Amphibious aircraft main landing gear fairing water load calculation method

Abstract

The invention belongs to the technical field of aircraft design, and discloses an amphibious aircraft main landing gear fairing water load calculation method, which comprises the following steps: firstly, calculating local pressure and distribution pressure of a hull of an amphibious aircraft according to a hull water load empirical formula, and then determining a main landing gear fairing load action area and a distribution form; and calculating the local pressure of the main landing gear fairing and the distribution pressure of the main landing gear fairing. According to the method, the problems that in the takeoff, dampening and control processes of the amphibious aircraft, impact force influence factors of splashing on the main landing gear fairing are many, quantitative analysis is difficult and the like are solved for the first time, and a water load mathematical model of the main landing gear fairing of the amphibious aircraft under the influence of multiple factors is established; the relation between the main landing gear fairing and the ship body water load is obtained, and the accurate calculation method for the water load of the main landing gear fairing of the amphibious aircraft suitable for engineering application is established.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft design, and relates to a water load design method for an amphibious aircraft, and in particular to a water load calculation method for a main landing gear fairing of an amphibious aircraft. Background Art

[0002] The main landing gear fairing is arranged in the middle of the fuselage, below the wing and behind the engine propeller, providing fairing for the main landing gear and its system. The structure includes the main fairing and the lower lock cover. When the amphibious aircraft taxis, takes off, lands and maneuvers, a large amount of water flow is generated to wash the fairing, causing the fairing to bear complex water loads, which may cause deformation or damage to the fuselage structure of the amphibious aircraft in severe cases. Therefore, it is very important to reasonably and accurately give the water load of the main fairing for the structural design and strength verification of the seaplane. Summary of the invention

[0003] In order to solve the above problems, the present invention provides a method for calculating the water load of the main landing gear fairing of an amphibious aircraft. Aiming at the problem of accurate calculation of the water load of the main landing gear fairing, the present invention provides accurate load input for the structural design and strength verification of the amphibious aircraft, thereby improving the safety of the amphibious aircraft in water taxiing, take-off and water landing.

[0004] The technical solution of the present invention is as follows:

[0005] A method for calculating water load of a main landing gear fairing of an amphibious aircraft comprises the following steps:

[0006] S1: Calculate the local pressure and distributed pressure of the hull of an amphibious aircraft according to the empirical formula of hull water load;

[0007] S2: Determine the load action area and distribution pattern of the main landing gear fairing;

[0008] S3: Calculate the local pressure of the main landing gear fairing;

[0009] S4: Calculate the distributed pressure on the main landing gear fairing.

[0010] Furthermore, in S1, the method for calculating the local pressure of the hull by the empirical formula of the hull water load is:

[0011] Local pressure:

[0012] In formula (1), P k is the local pressure of the hull, C2 is the empirical coefficient for determining the local pressure; V S1 is the stall speed of the aircraft at the design takeoff weight when the flaps are opened to the corresponding takeoff position; β kIt is the local sheer angle of the hull, specifically the sheer angle at the keel of the hull, and K2 is the empirical coefficient of pressure distribution along the longitudinal direction of the fuselage.

[0013] Furthermore, in S1, the method for calculating the distributed pressure of the hull by the empirical formula of the hull water load is:

[0014] Distributed Pressure:

[0015] In formula (2), P is pressure, C4 is the empirical coefficient for determining the distributed pressure, and V S0 It is the stall speed of the aircraft at the design landing weight when the flaps are opened to the corresponding landing position; K2 is the empirical coefficient of pressure distribution along the longitudinal direction of the fuselage, and β is the ramp angle.

[0016] Furthermore, in S2, the local position of the visible area of ​​the local pressure impact of the main landing gear fairing is checked as 0.2m*0.2m, and the wall panels and their connecting parts in the area are checked; the local pressure is evenly distributed in the action area.

[0017] Furthermore, in S2, the main landing gear fairing distributed pressure is evenly distributed in the entire upward visible area, and the hull frame and its connecting parts in the area are checked; when checking the hull frame, the bottom distributed pressure and the fairing distributed pressure must be considered at the same time; the distributed pressure is evenly distributed in the action area.

[0018] Furthermore, in S3, the calculation method of the local pressure of the main landing gear fairing is:

[0019] Min(Max(P1,P2),P3)

[0020] in:

[0021]

[0022] In formula (3), K2 is the empirical coefficient of pressure distribution along the longitudinal direction of the fuselage, β k is the minimum ramp angle of the fairing, C2 is the empirical coefficient for determining the local pressure, V S1 It is the stall speed of the airplane at the design takeoff weight when the flaps are opened to the corresponding takeoff position;

[0023] P2 is the local pressure at the exit of the main landing gear fairing;

[0024] P3 is the average local pressure at the bilge of the ship bottom before and after the step.

[0025] Furthermore, in formula (3), β k Take the minimum slope angle of the fairing, which shall not be less than 15°; K2 = 0.5;

[0026] Furthermore, in S4, the calculation method of the distributed pressure of the main landing gear fairing is:

[0027]

[0028] In formula (4), C2 is the empirical coefficient for determining local pressure, C4 is the empirical coefficient for determining distributed pressure, and P k The local pressure at the bottom of the main landing gear fairing is 1 / 3 of the local pressure at the side panels and their connections. k , P C The distributed pressure is applied to the main landing gear fairing. The distributed pressure acts on the entire visible area when viewed from above. The hull frame and its connecting parts in the verification area are not transmitted forward and backward as shear force and bending moment.

[0029] The beneficial effects of the present invention are as follows:

[0030] The present invention provides for the first time a method for calculating the water load of a main landing gear fairing of an amphibious aircraft, solves the problems of many factors affecting the impact force of splashing on the main landing gear fairing during take-off, landing and maneuvering of the amphibious aircraft and difficulty in quantitative analysis, establishes a mathematical model of the water load of the main landing gear fairing of an amphibious aircraft under the influence of multiple factors, obtains the relationship between the main landing gear fairing and the water load of the hull, and establishes an accurate calculation method for the water load of the main landing gear fairing of an amphibious aircraft that can be applied to engineering projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solution of the implementation method of the patent of the present invention, the following is a brief introduction to the drawings required for use in the implementation method. It should be understood that the following drawings only show certain embodiments of the patent of the present invention and should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 It is a schematic diagram of the main landing gear fairing of the amphibious aircraft of the present invention;

[0033] Figure 2 Define schematic diagrams for amphibious aircraft hull-related components;

[0034] Figure 3 The diagram is a schematic diagram of the oblique rise angle of the bottom of an amphibious aircraft;

[0035] Figure 4 It is a schematic diagram of the empirical coefficient of pressure distribution along the longitudinal direction of the hull of an amphibious aircraft;

[0036] Figure 5 It is a schematic diagram of the local pressure of the amphibious aircraft of the present invention. DETAILED DESCRIPTION

[0037] This section is an embodiment of the present invention, which is used to explain and illustrate the technical solution of the present invention. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0038] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate directions or positional relationships as given in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or case referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implying the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0039] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be interpreted in a broad sense, for example, it can be a fixed connection, a detachable connection or an integrated connection; it can be a mechanical connection or a point connection; it can be a direct connection or a connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0040] Embodiment 1:

[0041] A method for calculating water load of a main landing gear fairing of an amphibious aircraft comprises the following steps:

[0042] S1: Calculate the local pressure and distributed pressure of the hull of an amphibious aircraft according to the empirical formula of hull water load;

[0043] S2: Determine the load action area and distribution pattern of the main landing gear fairing;

[0044] S3: Calculate the local pressure of the main landing gear fairing;

[0045] S4: Calculate the distributed pressure on the main landing gear fairing.

[0046] In S1, the method for calculating the local pressure of the hull by the empirical formula of hull water load is:

[0047] Local pressure:

[0048] In formula (1), P k is the local pressure of the hull, C2 is the empirical coefficient for determining the local pressure; V S1 is the stall speed of the aircraft at the design takeoff weight when the flaps are opened to the corresponding takeoff position; β k It is the local sheer angle of the hull, specifically the sheer angle at the keel of the hull, and K2 is the empirical coefficient of pressure distribution along the longitudinal direction of the fuselage.

[0049] In S1, the method for calculating the distributed pressure of the hull using the empirical formula for hull water load is:

[0050] Distributed Pressure:

[0051] In formula (2), P is pressure, C4 is the empirical coefficient for determining the distributed pressure, and V S0 It is the stall speed of the aircraft at the design landing weight when the flaps are opened to the corresponding landing position; K2 is the empirical coefficient of pressure distribution along the longitudinal direction of the fuselage, and β is the ramp angle.

[0052] In S2, the local position of the visible area of ​​the main landing gear fairing local pressure impact is checked as 0.2m*0.2m, and the wall panels and their connections in the area are checked; the local pressure is evenly distributed in the action area.

[0053] In S2, the main landing gear fairing distributed pressure is evenly distributed in the entire visible area when viewed from above, and the hull frame and its connecting parts in the area are checked; when checking the hull frame, the bottom distributed pressure and the fairing distributed pressure must be considered at the same time; the distributed pressure is evenly distributed in the effective area.

[0054] In S3, the local pressure of the main landing gear fairing is calculated as:

[0055] Min(Max(P1,P2),P3)

[0056] in:

[0057]

[0058] In formula (3), K2 is the empirical coefficient of pressure distribution along the longitudinal direction of the fuselage, β k is the minimum ramp angle of the fairing, C2 is the empirical coefficient for determining the local pressure, V S1 It is the stall speed of the airplane at the design takeoff weight when the flaps are opened to the corresponding takeoff position;

[0059] P2 is the local pressure at the exit of the main landing gear fairing;

[0060] P3 is the average local pressure at the bilge of the ship bottom before and after the step.

[0061] In formula (3), βk Take the minimum slope angle of the fairing, which shall not be less than 15°; K2=0.5.

[0062] In S4, the calculation method of the distributed pressure of the main landing gear fairing is:

[0063]

[0064] In formula (4), C2 is the empirical coefficient for determining local pressure, C4 is the empirical coefficient for determining distributed pressure, and P k The local pressure at the bottom of the main landing gear fairing is 1 / 3 of the local pressure at the side panels and their connections. k , P C The distributed pressure is applied to the main landing gear fairing. The distributed pressure acts on the entire visible area when viewed from above. The hull frame and its connecting parts in the verification area are not transmitted forward and backward as shear force and bending moment.

[0065] like Figure 3 As shown, K2 is the empirical coefficient of the pressure distribution along the longitudinal direction of the amphibious aircraft. This coefficient is a piecewise function of the position along the fuselage. The horizontal axis is the longitudinal length of the hull, and the vertical axis is the K2 coefficient, that is, a piecewise function of the X-axis coordinate and K2.

[0066] Embodiment 2:

[0067] Aiming at the fact that there is no current calculation basis for the main landing gear fairing of amphibious aircraft, the present invention provides a water load calculation method for the main landing gear fairing of amphibious aircraft in combination with design and test experience, links the water load calculation method for the main landing gear fairing with the water load calculation of the hull, and reasonably and accurately provides a water load calculation method for the main landing gear fairing of amphibious aircraft, thereby providing accurate load input for the structural design and strength verification of amphibious aircraft and improving the safety of amphibious aircraft in water taxiing, take-off and water landing.

[0068] Step 1: Parameter preparation, including the shape of the hull and main landing gear fairing, as shown in Figure 1, as well as aerodynamic data, aircraft landing weight and take-off weight, etc.

[0069] Step 2: Select appropriate empirical coefficients of local pressure and distributed pressure of hull water load based on aircraft design parameters and usage mode.

[0070] Step 3: Calculate the stall speed of the aircraft without the influence of slipstream at the maximum takeoff and landing weight based on the maximum lift coefficient of the aircraft under the flaps during takeoff and landing.

[0071] Step 4: Calculate the local pressure and distributed pressure of the hull with the main landing gear fairing according to the empirical formula of the local pressure and distributed pressure of the amphibious aircraft hull.

[0072] in, Here P k is the pressure at the keel, unit: pa, see Figure 5 C2 is the empirical coefficient for determining local pressure; V S1 The stall speed of the aircraft when the flaps are opened to the corresponding takeoff position at the design takeoff weight, unit: m / s; β k is the slope angle at the keel, unit: °, see Figure 3 ; K2 is the empirical coefficient of pressure distribution along the longitudinal direction of the hull, see Figure 4 .

[0073] Step 5. Based on the design and test experience, the local position of the visible area of ​​the main landing gear fairing local pressure impact is divided into 0.2m*0.2m, and the wall panels and their connections in this area are mainly checked. The distributed pressure is evenly distributed over the entire visible area, and the hull frame and its connections are mainly checked, but it does not have to be transmitted forward and backward as shear force and bending moment. When checking the hull frame, the bottom distributed pressure and the fairing distributed pressure should be considered at the same time. The local pressure and distributed pressure are evenly distributed in the action area.

[0074] Step 6: The bottom of the main landing gear fairing can be used as the local pressure design of the hull. However, considering the installation position and function of the main landing gear fairing, and referring to the structural form of the relevant aircraft model, its local pressure shall not be less than the local pressure of the bottom of the ship at the exit of the main landing gear fairing, but shall not be greater than the pressure value of the corresponding station of the hull.

[0075] Step 7. Main landing gear fairing local pressure: Min(Max(P1,P2),P3), where:

[0076]

[0077] Here, β k Take the minimum deadrise angle of the fairing, but according to the specification, this value cannot be less than 15°, K2=0.5. Since the deadrise angle at the bottom of the main landing gear fairing is smaller than the deadrise angle of the hull at the corresponding station, it is calculated according to the empirical formula for local hull pressure.

[0078] The same frame is located at p k主起整流罩 >p k船体 , which is inconsistent with the previous regulation that the local pressure shall not be greater than the pressure value of the corresponding station on the hull. Therefore, after comparative analysis, C2 main landing gear fairing = 3 / 4C2 hull; P2 is the local pressure at the exit of the main landing gear fairing, unit: pa; P3 is the average local pressure at the bilge of the ship before and after the step, unit: pa.

[0079] Step 7: The main landing gear fairing distribution pressure is:

[0080]

[0081] The distributed action is applied to the entire visible area when looking up, and is mainly used to check the frame and its connections, but it does not have to be transmitted forward and backward as shear force and bending moment.

[0082] Step 8: The local pressure and distributed pressure are evenly distributed in the action area. For the structure not covered by the above load, the load on the bottom area of ​​the main landing gear fairing is P k , the side panels and their connections take 1 / 3 of the local pressure P k .

[0083] The above is only a specific embodiment of the present invention, but the protection scope of the present invention 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 by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for calculating water load on main landing gear fairing of amphibious aircraft, characterized in that: The following steps are involved: S1: Calculate the local pressure and distributed pressure of the hull of an amphibious aircraft according to the empirical formula of hull water load; S2: Determine the load action area and distribution pattern of the main landing gear fairing; S3: Calculate the local pressure of the main landing gear fairing; S4: Calculate the distributed pressure on the main landing gear fairing.

2. The method for calculating water load of main landing gear fairing of amphibious aircraft according to claim 1, characterized in that: In S1, the method for calculating the local pressure of the hull by the empirical formula of the hull water load is: Local pressure: In formula (1), P k is the local pressure of the hull, C2 is the empirical coefficient for determining the local pressure; V S1 is the stall speed of the aircraft at the design takeoff weight when the flaps are opened to the corresponding takeoff position; β k It is the local sheer angle of the hull, specifically the sheer angle at the keel of the hull, and K2 is the empirical coefficient of pressure distribution along the longitudinal direction of the fuselage.

3. The method for calculating water load of main landing gear fairing of amphibious aircraft according to claim 1, characterized in that: In S1, the method for calculating the distributed pressure of the hull by the empirical formula of the hull water load is: Distributed Pressure: In formula (2), P is pressure, C4 is the empirical coefficient for determining the distributed pressure, and V S0 It is the stall speed of the aircraft at the design landing weight when the flaps are opened to the corresponding landing position; K2 is the empirical coefficient of pressure distribution along the longitudinal direction of the fuselage, and β is the ramp angle.

4. The method for calculating water load of main landing gear fairing of amphibious aircraft according to claim 1, characterized in that: In the above S2, the local position of the visible area of ​​the main landing gear fairing local pressure impact is checked as 0.2m*0.2m, and the wall panels and connecting parts of the area are checked; the local pressure is evenly distributed in the action area.

5. The method for calculating water load of main landing gear fairing of amphibious aircraft according to claim 1, characterized in that: In the above-mentioned S2, the main landing gear fairing distributed pressure is evenly distributed in the entire upward visible area, and the hull frame and its connecting parts in the area are checked; when checking the hull frame, the bottom distributed pressure and the fairing distributed pressure are considered at the same time; the distributed pressure is evenly distributed in the effective area.

6. The method for calculating water load of main landing gear fairing of amphibious aircraft according to claim 1, characterized in that: In S3, the calculation method of the local pressure of the main landing gear fairing is: Min(Max(P1,P2),P3) in: In formula (3), K2 is the empirical coefficient of pressure distribution along the longitudinal direction of the fuselage, β k is the minimum ramp angle of the fairing, C2 is the empirical coefficient for determining the local pressure, and its value is not less than 55.4; V S1 It is the stall speed of the airplane at the design takeoff weight when the flaps are opened to the corresponding takeoff position; P2 is the local pressure at the exit of the main landing gear fairing; P3 is the average local pressure at the bilge of the ship bottom before and after the step.

7. The method for calculating water load of main landing gear fairing of amphibious aircraft according to claim 6, characterized in that: In the formula (3), β k Take the minimum slope angle of the fairing, which shall not be less than 15°; K2=0.

5.

8. The method for calculating water load of main landing gear fairing of amphibious aircraft according to claim 1, characterized in that: In the above S4, the calculation method of the distributed pressure of the main landing gear fairing is: In formula (4), C2 is the empirical coefficient for determining local pressure, C4 is the empirical coefficient for determining distributed pressure, and P k The local pressure at the bottom of the main landing gear fairing is 1 / 3 of the local pressure at the side panels and their connections. k , P C The distributed pressure is applied to the main landing gear fairing. The distributed pressure acts on the entire visible area when viewed from above. The hull frame and its connecting parts in the verification area are not transmitted forward and backward as shear force and bending moment.

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