Aircraft landing distance prediction method

Abstract

An aircraft landing distance prediction method is provided, which can obtain a more accurate and reliable landing distance prediction based on the real-time state of the aircraft and the landing performance of each flight stage. The method includes: determining the aircraft's state based on whether the ROAAS (Real-Time Off-Road Assurance System) activation conditions are met and whether a normal landing has occurred; upon entering a first state, further dividing the first state into a first stage and a second stage based on whether the aircraft is above the runway's prescribed altitude, and using different landing distance prediction models to predict the landing distance in different stages of the first state to obtain an initial landing distance; and calculating a landing distance correction amount by combining performance impact factors that affect the landing distance to obtain a corrected landing distance prediction value; upon entering a second state, using another different landing distance prediction model to predict the landing distance, obtaining an initial landing distance, and considering the aircraft configuration to obtain a corrected landing distance prediction value.

Description

Technical Field

[0001] This invention relates to the field of flight safety assistance systems, and in particular to a method for predicting aircraft landing distance applicable to Runway Overrun Awareness and Alerting System (ROAAS). Background Technology

[0002] Runway overrun accidents during the landing phase of commercial airliners rank first among all accident types in the international civil aviation field. To reduce the enormous cost and casualties caused by runway overrun accidents and improve flight safety, the European Aeronautical Electronics Organization (EAEA) released ED-250, "Minimum Performance Standards for Runway Overrun Warning and Alert Systems (ROAAS)," at the end of 2017. This standard requires ROAAS to predict the aircraft's landing distance in real time and alert pilots to take appropriate measures to avoid risks before a runway overrun occurs. In 2020, the European Aviation Safety Agency (EASA) mandated that all newly issued single-aircraft airworthiness certificates for large commercial transport aircraft from January 1, 2025, must be equipped with ROAAS. In 2024, the Civil Aviation Administration of China (CAAC) issued the "Rules for the Certification of Operational Qualifications of Large Aircraft Public Air Transport Carriers," requiring that "except with approval from the CAAC, all aircraft first issued single-aircraft airworthiness certificates on or after January 1, 2026, must be equipped with ROAAS."

[0003] Foreign civil aircraft manufacturers started their research on ROAAS earlier, and their technology is mature and widely used. In contrast, domestic ROAAS research is still in its early stages. Given the growing trend of foreign companies monopolizing ROAAS technology, China urgently needs to accelerate its research and development of ROAAS algorithms and launch mature and reliable products to achieve independent control over key ROAAS technologies.

[0004] Generally speaking, the target functions of ROAAS are divided into two parts: landing distance prediction and alarm triggering notification. Among them, landing distance prediction is the benchmark for alarm triggering, which determines the accuracy and reliability of alarm triggering and is one of the most important components of ROAAS.

[0005] Common methods for predicting landing distance include prediction methods based on physical motion models, prediction methods based on machine learning, and other comprehensive prediction methods.

[0006] Chinese patent CN107944701B discloses a landing distance prediction method that uses mathematical modeling and regression analysis to construct a "danger red line" model. This method can predict the remaining runway distance based on different environmental parameters to determine the likelihood of an aircraft overrunning the runway. However, this method, along with machine learning-based methods, relies on large amounts of historical data and complex prediction network models, placing high demands on data storage space and computing platforms. Furthermore, it does not yet meet the requirements for safety and cost-effectiveness. In contrast, landing distance prediction methods based on physical motion models offer greater practicality and operability.

[0007] It is also known that Chinese patent application CN115826599A discloses a landing distance prediction method that calculates the relative position of the aircraft's landing point on the runway based on energy maneuver theory and in combination with flight conditions such as radio altitude, attitude angle, and airspeed. However, this method does not consider the influence of runway conditions, environmental weather, and other factors on the landing distance.

[0008] Furthermore, Chinese patent application CN116451988A discloses a landing distance prediction method that comprehensively analyzes flight data, meteorological data, aircraft performance data, and personnel data to predict overrun and deviation thresholds to determine whether an aircraft will overrun the runway. However, this method does not consider the different landing characteristics of the aircraft when it is in the air and on the ground.

[0009] In other words, current technologies do not consider the differences in aircraft motion characteristics at different flight phases and therefore do not employ different landing distance prediction models. Furthermore, they lack consideration of the impact of runway conditions, environmental weather, and other factors on landing distance. This results in limitations in using existing landing distance prediction methods, and in certain specific situations, significant deviations may even occur. Therefore, there is an urgent need to find a novel aircraft landing distance prediction method that fully considers the aircraft motion characteristics and flight-landing performance at different flight phases to more accurately predict aircraft landing distances. Summary of the Invention

[0010] This disclosure is made to solve the above-mentioned problems in the prior art. Its purpose is to provide an aircraft landing distance prediction method that can obtain a more accurate and reliable prediction of the landing distance based on the real-time status of the aircraft and the landing performance of each flight stage.

[0011] To address the aforementioned problems in the prior art, this disclosure provides an aircraft landing distance prediction method. The method comprises: determining whether the aircraft is in a first state or a second state based on whether the ROAAS (Real-Time Off-Road Assurance System) activation conditions are met and whether a normal landing has occurred; upon entering the first state, further dividing the first state into a first stage and a second stage based on whether the aircraft is above the runway's prescribed altitude; employing different landing distance prediction models in different stages of the first state to predict the landing distance, thereby obtaining the initial landing distance; and combining this with a performance impact factor that influences the landing distance. The landing distance correction is calculated, and then the corrected landing distance prediction value is obtained using the landing distance correction. When entering the second state, a different landing distance prediction model than the one used in the first state is used to predict the landing distance, obtain the initial landing distance, and obtain the corrected landing distance prediction value considering the aircraft configuration. The corrected landing distance prediction value obtained by using different landing distance prediction models in each state and stage is compared with the runway length in real time. The ROAAS system generates runway overrun warning information to prompt the pilot to take appropriate measures.

[0012] Preferably, after entering the first state, based on the aircraft's altitude relative to the runway threshold in the input landing runway information, if the flight altitude is higher than the specified altitude of the runway threshold, the aircraft is determined to be in the first stage of the first state. At this time, based on the aircraft's current position and altitude, the expected latitude and longitude coordinates of the aircraft descending in a straight line at the current flight path angle FPA to a specified distance from the runway are calculated in real time. Then, based on the landing runway information, the horizontal distance from the expected point to the runway threshold is calculated. Next, the horizontal distance of the air segment, the horizontal distance of the transition segment, and the horizontal distance of the ground segment are calculated respectively. Thus, the horizontal distance from the expected point to the runway threshold, the horizontal distance of the air segment, the horizontal distance of the transition segment, and the horizontal distance of the ground segment are added together to obtain the initial landing distance in the first stage of the first state.

[0013] Preferably, after entering the first state, based on the aircraft's altitude relative to the runway threshold in the input landing runway information, if the flight altitude is lower than or equal to the specified runway threshold altitude, the aircraft is determined to be in the second stage of the first state. At this time, the distance from the real-time runway position to the runway threshold is calculated, and based on the aircraft's inertial vertical velocity and altitude, the time required for the aircraft to descend from the current position to touch down the main landing gear is estimated. Thus, the horizontal distance of the remaining air segment from the aircraft's current position to the main landing gear touchdown is calculated. Furthermore, the horizontal distance of the transition segment and the horizontal distance of the ground segment are calculated. The distance from the real-time runway position to the runway threshold, the horizontal distance of the remaining air segment from the aircraft's current position to the main landing gear touchdown, the horizontal distance of the transition segment, and the horizontal distance of the ground segment are added together to obtain the initial landing distance in the second stage of the first state.

[0014] More preferably, after calculating the initial landing distance in the first stage or the second stage of the first state, the landing distance correction amount is obtained based on the current state of the aircraft, the state of the landing runway, and the external environment, with reference to the landing performance table, and the initial landing distance is further corrected.

[0015] Preferably, after entering the second state, the distance from the aircraft's real-time position to the runway threshold is calculated, and the horizontal distance of the ground segment is calculated based on the aircraft's speed and deceleration rate, thereby obtaining the initial landing distance in the second state. The distance from the aircraft's main landing gear to the nose landing gear is considered as a correction amount to adjust the initial landing distance.

[0016] More preferably, the first state is ROAAS air mode, the second state is ROAAS ground mode, and the specified distance is 50ft.

[0017] Preferably, the aircraft landing distance prediction method is not executed when the ROAAS function activation conditions are not met, or when the ROAAS function activation conditions are met but the aircraft experiences an abnormal landing situation, including a go-around.

[0018] Based on the above-described configuration, the aircraft landing prediction method disclosed herein divides the aircraft landing phase into a first stage of a first state (air mode), a second stage of the first state (air mode), and a second state (ground mode). It reads real-time aircraft status data and combines it with an aircraft landing performance correction table to predict the aircraft landing distance. Specifically, the first state (air mode) is divided into two stages, using different landing distance prediction models for initial landing distance prediction. Furthermore, it considers landing performance influencing factors such as aircraft weight, flap / slat angle, runway pavement condition, runway slope, and ambient temperature. The landing distance correction amount is obtained from the landing distance correction table, and the initial landing distance prediction value is corrected. Therefore, compared to existing ROAAS landing distance calculation methods, it can obtain a more accurate and reliable predicted landing distance based on the aircraft's real-time status and the respective landing performance under different flight phases. Attached Figure Description

[0019] Figure 1 It is a segmented schematic diagram as defined in this disclosure, representing different stages (flight states) of an aircraft in flight.

[0020] Figure 2 This is a block diagram illustrating the prediction principle in the aircraft landing distance prediction method according to the embodiments of this disclosure.

[0021] Figure 3 This is a flowchart illustrating the prediction of landing distance in the first state (ROAAS air mode) of the aircraft landing distance prediction method according to the embodiments of the present disclosure.

[0022] Figure 4 This is a flowchart illustrating the landing distance prediction in the second state (ROAAS ground mode) of the aircraft landing distance prediction method according to the embodiments of this disclosure. Detailed Implementation

[0023] Hereinafter, with reference to the accompanying drawings, the aircraft landing distance prediction method of the present disclosure will be described.

[0024] First, use Figure 1 This document describes the different flight phases (flight states) defined in the aircraft landing distance of this disclosure.

[0025] In actual approach and landing, when the aircraft is at a certain altitude, the pilot controls the aircraft's attitude using the control stick and pedals, and adjusts the flap and slat angles and lowers the landing gear to put the aircraft into the landing configuration in preparation for the final approach phase.

[0026] Additionally, when the aircraft descends to 50 feet from the runway threshold, it officially enters the final approach and landing phase. According to the Federal Aviation Administration's airworthiness standard AC25-7D, "landing distance" refers to the horizontal distance an aircraft travels from 50 feet above the runway until it comes to a complete stop. Figure 1 As shown, the landing distance specified in AC25-7D will be divided into the following three stages:

[0027] (1) Air segment: Its length is the horizontal distance from 50ft from the aircraft to the touchdown of the main landing gear;

[0028] (2) Transition section: Its length is the horizontal distance from the main landing gear touchdown to the braking activation;

[0029] (3) Deceleration phase: Its length is the distance from when the brakes take effect to when the aircraft comes to a complete stop.

[0030] In this disclosure, for ease of comparison between landing distance and runway length, unless specifically stated as "landing distance as specified in AC25-7D", the term "landing distance" is defined as the distance from the runway start point to the point where the aircraft comes to a complete stop.

[0031] The aircraft landing distance prediction method disclosed herein is a method that can predict the landing distance based on real-time status and landing performance at different flight stages. This method first determines whether the aircraft is in air mode (first state: ROAAS air mode) or ground mode (second state: ROAAS ground mode) based on whether the ROAAS function activation conditions are met and whether a normal landing has occurred. That is, as... Figure 2 As shown, when the ROAAS function activation conditions are met (step S100: ROAAS activation successful), if the aircraft has not yet landed (determined as "No" in step S200), it enters the first state of ROAAS air mode (step S300). If the aircraft lands normally and does not go around (determined as "Yes" in step S200), it enters the second state of ROAAS ground mode (step S400). Conversely, when the ROAAS function activation conditions are not met, the prediction of landing distance is not performed. Figure 2 This is a block diagram illustrating the prediction principle in the aircraft landing distance prediction method according to the embodiments of this disclosure.

[0032] exist Figure 2In the process, after entering the ROAAS air mode as the first state (step S300), the ROAAS air mode is further divided into the first stage (step S310) and the second stage (step S320) based on whether the aircraft is 50ft (about 15 meters) above the runway. Different landing distance prediction models are used in different stages to predict the landing distance. The predicted landing distance at this time is the initial landing distance L0.

[0033] After entering the first state represented by step S300, the initial landing distance L0 calculated based on the air-stage landing distance prediction model still needs further correction (step S330). At this time, combining the real-time aircraft status (including position, altitude, speed, path angle, etc.) and landing performance influencing factors (such as aircraft weight, flap angle, runway surface condition, runway slope, ambient temperature, etc.), a landing distance correction amount ΔL is calculated (step S331). Then, the initial landing distance L0 predicted in steps S310 and S320 is corrected using the landing distance correction amount ΔL (step S330), finally obtaining the corrected landing distance prediction value L (=L0+ΔL). At this time, the landing distance prediction value L is compared with the runway length in real time to provide a warning benchmark for ROAAS.

[0034] Additionally, upon entering the ROAAS ground mode as the second state (step S400), another landing distance prediction model is used to predict the landing distance (step S410), at which point the predicted landing distance is the initial landing distance L0. Finally, considering the aircraft configuration (especially the distance from the main landing gear to the nose landing gear), the corrected landing distance prediction value L is obtained (step S420).

[0035] Combination Figure 3 and Figure 4 This paper explains the different landing distance prediction models used in the different stages of the ROAAS air mode (first state) and the ROAAS ground mode (second state).

[0036] When in Figure 2 When the judgment in step S200 is "No" and the aircraft enters the ROAAS air mode as the first state (step S300), real-time aircraft status data such as current position, barometric altitude, radio altitude, vacuum speed, path angle FPA, inertial vertical speed, landing runway information, and brake gear are read. At the same time, based on the aircraft's altitude relative to the runway threshold in the input landing runway information, it is determined whether the aircraft is in the first stage of the ROAAS air mode (i.e., the flight altitude is 50 feet above the runway threshold) or the second stage of the ROAAS air mode (i.e., the flight altitude is 50 feet below or equal to the runway threshold).

[0037] - Landing distance prediction in the first stage of ROAAS airborne mode (step S310)

[0038] In the first phase of ROAAS air mode, the initial landing distance L0 is calculated through the following steps and methods.

[0039] (a) Calculate the distance between the starting point of the estimated landing distance under the AC25-7D definition and the runway threshold. That is, based on the aircraft's current position and altitude, calculate in real time the latitude and longitude coordinates of the aircraft descending in a straight line at the current flight path angle FPA to an altitude of 50 feet above the runway, and then calculate the horizontal distance L from this estimated point to the runway threshold based on the landing runway information. 50_THD If the predicted point falls within the runway area, then L 50_THD A positive value indicates a positive value, while a negative value indicates a negative value.

[0040] (b) Calculate the horizontal distance L of the aerial segment air First, the relationship between flight time and vertical speed from 50ft from the runway to the main landing gear touchdown, as shown in Equation (1), and the relationship between vacuum speed and vertical speed, as shown in Equation (2), were established using the parametric analysis method.

[0041]

[0042] in: t air The flight time from 50 feet on the runway to the main landing gear touching down (in seconds). VS 50 and VS TD These are the vertical speeds of the aircraft at 50 feet from the runway and at the point where the main landing gear touches down (unit: ft / s). V TAS_50 and V TAS_TD These are the vacuum speeds at 50 feet from the runway and at the main landing gear touchdown point (unit: ft / s). , , , , , The coefficient is determined by the aircraft's landing performance.

[0043] V can be obtained from equations (1) and (2). TAS_TD and t air .

[0044] (c) Typically, an aircraft descends at approximately a constant speed from 1000 feet above the ground to 50 feet above the runway; therefore, V TAS_50In essence, this can be considered equivalent to the aircraft's real-time vacuum speed. The air segment, however, approximates uniformly decelerated motion; therefore, the horizontal distance L during the air segment... air The calculation method is as follows (3).

[0045]

[0046] The transition segment is also approximately a uniformly decelerated motion, and the speed when braking takes effect is k. V TAS_TD The transition period is t. trans The horizontal distance L of the transition section trans The calculation method is as follows (4).

[0047]

[0048] The ground segment also approximates uniformly decelerated motion. Based on the preset braking gear, the horizontal distance L of the ground segment is... gnd The calculation method is as follows (5).

[0049]

[0050] in: a brk This represents the deceleration rate corresponding to different braking gears.

[0051] Combining equations (1) to (5) above, the formula for calculating the initial landing distance L0 in the first stage of ROAAS aerial mode is:

[0052] - Landing distance prediction in the second stage of ROAAS airborne mode (step S320)

[0053] In the second phase of ROAAS air mode, the initial landing distance L0 is calculated through the following steps and methods.

[0054] (d) Calculate the distance L from the real-time position of the runway to the runway threshold. air_ppos_THD If the aircraft is on the runway, then L air_ppos_THD If it is positive, then L is negative. air_ppos_THD It is a negative value.

[0055] (e) The process of the aircraft descending from 50 feet above the runway to touch down with the main landing gear is the level float phase. At this time, based on data such as the aircraft's inertial vertical velocity and altitude, the estimated time t required for descent to the main landing gear touch down from the current position is calculated. flare The horizontal distance L from the aircraft's current position to the remaining air segment where the main landing gear touches down is... flare The calculation method is as follows (7).

[0056]

[0057] in: V TAS_ppos For the aircraft's real-time vacuum speed.

[0058] Horizontal distance L of transition section trans Horizontal distance L of ground section gnd The calculation method is the same as that of the second stage of ROAAS air mode, namely Equation (4) and Equation (5).

[0059] Combining equations (4), (5), and (7) above, the formula for calculating the initial landing distance L0 in the second stage of ROAAS aerial mode is:

[0060] - Landing distance correction (step S330)

[0061] The landing performance tables for various aircraft types provide information on the impact of factors such as aircraft mass, flap / slat angle, runway surface condition, runway slope, and ambient temperature on aircraft landing distance, as shown in Table 1. These tables are determined by the aircraft manufacturer's performance team during aircraft design and various landing performance tests.

[0062] Table 1:

[0063] The landing distance correction value varies depending on the flap positioning and runway pavement conditions. Runway pavement conditions and codes are shown in Table 2.

[0064] Table 2:

[0065] After calculating the initial landing distance, based on aircraft flight data, runway conditions, external environmental factors, and referring to the landing performance table, the landing distance correction ΔL is obtained. Therefore, the predicted landing distance in ROAAS air mode is:

[0066] - Landing distance prediction using ROAAS ground model (step S410)

[0067] In ROAAS ground mode, such as Figure 4 As shown, the landing distance L is calculated through the following steps and methods.

[0068] (a) Calculate the distance L from the aircraft's real-time position to the runway threshold. gnd_ppos_THD .

[0069] (b) Based on the aircraft speed and deceleration rate, the horizontal distance L of the ground segmentgnd The calculation formula is:

[0070] in: V GS For the aircraft's real-time ground speed; a gnd The aircraft deceleration rate is denoted as 'a', which is the deceleration rate 'a' corresponding to the aircraft's current longitudinal acceleration and the braking gear. brk The larger value.

[0071] Initial landing distance in ground mode The calculation method is as follows:

[0072] Additionally, consider the distance L between the aircraft's main landing gear and nose landing gear. MLG_NLG Therefore, the corrected landing distance prediction value L in ground mode can be obtained as follows:

[0073] Finally, the calculated corrected landing distance prediction value L is compared with the current runway length in real time. When the corrected landing distance prediction value L exceeds the current runway length, the ROAAS system generates a runway overrun warning message to prompt the pilot to take appropriate measures.

[0074] Other advantages and modifications will readily occur to those skilled in the art. Therefore, this disclosure is not limited in its broader sense to the specific details and representative embodiments shown and described herein. Modifications can thus be made without departing from the spirit or scope of the overall inventive concept as defined by the appended claims and their equivalents.

Claims

1. A method for predicting aircraft landing distance, characterized in that, The aircraft landing distance prediction method includes: The aircraft is judged to be in the first state or the second state based on whether the conditions for ROAAS activation are met and whether the landing is normal. Once the first state is entered, the first state is further divided into a first stage and a second stage based on whether the aircraft is above the runway's prescribed altitude. Different landing distance prediction models are used in different stages of the first state to predict the landing distance, and the initial landing distance (L0) is obtained. The landing distance correction amount (ΔL) is calculated by combining the performance impact factor that affects the landing distance, and then the corrected landing distance prediction value (L) is obtained using the landing distance correction amount (ΔL). Once the second state is entered, a different landing distance prediction model than the one used in the first state is used to predict the landing distance, and the initial landing distance (L0) is obtained. The corrected landing distance prediction value (L) is obtained by considering the aircraft configuration. The corrected landing distance prediction value (L), obtained by using different landing distance prediction models in each state and stage, is compared with the runway length in real time. The ROAAS system generates runway overrun warning information to prompt the pilot to take appropriate measures.

2. The aircraft landing distance prediction method as described in claim 1, characterized in that, After entering the first state, based on the aircraft's altitude relative to the runway threshold in the selected landing runway information, if the flight altitude is higher than the specified runway threshold altitude, the aircraft is determined to be in the first stage of the first state. At this time, based on the aircraft's current position and altitude, the predicted latitude and longitude coordinates of the aircraft descending in a straight line at the current flight path angle FPA to a specified distance from the runway are calculated in real time. Then, based on the landing runway information, the horizontal distance (L) from the predicted point to the runway threshold is calculated. 50_THD Next, the horizontal distance (L) of the aerial segment was calculated. air ), horizontal distance of the transition section (L) trans ) and the horizontal distance of the ground section (L) gnd ), thus determining the horizontal distance (L) from the projected point to the runway threshold. 50_THD ), horizontal distance in the air segment (L) air ), horizontal distance of the transition section (L) trans ) and the horizontal distance of the ground section (L) gnd The initial landing distance (L0) under the first stage of the first state is obtained by adding the two numbers together.

3. The aircraft landing distance prediction method as described in claim 1, characterized in that, After entering the first state, based on the aircraft's altitude relative to the runway threshold in the input landing runway information, if the flight altitude is lower than or equal to the specified runway threshold altitude, the aircraft is determined to be in the second stage of the first state. At this time, the distance (L) from the real-time runway position to the runway threshold is calculated. air_ppos_THD Based on the aircraft's inertial vertical velocity and altitude, the estimated time (t) required for descent to the main landing gear touchdown from the current position is calculated. flare This allows for the calculation of the horizontal distance (L) of the remaining air segment from the aircraft's current position to the main landing gear touchdown. flare Furthermore, the horizontal distance (L) of the transition section was calculated. trans ) and the horizontal distance of the ground section (L) gnd This will determine the real-time location of the runway from the runway threshold (L). air_ppos_THD ), the horizontal distance from the aircraft's current position to the remaining air segment where the main landing gear touches down (L) flare ), horizontal distance of the transition section (L) trans ) and the horizontal distance of the ground section (L) gnd The initial landing distance (L0) under the second stage of the first state is obtained by adding the two states together.

4. The aircraft landing distance prediction method as described in claim 2 or 3, characterized in that, After calculating the initial landing distance (L0) under the first stage or the second stage of the first state, the landing distance correction amount (ΔL) is obtained based on the current state of the aircraft, the state of the landing runway, and the external environment, with reference to the landing performance table, and the initial landing distance (L0) is further corrected.

5. The aircraft landing distance prediction method as described in claim 1, characterized in that, After entering the second state, calculate the distance (L) from the aircraft's real-time position to the runway threshold. gnd_ppos_THD And based on the aircraft's speed and deceleration rate, the horizontal distance (L) of the ground segment is calculated. gnd Thus, the initial landing distance (L0) in the second state is obtained. Considering the distance from the main landing gear to the nose landing gear (L) MLG_NLG The initial landing distance (L0) is corrected as a correction amount.

6. As claimed in claims 1 to 1 The aircraft landing distance prediction method described in any one of the following descriptions is characterized in that, The first state is ROAAS over-the-air mode. The second state is ROAAS ground mode. The specified distance is 50 feet.

7. As claimed in claims 1 to 1999 The aircraft landing distance prediction method described in any one of the following descriptions is characterized in that, The aircraft landing distance prediction method will not be executed if the ROAAS function activation conditions are not met, or if the ROAAS function activation conditions are met but the aircraft is experiencing an abnormal landing situation, including a go-around.

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