Analysis of the aircraft performance at cruise altitude within the tropopause layer

Analysis of the aircraft performance at cruise altitude within the tropopause layer

Measurements and models of the spatiotemporal variability of surface N2O mixing ratios and isotopic compositions are increasingly used to constrain the global N2O budget. However, large variability observed on the small spatial scales of soil chambers and shipboard sampling, which appears to be very sensitive to local environmental conditions, has made extrapolation to the global scale difficult. In this study, we present measurements of the isotopic composition of N2O (δ15Nbulk, δ15Nα, δ15Nβ, and δ18O) from whole‐air samples collected at altitudes of 0.5 to 19km by the NASA DC‐8 and WB‐57 aircraft during the Costa Rica‐Aura Validation Experiment (CR‐AVE) and the Tropical Composition, Cloud and Climate Coupling Experiment (TC4) campaigns in January–February 2006 and July–August 2007, respectively. The vertical profiles of isotopic composition showed predictable, repeating patterns consistent with the influence of a surface source at lower altitudes and the influence of stratospheric photochemistry in the lower stratosphere. Their correlations with marine tracers at lower altitudes are consistent with a predominantly oceanic source, although a soil source cannot be ruled out. Measurements in a combustion plume revealed a strong depletion in 15N at the central nitrogen atom (i.e., low δ15Nα values), providing new information on N2O isotopic compositions from combustion. This new data set demonstrates that a coherent picture of the isotopic composition of tropospheric N2O is possible at currently attainable precisions and that its variations from 0.5 km to the lower stratosphere are a useful tool in investigating the sources and distributions of this important greenhouse gas.

Abstract. We present in situ measurements of the trace gas composition of the upper tropospheric (UT) Asian summer monsoon anticyclone (ASMA) performed with the High Altitude and Long Range Research Aircraft (HALO) in the frame of the Earth System Model Validation (ESMVal) campaign. Air masses with enhanced O3 mixing ratios were encountered after entering the ASMA at its southern edge at about 150 hPa on 18 September 2012. This is in contrast to the presumption that the anticyclone's interior is dominated by recently uplifted air with low O3 in the monsoon season. We also observed enhanced CO and HCl in the ASMA, which are tracers for boundary layer pollution and tropopause layer (TL) air or stratospheric in-mixing respectively. In addition, reactive nitrogen was enhanced in the ASMA. Along the HALO flight track across the ASMA boundary, strong gradients of these tracers separate anticyclonic from outside air. Lagrangian trajectory calculations using HYSPLIT show that HALO sampled a filament of UT air three times, which included air masses uplifted from the lower or mid-troposphere north of the Bay of Bengal. The trace gas gradients between UT and uplifted air masses were preserved during transport within a belt of streamlines fringing the central part of the anticyclone (fringe), but are smaller than the gradients across the ASMA boundary. Our data represent the first in situ observations across the southern part and downstream of the eastern ASMA flank. Back-trajectories starting at the flight track furthermore indicate that HALO transected the ASMA where it was just splitting into a Tibetan and an Iranian part. The O3-rich filament is diverted from the fringe towards the interior of the original anticyclone, and is at least partially bound to become part of the new Iranian eddy. A simulation with the ECHAM/MESSy Atmospheric Chemistry (EMAC) model is found to reproduce the observations reasonably well. It shows that O3-rich air is entrained by the outer streamlines of the anticyclone at its eastern flank. Back-trajectories and increased HCl mixing ratios indicate that the entrained air originates in the stratospherically influenced TL. Photochemical ageing of air masses in the ASMA additionally increases O3 in originally O3-poor, but CO-rich air. Simulated monthly mean trace gas distributions show decreased O3 in the ASMA centre only at the 100 hPa level in July and August, but at lower altitudes and in September the ASMA is dominated by increased O3. The combination of entrainment from the tropopause region, photochemistry and dynamical instabilities can explain the in situ observations, and might have a larger impact on the highly variable trace gas composition of the anticyclone than previously thought.

PurposeTemperature anomalies in the upper troposphere have become a reality as a result of global warming, which has a noticeable impact on aircraft performance. The purpose of this study is to investigate the total air temperature (TAT) anomaly observed during the cruise level and its impact on engine parameter variations.Design/methodology/approachEmpirical methodology is used in this study, and it is based on measurements and observations of anomalous phenomena on the tropopause. The primary data were taken from the Boeing 747-8F's enhanced flight data recorder, which refers to the quantitative method, while the qualitative method is based on a literature review and interviews. The GEnx Integrated Vehicle Health Management system was used for the study's evaluation of engine performance to support the complete range of operational priorities throughout the entire engine lifecycle.FindingsThe study's findings indicate that TAT and SAT anomalies, which occur between 270- and 320-feet flight level, have a substantial impact on aircraft performance at cruise altitude and, as a result, on engine parameters, specifically an increase in fuel consumption and engine exhaust gas temperature values. The TAT and Ram Rise anomalies were the focus of the atmospheric deviations, which were assessed as major departures from the International Civil Aviation Organizations–defined International Standard Atmosphere, which is obvious on a positive tendency and so goes against the norms.Research limitations/implicationsNecessary fixed flight parameters gathered from the aircraft's enhanced airborne flight recorder (EAFR) via Aeronautical Radio Incorporated (ARINC) 664 Part 7 at a certain velocity and altitude interfacing with the diagnostic program direct parameter display (DPD), allow for analysis of aircraft performance in a real-time frame. Thus, processed data transmits to the ground maintenance infrastructure for future evaluation and for proper maintenance solutions.Originality/valueA real-time analysis of aircraft performance is possible using the diagnostic program DPD in conjunction with necessary fixed flight parameters obtained from the aircraft's EAFR via ARINC 664 Part 7 at a specific speed and altitude. Thus, processed data is transmitted to the ground infrastructure for maintenance to be evaluated in the future and to find the best maintenance fixes.

With the integration of unmanned aircraft systems into the U.S. National Airspace System, low altitude regions are being stressed in historically new ways. The FAA must understand and quantify the risk of UAS collision with manned aircraft during desired low altitude unmanned operations in order to produce regulations and standards. A key component of these risk assessments are statistical models of aircraft flight. Previous risk assessments used models for manned aircraft based primarily on Mode C-based secondary surveillance radar observations. However, these models have some important limitations when used at low altitude. We demonstrate a methodology for developing statistical models of low altitude manned flight or applicable at low altitudes that leverages the OpenSky Network, a crowdsourced ADS-B receiver network that provides open access to the aircraft data, and the FAA aircraft registry, an open database of registered aircraft. Unlike Mode C surveillance, a key advantage to this method is the availability of necessary metadata to distinguish between different types of low altitude aircraft. For example, previous models did not discriminate a large commercial aircraft transiting to higher altitudes from low altitude or small general aviation aircraft cruising at low altitudes. We use an aircraft's unique Mode S address to correlate ADS-B reports with aircraft type information from the FAA registry. We filter surveillance data and statistically characterize the low altitude airspace based on aircraft type, performance, and location. Lastly, we leverage the characterization and aircraft tracks to develop a Dynamic Bayesian Network that models the behavior of low altitude manned aircraft, an extension of previous aircraft modeling approaches that have employed Bayesian networks. By sampling representative trajectories from the Bayesian network, we can model encounters between manned and unmanned aircraft at low altitudes to assess collision risk, a key supporting technology to support safe integration of unmanned aircraft.

This paper presents the development and application of an integrated, higher-fidelity framework developed within CHARM (the Cranfield Hybrid electric Aircraft Model) for the design, performance analysis and overall evaluation of novel electrified propulsion systems. The developed framework is used to model and analyze the performance characteristics of a Fuel Cell (FC) regional aircraft system in comparison with a conventional regional aircraft and a hydrogen gas turbine regional aircraft retrofit. The FC propulsion system and the hydrogen gas turbine are retrofitted to the same conventional aircraft platform. Physics-based aircraft performance calculations, propeller maps, gas turbine component maps, off-design cycle analysis, electric component maps, calculations for the electric power management and distribution, and a Proton-Exchange Membrane FC (PEMFC) configuration sized to cover the power requirements of a regional aircraft, are integrated within this framework to capture the performance and interaction of components, sub-systems and aircraft during any flight mission and conditions. The aircraft performance, the propulsion system performance characteristics and the emissions of the three technologies are calculated and discussed to understand the challenges and opportunities of using hydrogen-electric propulsion (FC). The effect of capturing the variable mission parameters and flight phases on the performance of the electric power system and FC is presented and compared against a lower fidelity modeling approach for the electric powertrain. The sensitivity of the FC propulsion system and its attributes to varying mission requirements (island-hopping, range, cruise altitude, ambient conditions), as well as the change in the consumed fuel, are demonstrated. This framework can be used to inform the decision-making for the design of electric components and thermal management systems (TMS), and the importance of capturing the trade-off between mass, efficiency and operational constraints in the design process is highlighted. Also, the off-design performance of the electric power system designs and FC is modeled to decide if the design is within acceptable limits under various conditions, and capture the effect of mission requirements and flight conditions on the energy consumption of the overall aircraft system. Finally, a parametric analysis addresses the effect of power density improvement with future technology on the energy per passenger and feasibility of the FC regional aircraft.

Usually, in traditional Inverse Synthetic Aperture Radar (ISAR) systems design and mode selection for space satellite targets, coherent integration gain in azimuth direction hardly can be analyzed, which depends on target’s motion. In this study, we combine the target orbit parameters to determine its motion relative to radar and deduce coherent integration equation in ISAR imaging to realize the selection of imaging intervals based on coherent integration, which can ensure the resolution in azimuth direction. Meanwhile, we analyze the influence of target orbit altitude to echo power and imaging Signal-to-Noise Ratio (SNR) that provides a new indicator for space observation ISAR systems design. The result of simulation experiment illustrates that with target orbit altitude increasing, coherent integration gain in azimuth direction of large-angular observation offsets the decreasing of imaging SNR in a degree, which provides a brand-new perspective for space observation ISAR systems and signal processing design.

The objective of this paper is to study the performance of a low altitude long endurance UAV. One of the important aspects of performance analysis is the optimal speeds for maximum endurance and/or maximum range. With DATCOM method, although the drag coefficient of the UAV can be determined, the resulted maximum endurance is found to be much longer than the data obtained from the flight tests. The problem is caused by the landing gears of which the drag is not counted in the DATCOM analysis. To eliminate the error, by referring to results of flight tests, a correction method for the drag coefficient to include the effect of the landing gears is suggested and the optimal cruise speeds for the maximum endurance and the maximum range are determined accordingly. It is found that the speeds should be as slow as possible. This result is quite different from the typical case in which the optimal speed usually lies in between the minimum and the maximum possible ones.

Unmanned aerial vehicles (UAV) are a useful supplement to traditional synthetic aperture radar (SAR) platforms. In some cases, UAV-based SAR systems have to fly at low altitude. In this case, range-dependent phase errors due to platform motion affect the imaging quality. To solve the problem of motion compensation, an angle-dependent model and a second-order range-dependent model are introduced into autofocusing by previous researchers, but the first one relies too much on the geometric angle while the latter has limited fitting order for solution. We present a higher order range-dependent model, which can approximate analytical solution. Nevertheless, an increase in the fitting order makes the matrix in this model underdetermined. Based on the theoretical proof, this higher order model can be tackled by exploitation of compressive sensing (CS) theory. A CS reconstruction of higher order fitting coefficients is performed in the experiments, and corresponding performance analysis is given. Finally, the range-dependent phase error is compensated under the condition of low altitude.

: Enemy air defenses have increased their sophistication due to technological advancements. Response to these advancements requires new tactics and procedures to increase the B-52's chances of penetrating such air defenses. One such possible tactic is low altitude air refueling or LAAR. This article examines the need for LAAR and assesses the US Air Forces's ability to satisfy that need. Capabilities of the US military's air refueling aircraft are analyzed. The effects of low altitude flight on the KC-135's airframe, autopilot, navigation systems, and aircraft performance are examined. Finally the article discusses the degree to which LAAR missions impact on operational and maintenance organizations so tasked. Keywords: Systems analysis; Air Force planning.

This paper introduces an approach to aircraft design and analysis that focuses on the evaluation of aircraft as multi-state systems, where a multi-state system is one having a finite set of performance levels or ranges, differentiated in this case by distinct levels of failure. In order to accurately examine numerous aircraft performance states, a multidisciplinary design model was used, consisting of an open-source 6-DoF flight simulator integrated with a vortex lattice aerodynamics solver and a MATLAB routine for calculation of weights and inertias. The primary impetus for using a flight simulator run in batch mode was to facilitate a global approach for concurrent analysis of aircraft expected performance and availability. Namely, by allowing systematic calculation of performance metrics for differing aircraft states, the relationship between an aircraft’s global design variables and its performance and availability may be established. Such an approach allows designers to identify those elements that might drive system loss probability through an analysis of performance changes across system states and their respective sensitivity to design variables.

Community Initiative for Cellular Earth Remote Observation (CICERO) is a planned constellation of low-earth-orbiting 6U cubeSats for performing GNSS radio occultation (RO) of Earth’s atmosphere and surface. The goal of CICERO is to provide the first and high-quality commercial radio occultation data from space at low costs while enhancing weather and climate forecasting capabilities. Before CICERO data are used for reliable weather forecasting, the assessment of its performance is necessary. This study shows the performance of CICERO by comparing it with that of COSMIC I. The performance analysis was carried out with respect to geographic distribution, altitude distribution, and refractivity error. The results show that CICERO can acquire global coverage of data at low altitudes as well as COSMIC I, which is important for climate research. In addition, the analysis of refractivity error and its impact on temperature demonstrates that the miniature version of the GNSS RO receiver could satisfy certain accuracy requirements of the GNSS RO measurements. Thus, the cubeSat constellation CICERO can provide radio occultation measurements comparable to those of the COSMIC I mission. The study demonstrates the capabilities of nanosat-based LEO cubeSats to improve data obtainability and accuracy for weather forecasting.

Line-of-sight (LoS) path is essential for the reliability of air-to-ground (A2G) communications, but the existence of the LoS path is difficult to predict due to random obstacles on the ground. Based on the statistical geographic information and Fresnel clearance zone, a general stochastic LoS probability model for 3-D A2G channels under urban scenarios is developed. By considering the factors, that is, building height distribution, building width, building space, carrier frequency, and transceiver’s heights, the proposed model is suitable for different frequencies and altitudes. Moreover, in order to get a closed-form expression and reduce the computational complexity, an approximate parametric model is also built with the machine-learning (ML) method to estimate the model parameters. The simulation results show that the proposed model has good consistency with existing models at low altitude. When the altitude increases, it has a better performance by comparing with that of the ray-tracing (RT) Monte-Carlo simulation data. The analytical results of the proposed model are helpful for the channel modeling and performance analyses such as cell coverage, outage probability, and bit error rate in A2G communications.

This paper presents and investigates a dual-hop mixed radio frequency (RF) and underwater optical communication (UWOC) system. In the proposed system, an unmanned aerial vehicle (UAV) such as drone (S) located at low altitude is transmitting data signal towards the destination (D) which is located under water such as a submarine through a decode and forward (DF) relay (R) mounted on a ship over the sea surface. The data signal is transmitted from the UAV towards the relay located on the ship via RF channel modelled by the Nakagami- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ m$</tex-math></inline-formula> distributed fading statistics. The relay decodes the received RF data signal and re-transmits it towards the destination via visible light channel modelled by Exponential Generalized Gamma (EGG) distribution. Using the DF relaying protocol, we derive closed form analytical expressions for the outage probability and average bit error rate of the proposed mixed RF-UWOC system. Additionally, UAV optimal altitude analysis has been carried out to find the optimal elevation angle corresponding to the optimal altitude of the UAV where the system performance is maximized. The numerical simulation is carried out to support the performance analysis of the mixed RF-UWOC system and shows the influence of the various channel parameters such as air bubbles, UAV altitude, water salinity variations and scintillation on the end to end performance of the mixed RF-UWOC system.

Several MCAO systems are under study to improve the angular resolution of the current and of the future generation large ground-based telescopes (diameters in the 8-40 m range). The subject of this PhD Thesis is embedded in this context. Two MCAO systems, in dierent realization phases, are addressed in this Thesis: NIRVANA, the 'double' MCAO system designed for one of the interferometric instruments of LBT, is in the integration and testing phase; MAORY, the future E-ELT MCAO module, is under preliminary study. These two systems takle the sky coverage problem in two dierent ways. The layer oriented approach of NIRVANA, coupled with multi-pyramids wavefront sensors, takes advantage of the optical co-addition of the signal coming from up to 12 NGS in a annular 2' to 6' technical FoV and up to 8 in the central 2' FoV. Summing the light coming from many natural sources permits to increase the limiting magnitude of the single NGS and to improve considerably the sky coverage. One of the two Wavefront Sensors for the mid- high altitude atmosphere analysis has been integrated and tested as a stand- alone unit in the laboratory at INAF-Osservatorio Astronomico di Bologna and afterwards delivered to the MPIA laboratories in Heidelberg, where was integrated and aligned to the post-focal optical relay of one LINC-NIRVANA arm. A number of tests were performed in order to characterize and optimize the system functionalities and performance. A report about this work is presented in Chapter 2. In the MAORY case, to ensure correction uniformity and sky coverage, the LGS-based approach is the current baseline. However, since the Sodium layer is approximately 10 km thick, the articial reference source looks elongated, especially when observed from the edge of a large aperture. On a 30-40 m class telescope, for instance, the maximum elongation varies between few arcsec and 10 arcsec, depending on the actual telescope diameter, on the Sodium layer properties and on the laser launcher position. The centroiding error in a Shack-Hartmann WFS increases proportionally to the elongation (in a photon noise dominated regime), strongly limiting the performance. To compensate for this effect a straightforward solution is to increase the laser power, i.e. to increase the number of detected photons per subaperture. The scope of Chapter 3 is twofold: an analysis of the performance of three dierent algorithms (Weighted Center of Gravity, Correlation and Quad-cell) for the instantaneous LGS image position measurement in presence of elongated spots and the determination of the required number of photons to achieve a certain average wavefront error over the telescope aperture. An alternative optical solution to the spot elongation problem is proposed in Section 3.4. Starting from the considerations presented in Chapter 3, a first order analysis of the LGS WFS for MAORY (number of subapertures, number of detected photons per subaperture, RON, focal plane sampling, subaperture FoV) is the subject of Chapter 4. An LGS WFS laboratory prototype was designed to reproduce the relevant aspects of an LGS SH WFS for the E-ELT and to evaluate the performance of different centroid algorithms in presence of elongated spots as investigated numerically and analytically in Chapter 3. This prototype permits to simulate realistic Sodium proles. A full testing plan for the prototype is set in Chapter 4.