Method for Selecting Landing Site of Large Fixed-Wing Aircraft in Emergency

Abstract

The present invention provides a method for selecting a landing site in case of emergency for a large fixed-wing aircraft, including: combining an evaluation index system for emergency landing sites, obtaining evaluation index data of each candidate landing site, and determining the subjective weight values of each evaluation index in an analytic hierarchy process; determining an initial decision matrix according to the evaluation index system for emergency landing sites, and performing forwardization and standardization processing on the initial decision matrix to obtain a normalized decision matrix; using the CRITIC method to determine the objective weight values of each evaluation index in the normalized decision matrix, and jointly forming a combined weight value with the subjective weight values; calculating the evaluation values of each candidate landing site by using the non-integral rank combined weighted rank sum ratio method, and taking the landing site with the highest evaluation value as the selected emergency landing site. The present invention analyzes and calculates each candidate landing site based on the combined weight non-integral rank sum ratio method, which is beneficial to improving the survival probability of large fixed-wing aircraft in case of emergency.

Description

Technical Field

[0001] The present invention relates to the field of aerospace intelligent auxiliary decision-making, and particularly to a method for selecting a landing site in case of emergency for a large fixed-wing aircraft. Background Art

[0002] For large fixed-wing aircraft, a safe return to the airfield marks the successful completion of the flight mission. The selection of the landing site is usually determined at the beginning of the aircraft's mission execution. However, in case of emergency such as changes in the battlefield environment, damage to the aircraft, mission changes, and weather changes, the original landing site may be inaccessible or no longer suitable for landing, and it is necessary to re-screen a suitable landing site within the currently reachable area of the aircraft. When there are multiple landing sites within the reachable area of the aircraft, it is crucial to quickly determine the most favorable landing site for safe landing from them.

[0003] Currently, few achievements have addressed this problem with an evaluation method. The relevant achievements generally focus on proposing driving suggestions for emergency landings of aircraft from the perspective of fixed-type aircraft or specific airports, lacking in-depth research at the technical level. In addition, although the fitness function method has been applied to the problem of screening the best landing site, the function weight values are artificially set, and there are defects such as inaccurate evaluation results due to improper function weight values.

[0004] Therefore, how to quickly determine the most favorable landing site for safe landing in case of emergency is a technical problem that urgently needs to be solved for large fixed-wing aircraft. Summary of the Invention

[0005] In view of this, the present invention proposes a method for selecting a landing site in case of emergency for a large fixed-wing aircraft, which analyzes and calculates each candidate landing site based on the combined weighting non-integer rank sum ratio method, and quickly determines the most suitable emergency landing site in a scientific and accurate manner, which is beneficial to improving the survival probability of large fixed-wing aircraft in case of emergency.

[0006] To this end, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for selecting a landing site in case of emergency for a large fixed-wing aircraft, including the steps of:

[0008] Combined with the emergency landing site evaluation index system, obtaining the evaluation index data of each candidate landing site; the evaluation indexes in the emergency landing site evaluation index system mainly include: visibility, rainfall / snowfall, wind speed, remaining aircraft positions, runway length, and daily flight volume;

[0009] Determining the subjective weight values of each evaluation index in a hierarchical analysis manner;

[0010] Determine the initial decision matrix according to the emergency landing site evaluation index system, and perform positive and standardized processing on the initial decision matrix to obtain the normalized decision matrix;

[0011] Use the CRITIC method to determine the objective weight values of each evaluation index in the normalized decision matrix;

[0012] Form the combined weight value by combining the objective weight value and the subjective weight value;

[0013] Through rank transformation, convert the evaluation index data of each candidate landing site into a dimensionless statistic rank sum ratio, construct a combined weighted rank sum ratio based on the combined weight value and the rank sum ratio, use the combined weighted rank sum ratio as the evaluation value of each candidate landing site, and select the landing site with the highest evaluation value as the emergency landing site to be selected.

[0014] Furthermore, determine the subjective weight values of each evaluation index in the form of hierarchical analysis, including:

[0015] Combined with the scale judgment table, determine the judgment matrix A by pairwise comparison as:

[0016]

[0017] In the formula, a ij ×a ji = 1; m is the number of evaluation indexes;

[0018] Calculate the eigenvector β and the maximum eigenvalue λ of the judgment matrix max ;

[0019] Use the random consistency index CR to measure the consistency degree of the judgment matrix, and its calculation method is:

[0020]

[0021] In the formula, m is the number of evaluation indexes; λ max is the maximum eigenvalue of the judgment matrix; RI is the average random consistency index; if CR ≤ 0.1, it means that the judgment matrix meets the consistent test requirements; if CR > 0.1, the judgment matrix needs to be redesigned until the consistent test requirements are met;

[0022] Use the eigenvalue to obtain the subjective weight;

[0023]

[0024] Among them, w zj is the subjective weight, j = 1, 2,..., m.

[0025] Further, an initial decision matrix is determined according to the emergency landing site evaluation index system, and the initial decision matrix is normalized and standardized to obtain a normalized decision matrix, including:

[0026] Suppose there are n candidate landing sites and m evaluation indexes, then x ij (i = 1, 2…, n; j = 1, 2…, m) represents the value of evaluation index j in the i-th candidate landing site;

[0027] Perform positive normalization on the initial decision matrix;

[0028] For the data after positive normalization Perform standardization to obtain standardized data zij;

[0029] Use z ij To form a normalized decision matrix Z:

[0030]

[0031] Further, the CRITIC method is used to determine the objective weight values of each evaluation index in the normalized decision matrix, including:

[0032] Calculate the standard deviation σ of each index in the normalized decision matrix j And the correlation coefficient r kj ;

[0033] Calculate the objective weight w of the evaluation index kj (j = 1, 2…, m);

[0034]

[0035] In the formula, w j Is the weight value of index j, C j Represents the standard deviation and correlation coefficient of index j,

[0036] Further, the objective weight value and the subjective weight value are jointly formed into a combined weight value, including:

[0037] The construction method is as follows:

[0038]

[0039] Among them, w zj Is the subjective weight value, w kj Is the objective weight value, w j Is the combined weight value, j = 1, 2,…, m.

[0040] Further, through rank transformation, the evaluation index data of each candidate landing site is converted into a dimensionless statistic rank sum ratio. Based on the combined weight value and the rank sum ratio, a combined weighted rank sum ratio is constructed. The combined weighted rank sum ratio is used as the evaluation value of each candidate landing site, and the landing site with the highest evaluation value is selected as the emergency landing site, including:

[0041] Rank the index data;

[0042] For extremely large indicators, the ranking method is:

[0043]

[0044] In the formula, n is the number of emergency landing sites; X is the data under this index in the initial decision matrix; X min is the minimum value of the data under this index in the initial decision matrix;

[0045] For extremely small indicators, the ranking method is:

[0046]

[0047] In the formula, n is the number of emergency landing sites; X is the data under this index in the initial decision matrix; X max is the maximum value of the data under this index in the initial decision matrix;

[0048] Improve the non-integer rank sum ratio using the combined weight value, and construct the combined weighted rank sum ratio WRSR i :

[0049] In the formula, WRSR i is the rank sum ratio of the i-th emergency landing site; w j is the combined weight value of the evaluation index j; R ij is the rank of the i-th emergency landing site under the index j;

[0050] Sort the combined weighted rank sum ratios of each obtained emergency landing site from small to large, and calculate the downward cumulative frequency p i , and the calculation formula is:

[0051] In the formula, is the sample frequency;

[0052] Convert pi to the probability unit Probit. Probit is the pi normal deviation of the standard normal distribution plus 5. In addition, the last cumulative frequency is estimated according to ;

[0053] Calculate the linear regression equation; among them, the calculation formula of the linear regression equation is: WRSR = a + b × Probit;

[0054] In the formula, the combined weighted rank sum ratio WRSR is the dependent variable; the probit is the independent variable; a and b are parameters;

[0055] Based on the estimated value of the combined weighted rank sum ratio, candidate landing sites are ranked. The larger the value, the better the performance of the emergency landing site.

[0056] Advantages and positive effects of the present invention:

[0057] (1) In the present invention, the non-integer rank sum ratio method can make full use of the advantages of the original data, convert the information in the original data of each emergency landing site into the form of ranks for quantitative comparison, and combine statistical theory to obtain an accurate ranking result, effectively solving the problem of selecting the best landing site in an emergency.

[0058] (2) In the present invention, the weights of the evaluation indicators for the landing site in an emergency are determined in a subjective and objective combined weighting manner, fully considering the objective actual factors of each landing site and the subjective factors in an emergency, and can accurately assign weights to the evaluation indicators of the candidate landing sites, avoiding the defect that the evaluation result is not accurate enough caused by artificially setting the weights of each evaluation indicator. Description of the Drawings

[0059] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0060] Figure 1 It is a flowchart of a method for selecting a landing site in an emergency for a large fixed-wing aircraft in an embodiment of the present invention;

[0061] Figure 2 It is a schematic diagram of an evaluation index system for an emergency landing site in an embodiment of the present invention;

[0062] Figure 3 It is a comparison chart of the evaluation results of each emergency landing site in an embodiment of the present invention. Detailed Embodiments

[0063] In order to enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0064] It should be noted that the terms "first", "second", etc. in the description, claims and above-mentioned drawings of the present invention are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0065] As Figure 1 shown, a method for selecting an emergency landing site for a large fixed-wing aircraft provided in an embodiment of the present invention includes the following steps:

[0066] S1: Combine the emergency landing site evaluation index system to obtain the evaluation index data of each candidate landing site; S2: Determine the subjective weight values of each evaluation index in an analytic hierarchy process manner.

[0067] Among them, the core of the analytic hierarchy process is the judgment matrix formed by pairwise comparison between evaluation indexes, and the index weights are determined by a layer-by-layer comparison method. The analytic hierarchy process is applicable to evaluation index systems where the criterion layer (the number of layers of evaluation indexes) is 1 layer or more, but too many criterion layers will bring unnecessary complexity and difficulty to the analytic hierarchy process. In the embodiment of the present invention, the criterion layer has only 1 layer.

[0068] Among them, the emergency landing site evaluation index system is as Figure 2 shown. When selecting an emergency landing site, the factors considered, that is, the evaluation indexes, mainly include: visibility, rainfall (snowfall) amount, wind speed, remaining aircraft positions, runway length, and the number of flights on the day.

[0069] Since the present invention takes into account the problem of subjective factors and uses the analytic hierarchy process to solve it, this limits the number of evaluation indexes and cannot be too many. If the number of evaluation indexes is too large, it will lead to an excessive dimension of the judgment matrix of the analytic hierarchy process, and the consistency test cannot be passed. Moreover, it will consume a large amount of time in pairwise comparison and is not suitable for rapid decision-making in emergency situations. Considering the above two aspects comprehensively, 6 key indexes are determined in the embodiment of the present invention.

[0070] In specific implementation, first obtain and input the emergency landing site evaluation index system data, that is, the evaluation index data of each landing site, which specifically includes the following steps:

[0071] S21: Determine the judgment matrix.

[0072] In the embodiment of the present invention, the 9-scale judgment method is adopted, and the scale judgment for describing the mutual influence between various index factors is shown in Table 1.

[0073] Table 1

[0074]

[0075] Combined with the scale judgment table, by means of pairwise comparison, the judgment matrix A is determined as:

[0076]

[0077] where a ij × a ji = 1; m is the number of evaluation indicators.

[0078] S22: Calculate the eigenvector β and the maximum eigenvalue λ of the judgment matrix max ;

[0079] S23: Consistency test;

[0080] The consistency degree of the judgment matrix is measured by the random consistency index CR, and its calculation method is:

[0081]

[0082] where m is the number of evaluation indicators; λ max is the maximum eigenvalue of the judgment matrix; RI is the average random consistency index, and the specific values are shown in Table 2.

[0083] Table 2

[0084]

[0085] If CR ≤ 0.1, it means that the judgment matrix meets the requirements of the consistency test; if CR > 0.1, the judgment matrix needs to be redesigned until the requirements of the consistency test are met.

[0086] S24: Use the eigenvalue to obtain the subjective weight w zj (j = 1, 2,..., m);

[0087]

[0088] The condition for generating the judgment matrix is that the decision maker needs to compare each evaluation indicator pairwise according to subjective factors. Therefore, the weight composed of the eigenvalues of the judgment matrix includes the participation of subjective factors. Therefore, in the embodiment of the present invention, the weight obtained from the eigenvalues of the judgment matrix is called the subjective weight. S3: Determine the initial decision matrix according to the emergency landing site evaluation index system, and perform positive and standardization processing on the initial decision matrix to obtain the normalized decision matrix;

[0089] There are n evaluation objects (emergency landing sites) and m evaluation indicators, then x ij (i = 1, …, 2, n; j = 1, …, 2, m represents the value of evaluation indicator j in the i-th emergency landing site; the n*m matrix composed of the indicator data determined by the evaluation indicator system is the initial decision matrix.)

[0090] In specific implementation, S3 specifically includes the following steps:

[0091] S31: Perform positive normalization on the initial decision matrix;

[0092] In positive normalization, generally all types of indicator data are converted into extremely large type indicator data. Therefore, for the data under the extremely large type indicator j, the data remains unchanged before and after positive normalization, that is:

[0093]

[0094] For the extremely small type indicator j, the positive normalization method is:

[0095]

[0096] In the formula, x max is the maximum value of the data under this indicator;

[0097] S32: For the data after positive normalization perform standardization processing, and the calculation formula is:

[0098]

[0099] S33: Use z ij to form the normalized decision matrix Z:

[0100]

[0101] The normalized decision matrix can eliminate the influence of the dimension between indicators and is convenient for subsequent use of the CRITIC method to determine the objective weight.

[0102] S4: Use the CRITIC method to determine the objective weight values of each evaluation indicator in the normalized decision matrix, and jointly form the combined weight value with the subjective weight values determined in S2;

[0103] In specific implementation, S4 specifically includes the following steps:

[0104] S41: Calculate the standard deviation and correlation coefficient of each indicator in the normalized decision matrix;

[0105] The CRITIC method is an objective weighting method for determining index weights based on data fluctuations. It reflects the comparison intensity and conflict of evaluation indexes through the standard deviation and correlation coefficient, and then determines the weights of each index.

[0106] The standard deviation calculation formula is as follows:

[0107]

[0108] The correlation coefficient calculation formula is as follows:

[0109]

[0110] In the formula, Z k and Z j are the average values of the data under indexes k and j respectively; Cov(Z k , Z j ) is the covariance of indexes k and j; σ k and σ j are the standard deviations of indexes k and j respectively; rk j is the correlation coefficient of indexes k and j;

[0111] S42: Calculate the objective weight w kj (j = 1, 2…, m);

[0112]

[0113] In the formula, w j is the weight value of index j, and C j represents the amount of information contained in index j (including the standard deviation and correlation coefficient):

[0114] Construct the combined weight value w j (j = 1, 2…, m) based on the objective weight obtained from S42 and the subjective weight obtained from S2. The construction method is as follows:

[0115]

[0116] S5: Use the non-integer rank combination weighted rank sum ratio method to calculate the evaluation values of each candidate landing site. The combined weighted rank sum ratio is the rank sum ratio after combining and weighting the combined weight values, and complete the evaluation of the emergency landing site.

[0117] Among them, the non-integer rank sum ratio method is a non-parametric statistical analysis method. Its core idea is to convert the original data into a dimensionless statistic, the rank sum ratio, through rank transformation, and comprehensively analyze the evaluation object with the rank sum ratio. The advantage of the non-integer rank sum ratio method is that it is not sensitive to extreme values, does not lose the information of the original data, and the ranking method is appropriate. In order to make the evaluation method more suitable for the selection of landing sites in case of emergency for large fixed-wing aircraft, in the embodiments of the present invention, the non-integer rank sum ratio method is further improved. First, the original data is converted into a dimensionless statistic, the rank sum ratio, through rank transformation, and a combined weighted rank sum ratio is constructed based on the combined weight value and the rank sum ratio, and the evaluation object is comprehensively analyzed with the combined weighted rank sum ratio.

[0118] In specific implementation, S5 specifically includes the following steps:

[0119] S51: Conduct rank transformation on the index data;

[0120] The indexes can be divided into extremely large indexes and extremely small indexes. The index type with the larger the value, the better is the extremely large index; correspondingly, the index type with the smaller the value, the better is the extremely small index.

[0121] The rank transformation is essentially a rank conversion. The non-integer rank sum ratio method uses linear interpolation for ranking. Except for the maximum and minimum values, which must be integers, the remaining ranks are non-integers. During the ranking process, the maximum value of the same index is ranked as n, the minimum value is ranked as 1, and the remaining values are ranked as non-integer ranks that increase linearly between 1 and n. There is a quantitative linear correspondence between the ranked order and the original index value, that is, the original index value is quantitatively converted into a rank, rather than simply being ranked. In this way, the loss of quantitative information of the original index value after direct ranking is avoided, so the comprehensive evaluation result is more accurate and objective compared with the rank sum ratio method.

[0122] For extremely large indexes, the ranking method is:

[0123]

[0124] In the formula, n is the number of emergency landing sites; X is the data under this index in the initial decision matrix; X min is the minimum value of the data under this index in the initial decision matrix.

[0125] For extremely small indexes, the ranking method is:

[0126]

[0127] In the formula, n is the number of emergency landing sites; X is the data under this index in the initial decision matrix; X max is the maximum value of the data under this index in the initial decision matrix.

[0128] S52: Improve the non-integer rank sum ratio using the combined weight value;

[0129] Construct the combined weighted rank sum ratio WRSR i (i = 1, 2…, n) is as follows:

[0130]

[0131] In the formula, WRSR i is the rank sum ratio of the i-th emergency landing site; w j is the combined weight value of the evaluation index j; R ij is the rank of the i-th emergency landing site under the index j;

[0132] S53: Calculate the downward cumulative frequency and probit;

[0133] Sort the combined weighted rank sum ratios of each emergency landing site obtained from small to large, and calculate the downward cumulative frequency p i , and the calculation formula is:

[0134]

[0135] In the formula, is the sample frequency.

[0136] Convert pi to probit. Probit is the pi normal deviation of the standard normal distribution plus 5. In addition, the last cumulative frequency is estimated according to estimation.

[0137] S54: Calculate the linear regression equation;

[0138] The calculation formula of the linear regression equation is: WRSR = a + b×Probit;

[0139] In the formula, the combined weighted rank sum ratio WRSR is the dependent variable; the probit is the independent variable; a and b are parameters.

[0140] S55: Sorting;

[0141] Estimate the corresponding combined weighted rank sum ratio value through the linear regression equation, and complete the grading and sorting of the emergency landing sites based on this. The larger the value, the better the performance of the emergency landing site. Among them, the number of grades is equal to the number of emergency landing sites.

[0142] To verify the effectiveness and feasibility of the method proposed in this embodiment, an analysis is carried out on the actual flight mission of a fixed-wing aircraft. After calculating the remaining fuel, there are 6 emergency landing sites within the reachable area, and combined with Figure 2 the emergency landing site evaluation index system, x ij(i = 1, 2…, 6; j = 1, 2…, 6) constitutes the initial decision matrix X as follows:

[0143]

[0144] By analyzing the importance degree among various evaluation index factors, the judgment matrix A is obtained as follows:

[0145]

[0146] Use CR to measure the consistency degree of the judgment matrix:

[0147]

[0148] CR = 0.0628;

[0149] Since CR < 0.1, it indicates that the judgment matrix meets the requirements of the consistency test.

[0150] Using the eigenvalues of the judgment matrix to solve, the subjective weight w zj (j = 1, 2,…, 6) is as follows:

[0151] w zj = [0.2644 0.1422 0.1329 0.2945 0.1242 0.0418];

[0152] Furthermore, using the original decision matrix X, solve the objective weight value of the evaluation index;

[0153] Perform positive and standardization processing on the initial decision matrix X to obtain the normalized decision matrix Z;

[0154]

[0155] Use the CRITIC method to determine the evaluation index weight w j (j = 1, 2…, m);

[0156] w kj = [0.0538 0.1707 0.3092 0.1666 0.0274 0.2723];

[0157] Furthermore, calculate the combined weighting result as follows:

[0158]

[0159] w j = [0.1379 0.1803 0.2345 0.2563 0.0675 0.1235].

[0160] After obtaining the combined weighting value w jAfter that, it is used to improve the non-integer rank sum ratio and construct the combined weighted rank sum ratio WRSR;

[0161]

[0162] WRSR = [0.5922 0.5811 0.7780 0.5551 0.4501 0.5436];

[0163] Sort the combined weighted rank sum ratios of each emergency landing site obtained from small to large, count the cumulative frequency downward, and convert it into the probability unit Probit to obtain Probit as follows:

[0164] Probit = [4.0326 4.5693 5 5.4307 5.9674 6.7317];

[0165] Combined with the calculation results of Probit, the linear regression equation is obtained as;

[0166] WRSR = 0.0359 + 0.1035Probit;

[0167] Estimate the corresponding combined weighted rank sum ratio value through the linear regression equation, and complete the grading and sorting of the emergency landing sites based on this. Finally, the evaluation results of each emergency landing site are as follows:

[0168]

[0169] Furthermore, based on the results, a comparison chart of the evaluation results of each emergency landing site as shown in Figure 3 is obtained. Based on the numerical values, the sorting of the emergency landing sites is completed. The larger the numerical value, the better the emergency landing site. Therefore, the sorting result from high to low in numerical value represents the evaluation result of the combined weighted non-integer rank sum ratio method for each emergency landing site from excellent to poor. The specific sorting result is: Emergency Landing Site No. 3 > Emergency Landing Site No. 1 > Emergency Landing Site No. 2 > Emergency Landing Site No. 4 > Emergency Landing Site No. 6 > Emergency Landing Site No. 5. Obviously, Emergency Landing Site No. 3 is the best landing site, effectively solving the problem of choosing a landing site in an emergency.

[0170] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for selecting an emergency landing site for a large fixed-wing aircraft, comprising the following steps: Combining the emergency landing site evaluation index system to obtain the evaluation index data of each candidate landing site; The evaluation indexes in the emergency landing site evaluation index system mainly include: visibility, rainfall / snowfall, wind speed, remaining aircraft positions, runway length, and daily flight volume; Determining the subjective weight values of each evaluation index by means of analytic hierarchy process; Determining an initial decision matrix according to the emergency landing site evaluation index system, and performing positive and standardization processing on the initial decision matrix to obtain a normalized decision matrix; Using the CRITIC method to determine the objective weight values of each evaluation index in the normalized decision matrix; Combining the objective weight values and the subjective weight values to form a combined weight value; Converting the evaluation index data of each candidate landing site into a dimensionless statistic rank sum ratio through rank transformation, constructing a combined weighted rank sum ratio based on the combined weight value and the rank sum ratio, using the combined weighted rank sum ratio as the evaluation value of each candidate landing site, and taking the landing site with the highest evaluation value as the selected emergency landing site; Among them, converting the evaluation index data of each candidate landing site into a dimensionless statistic rank sum ratio through rank transformation, constructing a combined weighted rank sum ratio based on the combined weight value and the rank sum ratio, using the combined weighted rank sum ratio as the evaluation value of each candidate landing site, and taking the landing site with the highest evaluation value as the selected emergency landing site, including: Performing rank processing on the index data; For extremely large indexes, the ranking method is: Where n is the number of emergency landing sites; X is the data under this index in the initial decision matrix; X min is the minimum value of the data under this index in the initial decision matrix; For extremely small indexes, the ranking method is: Where n is the number of emergency landing sites; X is the data under this index in the initial decision matrix; X max is the maximum value of the data under this index in the initial decision matrix; Improve the non-integer rank sum ratio by using the combined weight value, and construct the combined weighted rank sum ratio WRSR i : i = 1, 2, …, n; Where, WRSR i is the rank sum ratio of the i-th emergency landing site; w j is the combined weight value of evaluation index j; R ij is the rank of the i-th emergency landing site under index j; Sort the combined weighted rank sum ratios of the obtained emergency landing sites from smallest to largest, and calculate the downward cumulative frequency p i , and the calculation formula is: In the formula, is the sample frequency; Convert pi to the probit, where the probit is the normal deviate of pi from the standard normal distribution plus 5. Additionally, the last cumulative frequency is estimated according to estimation; Calculating the linear regression equation; where the calculation formula of the linear regression equation is: WRSR = a + b×Probit; In the formula, the combined weighted rank sum ratio WRSR is the dependent variable; the probit is the independent variable; a and b are parameters; Based on the estimated value of the combined weighted rank sum ratio, performing grading and ranking on the candidate landing sites, and the larger the value, the better the performance of the emergency landing site.

2. The method for selecting a landing site in an emergency for a large fixed-wing aircraft according to claim 1, wherein Determining the subjective weight values of each evaluation index by means of analytic hierarchy process, including: Combining the scale judgment table, and determining the judgment matrix A by pairwise comparison as: where a ij × a ji = 1; m is the number of evaluation indicators; Calculate the eigenvector β and the maximum eigenvalue λ of the judgment matrix max ; Using the random consistency index CR to measure the consistency degree of the judgment matrix, and its calculation method is: where m is the number of evaluation indicators; λ max is the maximum eigenvalue of the judgment matrix; RI is the average random consistency index; if CR ≤ 0.1, it indicates that the judgment matrix meets the requirements of the consistency test; if CR > 0.1, the judgment matrix needs to be redesigned until the requirements of the consistency test are met; Using the eigenvalue to obtain the subjective weight; Among them, w zj is the subjective weight, and j = 1, 2, …, m.

3. The method for selecting a landing site in an emergency for a large fixed-wing aircraft according to claim 1, characterized in that, Determining an initial decision matrix according to the emergency landing site evaluation index system, and performing positive and standardization processing on the initial decision matrix to obtain a normalized decision matrix, including: There are n candidate landing sites and m evaluation indicators, then x ij (i = 1, 2..., n; j = 1, 2..., m) represents the value of evaluation indicator j in the i-th candidate landing site; Performing positive processing on the initial decision matrix; For the data after forward processing perform standardization processing to obtain standardized data z ij ; Using z ij Construct a normalized decision matrix Z:

4. The method for selecting a landing site in case of emergency for a large fixed-wing aircraft according to claim 3, wherein, Using the CRITIC method to determine the objective weight values of each evaluation index in the normalized decision matrix, including: Calculate the standard deviation σ of each index in the normalized decision matrix j and the correlation coefficient r kj ; Calculate the objective weight w of the evaluation index kj (j = 1, 2…, m); where w j is the weight value of index j, C j represent the standard deviation and correlation coefficient of index j, 5. The method for selecting a landing site in an emergency for a large fixed-wing aircraft according to claim 4, characterized in that, Combining the objective weight values and the subjective weight values to form a combined weight value, including: The construction method is as follows: Among them, w zj is the subjective weight value, w kj is the objective weight value, w j is the combined weight value, j = 1, 2, …, m.

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