Air Data Probes Research Articles

Robust fault detection and diagnosis of primary air data sensors in the presence of atmospheric turbulence

Abstract This paper presents a fault detection and diagnosis (FDD) algorithm for various faults in the primary air data sensors (PADS) of an aircraft in the presence of external disturbances such as atmospheric turbulence. Rapid wind variations due to turbulence induce excessive error in the externally fitted air data probe measurements, which may lead to loss of control and misinterpretations by the flight crew. In adverse environmental conditions, the FDD of air data prefers robust and adaptive air data estimates that use an analytical redundancy approach with fewer computations. The proposed method considers the kinematics of the aircraft instead of the dynamics used in the state-of-the-art algorithms. The advantage of using kinematics is that it can reduce modeling errors significantly, avoiding high false alarm rates in the FDD process. For the estimation of stable and accurate air data under external disturbance, the inertial navigation system and global positioning system (INS/GPS) output are considered instead of actual air data probe or sensor measurements. The proposed algorithm uses estimates of air data using an exponentially weighted adaptive extended Kalman filter (EW-AEKF) to detect and diagnose PADS faults, which can perform well even in the presence of uncertain noise due to atmospheric turbulence experienced during flight. The simulation was carried out to validate the algorithm with flight data obtained from the X-Plane flight simulator under moderate atmospheric turbulence. The simulation experiments were carried out using the MATLAB programming platform. The results show that the proposed method achieves satisfactory FDD performance with lower root mean square error (RMSE) and computation time than traditional EKF-based algorithms.

High Ice Water Content Conditions Associated with Wintertime Elevated Convection in the Midwest

AbstractAircraft flying through areas of high ice water content (HIWC) can experience engine damage and/or failure. HIWC is typically associated with convection and the microphysical properties of tropical oceanic and coastal convection are well documented as a result of several field campaigns in the past decade. HIWC appears to be less common in extratropical convection, but instances of HIWC-related aircraft issues have been recorded in extratropical weather, even during winter. The present study documents the microphysical properties of HIWC between −25° and 0°C and the meteorological and thermodynamic conditions around that HIWC from five flights from the In-Cloud Icing and Large-Drop Experiment (ICICLE) in the midwestern United States in February 2019. All five cases contained elevated convection above a strong low-level temperature inversion. Values for top-of-inversion mixing ratios and total column precipitable water were about 5 g kg−1and 20 mm, respectively, according to soundings near each case. A maximum ice water content of 2.1 g m−3was observed over a length scale of about 500 m, and ice particle size distributions had mean volume equivalent diameters around 1000μm. Supercooled drizzle droplets were also observed in the vicinity of the HIWC, raising questions about the possible role of secondary ice production via the freezing and shattering of supercooled large droplets in HIWC formation. The generalizability of these results is limited by the small number of cases, but they provide some of the first in situ observations of extratropical winter HIWC and highlight the need for continued research on these conditions.Significance StatementHigh ice water content (HIWC) conditions can cause engine damage, stall, and failure in aircraft and can cause air data probes to report erroneous values. Most research on HIWC has focused on tropical convection. This paper serves to draw more attention to the aviation hazard posed by extratropical winter HIWC and the need for additional research into these environments. The cases examined also contained supercooled precipitation-sized liquid droplets. Combined with other recent research, these observations may help to motivate laboratory experiments investigating the role of secondary ice production via droplet freezing and shattering in the formation of HIWC.

플러쉬형 대기 자료 프로브 주위의 다상유동과 복합 열전달 전산해석

An air data probe is an important apparatus for measuring flight speed and altitude during flight. The tip of the probe could be blocked by ice, thus leading to malfunction and dangerous situations. In this study, multiphase flow and conjugate heat transfer around a flush-type air data problem were analyzed using COMSOL multiphysics software. For the validation, the numerical results of the L-type pitot probe were compared to the experimental data. The comparison between the results obtained by the single-phase and multiphase flow simulations showed that the surface temperature at the inlet region of the flush-type probe decreased in the multiphase flow due to the increased loss of heat. Moreover, the pressure fields around the flush-type probe were found to be slightly different in the single-phase and multiphase flow simulations. This indicates that the conjugate heat transfer analysis of the multiphase flow is required to evaluate the pressure, surface temperature, and power output of the flush-type probe.

항공기 대기자료 시스템의 방빙 소요전력량 산정을 위한 다물리 전산해석

Aircraft air data systems provide important information necessary for the operation and control of aircraft, such as speed, altitude, and temperature. Air data probes are mainly located in front of aircraft or outside such as nose and wing and are directly affected by icing. Therefore, it is important to design an anti-icing system to prevent icing in the air data probe. Compared to costly icing tests, icing and anti-icing simulations using computational fluid dynamics are very effective. In this study, the most critical icing condition was selected by performing ice accretion simulations for various icing conditions experienced by the aircraft air data system. In addition, the amount of power required for anti-icing was calculated under various icing conditions through multiphysics computational simulation, and the tendency of the amount of power required was analyzed.

Design and Integration of a Dual Redundancy Air Data System for Unmanned Air Vehicles

Air data systems measure airspeed, pressure altitude, angle of attack and angle of sideslip. These measurements are essential for operating flight control laws to ensure safe flights. Since the loss or corruption of air data measurements is considered as catastrophic, a high level of operational reliability needs to be achieved for air data systems. In the case of unmanned air vehicles, failure of any of air data sensors is more critical due to the absence of onboard pilot decision aid. This paper presents design of a dual redundancy air data system and the integration process for an unmanned air vehicle. The proposed dual-redundant architecture is based on two independent air data probes and redundancy management by central processing in two independent flight control computers. Starting from unit testing of single air data sensor, details are provided of system level tests used to meet overall requirements. Test results from system integration demonstrate the efficiency of the proposed process. Keywords: ëŒ€ê¸°ìžë£Œì‹œìŠ¤í œ, 이중화설계, 체계통합, ëŒ€ê¸°ìžë£Œë³´ì • Keywords: Air Data System, Dual Redundancy Design, System Integration, Air Data Calibration

NRC particle detection probe: test cell to flight

Purpose High-altitude ice crystals (HAICs) are causing one in-flight event or more per month for commercial aircraft. The effects include preventing air data probes (pitot pressure and total air temperature in particular) from functioning correctly and causing engines to roll back and shut down. The purpose of this study is to describe the process used by the National Research Council Canada (NRC) to develop and test a particle detection probe (PDP). The probe mounts on the fuselage of aircraft to sense and quantify the ice crystals in the environment. Design/methodology/approach The probe was demonstrated on the NRC Convair and Airbus A340 research aircraft as part of the European Union HAIC programme. The probe was ruggedised, adapted for easy installation in standard aircraft fittings and tested in a variety of conditions for longevity and endurance. Findings Efforts to achieve the safety requirements for flight on aircraft are discussed. The challenges, surprises and opportunities for testing on which the development group is capitalised are also presented. Practical implications It was demonstrated that the detectors gave signals proportional to the ice crystal content of clouds, and results demonstrating the functionality of the probe are presented. Originality/value This paper describes the multi-year process of developing the NRC PDP from a test cell sensor for detecting engine exhaust contaminants on an aircraft ice crystal detection probe. The work included over 20 flight tests on NRC aircraft and the Airbus HAIC test programme.

An innovative analytic redundancy approach to air data sensor fault detection

ABSTRACTThis article presents a potential analytic redundancy approach to detect faults in the air data sensor of an aircraft. In modern aircraft, fault detection of air data sensors is performed using a complex voting mechanism, which requires the availability of redundant air data sensor in all situations. However, to continuously monitor operation and performance of these sensors, the analytic redundancy-based air data estimation and fault detection is highly preferred than estimation with air data probe measurements. The proposed algorithm uses the kinematics of aircraft to estimate air data and detect air data sensor fault. In this paper, a simple mathematical model is developed, which does not consider the forces and moments acting on aircraft and uses measurements only from the Inertial Measurement Unit (IMU) and Navigation System Data (NSD). In order to implement this approach, the Iterated Optimal Extended Kalman Filter (IOEKF) is developed to estimate air data, which provides an accurate and stable estimation. With the estimated states, the physical air data sensor measurements are compared and the residual is calculated to track each sensor performance and to detect the occurrence of a fault. The key advantage of this approach is that it does not require complex dynamic equations and is free from system uncertainties. The proposed algorithm is simulated in MATLAB software using flight simulator flight data and validated using the real-time flight data of Cessna Citation II transport aircraft.

Total air temperature anomalies as a metric for detecting high-altitude ice crystal events: Development of a failure indicator heuristic

High-Altitude Ice Crystals (HAIC) constitute a hazard to commercial aircraft flying near deep convective weather due to jet-engine power loss and air data probes malfunction. HAIC can stick to warm metal surfaces in jet-engines and cause engine surge, stall, flameout and rollback, power loss, as well as engine compressor damage due to ice shedding. Along with these events, disruption to aircraft systems are noted when HAIC are ingested into air data probes (Pitot tube and/or Total Air Temperature -TAT- sensor), causing erroneous measurements of temperature and air speed. Particularly, the TAT probe incorrectly reporting zero degrees Celsius or in error is known to be evidence of ice crystals in the atmosphere surrounding the aircraft. These TAT anomalies are due to the accumulation of ice crystals in the TAT sensor, producing a zero degrees Celsius reading, generating failures in airspeed indicators and acting as potential incident/accident precursors.In this paper, TAT events from pilot reports and Flight Data Monitoring (FDM) are analyzed. TAT FDM data analysis covers two types of engines, which are used on short, medium and long-range routes. The study includes eight aircraft fleet types.Based on these analyses, we present a sensor-failure-tolerant heuristic that generates a reliability indicator, founded on the differences between the TAT and the engine's inlet temperature sensors. It aims to provide early warnings to pilots regarding HAIC events and prevent potential data errors and system failures.

Uncertainty of the Ice Particles Median Mass Diameters Retrieved from the HAIC-HIWC Dataset: A Study of the Influence of the Mass Retrieval Method

<div class="section abstract"><div class="htmlview paragraph">In response to the ice crystal icing hazard identified twenty years ago, aviation industry, regulation authorities, and research centers joined forces into the HAIC-HIWC international collaboration launched in 2012. Two flight campaigns were conducted in the high ice water content areas of tropical mesoscale convective systems in order to characterize this environment conducive to ice crystal icing. Statistics on cloud microphysical properties, such as Ice Water Content (IWC) or Mass Median Diameter (MMD), derived from the dataset of in situ measurements are now being used to support icing certification rulemaking and anti-icing systems design (engine and air data probe) activities. This technical paper focuses on methodological aspects of the derivation of MMD. MMD are estimated from PSD and IWC using a multistep process in which the mass retrieval method is a critical step. Complementary to previous studies reporting on MMD values calculated from the HAIC-HIWC dataset, this paper deals with the uncertainty in MMD by comparing two different approaches for the retrieval of the mass-size (m-D) relationship. The analysis encompasses the data collected in the high IWC areas (IWC > 1g.m<sup>-3</sup>) sampled during the two HAIC-HIWC field campaigns. MMD series are computed using three different mass-size relationships and statistical values are compared. Overall, MMD values are in good agreement, at least for two methods although they imply quite different assumptions. On the variability in MMD values at a given temperature level, results show that MMD may vary significantly from one flight to the other, even though MMD series produced with the different mass retrieval methods follow a similar pattern. A strong temperature dependence is observed regardless the assumption on the m-D relationship, making MMD to increase by more than a factor of 2 as temperature increases from -50°C to -10°C. Finally, the influence on calculated MMD of two different definitions for particle size (D<sub>eq</sub> and D<sub>max</sub>) is demonstrated. Generally, MMD computed with D<sub>max</sub> are a few percent larger as compared to MMD calculated from D<sub>eq</sub> definition, supporting the conclusions from previous studies.</div></div>

ON THE IMPACT OF FLIGHT SAFETY CERTIFICATION REQUIREMENTS ON THE AERODYNAMIC EFFICIENCY OF COMMERCIAL AIRPLANES

The article considers the issue of aerodynamics efficiency implementation taking into account certification requirements for flight safety. Aerodynamics efficiency means high aerodynamic performance (depending on the airplane size), aerodynamic performance in cruise flight, high aerodynamic performance at takeoff, as well as lift performance at landing. The author estimated the impact on aerodynamics efficiency of both the requirements for aerodynamics performance and requirements for aircraft systems, noncompliance with which may result in significant change of expected operating conditions. It was shown that the use of supercritical wing profiles may result in flight mode limitations due to failure of the required buffeting capacities. It does not allow engaging all the advantages of aerodynamics layout and requires special design solutions to prevent such cases. There were reviewed certification requirements for flight level pressure altitude accuracy and icing conditions warning sysytem. The research presented the methods of aerodynamic efficiency increase by meeting the requirements for reduced vertical separation minima flights and in icing conditions, including requirements for air data probes. Reduced vertical separation minima flight requirements are met by means of efficient air data probes location. Theoretical methods of flow calculation determine areas on the airplane skin surface where static probes minimize errors depending on angle-of-attack and sideslip. It was shown that if certification requirements are not met and in case of flight out of reduced vertical separation minima area, aerodynamics efficiency is significantly reduced and fuel consumption can be increased by 10% and higher. Suggested approaches implementation allows increasing commercial airplanes competitiveness.

Ice Crystal Sizes in High Ice Water Content Clouds. Part II: Statistics of Mass Diameter Percentiles in Tropical Convection Observed during the HAIC/HIWC Project

AbstractHigh ice water content (IWC) regions in mesoscale convective systems (MCSs) are a potential threat to commercial aviation, as they are suspected to cause in-service engine power-loss events and air data probe malfunctions. To investigate this, the high-altitude ice crystals (HAIC)/high ice water content (HIWC) projects set up a first field campaign in Darwin (Australia) in 2014. The airborne instrumentation was selected to provide the most accurate measurements of both the bulk total water content (TWC), using a specially developed isokinetic evaporator, and the individual ice crystals properties, using particle imaging probes.This study focuses on determining the size ranges of ice crystals responsible for the mass in high IWC regions, defined here as cloud regions with IWC greater than 1.5 g m−3. It is shown that for high IWC areas in most of the encountered MCSs, median mass diameters (MMDs) of ice crystals range from 250 to 500 μm and decrease with increasing TWC and decreasing temperature. At the same time, the mass contribution of the smallest crystals (below 100 μm) remains generally low (below 15%).In contrast, data from two flight missions in a long-lasting quasi-stationary tropical storm reveal that high IWC values can also be associated with MMDs in the range 400–800 μm and peak values of up to 2 mm. Ice crystal images suggest a major growth contribution by vapor deposition (columns, capped columns) even for such larger MMD values.

Ice Crystal Sizes in High Ice Water Content Clouds. Part I: On the Computation of Median Mass Diameter from In Situ Measurements

AbstractEngine and air data probe manufacturers, as well as aviation agencies, are interested in better characterization of high ice water content (HIWC) areas close to thunderstorms, since HIWC conditions are suspected to cause in-service engine power loss and air data events on commercial aircraft. In this context, a collaborative field campaign has been conducted by high-altitude ice crystals (HAIC) and HIWC projects in order to provide ice water content and median mass diameter (MMD) of ice crystals in the HIWC environment.The computation of MMD from in situ measurements relies mainly on the definition of the crystal dimension D and on the relationship, which is used to convert number into mass distributions. The first part of this study shows that MMD can significantly deviate when using different mass–size relationships from the literature. Sensitivity tests demonstrate that MMD is significantly impacted by the choice of β. However, the larger contributor to MMD differences seems to be the choice of the size definition D itself.Since MMDs are quite sensitive to β, this study suggests a generic method for deducing β solely from optical array probes (OAPs) image data for various size definitions. The method is based on simulations of 3D crystal objects projected onto a 2D plane, thereby relating crystal mass to 2D area (projection) and perimeter. The MMD values calculated for different size definitions are quite similar, at least much closer than MMDs derived from different m(D) relationships in the literature.

Direct and indirect lightning tests to the Z11 helicopter radome in China

A 4.8 MV impulse voltage generator and impulse current generators are used to perform lightning simulation on the Z11 helicopter radome. The radome system is composed of lightning diverter strips, air data probe and a 0.5 m long metal structure attached to the radome to simulate the helicopter body. The test facilities, process and the results are presented according to the Chinese CCAR27 standard. This test improved considerably the lightning protection performance of the Z11 radome system by optimizing the diverters. This resulted in successful passing of ground simulated lightning test requirements.

Aerodynamic Damping Analysis of a Vane-type Multi-Function Air Data Probe

Configuration design, analysis, and wind tunnel test of a vane-type multi-function air data probe (MFP) was described. First, numerical analysis was conducted for the initial configuration of the MFP in order to investigate aerodynamic characteristics. Then, the design was modified to improve static and dynamic stability for better response characteristics. The modified configuration design was verified through wind tunnel tests. The test results are also used to verify the accuracy of the analytical method. The analytically estimated aerodynamic damping provided by the Navier-Stokes equation solver correlated well with the wind tunnel test results. According to the calculation, the damping coefficient estimated from ramp motion analysis yielded a better correlation with the wind tunnel test than pitch oscillation analysis.

Implementation of the Rauch-Tung-Striebel Smoother for Sensor Compatibility Correction of a Fixed-Wing Unmanned Air Vehicle

This paper presents a complete procedure for sensor compatibility correction of a fixed-wing Unmanned Air Vehicle (UAV). The sensors consist of a differential air pressure transducer for airspeed measurement, two airdata vanes installed on an airdata probe for angle of attack (AoA) and angle of sideslip (AoS) measurement, and an Attitude and Heading Reference System (AHRS) that provides attitude angles, angular rates, and acceleration. The procedure is mainly based on a two pass algorithm called the Rauch-Tung-Striebel (RTS) smoother, which consists of a forward pass Extended Kalman Filter (EKF) and a backward recursion smoother. On top of that, this paper proposes the implementation of the Wiener Type Filter prior to the RTS in order to avoid the complicated process noise covariance matrix estimation. Furthermore, an easy to implement airdata measurement noise variance estimation method is introduced. The method estimates the airdata and subsequently the noise variances using the ground speed and ascent rate provided by the Global Positioning System (GPS). It incorporates the idea of data regionality by assuming that some sort of statistical relation exists between nearby data points. Root mean square deviation (RMSD) is being employed to justify the sensor compatibility. The result shows that the presented procedure is easy to implement and it improves the UAV sensor data compatibility significantly.

AIRCRAFT AIR DATA ESTIMATION USING A MODEL-BASED APPROACH

Air data consists of flight parameters such as pressure altitude, Mach number, angle of attack and angle of sideslip. Traditionally these are derived from measurements of local pressures and local flow angles on the fuselage using external air data probes and vanes. This paper describes the formulation of a Kalman Filter for the estimation of aircraft air data states associated with the pitch aerodynamics. The mathematical model of the aircraft embedded within the Kalman Filter contains the highly non-linear aerodynamic coefficients for the pitch dynamics of the aircraft. A selection of results from a comprehensive simulation assessment are also presented.

Air Data Computation in Fly-By-Wire Flight-Control Systems

The aim of air data systems is the determination of flight parameters (such as pressure altitude, Mach number, angles of attack and sideslip) from measurements of local pressures and of local flow angles on wings or fuselage provided by a proper set of sensors. The active and integrated use of flight parameters in a full-authority fly-bywire flight-control system imposes redundant system architecture to achieve an adequate level of reliability and safety. In this paper a methodology for air data computation is proposed that allows the flight parameters to be evaluated on the basis of data measured by four multifunction air data probes. It takes into account the effects of the modification of aircraft configuration during flight, as well as the effects of aircraft maneuver. Finally, it includes dedicated algorithms for the management of redundancy, which are able to detect possible system failures and to provide consolidated outputs. The methodology has been implemented in the Matlab/Simulink environment and a preliminary comparison of the results with flight test data showed satisfactory performance. Nomenclature a = asymptotic speed of sound C pfront i = frontal pressure coefficient of the ith probe C pslot i = slot pressure coefficient of the ith probe Config = aircraft configuration parameter d = (X s, 0, 0) = distance between the section of installation of the probes and the center of mass of the aircraft ffront = characteristic function of the stand alone probe for the frontal pressure fi = flow angle function of the ith probe f Li

Development and test of an integrated sensory system for advanced aircraft

This paper presents the results of the second phase of an integrated sensory subsystem (ISS) development effort. The ISS is a combination of redundant inertial sensors, air data probes, transducers, other flight control related sensors, interfaces, and the associated data handling system (DHS). The sensor data derived within the ISS meets the requirements (performance, redundancy, survivability, etc.) for digital fly-by-wire flight control systems. The key task of this development phase was the synthesis and development of a DHS for dispersed arrays of flight control inertial sensors subjected to dissimilar motions due to body bending of the aircraft structure. The system design is described in terms of the hardware and data handling system synthesis, followed by a discussion of the methods and results utilized to verify the system design.