A method for safety assessment of an eVTOL aircraft crossing a runway extension

Abstract

The present application relates to the field of aircraft safe operation evaluation, and specifically discloses a kind of eVTOL aircraft crossing runway extension line safety evaluation method, method includes: S1: the safety interval of eVTOL in lateral and vertical direction is calculated, the size parameter of crossing zone is determined, the minimum safety interval of civil aircraft and eVTOL is calculated, according to the size parameter of crossing zone and minimum safety interval, the position of crossing zone is determined;S2: from traffic warning and anti-collision system alarm logic, the collision risk of civil aircraft and eVTOL in crossing zone, the influence of civil aircraft wake vortex sinking is evaluated from three safety evaluation dimensions to the position scheme of crossing zone;S3: if crossing zone position meets the requirement of three evaluation dimensions in above-mentioned step S2 simultaneously, then it is judged as the position of crossing zone that safety evaluation meets the requirement and is output.The present application comprehensively considers multiple safety evaluation dimensions, and improves the safety of crossing zone.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aircraft safe operation evaluation, in particular to a safety evaluation method for eVTOL aircraft crossing runway extension line. BACKGROUND

[0002] As a new emerging transportation mode, eVTOL (electric Vertical Take-off and Landing) is expected to undertake the task of passenger transfer between city and airport in the future, thereby effectively relieving the ground traffic pressure and significantly improving the travel efficiency. However, considering that eVTOL may have potential impact on the normal operation and flight safety of civil aircraft during task execution, it is essential to set a scientific and reasonable crossing zone to better meet the actual operation requirements in the future.

[0003] At present, the existing methods for evaluating the safety of eVTOL and civil aircraft integrated operation mostly only analyze from a single factor, and such one-sided consideration makes the evaluation results lack sufficient persuasiveness. Meanwhile, in the key field of setting a crossing zone to ensure the safe operation of eVTOL in the airport area, relevant research is less and further in-depth study is urgently needed. SUMMARY

[0004] The present application aims to solve the problems of unreasonable setting of crossing zone and single dimension of eVTOL and civil aircraft integrated operation safety evaluation. To this end, the present application provides a safety evaluation method for eVTOL aircraft crossing runway extension line, which can calculate the lateral and vertical safety intervals of eVTOL, obtain the size parameters of the crossing zone, obtain the minimum safety interval of the crossing zone and runway glide path according to the traffic alert and collision avoidance system alarm event frequency, set the position of the crossing zone, and comprehensively consider the influence of traffic alert and collision avoidance system alarm event frequency, manned aircraft and eVTOL collision risk, and manned aircraft wake vortex. The present application improves the safety of eVTOL aircraft crossing runway extension line and provides a reference for the integrated operation of manned aircraft and eVTOL in the airport range in the future.

[0005] The present application provides a safety evaluation method for eVTOL aircraft crossing runway extension line, which adopts the technical scheme as follows:

[0006] S1: based on the performance parameters of eVTOL, calculate the required safety interval in the lateral and vertical directions, determine the size parameters of the crossing zone, and specifically the length and width;

[0007] Calculate the minimum safety interval of the civil aircraft and eVTOL, determine the position of the crossing zone based on the size parameters of the crossing zone and the minimum safety interval;

[0008] S2: Based on the traffic alert and collision avoidance system warning logic, an alarm judgment simulation model is constructed, the frequency of civil aircraft alarm caused by eVTOL in the crossing zone position is counted, and whether the alarm frequency is lower than the preset safety threshold is judged;

[0009] A collision risk model of civil aircraft and eVTOL in the crossing zone is constructed, and the collision risk value in the crossing zone is calculated based on the model to determine whether the value is lower than the safety target threshold;

[0010] A civil aircraft wake vortex sinking model is constructed, the wake vortex sinking height is calculated, and whether the height is higher than the upper limit of the height of the crossing zone is determined;

[0011] S3: If the crossing zone position meets the evaluation requirements of the three dimensions in step S2 above, it is determined that it is a safe evaluation qualified crossing zone position, and the crossing zone position and evaluation result are output. When the safety evaluation is not up to standard, the crossing zone size parameters are adjusted according to experience, and the crossing zone position is reset according to the reason.

[0012] Further, according to the performance parameters of eVTOL, the required safety interval in the lateral and vertical directions is calculated, the length of the crossing zone is determined according to the lateral safety interval between aircrafts, and the width of the crossing zone is determined according to the vertical safety interval between aircrafts, including:

[0013] S11: The calculation formula of the lateral direction aircraft overlap probability is:

[0014]

[0015] Wherein, is the lateral direction aircraft overlap probability, is the lateral direction interval between aircrafts, is the boundary value of the lateral protection area in the negative direction, is the boundary value of the lateral protection area in the positive direction, is the combined standard deviation of the lateral direction positioning error, is the deviation between the actual interval and the expected interval;

[0016] The calculation formula of the vertical direction aircraft overlap probability is:

[0017]

[0018] Wherein, is the vertical direction aircraft overlap probability, is the vertical direction interval between aircrafts, is the boundary value of the vertical protection area in the negative direction, is the boundary value of the vertical protection area in the positive direction, The combined standard deviation of the vertical positioning error;

[0019] S12: The formula for calculating the risk of collision in the lateral direction is:

[0020]

[0021] in, To mitigate the risk of lateral collisions, The loss rate per flight hour in the lateral direction. The probability of vertical overlap when the vertical spacing is zero. E ( s () represents the vertical proximity rate. For the fuselage length of eVTOL, For the eVTOL's chassis width, For the height of eVTOL, The longitudinal spacing between aircraft. The relative speed between civil aircraft and eVTOL in the longitudinal direction, The relative speed between civil aircraft and eVTOL in the lateral direction, The relative speed between the civil aircraft and the eVTOL in the vertical direction;

[0022] The calculation formula is:

[0023]

[0024] The formula for calculating collision risk in the vertical direction is:

[0025]

[0026] in, For the risk of collision in the vertical direction, The vertical loss rate per flight hour interval. This represents the probability density function when the vertical error between aircraft is zero. The probability of lateral overlap when the lateral spacing is zero;

[0027] The calculation formula is:

[0028]

[0029] S13: Set up the iterative calculation process, starting from the initial interval, adjust the interval parameters in the lateral and vertical directions, substitute the adjusted interval values ​​into the formula to calculate the collision risk. When the collision risk is equal to or lower than the civil aviation safety target level, the corresponding lateral and vertical interval parameters are the minimum crossing zone size parameters that meet the safety requirements.

[0030] Further, the minimum safety separation between the general aircraft and the eVTOL is calculated, and the crossing zone position is determined according to the crossing zone size parameter and the minimum safety separation, including:

[0031] The height calculation formula of the general aircraft on the runway glide path is:

[0032]

[0033] wherein, is the height of the general aircraft, is the altitude of the runway entrance, is the height of the reference datum point, is the horizontal distance of the general aircraft from the runway entrance, is the length of the runway, is the glide angle of the runway glide path;

[0034] The warning boundary calculation formula is:

[0035]

[0036]

[0037] wherein, is the warning boundary, is the TCAS warning threshold, is the fixed separation parameter, is the variable warning threshold, is the current height;

[0038] The runway glide path height calculation formula is:

[0039]

[0040] wherein, is the height of the runway glide path, is the horizontal position of the current calculation point, is the horizontal position of the runway glide path datum point, which is usually located at the runway entrance;

[0041] The difference between the height of the general aircraft on the runway glide path and the warning boundary is the minimum safety separation;

[0042] The crossing zone position of the eVTOL is set at the lower part of the warning boundary, and the optimal position of the crossing zone in the range of the lower part of the warning boundary is determined by the following method: under the premise of ensuring the minimum safety separation, the distance between the crossing zone and the runway, the minimum height of the crossing zone are comprehensively considered to obtain the optimal position.

[0043] Further, based on the traffic alert and collision avoidance system warning logic, an alarm judgment simulation model is constructed;

[0044] The construction of the alarm decision simulation model includes: importing navigation data, performance data and external wind disturbance data of the eVTOL, and simulating various running states of the eVTOL in the crossing area through the Monte Carlo method;

[0045] Based on the alarm decision simulation model and the simulated various running states, the alarm frequency of the eVTOL and the civil aircraft triggering an alarm is counted, and if the alarm frequency is lower than the preset safety threshold, it is determined that the safety of the crossing area position scheme meets the requirements.

[0046] Further, the collision risk model calculation process of the civil aircraft and the eVTOL in the crossing area is as follows:

[0047] Horizontal overlap probability calculation formula:

[0048]

[0049] Among them, is the longitudinal direction spacing between aircrafts, is the lateral direction spacing between aircrafts, is the horizontal overlap probability, is the horizontal relative speed, is the horizontal conflict rate;

[0050] Vertical crossing probability calculation formula:

[0051]

[0052]

[0053] Among them, is the vertical crossing probability, is the vertical direction spacing between aircrafts, is the minimum safety spacing threshold, is the attenuation scale coefficient, is the vertical height of the civil aircraft, is the vertical height of the eVTOL;

[0054] System reliability calculation:

[0055] Vertical collision risk calculation formula:

[0056]

[0057] Among them, is the vertical collision risk value, is the horizontal overlap probability, is the vertical relative speed, is the height of the civil aircraft collision box, is the height of the eVTOL collision box;

[0058] The probability calculation formula of collision risk is:

[0059]

[0060] Wherein, is the probability of collision risk, is the effectiveness of the unmanned aerial vehicle collision avoidance system, is the reliability of ATC intervention for conflict, is the reliability of TCAS, is the reliability of manned aircraft pilot collision avoidance, is the reliability of STCA;

[0061] The collision risk calculation formula is:

[0062]

[0063] Wherein, is the collision risk value, is the environmental influence coefficient, when in an ideal environment, when encountering bad weather, , is the coefficient of airspace management impact on collision risk, when the control measures can effectively avoid collision, when the control measures cannot effectively avoid collision, .

[0064] Further, the calculation process of the civil aircraft wake vortex sinking model includes:

[0065] S21: Basic parameter calculation;

[0066] S22: Construction of circulation decay model;

[0067] S23: Construction of wake vortex sinking model.

[0068] Further, the basic parameter calculation process includes:

[0069] S211: Initial vortex spacing calculation formula:

[0070]

[0071] Wherein, is the initial vortex spacing, B is the wingspan of the aircraft;

[0072] S212: Initial circulation calculation formula:

[0073]

[0074] Wherein, is the initial circulation, is the mass of the aircraft, for air density, for aircraft speed;

[0075] S213: Wake sink velocity calculation formula:

[0076]

[0077] where, is the wake sink velocity;

[0078] S214: Parameter normalization calculation formula:

[0079]

[0080]

[0081] where, is the actual turbulent dissipation rate, is the normalized turbulent dissipation rate, is the actual B-V frequency, is the normalized B-V frequency, is the normalized time.

[0082] Further, the circulation decay model construction includes:

[0083] S221: Diffusion stage:

[0084]

[0085] where, is the dimensionless time, is the average circulation with a wake vortex radius of 5-15m, is the constant amplitude, is a constant related to the average integral radius, is the first stage start time, is the effective viscosity of the first stage;

[0086] S222: Rapid decay stage:

[0087]

[0088] where, is the second stage start time, is the effective viscosity of the second stage, the formula is as follows:

[0089]

[0090]

[0091]

[0092] wherein, is a dimensioned time, is a dimensionless time, is a reference time for the rapid decay phase.

[0093] Further, the wake vortex sinking model construction comprises:

[0094]

[0095]

[0096]

[0097] wherein, denotes time, is a wake vortex sinking velocity, is a time-varying wake vortex circulation, is a vortex core sinking height.

[0098] Further, the step S3 comprises:

[0099] If the crossing zone position meets the following three conditions at the same time:

[0100] The eVTOL causes the frequency of civil aircraft alarm to be lower than a preset safety threshold value;

[0101] The collision risk value of the civil aircraft and the eVTOL is lower than a safety target threshold value;

[0102] The wake vortex sinking height of the civil aircraft is higher than the upper limit of the height of the crossing zone;

[0103] The crossing zone position safety evaluation is determined to be up to standard, a safety evaluation up to standard signal is generated, and geographical coordinate information of the crossing zone position is outputted.

[0104] The one or more technical solutions in the embodiments of the present application have at least one of the following technical effects:

[0105] 1. The present application provides a safety evaluation method for an eVTOL aircraft crossing a runway extension line, which innovatively comprehensively evaluates the safety of the crossing zone from multiple key dimensions, provides scientific and reliable reference basis for the future integration of manned aircraft and eVTOL in the airport range, and ensures the safety of the collaborative operation of the two types of aircraft from multiple dimensions.

[0106] 2.The present application obtains the size parameters of the crossing area by calculating the safety interval of eVTOL in lateral and vertical directions, and sets the position of the crossing area.Meanwhile, the present application innovatively takes into account the three core dimensions of traffic alert and collision avoidance system warning event frequency, manned aircraft and eVTOL collision risk, and manned aircraft wake vortex to form a multi-dimensional safety guarantee system, effectively improves the safety performance of the crossing area, and lays a foundation for the safe operation of eVTOL in complex environment.

[0107] Additional aspects and advantages of the present application will be made apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0108] In order to more clearly illustrate the technical solutions in the present application or in the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0109] Figure 1 is a flowchart of the method provided by the present application.

[0110] Figure 2 is a collision risk change diagram of heavy composite wing eVTOL.

[0111] Figure 3 is a crossing area setting diagram.

[0112] Figure 4 is an eVTOL alarm situation diagram.

[0113] Figure 5 is an alarm boundary violation distribution diagram.

[0114] Figure 6 is a collision risk change diagram with vertical interval.

[0115] Figure 7 is a collision risk distribution diagram.

[0116] Figure 8 is a wake vortex influence diagram on the crossing area. DETAILED DESCRIPTION

[0117] In order to make the objects, technical solutions and advantages of the present application clearer, the following will be combined with the drawings in the present application to make a clear and complete description of the technical solutions in the present application. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the protection scope of the present application. The following embodiments are used to illustrate the present application, but cannot be used to limit the scope of the present application.

[0118] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example" or "some examples" means that the specific features, structures or characteristics described in combination with the embodiment or example are contained in at least one embodiment or example of the embodiments of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0119] The following will be combined Figures 1 to 8 The present application is further described, and a safety evaluation method for an eVTOL aircraft crossing a runway extension line is described:

[0120] In the present embodiment, as Figure 1 shown, a safety evaluation method for a typical composite wing eVTOL aircraft crossing a runway extension line is provided, including the following steps:

[0121] S1: Based on the performance parameters of eVTOL, the required safety interval in the lateral and vertical directions is calculated, and the size parameters of the crossing area are determined, including length and width.

[0122] According to the performance parameters of eVTOL, the required safety interval between the aircraft in the lateral direction and the required safety interval in the vertical direction are calculated, the length of the crossing area is determined according to the lateral safety interval between the aircraft, and the width of the crossing area is determined according to the vertical safety interval between the aircraft, including:

[0123] S11: The calculation formula of the overlap probability between the aircraft in the lateral direction is:

[0124]

[0125] Among them, is the overlap probability between the aircraft in the lateral direction, is the lateral direction interval between the aircraft, This represents the boundary value of the lateral protection zone in the negative direction. This represents the boundary value of the lateral protection zone in the positive direction. This represents the combined standard deviation of the lateral positioning error. This represents the deviation between the actual interval and the expected interval.

[0126] The formula for calculating the probability of overlap between aircraft in the vertical direction is:

[0127]

[0128] in, This represents the probability of overlap between aircraft in the vertical direction. The vertical spacing between aircraft. This represents the boundary value of the vertically protected area in the negative direction. This represents the boundary value of the vertically protected area in the positive direction. The combined standard deviation of the vertical positioning error;

[0129] S12: The formula for calculating the risk of collision in the lateral direction is:

[0130]

[0131] in, To mitigate the risk of lateral collisions, The loss rate per flight hour in the lateral direction. The probability of vertical overlap when the vertical spacing is zero. E ( s () represents the vertical proximity rate. For the fuselage length of eVTOL, For the eVTOL's chassis width, For the height of eVTOL, The longitudinal spacing between aircraft. The relative speed between civil aircraft and eVTOL in the longitudinal direction, The relative speed between civil aircraft and eVTOL in the lateral direction, The relative speed between the civil aircraft and the eVTOL in the vertical direction;

[0132] The calculation formula is:

[0133]

[0134] The formula for calculating collision risk in the vertical direction is:

[0135]

[0136] in, The collision risk in the vertical direction, The loss rate of the vertical direction per flight time interval, The probability density of the error in the vertical direction between aircrafts, The lateral overlap probability when the lateral separation is zero;

[0137] The calculation formula is:

[0138] .

[0139] According to the typical composite wing eVTOL, the safety separation in the lateral and vertical directions is calculated to obtain the size parameters of the crossing area. The related parameters of the heavy composite wing under low precision conditions are shown in Table 1, and the related parameters of the collision model are shown in Table 2.

[0140] Table 1

[0141]

[0142] Table 2

[0143]

[0144] Under the condition of low-precision navigation, the safety target level of the heavy composite wing eVTOL is set to 10 -9 . Based on the collision risk formula in step S1, an iterative calculation process is set, starting with the initial separation, adjusting the lateral and vertical separation parameters, and substituting the adjusted separation values into the formula to calculate the collision risk. When the collision risk is equal to or lower than the civil aviation safety target level, the corresponding lateral and vertical separation value parameters are the minimum crossing area size parameters that meet the safety requirements.

[0145] Figure 2 The lateral collision risk of the heavy composite wing eVTOL is represented by equation (a), Figure 2 The vertical collision risk is represented by equation (b). The collision risk shows a clear pattern with the change of lateral separation and vertical separation: the smaller the separation, the higher the collision risk. When the collision risk is reduced to the safety target level of 10 -9 , the corresponding lateral separation is 75m and the vertical separation is 24.6m. This indicates that in order to make the collision risk of the heavy composite wing eVTOL reach the safety target, the lateral separation must be no less than 75m and the vertical separation must be no less than 24.6m.

[0146] Combined with the frequency of traffic alerts and collision avoidance system warning events, the minimum safety separation required between the crossing area and the runway glide path is calculated, including:

[0147] The height calculation formula of the civil aircraft on the runway glide path is:

[0148]

[0149] wherein, H is the height of the civil aircraft, H is the altitude of the runway threshold, H is the height of the reference point, D is the horizontal distance of the civil aircraft from the runway threshold, L is the length of the runway, a is the glide angle of the runway glide slope;

[0150] The alert boundary calculation formula is:

[0151]

[0152]

[0153] wherein, H is the alert boundary, H is the TCAS alert threshold, H is the fixed separation parameter, H is the variable alert threshold, H is the current height;

[0154] The runway glide slope height calculation formula is:

[0155]

[0156] wherein, H is the height of the runway glide slope, D is the horizontal position of the current calculation point, D is the horizontal position of the reference point of the runway glide slope, usually located at the runway threshold;

[0157] The difference between the height of the civil aircraft on the runway glide slope and the alert boundary is the minimum safety separation.

[0158] According to the crossing zone size parameter and the minimum safety separation, the crossing zone position is generated, the airport related parameters are as shown in Table 3, the alert rate level is as shown in Table 4, and the eVTOL crossing zone related parameters are as shown in Table 5.

[0159] The eVTOL crossing zone is as shown in Figure 3 The blue solid line represents the aircraft glide slope, the green color is the alert boundary, and the height of both increases linearly with the increase of the distance. The red color is the crossing zone position. The eVTOL crossing zone position is located at the lower part of the alert boundary, and the optimal position of the crossing zone in the lower part of the alert boundary is determined by the following method: under the premise of ensuring the minimum safety separation, the distance between the crossing zone and the runway, the minimum height of the crossing zone are comprehensively considered to obtain the optimal position.

[0160] Table 3

[0161]

[0162] Table 4

[0163]

[0164] Table 5

[0165]

[0166] S2: Based on the traffic alert and collision avoidance system warning logic, a warning decision simulation model is constructed, the frequency of the eVTOL triggering the warning of the general aircraft in the crossing zone position is counted, and whether the warning frequency is lower than the preset safety threshold is determined.

[0167] 200 million times of Monte Carlo simulation experiments are set, an eVTOL position is generated in the crossing zone in each time, and random errors in three aspects of navigation positioning, flight performance factors and wind disturbance factors of the eVTOL are introduced to simulate the real situation. As shown in Figure 4 , the red dot is near the warning boundary, which is a violation position.

[0168] Based on the warning decision simulation model and the simulation generated multiple operating states, the warning frequency of the eVTOL triggering the warning of the general aircraft is counted, and if the warning frequency is lower than the preset safety threshold, it is determined that the safety of the crossing zone position scheme meets the requirements. The spatial distribution of the warning points is shown in Figure 5 , there are a total of 18 warning points in 200 million experiments, and the warning rate is 9x10 -6 , which is less than the set level that requires mitigation measures, and the maximum violation of the eVTOL warning boundary value is 25.6ft. The minimum vertical distance between the general aircraft and the eVTOL is 341.3m, which is greater than the requirement of the minimum safety interval between the passenger aircraft, verifying that under ideal conditions, the eVTOL flying in the set crossing zone will not affect the approach of the passenger aircraft and trigger the warning of the general aircraft.

[0169] A collision risk model of the general aircraft and the eVTOL in the crossing zone is constructed, the collision risk value in the crossing zone is calculated based on the model, and whether the value is lower than the safety target threshold is determined to analyze the safety of the crossing zone. The collision risk model calculation process of the general aircraft and the eVTOL in the crossing zone is as follows:

[0170] Horizontal overlap probability calculation formula:

[0171]

[0172] wherein, is the longitudinal direction separation between aircrafts, is the lateral direction separation between aircrafts, is the horizontal overlap probability, is the horizontal relative velocity, is the horizontal collision rate;

[0173] Vertical crossing probability calculation formula:

[0174]

[0175]

[0176] wherein, is the vertical crossing probability, is the vertical distance between aircrafts, is the minimum safety distance threshold, is the attenuation scale coefficient, is the vertical height of the general aircraft, is the vertical height of the eVTOL;

[0177] System reliability calculation:

[0178] Vertical collision risk calculation formula:

[0179]

[0180] wherein, is the vertical collision risk value, is the horizontal overlap probability, is the vertical relative velocity, is the height of the general aircraft collision box, is the height of the eVTOL collision box;

[0181] Collision risk probability calculation formula:

[0182]

[0183] wherein, is the collision risk probability, is the effectiveness of the UAV collision avoidance system, is the reliability of ATC intervention on collision, is the reliability of TCAS, is the reliability of manned aircraft pilot collision avoidance, is the reliability of STCA;

[0184] Collision risk calculation formula:

[0185]

[0186] wherein, is the collision risk value, is the environmental influence coefficient, when in an ideal environment, When encountering bad weather, , is the coefficient of airspace management impact on collision risk when the control measures can effectively avoid collision, is the coefficient of airspace management impact on collision risk when the control measures cannot effectively avoid collision, .

[0187] System reliability parameters are shown in Table 6, aircraft speed parameters are shown in Table 7, collision box parameters are shown in Table 8, and collision model parameters are shown in Table 9. The safety target level is set to 1 x 10 -7 accidents per flight hour.

[0188] Table 6

[0189]

[0190] Table 7

[0191]

[0192] Table 8

[0193]

[0194] Table 9

[0195]

[0196] wherein V x1 is the speed of the civil aircraft in the longitudinal direction, V x2 is the speed of the eVTOL in the longitudinal direction, V y1 is the speed of the civil aircraft in the lateral direction, V y2 is the speed of the eVTOL in the lateral direction, V z1 is the speed of the civil aircraft in the vertical direction, V z2 is the speed of the eVTOL in the vertical direction, is the length of the civil aircraft collision box, is the length of the eVTOL collision box, is the width of the civil aircraft collision box, is the width of the eVTOL collision box, is the height of the civil aircraft collision box, is the height of the eVTOL collision box.

[0197] After 1 million Monte Carlo experiments, considering the navigation error of the eVTOL in the vertical direction, the results are shown in Figure 6 , Figure 7 The collision risk gradually decreases with the increase of the vertical interval, and the average collision risk is , which is less than the safety target level, verifying that the setting of the crossing zone at this time is safe.

[0198] The civil aircraft wake vortex sinking model is constructed, the wake vortex sinking height of the civil aircraft is calculated, and whether the height is higher than the height upper limit of the penetration area is determined. The calculation process of the civil aircraft wake vortex sinking model includes:

[0199] The basic parameter calculation process includes:

[0200] S211: Initial vortex spacing calculation formula:

[0201]

[0202] Wherein, is the initial vortex spacing, B is the wingspan of the aircraft;

[0203] S212: Initial circulation calculation formula:

[0204]

[0205] Wherein, is the initial circulation, is the mass of the aircraft, is the air density, is the speed of the aircraft;

[0206] S213: Wake sinking velocity calculation formula:

[0207]

[0208] Wherein, is the wake sinking velocity;

[0209] S214: Parameter normalization calculation formula:

[0210]

[0211]

[0212] Wherein, is the actual turbulent dissipation rate, is the normalized turbulent dissipation rate, is the actual B-V frequency, is the normalized B-V frequency, is the normalized time.

[0213] Circulation decay model construction:

[0214] S221: Diffusion stage:

[0215]

[0216] Wherein, is the dimensionless time, is the average circulation of the wake vortex with a radius of 5-15 m, is a constant amplitude, is a constant related to the average integral radius, is the first stage start time, is the effective viscosity of the first stage;

[0217] S222: rapid decay stage:

[0218]

[0219] wherein, is the second stage start time, is the effective viscosity of the second stage, the formula is as follows:

[0220]

[0221]

[0222]

[0223] wherein, is a dimensional time, is a dimensionless time, is the reference time of the rapid decay stage.

[0224] The tail vortex sinking model construction includes:

[0225]

[0226]

[0227]

[0228] wherein, denotes time, is the time-varying vortex ring, is the tail vortex sinking speed, is the vortex core sinking height.

[0229] Taking a civil aircraft A380 model as an example, the influence of the tail vortex sinking height on the eVTOL crossing area is analyzed, the A380 model related parameters are as shown in Table 10, and the tail vortex sinking model related parameters are as shown in Table 11.

[0230] Table 10

[0231]

[0232] Table 11

[0233]

[0234] Two typical wake vortexes with significant differences in two-stage evolution characteristics are simulated and analyzed. The first type is characterized by a longer first-stage dissipation time, and the second type is characterized by a longer second-stage dissipation time. The descent heights of the two types of wake vortexes during the entire evolution process are significantly different. To further improve the spatial distribution of the wake vortex, interpolation processing of the wake vortex is performed around the crossing zone. The results are shown in Figure 8 , which show the changes in runway glide path height, wake vortex affected height, and the range of the intrusion into the dangerous zone at different distances.

[0235] The safety evaluation method of the eVTOL aircraft crossing the runway extension line provided by the present application comprehensively considers the safety of setting the crossing zone from three aspects, and provides a reference for the future integration of manned aircraft and eVTOL in the airport range.

[0236] Through mathematical analysis of the constructed model, it is found that in the 200 million experiments, there are 18 alarm points, and the alarm rate is , which is less than the set level that requires mitigation measures. The eVTOL flying in the set crossing zone will not affect the approach of the passenger aircraft and trigger the alarm of the civil aircraft. In terms of collision risk, the average collision risk of the civil aircraft and the eVTOL in 100 million experiments is , which is less than the safety target level, verifying that the setting of the crossing zone at this time is safe. In terms of the influence of the wake vortex of the manned aircraft, the wake vortex generated by the civil aircraft flying on the runway glide path will not affect the flight of the eVTOL in the crossing zone.

[0237] The present application solves the problem of unreasonable setting of the crossing zone and the single dimension of safety evaluation of eVTOL and civil passenger aircraft integration, improves the safety of the crossing zone, and provides a reference for the future integration of manned aircraft and eVTOL in the airport range.

[0238] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of safety assessment of an eVTOL aircraft crossing a runway extension, characterized in that, The method comprises the following steps: S1: based on the eVTOL performance parameters, calculate the required safety interval in the lateral and vertical directions to determine the size parameters of the crossing zone; Calculate the minimum safety interval between the general aircraft and the eVTOL, and determine the crossing zone position based on the size parameters of the crossing zone and the minimum safety interval; S2: based on the traffic alert and collision avoidance system warning logic, build a warning judgment simulation model, count the frequency of the eVTOL triggering the warning of the general aircraft in the crossing zone position, and judge whether the warning frequency is lower than the preset safety threshold; The construction of the warning judgment simulation model includes: importing the navigation data, performance data and external wind disturbance data of the eVTOL, and simulating the various operating states of the eVTOL in the crossing zone by the Monte Carlo method; Based on the warning judgment simulation model and the simulated various operating states, the warning frequency of the eVTOL triggering the warning of the general aircraft is counted, and if the warning frequency is lower than the preset safety threshold, it is determined that the safety of the crossing zone position scheme meets the requirements; A collision risk model of the general aircraft and the eVTOL in the crossing zone position is constructed, and the collision risk value in the crossing zone is calculated based on the model to determine whether the value is lower than the safety target threshold; The collision risk model of the general aircraft and the eVTOL in the crossing zone position is calculated as follows: Horizontal overlap probability calculation formula: wherein, is the horizontal overlap probability, is the inter-aircraft longitudinal-direction separation, is the inter-aircraft lateral-direction separation, is the horizontal plane relative velocity, is the horizontal plane conflict rate; Vertical crossing probability calculation formula: wherein, is a vertical crossing probability, is an inter-aircraft vertical separation, is a minimum safety separation threshold, is a decay scale factor, is a civil aircraft vertical height, is an eVTOL vertical height; System reliability calculation: Collision risk calculation formula in the vertical direction: wherein, is a vertical direction collision risk value, is an overlap probability in the horizontal plane, is a vertical relative velocity, is a height of the general aviation collision box, is a height of the eVTOL collision box; Collision risk probability calculation formula: wherein, is the probability of a collision risk, is the effectiveness of the UAV collision avoidance system, is the reliability of ATC intervention on conflicts, is the reliability of TCAS, is the reliability of the manned pilot collision avoidance, is the reliability of STCA; Collision risk calculation formula: wherein, is a collision risk value, is an environmental impact coefficient, is a coefficient for the impact of airspace management on collision risk; A general aircraft wake vortex sinking model is constructed to calculate the wake vortex sinking height and determine whether the height is higher than the height upper limit of the crossing zone position; The calculation process of the general aircraft wake vortex sinking model includes: S21: basic parameter calculation; The basic parameter calculation process includes: S211: calculate the initial vortex spacing; S212: calculate the initial circulation; S213: calculate the wake vortex sinking velocity; S214: calculate the normalized parameter; S22: circulation decay model construction; The circulation decay model construction includes: S221: diffusion stage: wherein, is the average circulation for a tail vortex radius of 5-15 m, is the dimensionless time, is the constant amplitude, is a constant related to the average integral radius, is the first phase start time, is the effective viscosity of the first phase; S222: rapid decay stage: wherein, is the second phase start time, is the second phase effective viscosity, which is given by the formula: wherein, is a dimensional time, is a dimensionless time, is a reference time for the rapid decay phase, is a normalized turbulent dissipation rate; S23: wake vortex sinking model construction; The wake vortex sinking model construction includes: wherein, is the time-varying wake vortex circulation, denotes time, is the initial circulation, is the sink velocity of the wake vortex, B is the wingspan of the aircraft, is the sink height of the vortex core; S3: if the crossing zone position meets the evaluation requirements of the three dimensions in step S2 above, it is determined that it is a safe evaluation qualified crossing zone position, and the crossing zone position and the evaluation result are output.

2. A method of safety assessment of an eVTOL aircraft crossing a runway overrun as claimed in claim 1, wherein, According to the performance parameters of the eVTOL, the required safety interval in the lateral and vertical directions is calculated, the length of the crossing zone is determined according to the lateral safety interval between the aircrafts, and the width of the crossing zone is determined according to the vertical safety interval between the aircrafts, which comprises: S11: calculate the overlap probability between the aircrafts in the lateral and vertical directions; S12: calculate the collision risk in the lateral and vertical directions; S13: set an iterative calculation process, take the initial interval as the starting point, adjust the interval parameters in the lateral and vertical directions, substitute the adjusted interval values into the formula to calculate the collision risk, and when the collision risk is equal to or lower than the civil aviation safety target level, the interval value parameters in the lateral and vertical directions at this time are the minimum crossing zone size parameters that meet the safety requirements.

3. The method for safety assessment of an eVTOL aircraft crossing a runway overrun as defined in claim 1, wherein, The minimum safety interval between the general aircraft and the eVTOL is calculated, the crossing zone position is determined according to the crossing zone size parameter and the minimum safety interval, and the crossing zone position includes: The height calculation formula of the general aircraft on the runway glide path: wherein, is the height of the civil aircraft, is the elevation of the runway threshold, is the height of the reference datum, is the horizontal distance of the civil aircraft from the runway threshold, is the length of the runway, is the glide angle of the runway glide slope; The alarm boundary calculation formula: wherein, is an alert boundary, is a TCAS alert threshold, is a fixed separation parameter, is a variable alert threshold, is a current altitude; The runway glide path height calculation formula: wherein, is the height of the runway threshold, is the horizontal position of the current calculation point, is the horizontal position of the runway threshold reference point, typically at the runway threshold; The difference between the height of the general aircraft on the runway glide path and the alarm boundary is the minimum safety interval; The crossing zone position of the eVTOL is located below the alarm boundary, and the optimal position of the crossing zone in the lower part of the alarm boundary is determined by the following method: under the premise of ensuring the minimum safety interval, the distance between the crossing zone and the runway, the minimum height of the crossing zone are comprehensively considered to obtain the optimal position.

4. The method for safety assessment of an eVTOL aircraft crossing a runway overrun as defined in claim 1, wherein, The step S3 includes: If the crossing zone position meets the following three conditions at the same time: The frequency of the eVTOL triggering the alarm of the general aircraft is lower than the preset safety threshold value; The collision risk value of the general aircraft and the eVTOL is lower than the safety target threshold value; The tail vortex sinking height of the general aircraft is higher than the height upper limit of the crossing zone; Then it is determined that the safety evaluation of the crossing zone position meets the standard, a safety evaluation meeting the standard signal is generated, and the geographic coordinate information of the crossing zone position is output.

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