139 results about "Air safety" patented technology

The invention belongs to the technical field of aviation safety management and pilot efficiency evaluation, relates to a pilot multi-task processing efficiency evaluation method under a complex situation, and aims to solve the problem that a traditional method does not comprehensively consider a real flight environment and has a blank in the field of multi-task processing efficiency evaluation. The method comprises the steps that flight parameter data, eye movement data and task data of a pilot during flight are acquired and preprocessed; screening and calculating from three dimensions of attention distribution, work memory and task switching and burst task processing efficiency to obtain a key parameter data set; performing flight stage division based on flight parameter data in combination with the flight stage transfer atlas and the weighted multi-dimensional matching distance; presetting a weight matrix according to cognitive requirements of different flight stages; and matching a preset weight matrix according to a flight stage division result, and carrying out weighted fusion on each key parameter value to obtain a final performance evaluation value. In combination with multi-source data analysis, efficient evaluation of pilot multi-task processing efficiency is realized.

The invention provides an updating method and system for aviation ice accretion identification based on aircraft real-time detection. The method comprises the following steps: acquiring real-time data of an aircraft to judge icing generation information; constructing an ice accumulation report membership function according to the ice accumulation generation information, wherein the function is used for representing the space and time distribution of the ice accumulation generation probability; and through combination of the icing report membership function and a basic icing index, an icing potential index is obtained through calculation and is used for identifying three-dimensional distribution of an icing area. According to the method, accurate positioning, dynamic prediction and real-time early warning of the accumulated ice are realized, and the aviation safety and the flight efficiency are improved.

The invention discloses a heterogeneous unmanned aerial vehicle cooperative operation air safety assessment method, and relates to the technical field of unmanned aerial vehicle cooperative operation safety, and the method comprises the steps: obtaining static parameters and operation dynamic parameters of a heterogeneous unmanned aerial vehicle; constructing a dynamic and static parameter incidence matrix based on a gradient lifting decision tree algorithm; constructing a positioning precision probability matrix based on Bayesian updating; task and operation dynamic data are collected in real time; in combination with the environment interference coefficient and the task priority weight, collision time prediction is optimized by using LSTM, and the air collision probability is calculated; and triggering the graded security risk alarm. According to the invention, refined quantitative evaluation and graded early warning of safety risks in a heterogeneous unmanned aerial vehicle cooperative scene are realized, and the problems of extensive evaluation and insufficient collaboration in the prior art are solved.

The invention relates to the technical field of aviation safety and data processing, in particular to a flight data anomaly detection method based on DEWMA-IForest, and the method comprises the following steps: carrying out the preprocessing of original flight data; initializing a smoothing coefficient and a sliding window size parameter; calculating an arithmetic mean value and a standard deviation by taking data in the sliding window as a statistical sample, and respectively taking the arithmetic mean value and the standard deviation as a DEWMA statistic initial value and a control limit calculation reference value; setting an initial control limit range; calculating the DEWMA statistical magnitude and the standard deviation of the data to be measured; dynamically updating the control limit range; and DEWMA fitting reconstruction data and a control limit are calculated. According to the method, the dynamic control limit is adapted to the time-varying property of the QAR data, so that the sensitivity of small-amplitude trend anomaly is improved; high-dimensional data dimension disasters are avoided through multi-algorithm fusion; and the abnormal criterion can be explained, so that a scientific basis is provided for aircraft operation monitoring and intelligent maintenance decision making.

The invention relates to the technical field of aircraft part detection, and particularly discloses an intelligent detection device for aircraft part processing, which comprises a box-type base, a mounting groove, a simulation mounting mechanism, a test mechanism, a top reset mechanism, a top shell, a controller, temperature adjusting equipment and humidity adjusting equipment, the simulation mounting mechanism can simulate flight vibration; the testing mechanism is arranged at the top end of the mounting groove and located on the rear side of the mounting groove, and the testing mechanism can simulate the using action of a passenger; the top resetting mechanism is arranged above the testing mechanism and can be used for resetting assistance and cyclic testing. Through the detection mode of scene simulation and automatic operation, the problem that a traditional single vibration or isolated action test is disjointed with an actual scene is solved, the detection efficiency and reliability are improved, the performance of the seat in an extreme environment is reflected more accurately, and a core guarantee is provided for aviation safety.

The invention relates to the technical field of aviation safety, in particular to a fixed-wing aircraft natural icing prediction system based on a prediction model and big data analysis. Comprising a multi-source data acquisition module, a data processing module, a feature extraction module, an icing case database, a prediction model module, a prediction analysis module and an early warning result output module. The data processing module is used for preprocessing and cleaning the collected original data; the feature extraction module is used for extracting key feature variables having significant influence on natural icing of the aircraft from the processed data; the prediction model module is used for taking the extracted key feature variables as input and combining big data analysis to construct a prediction model; and the prediction analysis module is used for inputting the currently collected multi-source data into the trained prediction model for analysis, and by adopting the mode, the icing risk is predicted in advance, the operation fault-tolerant space is greatly increased, and the accurate prediction requirement in the flight scene can be met.

The invention relates to the technical field of aviation safety prediction, and discloses a bumping prediction correction method and system based on aircraft geometric configuration and shipping space information, electronic equipment and a storage medium, and the method comprises the steps: obtaining input features, carrying out the cross-aircraft-type feature enhancement through comparative learning, generating an enhanced feature vector, and carrying out the recognition of the enhanced feature vector; and performing structured combination on the enhanced feature vector, the distance from the shipping space to the lift center, the normal overload value of the shipping space and the distance from the target seat to the lift center, fusing model embedded vectors and spatial position codes, generating a plurality of feature marks, and inputting the feature marks into an attention model adjusted by a geometric perception mechanism to perform spatial dependency relationship modeling. Outputting morphological parameters for representing an overload distribution form; through parameterized curve constraint calculation, obtaining a preliminary normal overload prediction value of the target seat; and performing adaptive weighted fusion based on the rule constraint prediction value, and outputting a normal overload prediction correction value of the target seat. According to the invention, the overload value of any target seat in the cabin can be accurately predicted.

The invention relates to the technical field of computer vision and aviation safety, and discloses an airport clearance area unmanned aerial vehicle intrusion monitoring and positioning method based on improved YOLOv8n, and the method comprises the steps: constructing an improved YOLOv8n detection model, enhancing multi-scale feature fusion through integrating BiFPN at a neck network, and introducing an attention mechanism at a prediction head to improve feature selectivity; deploying the trained and optimized model at an intelligent sensing node, and detecting and acquiring pixel coordinates of the unmanned aerial vehicle in real time; the geographic coordinates and the attitude parameters of the nodes are fused, and the three-dimensional geographic coordinates of the unmanned aerial vehicle are calculated through space coordinate transformation in combination with a camera model and target prior information; and finally, intelligent alarm and visual display are realized. According to the method, the detection capability of the tiny unmanned aerial vehicle target under the complex background is effectively improved, an integrated solution from image recognition to precise geographic positioning is realized, and the method has the advantages of accurate detection, precise positioning and reliable system.

The aviation safety oversight software will be utilized by the civil aviation authority to monitor the safety performance of aviation service providers. This software will first classify the air operating companies and then create an electronic file to update the regulatory processes of the civil aviation authority according to the applicable air operating companies and the aviation safety performance indicators of the country. The software aims to streamline the implementation of the regulatory processes of the Civil Aviation Authority. It will use statistical analysis to convert safety data into safety information for better analysis and decision-making.

The invention relates to the technical field of low-altitude meteorological science and aviation safety, in particular to a low-altitude turbulence prediction method based on multi-source observation data. The method is realized based on multi-source data, and specifically comprises the steps of data acquisition and preprocessing, unification of observation data of different data sources to a target height layer and realization of space-time matching, calculation of turbulent kinetic energy by physical characteristic quantity, wind shear, turbulence intensity weighted calculation, design of a height weight function of exponential attenuation, and calculation of turbulence intensity through weighted combination. Therefore, turbulence intensity distribution in a two-dimensional vertical plane is obtained. Through systematic multi-source data fusion, characteristic quantity extraction based on a physical mechanism, intelligent weight design and reliability evaluation, high-precision two-dimensional and three-dimensional low-altitude turbulence prediction is realized, and powerful technical support is provided for low-altitude flight safety. Meanwhile, the adaptability scheme of the single-source data ensures the practicability of the method under different equipment configuration conditions, and the method has a wide application prospect.

The invention relates to the technical field of aviation safety and weather prediction, in particular to an aircraft bumping prediction method, system and equipment based on decoupling type physical constraint. Aligning pre-collected multi-time-sequence weather forecast data and airplane EDR data on the same space-time grid, and converting the data into probabilistic features including a mean value and a standard deviation; for sparse airplane EDR data, introducing an atmospheric physical model correction term based on a wind shear and turbulence energy dissipation rate relationship for filling, and obtaining a probabilistic input tensor; inputting the probabilistic input tensor into a pre-constructed and trained self-correlation attention model fused with physical constraints; and extracting a contribution degree matrix from the attention weight of the trained model, quantifying the contribution ratio of each forecast time point to a prediction result, and outputting a probabilistic prediction result of the airplane bumping and the corresponding contribution degree matrix as a final prediction result. A reliable basis is provided for flight decision making, and the accuracy and robustness of airplane bumping prediction are improved.

The invention discloses an aviation safety report classification method, device and equipment and a storage medium, and the method comprises the steps: obtaining a historical data set, including a text data set and an image data set, of an aviation safety report; constructing a security report text classification model according to the text data set; constructing a security report image classification model according to the image data set; obtaining a to-be-classified aviation safety report, obtaining a text classification result by adopting the safety report text classification model according to the text data, and obtaining an image classification result by adopting the safety report image classification model according to the image data; performing quality evaluation on the text data and the image data, and determining a text weight and an image weight according to an evaluation result; and based on the text weight and the image weight, performing weighted summation on the text classification result and the image classification result to obtain a classification result of the to-be-classified aviation safety report. According to the invention, the accuracy of aviation safety report classification is effectively improved.

The present application relates to the technical field of aviation safety and artificial intelligence, in particular to an ADS-B time series data adversarial sample generation method based on improved WGAN-GP, comprising the following steps: obtaining ADS-B historical flight data, extracting the longitude, latitude, height, speed and heading five-dimensional features to construct a time series data set; building an adversarial sample generation model based on an improved Wasserstein distance generative adversarial network, and configuring a multi-objective composite loss function for the generator; the present application builds a generator and a discriminator based on LSTM, designs a composite loss function that integrates adversarial loss, concealment loss and time series smoothness loss, adopts gradient penalty and asymmetric update strategy to train the model, and the generated adversarial sample has high concealment and physical consistency, can effectively avoid various unsupervised anomaly detection models, the model training is stable, and technical support is provided for building a safer air traffic control defense mechanism.

The utility model relates to a low-light-intensity obstacle lamp for a wind driven generator, and aims to solve the problems of difficulty and potential safety hazards caused by a traditional mounting method. The lamp is compact in design and is directly attracted to the pipe wall of the wind driven generator through the magnet, an additional support is not needed, the installation process of high-altitude operation is simplified, and risks are reduced. The lamp body is composed of a rod body and a shell, an annular groove is formed in the surface of the rod body and used for installing a sealing ring, and rainwater is prevented from entering the supporting rod. One end of the rod body is connected with the condensing lens lampshade, more than two LED light sources are arranged in the rod body, and good aviation safety indication is provided. A driving circuit board is arranged in the shell, and a plug is arranged to be connected with an external circuit. The adjustable magnet frames are arranged on the two sides of the shell, the distance between the magnet and the pipe wall can be adjusted according to different wall thicknesses, and universality is enhanced. The installation safety and convenience are improved, the adaptability and the protection level of products are enhanced, and a new solution is provided for installation of the aviation obstruction beacon in the wind power generation industry.

The utility model provides a 360-degree light-emitting high-light-intensity aviation obstruction light which comprises a main support and obstruction lights installed on the main support, the number of the obstruction lights is more than three, the obstruction lights are installed outwards in a surrounding mode, the irradiation angle of the obstruction lights is 360 degrees, the obstruction lights are installed on the main support in a rotating mode in the vertical direction, and the obstruction lights are arranged on the main support. The function of adjusting the vertical light-emitting angle of the obstruction lamp in a single direction is achieved, and the actual installation scene requirement is met. The three obstruction lights are installed on the main support and installed outwards in a surrounding mode, 360-degree all-dimensional light emitting is achieved, the visual blind area of a traditional lamp is eliminated, and aviation safety is improved. The obstruction lights can rotate around the main support, a user can flexibly adjust the vertical light-emitting angle of each obstruction light according to the actual installation environment and requirements, and the best warning effect is ensured. According to the design, the applicability of the lamp is improved, and the installation and maintenance processes are simplified.

The method for quickly inverting aircraft wake vortex parameters based on mobile platform laser remote sensing comprises the following steps: a laser radar system scans a wake vortex influence area, and measurement data are subjected to quality control processing; a wake vortex core position and a vortex core radius are estimated; a wind speed of an arbitrary measurement point A located in the wake vortex range is subjected to vector decomposition, and the wind speed is expressed as a function of a wake vortex circulation parameter W 、 V 、 U A background wind speed and a laser radar motion speed are eliminated by using a non-wake vortex area measurement point; a difference between radial velocities of two measurement points in and out of a wake vortex influence range in the same laser emission direction is expressed as a function of a wake vortex circulation; and a turbulent disturbance is weakened by multiple measurements in the wake vortex influence range, and then a least square method is used to fit and solve the wake vortex circulation. The present application can accurately invert and correct aircraft wake vortex parameters by using less observation data. The calculation result is fast and accurate, and can provide scientific and reliable data support for aviation safety and aircraft cooperative operation.

The invention provides an evidence-driven large language model MISRA C rule review method and system for aviation safety. According to the method, formalized feature extraction is carried out from four aspects of grammar structure features, semantic structure features, logic analysis features and preprocessing behavior features for target codes according to various rules of MISRA C forcing class rules, and diagnosis information is diagnosed in combination with an industrial-grade compiler; generating a structured evidence set comprising abstract syntax tree node statistical features, code context structure features, control flow graph features, function internal data flow analysis features, symbol and type table features and macro definition analysis features; and based on the structured evidence set and the large language model, executing evidence tracing, rule matching and logical reasoning according to a preset thinking chain process, and outputting a structured judgment result containing illegal rule numbers, evidence description and code positions. According to the method, the false alarm rate can be remarkably reduced while the high rule coverage rate and the detection accuracy are kept.

1. Name of the design product: handbag. 2. Use of the design product: handbag for air safety officer. 3. Design points of the design product: in shape. 4. Picture or photo best indicating the design points: perspective view.

The invention provides a GNSS interference detection positioning method and system based on an ADS-B network, and relates to the technical field of satellite navigation. And based on the historical state data of the aircraft, predicting the state of the aircraft by using the time sequence prediction model to obtain a predicted value of the state of the aircraft. And if the deviation between the predicted value and the received true value is greater than a preset threshold value, judging that the aircraft is interfered, and calculating the interference confidence coefficient. A monitoring area is divided into grids, interference indexes in the grids are calculated, and a potential interference area is determined. And the ADS-B message of the aircraft with the highest interference confidence in the potential interference area is selected as an interference source to trigger a virtual signal. And finally, calculating the time when the interference source triggers the virtual signal to the ground station, and obtaining the position of the GNSS interference source based on the time. According to the interference detection positioning provided by the invention, the GNSS interference source can be efficiently and accurately detected and positioned, and the reliability of interference identification and the aviation safety monitoring capability are improved.

The invention belongs to the technical field of aviation safety, relates to an accident reproduction method and system based on QAR data and simulator reverse drive, and aims to solve the problems of low reproduction precision and poor compliance in the prior art. The method comprises the following steps: acquiring an accident QAR data set; locking accident time sequence nodes, and screening key parameter subsets; the analog machine is reversely driven, a reverse driving control strategy of the analog machine is optimized based on the key parameter subset and the time sequence node, and preliminary reproduction data is generated; calculating a time sequence deviation and a physical deviation of the preliminary reproduction data and the accident QAR data set, and dynamically fusing the two deviations according to a time sequence node to generate a dynamic correction coefficient; and calibrating the analog machine reverse driving process by using the dynamic correction coefficient to obtain calibrated reproduction data. According to the method, a technical system of data preprocessing, reverse driving optimization and closed-loop dynamic correction is constructed, so that deep coupling of the QAR data and the simulator is realized, and the accuracy, objectivity and compliance of accident reproduction are improved.

The application discloses a safety belt device of a penetrating anchor of a civil aviation safety belt, which comprises a safety belt assembly, a buffer assembly and an anchoring assembly, the safety belt assembly comprises two shoulder binding safety belts, two waist binding safety belts and two leg binding safety belts, and the same-side shoulder binding safety belts, waist binding safety belts and leg binding safety belts are connected and fixed through safety connection boxes, and the buffer assembly comprises a mounting box fixedly arranged between the two safety connection boxes, the safety belt assembly, the buffer assembly and the anchoring assembly are arranged, the safety belt assembly is used for fixing the body of a flight attendant, can be used in standing posture or sitting posture and the like, the buffer assembly can protect the body of the flight attendant, reduces injuries caused by stress of the safety belt and the like, the anchoring assembly cooperates with the buffer assembly and the safety belt assembly to ensure the stability of the flight attendant, and harm caused by plane bumping is avoided.

The invention discloses a robotized aircraft pre-takeoff inspection system and method based on a hybrid expert vision model, and belongs to the technical field of aviation safety and automatic detection. In order to solve the problems of strong subjectivity, low efficiency, existence of blind areas and incapability of all-weather operation of the existing aircraft manual inspection, and poor flexibility and incapability of detecting unknown defects of a fixed automatic system, the invention provides a system which comprises a robot inspection unit provided with an autonomous mobile platform and a multi-modal sensor head. The robot scans an aircraft along a pre-planned path, and the core of the robot is a hybrid expert (MoE) visual anomaly detection model deployed on a server. According to the model, a zero sample anomaly detection (ZSAD) normal form is adopted, and image data are routed to corresponding expert sub-models for analysis through a gating network, so that novel and unknown surface defects can be accurately identified. According to the invention, high-efficiency, high-precision and all-weather automatic inspection of the aircraft is realized, the flight safety and the operation efficiency are remarkably improved, and a traceable digital inspection report is generated.

Disclosed are a method and device for prompting a horizontal stabilizer trim state, which add a corresponding trim display when a "horizontal stabilizer failure" and "current trim position inconsistent with optimal trim position" alarm is triggered, so as to better meet the requirements of aviation safety regulations for alarms.

The invention belongs to the technical field of aviation safety, and discloses a civil aviation multi-scene coupled intelligent auxiliary model construction method and system, and the method comprises the steps: 1, constructing a risk scene coupled flight simulation model based on risk scene and coupling action mechanism research, and generating basic data for artificial intelligence learning training; 2, for each group of coupling risk scenes, setting a triggering condition and a triggering action which conform to the actual situation of the scene and contain randomness, and generating coupling scene data; and step 3, by constructing a hybrid deep learning model which combines a long short-term memory network and a full convolutional neural network and is used for time sequence modeling and feature extraction, training and verification of an identification model of the coupling risk scene are carried out, and the identification success rate needs to be greater than 95%. According to the method, the problem that the traditional identification and early warning research aiming at the risk scene generally only aims at a single scene and does not consider the coupling condition of multiple risk scenes is solved, and the pilot is assisted through the identification and early warning of the coupling risk.

The invention discloses a low-altitude aircraft endogenous safety navigation system and method based on formalized verification, and belongs to the field of aviation safety key systems. According to the system, the first low-altitude aircraft endogenous safety navigation system passing formalized verification in the world is constructed, the core is that'endogenous credibility 'is defined as the unified measurement of system output, and a five-dimensional credibility enhancement engine is innovatively provided. The endogenous credibility is generated and continuously verified through the synergistic effect of the physical unclonable fingerprint of the signal layer, the anti-quantum trust chain of the data layer, the mathematical proof stability of the algorithm layer, the causal traceable evaluation of the decision-making layer and the dynamic minimum permission strategy of the control layer. Through fourth-level conformity verification of the Chinese civil aviation bureau, the integrity risk probability of the system in 2000-hour continuous testing is 8.3 * 10 / hour and is improved by two orders of magnitude compared with the DO-365C standard, and the limit of the prior art is substantially exceeded. According to the invention, through tight integration of hardware and software, the problems of loss of trust roots and incomplete verification in navigation of the low-altitude aircraft are solved, and qualitative leap of safety performance is realized.

This invention relates to the field of aviation safety technology, and discloses a suppression device and control method for abnormal lithium battery fires in civil aviation. The device includes an openable, closable box-shaped suppression isolator, which consists of a flame-retardant intermediate layer, a metal partition inner layer, and a plastic outer layer. An integrated detection component monitors temperature, smoke, and characteristic gases. An extinguishing agent release component includes an aerosol extinguishing agent generator and a perfluorohexanone coolant storage tank. The control system performs graded early warning and linkage control based on multi-sensor data regarding thermal runaway intensity and lithium battery capacity. A fire-resistant sealed bag is connected to the isolator via a pressure relief valve to achieve directional emission of harmful gases. Through automatic detection, graded response, two-stage fire extinguishing cooling, and closed-loop feedback regulation, open flames can be quickly extinguished in a confined environment and reignition prevented, while simultaneously avoiding the spread of toxic fumes, thus improving the safety and efficiency of handling high-altitude lithium battery fires.

The application discloses a kind of heterogeneous unmanned aerial vehicle cooperative operation air safety evaluation method, it is related to unmanned aerial vehicle cooperative operation safety technical field, comprising: obtaining the static parameters and running dynamic parameters of heterogeneous unmanned aerial vehicle;Dynamic and static parameter association matrix based on gradient boosting decision tree algorithm is constructed;Positioning accuracy probability matrix based on bayesian update is constructed;Real-time collection task and running dynamic data;Combined with environmental interference coefficient and task priority weight, the collision time prediction is optimized using LSTM, to calculate the probability of air collision;Trigger hierarchical safety risk alarm.The application realizes the fine quantification evaluation and hierarchical early warning of safety risk in the cooperative scenario of heterogeneous unmanned aerial vehicle, solves the problem of extensive evaluation and insufficient cooperation in the prior art.

The invention belongs to the technical field of meteorological data extraction and processing, and particularly provides a method and system for extracting an atmospheric fine vertical structure under a mountain complex terrain, and the method comprises the steps: collecting multi-source observation data of an atmospheric vertical profile under the mountain complex terrain, carrying out the normalization of the multi-source observation data, and obtaining the normalized multi-source observation data; performing space-time matching on the normalized multi-source observation data by using the altitude of the data acquisition point to obtain space-time groups; analyzing the normalized multi-source observation data in the space-time grouping, and constructing a multi-source profile merging system; extracting an atmospheric fine vertical structure based on the multi-source profile merging system and normalized multi-source observation data; and arranging the atmospheric fine vertical structures in different time-space groups according to a time sequence, predicting changes of the atmospheric fine vertical structures, and obtaining a prediction result. According to the technical scheme, fine observation of the vertical structure of the atmosphere is facilitated, and the method is of great significance to improvement of disastrous weather defense capability, guarantee of aviation safety and the like.

The present invention relates to the field of aviation safety technologies, and provides a method, a system, a device, a product and a medium for lidar wake vortex inversion. The method includes: obtaining meteorological parameters, aircraft type parameters and ADS-B data, and calculating the wake vortex circulation; constructing an axial scanning coordinate system; constructing a first radial velocity algorithm; calculating the background wind velocity through the first radial velocity algorithm; constructing a second radial velocity algorithm through the background wind velocity and the first radial velocity algorithm; determining range gates and obtaining corresponding probe point coordinate pairs, and traversing the absolute values of the gradients of the probe point coordinate pairs in the set of probe points to obtain the relative vortex core position; obtaining a first true vortex core position and a second true vortex core position and the distance therebetween in the region where the relative vortex core position is located, and iterating until the distance therebetween converges to determine the true vortex core position. The present invention effectively eliminates the interference of the background wind, and realizes the axial scanning of the aircraft wake based on lidar by calculating the true vortex core position.

The application belongs to the technical field of target detection, and provides a flying bird detection method, which comprises the following steps: constructing a flying bird target detection data set and dividing the data set into a training set; the flying bird target detection data set comprises flying bird samples in different flight postures, sizes and backgrounds; a multi-scale real-time detection model is constructed, which is obtained by improving a YOLOv8 model; the multi-scale real-time detection model is trained based on the flying bird target detection data set to determine optimal parameters; and the to-be-tested data is input into the trained multi-scale real-time detection model to output the category and position information of the flying bird target. The application detects flying birds based on the trained multi-scale real-time detection model, significantly improves the accuracy of model detection and recognition while ensuring that the test rate reaches 178 FPS, has excellent average accuracy in complex flying bird scene detection applications, and can be applied to airport clearance area safety early warning to improve aviation safety.