Method for determining rolling friction coefficient of airplane on simple runway

Abstract

The invention belongs to the technical field of flight tests, and particularly relates to a method for determining the rolling friction coefficient of an aircraft on a simple runway. The method comprises the steps that 1, test equipment is built and comprises a test vehicle and a tractor, test wheels, an aircraft brake and a brake control rate module are installed on the test vehicle, and a tension meter is arranged between the test vehicle and the tractor; 2, calculating the equivalent single-wheel load of the airplane, and determining the load of the test wheel according to the equivalent single-wheel load of the airplane; 3, determining the counterweight of the test vehicle according to the load of the test wheel; step 4, determining a plurality of different brake efficiencies; 5, loading the balance weight and the brake efficiency of the test vehicle to the test equipment, and carrying out a sliding test to obtain tension data under different brake efficiencies; and 6, processing the tension data to obtain the rolling friction coefficient. According to the method, the rolling friction coefficient of the aircraft on the simple runway during braking and non-braking can be determined.

Description

Technical Field

[0001] The present invention belongs to the field of flight test technology, and in particular relates to a method for determining the rolling friction coefficient of an aircraft on a simple runway. Background Art

[0002] Simple runways generally refer to runways that are not paved or can be used for takeoff and landing of aircraft with only simple treatment. There are many types of runway materials, including land, snow, ice, grass, sand, Gobi, etc. As the main form of simple runways, soil simple runways are the simplest and easiest to build. When an aircraft taxis on a simple runway, the rolling of the wheels causes the pavement to deform significantly, forming deep wheel tracks on the pavement. When the aircraft taxis, it is subject to greater rolling friction, which seriously affects the take-off and landing performance of the aircraft.

[0003] The rolling friction that an aircraft experiences when taxiing on a simple runway is related to the pavement material, pavement strength, tire pressure, aircraft weight, tire type, braking efficiency, etc. In particular, different pavement strengths result in different wheel track depths, and it is difficult to establish a mathematical model for accurate calculation. The rolling friction coefficient directly affects the takeoff and landing distance of an aircraft, and has a huge impact on the aircraft's runway length requirements. Therefore, determining the rolling friction coefficient of an aircraft on a simple runway has become one of the key factors in evaluating the takeoff and landing performance of an aircraft on a simple runway.

[0004] At present, there are two main methods for measuring the rolling friction coefficient of an aircraft on a simple runway: one is to have the aircraft taxi directly on the simple runway and calculate the rolling friction coefficient through the dynamic equation of the aircraft taxiing; the other is to use a tractor to tow the aircraft on the simple runway at a constant speed, and use a dynamometer to measure the tension value to calculate the rolling friction coefficient. However, both methods require the aircraft to taxi on the test site, which has high test costs and risks, especially for large aircraft.

[0005] Therefore, it is desired to have a technical solution to overcome or at least alleviate at least one of the above-mentioned defects of the prior art. Summary of the invention

[0006] The purpose of the present application is to provide a method for determining the rolling friction coefficient of an aircraft on a simple runway to solve at least one problem existing in the prior art.

[0007] The technical solution of this application is: A method for determining the rolling friction coefficient of an aircraft on a simple runway comprises: Step 1: Building a test device, the test device comprising a test vehicle and a tractor, the test vehicle being equipped with a test wheel, an aircraft brake and a brake control rate module, and a dynamometer being arranged between the test vehicle and the tractor; Step 2: Calculate the equivalent single wheel load of the aircraft, and determine the load of the test wheel according to the equivalent single wheel load of the aircraft; Step 3: Determine the test vehicle counterweight according to the load of the test wheel; Step 4: Determine multiple different braking efficiencies; Step 5: Load the test vehicle counterweight and the brake efficiency onto the test equipment, conduct a coasting test, and obtain the pulling force data under different brake efficiencies; Step six: Process the tension data to obtain the rolling friction coefficient.

[0008] In at least one embodiment of the present application, in step one, a single wheel of the main landing gear is used as a test wheel, and two of the test wheels are installed on the test vehicle.

[0009] In at least one embodiment of the present application, in step 1, the tire pressure of the test wheel is equal to the tire pressure of the aircraft at the maximum take-off weight.

[0010] In at least one embodiment of the present application, the dynamometer has a data recording function, and the data recording frequency is not less than 4 times per second.

[0011] In at least one embodiment of the present application, in step 2, calculating the equivalent single wheel load of the aircraft, and determining the load of the test wheel according to the equivalent single wheel load of the aircraft, includes: Calculate the aircraft equivalent single wheel load borne by the main landing gear single wheel, the aircraft equivalent single wheel load is: ; Where ESWL is the equivalent single wheel load of the aircraft, W is the weight of the aircraft, and D n is the distance between the front landing gear and the center of gravity, D 0 is the distance between the front landing gear and the main landing gear center, n is the number of wheels, K is the equivalent single wheel load magnification factor; The aircraft equivalent single wheel load is taken as the load of the test wheel.

[0012] In at least one embodiment of the present application, in step three, determining the test vehicle counterweight according to the load of the test wheel includes: After the test vehicle counterweight is loaded onto the test vehicle, the load on each of the test wheels is equal to the equivalent single wheel load of the aircraft.

[0013] In at least one embodiment of the present application, in step 4, determining a plurality of different braking efficiencies includes: Select multiple different braking efficiencies from [0%, 100%].

[0014] In at least one embodiment of the present application, in step five, when the coasting test is carried out, it is ensured that the wheel tracks of the test wheels do not overlap with the wheel tracks of the tractor during the coasting process.

[0015] In at least one embodiment of the present application, in step six, the tension data is processed to obtain a rolling friction coefficient, including: S601, plotting the tension values ​​in the tension data into a curve in chronological order; S602, sorting the tension values ​​in the tension data according to size: T 1 ≤T 2 ≤……≤T n ; Among them, T 1 、T 2 ,……,T n are different tension values, and n is the number of tension values; Determine the lower limit a and the upper limit b so that all tension values ​​are contained in the interval [a, b]; S603, divide the interval [a, b] into equal parts to obtain m+1 different separation points: a=c 1 ≤c 2 ≤……≤c m+1 =b; m=(n / 3) round up; Among them, c 1 、c 2 ,……,c m+1 For different separation points; S604, determine whether the tension value falls within each sub-interval [c i , c i+1 The number of f in ] i , and sort by size: f 1 ≥f 2 ≥……≥f m ; And for the first x f i Find the sum so that: ; The x value when the above conditions are met is k; S605, calculate the first k f i The corresponding average value of the tension is: ; in, is the first k f i The average value of the corresponding tensile force; S606, calculate the rolling friction coefficient: ; Where μ is the rolling friction coefficient.

[0016] In at least one embodiment of the present application, in S601, the tension values ​​of the starting phase and the stopping phase in the curve are deleted, and the tension value of the coasting phase is retained.

[0017] The invention has at least the following beneficial technical effects: The method for determining the rolling friction coefficient of an aircraft on a simple runway in the present application can determine the rolling friction coefficient of an aircraft when braking and not braking on a simple runway, thereby reducing test costs, providing accurate test data support for evaluating the take-off and landing performance of an aircraft on a simple runway, ensuring the safety of aircraft test flights on simple runways, and effectively resolving safety hazards caused by aircraft test flights. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flow chart of a method for determining a rolling friction coefficient of an aircraft on a simple runway according to an embodiment of the present application; Figure 2 is a schematic diagram of a test device according to one embodiment of the present application; Figure 3 is a test wheel layout diagram of a test device according to one embodiment of the present application; Figure 4 It is a schematic diagram of the aircraft landing gear layout according to one embodiment of the present application. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the implementation of this application clearer, the technical scheme in the embodiment of this application will be described in more detail below in conjunction with the drawings in the embodiment of this application. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described embodiments are part of the embodiments of this application, not all of them. The embodiments described below with reference to the drawings are exemplary and are intended to be used to explain this application, and should not be construed as limitations on this application. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The embodiments of this application are described in detail below in conjunction with the drawings.

[0020] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the scope of protection of the present application.

[0021] The following is combined with Figures 1 to 4 This application is described in further detail.

[0022] The present application provides a method for determining the rolling friction coefficient of an aircraft on a simple runway, such as Figure 1 As shown, the following steps are included: Step 1: Build the test equipment, which includes a test vehicle and a tractor. The test vehicle is equipped with test wheels, aircraft brakes and a brake control rate module, and a dynamometer is set between the test vehicle and the tractor. Step 2: Calculate the equivalent single wheel load of the aircraft, and determine the load of the test wheel according to the equivalent single wheel load of the aircraft; Step 3: Determine the test vehicle counterweight according to the load of the test wheel; Step 4: Determine multiple different braking efficiencies; Step 5: Load the test vehicle's counterweight and brake efficiency onto the test equipment, conduct a coasting test, and obtain the pulling force data under different brake efficiencies; Step 6: Process the tension data to obtain the rolling friction coefficient.

[0023] The method for determining the rolling friction coefficient of an aircraft on a simple runway in the present application is as follows: Figure 2 , 3 As shown, in step one, the test equipment is built, and the test vehicle can glide at a constant speed through the simple runway under the traction of the tractor. In the preferred embodiment of the present application, a single wheel of the main landing gear is used as a test wheel, and two test wheels are installed on the test vehicle. The test wheel should be the same as the wheel of the aircraft under test, and the tire pressure of the test wheel should be consistent with the tire pressure of the aircraft at the maximum take-off weight. The dynamometer is used to measure the pulling force of the tractor on the test vehicle. The dynamometer has a data recording function and can read data. The data recording frequency is not less than 4 times per second.

[0024] The method for determining the rolling friction coefficient of an aircraft on a simple runway of the present application, in step 2, takes determining the rolling friction coefficient of a certain type of aircraft on a simple soil runway as an example, the strength of the simple soil runway can meet the take-off and landing of the aircraft, the maximum take-off weight of the aircraft on the simple soil runway is known, the aircraft adopts a rear center of gravity, a front three-point landing gear, 2 front wheels, 8 main wheels (4 wheels on one side), such as Figure 4 The aircraft weight W is the maximum take-off weight of the aircraft.

[0025] In this embodiment, the aircraft equivalent single wheel load borne by a single wheel of the main landing gear is calculated, and the aircraft equivalent single wheel load is: ; Where ESWL is the equivalent single wheel load of the aircraft, W is the weight of the aircraft, and D n is the distance between the front landing gear and the center of gravity, D 0 is the distance between the front landing gear and the main landing gear center, n is the number of wheels, K is the equivalent single wheel load magnification factor; The aircraft equivalent single wheel load is used as the test wheel load.

[0026] The equivalent single wheel load magnification factor K is related to the landing gear structure. The load distribution of each landing gear wheel may be different. Please refer to the relevant manual to determine it.

[0027] In a preferred embodiment of the present application, in step three, after the test vehicle counterweight is loaded onto the test vehicle, the load on each test wheel is equal to the equivalent single wheel load of the aircraft. In step four, multiple different braking efficiencies are selected from [0%, 100%]. Before conducting the taxi test, the braking efficiency of the test is clarified, and the braking efficiency is input into the aircraft brake and brake control rate module of the test vehicle. The braking efficiency input value is a number between 0 and 1, such as no braking when the input value is 0, the braking efficiency is 70% when the input value is 0.70, and the braking efficiency is 100% when the input value is 1.

[0028] In the method for determining the rolling friction coefficient of an aircraft on a simple runway of the present application, in step 5, when carrying out the taxiing test, ensure that the wheel tracks of the test wheels do not overlap with the wheel tracks of the tractor during the taxiing process. In one embodiment of the present application, under the traction of the tractor, the weighted test vehicle passes through the simple runway at a uniform speed of 20 km / h, the taxiing time is 5 minutes, and the pulling force value is recorded in real time. During the taxiing process, ensure that the wheel tracks of the test wheels do not overlap with the wheel tracks of the tractor, and there is a certain distance between the two.

[0029] The method for determining the rolling friction coefficient of an aircraft on a simple runway of the present application, finally, in step 6, after the taxiing test is completed, the real-time tension value recorded is downloaded from the data recorder of the dynamometer, and the data is processed to obtain the rolling friction coefficient. In this embodiment, the specific process of data processing includes: S601, plotting the tension values ​​in the tension data into a curve in chronological order; In this embodiment, the dynamometer records 4 data of the tension value per second. There are about 1200 data in 5 minutes of sliding. These data are plotted into a curve in chronological order, and the tension values ​​with large discreteness in the starting and stopping stages of the curve are deleted, while the relatively stable tension values ​​in the intermediate sliding stage are retained.

[0030] S602, sorting the tension values ​​in the tension data according to size: T 1 ≤T 2 ≤……≤T n ; Among them, T 1 、T 2 ,……,T n are different tension values, and n is the number of tension values; Determine the lower limit a and the upper limit b so that all tension values ​​are contained in the interval [a, b]; In this embodiment, a is slightly smaller than T 1 , b is slightly larger than T n .

[0031] S603, divide the interval [a, b] into equal parts to obtain m+1 different separation points: a=c 1 ≤c 2 ≤……≤c m+1 =b; m=(n / 3) round up; Among them, c 1 、c 2 ,……,c m+1 For different separation points; S604, determine whether the tension value falls within each sub-interval [c i , c i+1 The number of f in ] i , and sort by size: f 1 ≥f 2 ≥……≥f m ; And for the first x f i Find the sum so that: ; The x value when the above conditions are met is k; S605, calculate the first k f i The corresponding average value of the tension is: ; in, is the first k f i The average value of the corresponding tensile force; S606. Calculate the rolling friction coefficient: ; Where μ is the rolling friction coefficient.

[0032] The method for determining the rolling friction coefficient of an aircraft on a simple runway of the present application is to build a test device, carry out a taxiing test, and process the test data to obtain the rolling friction coefficient. The present application can accurately measure the rolling friction coefficient of the aircraft when it is not braking and the equivalent rolling friction coefficient under different braking efficiencies, and can accurately evaluate the take-off and landing performance of the aircraft on the simple runway, and ensure the safety of the aircraft taking off and landing on the simple runway, thereby effectively reducing the cost of flight tests, reducing the flight test cycle, and speeding up the development process of the aircraft. The present application is applicable to the measurement of the rolling friction coefficient of an aircraft on a simple runway, and has the characteristics of strong versatility, simple implementation, low cost, and accurate results.

[0033] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for determining the rolling friction coefficient of an aircraft on a simple runway, characterized in that: include: Step 1: Building a test device, the test device comprising a test vehicle and a tractor, the test vehicle being equipped with a test wheel, an aircraft brake and a brake control rate module, and a dynamometer being arranged between the test vehicle and the tractor; Step 2: Calculate the equivalent single wheel load of the aircraft, and determine the load of the test wheel according to the equivalent single wheel load of the aircraft; Step 3: Determine the test vehicle counterweight according to the load of the test wheel; Step 4: Determine multiple different braking efficiencies; Step 5: Load the test vehicle counterweight and the brake efficiency onto the test equipment, conduct a coasting test, and obtain the pulling force data under different brake efficiencies; Step six: Process the tension data to obtain the rolling friction coefficient.

2. The method for determining the rolling friction coefficient of an aircraft on a simple runway according to claim 1, characterized in that: In step 1, a single wheel of the main landing gear is used as a test wheel, and two of the test wheels are installed on the test vehicle.

3. The method for determining the rolling friction coefficient of an aircraft on a simple runway according to claim 2, characterized in that: In step 1, the tire pressure of the test wheel is equal to the tire pressure of the aircraft at the maximum take-off weight.

4. The method for determining the rolling friction coefficient of an aircraft on a simple runway according to claim 3, characterized in that: The dynamometer has a data recording function, and the data recording frequency is not less than 4 times per second.

5. The method for determining the rolling friction coefficient of an aircraft on a simple runway according to claim 4, characterized in that: In step 2, the equivalent single wheel load of the aircraft is calculated, and the load of the test wheel is determined according to the equivalent single wheel load of the aircraft, including: Calculate the aircraft equivalent single wheel load borne by the main landing gear single wheel, the aircraft equivalent single wheel load is: ； Where ESWL is the equivalent single wheel load of the aircraft, W is the weight of the aircraft, and D n is the distance between the front landing gear and the center of gravity, D0 is the distance between the front landing gear and the center of the main landing gear, n is the number of wheels, and K is the equivalent single wheel load magnification factor; The aircraft equivalent single wheel load is taken as the load of the test wheel.

6. The method for determining the rolling friction coefficient of an aircraft on a simple runway according to claim 5, characterized in that: In step three, the test vehicle counterweight is determined according to the load of the test wheel, including: After the test vehicle counterweight is loaded onto the test vehicle, the load on each of the test wheels is equal to the equivalent single wheel load of the aircraft.

7. The method for determining the rolling friction coefficient of an aircraft on a simple runway according to claim 6, characterized in that: In step 4, multiple different braking efficiencies are determined, including: Select multiple different braking efficiencies from [0%, 100%].

8. The method for determining the rolling friction coefficient of an aircraft on a simple runway according to claim 7, characterized in that: In step 5, when carrying out the sliding test, ensure that the wheel track of the test wheel does not overlap with the wheel track of the tractor during the sliding process.

9. The method for determining the rolling friction coefficient of an aircraft on a simple runway according to claim 8, characterized in that: In step six, the tension data is processed to obtain a rolling friction coefficient, including: S601, plotting the tension values ​​in the tension data into a curve in chronological order; S602, sorting the tension values ​​in the tension data according to size: T1≤T2≤……≤T n ; Among them, T1, T2, ..., T n are different tension values, and n is the number of tension values; Determine the lower limit a and the upper limit b so that all tension values ​​are contained in the interval [a, b]; S603, divide the interval [a, b] into equal parts to obtain m+1 different separation points: a=c1≤c2≤……≤c m+1 =b; m=(n / 3) round up; Among them, c1, c2, ..., c m+1 For different separation points; S604, determine whether the tension value falls within each sub-interval [c i , c i+1 The number of f in ] i , and sort by size: f1≥f2≥……≥f m ; And for the first x f i Find the sum so that: ； The x value when the above conditions are met is k; S605, calculate the first k f i The corresponding average value of the tension is: ； in, is the first k f i The average value of the corresponding tensile force; S606, calculate the rolling friction coefficient: ； Where μ is the rolling friction coefficient.

10. The method for determining the rolling friction coefficient of an aircraft on a simple runway according to claim 9, characterized in that: In S601, the pulling force values ​​in the starting stage and the stopping stage in the curve are deleted, and the pulling force value in the coasting stage is retained.

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