

The impact an aircraft has on its tires when it lands has been problematic practically since the invention of the airplane. Upon touchdown, the tires frequently smoke as rubber burns off and tire material is worn away while the tires slip up to a steady rolling speed. To minimise tire slip, torque or spin mechanisms could be added to each tire assembly to accelerate the tire to match the landing speed. Patents have been registered since the 1940s to improve tire safety and performance, decrease the substantial wear that results from every landing, and save airline companies the cost of regularly replacing expensive worn tires and to clean tarmacs. In this paper, a case study is presented of a Boeing 747-400 aircraft touching down on a runway and its wheels spinning up to match the forward speed of the aircraft as it rolls along the runway. A LuGre friction model is employed to simulate the dynamic behaviour of the tires during a typical landing, and Archard wear theory is used to compare tire wearing between initially static and pre-spun wheels. We conclude that the amount of rubber worn from the tire on each landing is proportional to the kinetic energy that the wheel must gain to reach a free-rolling velocity. Therefore tire wear is proportional to the square of the initial difference between wheel speed and horizontal aircraft velocity.

The Geolocation Accuracy of Lidar Footprint

This paper describes the geometric geolocation accuracy of LiDAR footprint, utilizing an aircraft configuration that supports a sensor designed to scan the surface of the Earth, a DGPS and INS/IMU system. It is presented a review of LiDAR’s footprints accuracy as a relationship between the input parameters, which include errors of the orbital state, attitude information of the aircraft and the look vector errors of the active sensor (LiDAR scanner), that give us the coordinates of the point of intersection of the line of sight scanning system and the Earth's surface as a function of: terrestrial ellipsoid surface, aircraft position, aircraft velocity, aircraft attitude (spatial situation) and the orientation of the LiDAR scanner. Using the derived error formulas, based on the accuracy of the navigation solution, the boresight misalignment angles, the ranging and scan angle accuracy, and laser beam divergence, the achievable point positioning accuracy can be computed for any given LiDAR system which operates at different flying heights between 70 m - 6,000 m.

Transition from geostrophic turbulence to inertia-gravity waves in the atmospheric energy spectrum.

Midlatitude fluctuations of the atmospheric winds on scales of thousands of kilometers, the most energetic of such fluctuations, are strongly constrained by the Earth's rotation and the atmosphere's stratification. As a result of these constraints, the flow is quasi-2D and energy is trapped at large scales—nonlinear turbulent interactions transfer energy to larger scales, but not to smaller scales. Aircraft observations of wind and temperature near the tropopause indicate that fluctuations at horizontal scales smaller than about 500 km are more energetic than expected from these quasi-2D dynamics. We present an analysis of the observations that indicates that these smaller-scale motions are due to approximately linear inertia-gravity waves, contrary to recent claims that these scales are strongly turbulent. Specifically, the aircraft velocity and temperature measurements are separated into two components: one due to the quasi-2D dynamics and one due to linear inertia-gravity waves. Quasi-2D dynamics dominate at scales larger than 500 km; inertia-gravity waves dominate at scales smaller than 500 km.

Traffic monitoring with noise: Investigations on an urban seismic network

Traffic in urban areas generates not only acoustic noise but also much seismic noise. The latter is typically not perceptible by humans but could, in fact, offer an interesting data source for traffic information systems. To explore the potential for this, we study a 5300 geophone network, which covered an area of over 70 km2 in Long Beach, CA, and was deployed as part of a hydrocarbon industry survey. The sensors have a typical spacing of about 100 m, which presents a two-sided processing challenge here: signals beyond a few receiver spacings from the sources are often strongly attenuated and scattered whereas nearby receiver signals may contain complicated near-field effects. We illustrate how we address this issue and give three simple applications: counting cars on a highway section, classifying different types of vehicles passing along a road, and measuring time and take-off velocity of aircraft at Long Beach airport. We discuss future work toward traffic monitoring and also possible connections with acoustical problems.

Dynamics and heat and mass transfer under spreading of liquid-droplet aviation fuel in the atmosphere

A physical-mathematical model of dynamics and heat and mass transfer during spreading of liquid-droplet aviation fuel in the atmosphere is presented. The optimal emergency discharge height of kerosene for different Russian regions was evaluated based on the proposed mathematical model. The developed model can be used to select the height limit of reset kerosene, guaranteeing complete evaporation of the droplets in the atmosphere to the different aircraft velocities.

An Efficient Broadcast Authentication Scheme with Batch Verification for ADS-B Messages

As a cornerstone of the next generation air traffic management (ATM), automatic dependent surveillance-broadcast (ADS-B) system can provide continual broadcast of aircraft position, identity, velocity and other messages over unencrypted data links to generate a common situational awareness picture for ATM. However, since ADS-B messages are unauthenticated, it is easy to insert fake aircrafts into the system via spoofing or insertion of false messages. Unfortunately, the authentication for ADS-B messages has not yet been well studied. In this paper, we propose an efficient broadcast authentication scheme with batch verification for ADS-B messages which employs an identity-based signature (IBS). Security analysis indicates that our scheme can achieve integrity and authenticity of ADS-B messages, batch verification, and resilience to key leakage. Performance evaluation demonstrates that our scheme is computationally efficient for the typical avionics devices with limited resources, and it has low communication overhead well suitable for low-bandwidth ADS-B data link.

A novel Whole Air Sample Profiler (WASP) for the quantification of volatile organic compounds in the boundary layer

Abstract. The emission and fate of reactive volatile organic compounds (VOCs) is of inherent interest to those studying chemical biosphere–atmosphere interactions. In-canopy VOC observations are obtainable using tower-based samplers, but the lack of suitable sampling systems for the full boundary layer has limited the availability of data characterizing the vertical structure of such gases above the canopy height and still in the boundary layer. This is an important region where many reactive VOCs are oxidized or otherwise removed. Here we describe an airborne sampling system designed to collect a vertical profile of air into a 3/8 in. OD (outer diameter) tube 150 m in length. The inlet ram air pressure is used to flow sampled air through the tube, which results in a varying flow rate based on aircraft speed and altitude. Since aircraft velocity decreases during ascent, it is necessary to account for the variable flow rate into the tube. This is accomplished using a reference gas that is pulsed into the air stream so that the precise altitude of the collected air can be reconstructed post-collection. The pulsed injections are also used to determine any significant effect from diffusion/mixing within the sampling tube, either during collection or subsequent extraction for gas analysis. This system has been successfully deployed, and we show some measured vertical profiles of isoprene and its oxidation products methacrolein and methyl vinyl ketone from a mixed canopy near Columbia, Missouri.